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Form PG-1028-E
March, 2003
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INSTRUCTIONS
for
OPERATING
and
SERVICING

HOS
COMPRESSOR

GAS FIELD COMPRESSORS

© Dresser-Rand Company 2003

Printed in U.S.A.
Front Matter PG-1028-E (HOS)

FOREWORD

This manual is divided into two major sections.

(1) FRONT MATTER; containing WARNING, FOREWORD, SAFETY SUMMARY, STATEMENT OF

WARRANTY, LIMITATIONS of LIABILITY and other comments of interest to our customers.

(2) TECHNICAL SECTION; consisting of five chapters.

· CHAPTER 1, INTRODUCTION
· CHAPTER 2, LUBRICATION
· CHAPTER 3, OPERATING AND TROUBLESHOOTING
· CHAPTER 4, MAINTENANCE
· CHAPTER 5, GENERAL DATA & SPECIFICATIONS

Do not remove the stainless steel nameplates that are attached to the machine. These plates give serial
numbers that are necessary when communicating with Dresser-Rand about the equipment.

Also, do not remove safety labels. If these labels are removed or defaced, new ones should be obtained
from Dresser-Rand Company. Refer all communications to the nearest Dresser-Rand Authorized
Packager or the Dresser-Rand Gas Field Compressor Group.

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PG-1028-E (HOS) Front Matter

SAFETY PRECAUTIONS
Safety Information

WARNING
DO NOT OPERATE THIS EQUIPMENT IN EXCESS OF ITS RATED
CAPACITY, SPEED, PRESSURE AND TEMPERATURE, NOR OTHERWISE
THAN IN ACCORDANCE WITH THE INSTRUCTIONS CONTAINED IN THIS
SERVICE MANUAL. OPERATION OF THE EQUIPMENT IN EXCESS OF THE
CONDITIONS SET FORTH IN THE SALES CONTRACT WILL SUBJECT IT TO
STRESSES AND STRAINS WHICH IT WAS NOT DESIGNED TO
WITHSTAND. FAILURE TO HEED THIS WARNING MAY RESULT IN AN
ACCIDENT CAUSING PERSONAL INJURY OR PROPERTY DAMAGE.

WARNING
READ CAREFULLY AND UNDERSTAND THIS SERVICE MANUAL BEFORE INSTALLING
OR OPERATING THE COMPRESSOR.

This service manual contains important instructions and information on the installation,
operation and servicing of Dresser-Rand HOS Model compressors. THE IMPORTANCE
OF GETTING THIS SERVICE MANUAL INTO THE HANDS OF THE PERSON IN
CHARGE OF INSTALLING THE COMPRESSOR CANNOT BE OVEREMPHASIZED.
All personnel involved in the installation, operation and servicing of the compressor
should have access to this service manual and be familiar with its contents. Strict
adherence to these instructions will be repaid by satisfactory compressor performance
and acceptable upkeep costs.

Do not remove the stainless steel nameplates that are attached to the machine. These
plates give serial numbers that are necessary when communicating with Dresser-Rand
about the equipment. Also, do not remove safety labels. If these labels are removed or
defaced, new ones should be obtained from Dresser-Rand Company.

REFER ALL COMMUNICATIONS TO THE NEAREST DRESSER-RAND COMPANY

OFFICE.

iii
Front Matter PG-1028-E (HOS)

Dangers, warnings and cautions appearing throughout this service manual are of
paramount importance to personnel and equipment safety. Prior to any attempt to operate,
maintain, troubleshoot, or repair any part of the compressor, all DANGERS, WARNINGS and
CAUTIONS should be thoroughly reviewed and understood. Refer to the Safety Summary that
starts on the next page. The information immediately following defines "signal words" as they
are used in this manual.

SIGNAL WORDS ARE USED TO IDENTIFY LEVELS OF HAZARD SERIOUSNESS. THEIR

SELECTION IS BASED ON THE LIKELY CONSEQUENCE OF HUMAN INTERACTION WITH
THE HAZARD IN TERMS OF:

● DEGREE OF SEVERITY (minor injury, severe injury, death)

● THE PROBABILITY OF SEVERITY (will result, could result)

DANGER
The word DANGER signifies immediate hazards that WILL result in severe
personal injury or death. In the service manual, this should be construed
to be a VERY STRONG Warning (see below).

WARNING
The word WARNING refers to hazards or unsafe practices that COULD
result in severe personal injury or death. This is found quite often in the
service manual due to its association with unsafe practices.

CAUTION
The word CAUTION refers to hazards or unsafe practices that COULD
result in minor personal injury, or product or property damage. This word
is found frequently in the service manual due to the fact that bad mainte-
nance practices or procedures can so often result in damage to the com-
pressor. Because what constitutes a "minor" injury is open to debate, we
have upgraded many CAUTIONS to WARNING.

NOTE

NOTES are used to highlight certain operating or maintenance conditions or

statements that are essential but not of a known hazardous nature, as would be
indicated by DANGER, WARNING or CAUTION.

iv
PG-1028-E (HOS) Front Matter

SAFETY SUMMARY

The following safety precautions are being recommended only in regard to the
compressor and other Dresser-Rand supplied equipment (ex: motors, consoles, etc.). Abide by
all OSHA and all other applicable safety regulations, including all site-specific safety and work
procedures.

The installation, operation and maintenance of a compressor and auxiliary components

may present certain hazards that are unique to this type of equipment. The following list of
safety precautions must be thoroughly read and reviewed by all personnel prior to working with
or on the compressor equipment and systems. These general statements are expanded upon
in the sections of the manual appropriate to their application. Failure to heed these statements
can result in an incident causing property damage, personal injury or death.

● All electrical motor and control wiring must be carefully installed in accordance with the
National Electric Code, the Occupational Safety and Health Act of 1970 (OSHA) and any
other code requirements at the installation site.

● Piping subject to temperatures in excess of 175ºF (80ºC) which may be touched by

personnel must be suitably guarded or insulated.

● It is imperative that all gases lighter or heavier than air, active or inactive, toxic, combusti-
ble, obnoxious, objectionable, or in any way harmful to personnel or equipment, be piped
away from the compressor. There must be no manifolding of vent tubing or piping; nor
can back pressure be allowed to develop in any vent line. Gases may be re-circulated
as required by the process, but in any case must be controlled and/or disposed of in
accordance with OSHA regulations and local pollution laws.

● The compressor must be fitted with pressure relief valves or rupture disks to limit the
discharge pressures to a safe maximum. NEVER install an intervening valve between
a compressor cylinder and the pressure relief valve or rupture disk.

● Pressure relief valves must have their settings tested at least once a year, and more
often under extreme operating conditions, using an appropriate bench test.

● If a pressure relief valve or rupture disk blows during operation, stop the unit immediately
and determine the cause.

● Pressure relieving devices that are vented to the atmosphere must have their outlet
connections directed away from operator stations.

● Rotating equipment must not be placed in operation unless adequate safeguards have
been provided to protect operating personnel.

● Service on a machine shall always start with cleaning the floor and the outside of the
machinery to remove oil that could cause maintenance personnel to slip.

v
Front Matter PG-1028-E (HOS)

● Whenever a compressor is shut down for repairs, positive steps must be taken to
prevent the prime mover from being inadvertently energized and started. Equipment
being worked on should be “Locked Out” and “Tagged Out” to ensure against
inadvertently providing power and accidentally starting. In addition, a warning sign
bearing the legend "WORK IN PROGRESS-DO NOT START", or similar wording, shall
be attached to the starting equipment.

● Whenever the compressor is shut down because overheating is suspected, a minimum

period of 30 minutes must elapse before the crankcase is opened. Premature opening
of the crankcase can result in a crankcase explosion.

● Prior to opening the compressor, or undertaking a major overhaul, the unit must be
positively blocked against rollover and movement of the running gear. When the unit is
equipped with a flywheel locking device, this device must be used to prevent rollover.
Blocking of the crankshaft or crossheads is an alternate method of preventing accidental
rollover.

● Never open a compressor cylinder or any other part of the compression system without
first completely relieving all pressure within the compressor cylinders, piping, vessels
and coolers; and taking all necessary precautions to prevent accidental pressurizing of
the system.

● Compressors handling toxic or flammable gases must be isolated from the process
piping by means of blinds, or double valves and bleeders, when major maintenance is
required. Before opening such compressors, the equipment MUST be purged or
evacuated.

● Incorrect placement of the inlet and discharge valves in the cylinders can cause an ex-
tremely hazardous condition. INSTALLING AN INLET VALVE IN A DISCHARGE
VALVE PORT, OR INSTALLING A DISCHARGE VALVE UPSIDE DOWN, MAY CAUSE
EXCESSIVE PRESSURE IN THE CYLINDER RESULTING IN RUPTURE AND/OR AN
EXPLOSION.

● Discharge valve ports usually are made slightly smaller at the minor diameter below the
valve gasket seat; this is called "polarization". When an inlet valve is installed in a
discharge port by mistake, it will not fit down into the port properly and the mechanic will
be alerted to the error.

● In many cases, the inlet valve stop plates have lugs that will prevent an inlet valve from
being installed in a discharge valve port by mistake; this is another type of "polarization".
The minor diameter of the discharge port is slightly smaller so the inlet valve will not fit
properly, alerting the mechanic to the error.

● If IN DOUBT as to whether a valve is inlet or discharge, or as to which cylinder valve

ports receive inlet or discharge valves, CHECK WITH YOUR SUPERVISOR.

● Corrective action must be taken when the piston rod pressure packing vent gas leakage
is excessive, or when there is a sudden increase in the leakage rate.

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PG-1028-E (HOS) Front Matter

● After any maintenance or overhaul of the compressor, the unit must be barred through
at least one complete revolution to ensure that there are no mechanical obstructions
within the machine.

● A manual bar and fulcrum and/or a hydraulic or pneumatic barring rig may have been
provided as a means of rotating the compressor crankshaft during installation, during
maintenance, prior to start-up after maintenance or overhaul, and at any other time exact
positioning of the running gear is required. Compressor cylinders must be depressurized
to atmospheric pressure before barring. Compressor pistons will move to crank end
dead center as an equilibrium condition due to the difference in crank end and head end
piston surface areas if exposed to the process gas pressure. Failure to depressurize the
compressor cylinders prior to barring may result in unexpected rotation that can cause
personal injury.

● Established operating and maintenance procedures, as well as basic safety precautions,

must be reviewed with the operating and maintenance personnel at regular intervals, not
to exceed six months. Newly assigned operators must be thoroughly trained in the safe
operation of this equipment before they are permitted to operate it.

● Whenever an outer head is removed from the compressor cylinder, make certain that
the piston vent hole(s), if used, located in the outer face of the piston are open and that
the piston does not contain pressure. If the compressor has been handling a flammable
or toxic gas, appropriate precautions shall be taken before clearing a vent hole that has
become plugged.

● Never use an air impact wrench for ANY tightening of critical fasteners. An impact
wrench cannot accurately impart the proper bolt or stud pre-stress. See CHAPTER 5
of this manual for detailed fastener tightening requirements and procedures.

● Special attention should be paid to all detailed DANGER, WARNING and CAUTION
statements located throughout this manual, and to all SAFETY LABELS affixed to the
equipment.

vii
Front Matter PG-1028-E (HOS)

WARRANTY, REMEDY, DISCLAIMER

A. Dresser-Rand warrants that the equipment manufactured and delivered by Dresser-Rand under
the terms of this Agreement will be free from defects in material and workmanship until the
earliest to occur of the following events:

1. One year after startup.

2. Eighteen (18) months after shipment by packager.
3. Twenty-four (24) months after shipment by Dresser-Rand to Packager.

The Packager shall be obligated to promptly report any claimed defects in writing to Dresser-
Rand immediately upon discovery and, in any event, within the above period. After notice from
Packager and substantiation of the claim, Dresser-Rand shall, at its option, correct such defect
either by suitable repair to such equipment or part, or by furnishing replacement equipment or
part(s), as necessary, to the original ex-works point of shipment.

B. DRESSER-RAND MAKES NO OTHER WARRANTY OR REPRESENTATION OF ANY KIND.

ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE HEREBY DISCLAIMED.

C. With respect to equipment, parts and work not manufactured or performed by Dresser-Rand,
Dresser-Rand's only obligation shall be to assign to Packager whatever warranty Dresser-Rand
receives from the manufacturer.

D. Dresser-Rand shall not be liable for the cost of any repair, replacement, or adjustment to the
equipment or parts made by the Packager or for labor performed by the Packager or others,
without Dresser-Rand's prior written approval.

E. No equipment or part furnished by Dresser-Rand shall be deemed to be defective by reason

of normal wear and tear, failure to resist erosive or corrosive action of any fluid or gas, or of
Packagers's failure to properly store, install, operate or maintain the equipment in accordance
with good industry practices or specific recommendations of Dresser-Rand.

F. The Packager shall not operate equipment which is considered to be defective without first
notifying Dresser-Rand in writing of its intention to do. Any such use of the equipment will be
at the Packager's sole risk and expense.

G. The repair or replacement of the equipment, spare or replacement part(s) by Dresser-Rand

under this Warranty schedule shall constitute Dresser-Rand's sole obligation and Packager's
sole and exclusive remedy for all claims of defects regarding the equipment and parts furnished
hereunder.

H. The compressor owner should contact an authorized Dresser-Rand Packager for all required
warranty or non-warranty service.

viii
PG-1028-E (HOS) Front Matter

LIMITATIONS OF LIABILITY

A. The remedies of the Packager set forth herein are exclusive and the total liability of Dresser-
Rand with respect to claims under this Agreement or regarding the equipment, spare or
replacement parts and services incidental thereto as furnished hereunder, whether based in
contract, tort (including negligence and strict liability) or otherwise, shall not exceed the purchase
price of the services or the unit of equipment or part(s) upon which such liability is based.

B. Dresser-Rand shall in no event be liable for any consequential, incidental, indirect, special or
punitive damages arising out of this Agreement or any breach thereof, or any defect in, or failure
of, or malfunction of the equipment or part(s) hereunder, including but not limited to claims
based on loss of use, lost profits or revenue, interest, lost goodwill, work stoppage, impairment
of other goods, loss by reason of shutdown or non-operation, increased expenses of operation,
cost of purchase of replacement power or claims of Packager or customers of Packager for
service interruption whether or not such loss or damage is based on contract, tort (including
negligence and strict liability) or otherwise.

COMMENTS OF INTEREST TO OUR CUSTOMERS

General

Service Manuals are furnished for every Dresser-Rand Compressor. If additional details of your
job are required, we will be happy to furnish this information.

This book is intended to cover many of the special points of operating and maintenance of the
compressor components, and to supplement the experience and mechanical ability of a competent
engineer.

Dresser-Rand service is available to every compressor owner. We have a continued interest

in the welfare of our machinery. We wish to build and stand by every unit so that the purchase of this
compressor will always be considered a wise investment.

Consultation

Our engineering department welcomes inquiries regarding any phase of compressor practice,
operation and repairs or changes to meet unexpected conditions. Our sales department and branch
representatives will confer with you on any prospective installation or change. Call, write or wire our
branch offices for information and advice on any point.

Inspection

These compressors will operate satisfactorily for years with little special attention. A
preventative maintenance schedule will do much to ensure optimum performance of the unit, while
avoiding possible difficulties at some inconvenient time.

ix
Front Matter PG-1028-E (HOS)

Renewal Parts

If you will write us fully about your trouble or unusual wear, we may be able to make helpful
suggestions that will correct your problem. We keep standard parts on hand for replacement when
required.

Service

Dresser-Rand distributors maintain a force of highly trained Field Service Representatives,

skilled in compressor work, who are available for installation, inspection or repair. They can be secured
on reasonable notice. Contact your nearest Dresser-Rand distributor for service information.

Proper erection and starting of the compressor is extremely important. The success of a unit
frequently depends on how it is installed. We strongly urge that such work be supervised by skilled Field
Service Representatives, who are thoroughly familiar with construction, and who can also instruct the
operators in the care and handling of the equipment.

Many customers, especially those operating several units, have Field Service Representatives
make periodic inspections to prevent malfunctions and to ensure the best possible operating results.
These representatives can explain how to operate D-R units to achieve the greatest possible operating
results with the greatest efficiency and economy, while obtaining the longest possible equipment life.

x
 Table of Contents
for
Type HOS Instructions

CHAPTER 1 - INTRODUCTION

Paragraph Page

1-1. GENERAL INFORMATION ............................................................... 1-2

1-1.1. Ratings and Performance Characteristics.................................... 1-2
1-1.2. Design Improvements .................................................................. 1-2
1-2. SERIAL NUMBERS........................................................................... 1-3
1-3. CYLINDER NAMEPLATE INFORMATION........................................ 1-4
1-3.1. Cylinder Type, Serial Number, Bore & Stroke.............................. 1-4
1-3.2. Rated Discharge Pressure ........................................................... 1-4
1-3.3. Maximum Allowable Working Pressure........................................ 1-5
1-3.4. Hydrostatic Test Pressure............................................................ 1-5
1-3.5. Maximum Cooling Water Pressure .............................................. 1-5
1-3.6. Maximum Allowable Discharge Gas Temperature ....................... 1-5
1-3.7. Maximum Speed .......................................................................... 1-5
1-3.8. Base Clearance ........................................................................... 1-5
1-3.9. Normal Lineal Clearance.............................................................. 1-5
1-3.10. Added Fixed Clearance................................................................ 1-5

CHAPTER 2 -LUBRICATION

Paragraph Page

2-1. GENERAL....................................................................................................................... 2-2

2-2. FRAME AND RUNNING GEAR LUBRICATION SYSTEM ............................................ 2-2
2-2.1. Main Oil Pump.......................................................................................................... 2-3
A. Main Oil Pump Removal & Disassembly..................................................... 2-3
B. Main Oil Pump Assembly & Installation ...................................................... 2-5
2-2.2. Oil Pressure Regulation Valve ................................................................................. 2-6
2-2.3. Oil Pressure Safety Relief Valve .............................................................................. 2-7
2-2.4. Hand Oil Priming Pump............................................................................................ 2-7
A. Hand Oil Priming Pump Removal & Disassembly ...................................... 2-8
B. Hand Oil Priming Pump Assembly & Installation ........................................ 2-9
2-2.5. Oil Pressure Gauges................................................................................................ 2-9
2-2.6. Low Oil Pressure Shutdown Protection.................................................................... 2-10
2-2.7. Oil Cooler (Heat Exchanger) .................................................................................... 2-10
2-2.8. Oil Filter .................................................................................................................... 2-11
2-2.9. Frame Oil Recommendations ................................................................................. 2-11
A. General Requirements ................................................................................ 2-12
B. Viscosity Requirements............................................................................... 2-12
C. Inspection ................................................................................................... 2-12
D. Oil Change Schedule .................................................................................. 2-12
2-2.10. Frame Oil Level ....................................................................................................... 2-13
2-2.11. Frame Breather ....................................................................................................... 2-13
2-3. CYLINDER LUBRICATION SYSTEM............................................................................. 2-14
Table of Contents PG-1028-E (HOS)

CHAPTER 2 –LUBRICATION (Continued)

Paragraph Page

2-3.1. Block-type Lubrication System ................................................................................. 2-14

A. Filling and Purging the System .................................................................... 2-16
B. Maintenance and Troubleshooting .............................................................. 2-18
2-3.2. Pump-to-Point Lubrication System .......................................................................... 2-19
A. Lubricator Operation .................................................................................... 2-19
B. Lubricator Adjustment.................................................................................. 2-20
2-3.3. Cylinder Oil Recommendations ................................................................................ 2-22
A. General Requirements ................................................................................ 2-22
B. Service Considerations................................................................................ 2-23
C. Inspection .................................................................................................... 2-24
D. Synthetic Lubricants .................................................................................... 2-24
2-3.4. Break-in and Operation............................................................................................. 2-24
2-3.5. Extended Shutdown.................................................................................................. 2-26
2-3.6. System Malfunctions and their Causes .................................................................... 2-27

CHAPTER 3 -OPERATION & TROUBLESHOOTING

Paragraph Page

3-1. GENERAL ..................................................................................................................... 3-2

3-2. PREPARATION FOR INITIAL START .......................................................................... 3-2
3-2.1. Alignment Check ..................................................................................................... 3-2
3-2.2. Lubrication Systems ................................................................................................ 3-4
3-2.3. Compressor Cylinders ............................................................................................. 3-4
3-2.4. General Inspections and Adjustments..................................................................... 3-5
3-2.5. Compressor Cooling System................................................................................... 3-5
3-3. CAPACITY CONTROL ................................................................................................. 3-5
3-3.1. Cylinder Clearance Volume ..................................................................................... 3-6
3-3.2. Cylinder Unloading. ................................................................................................. 3-6
3-3.3. Suction Pressure Control......................................................................................... 3-6
3-3.4. Capacity Control Bypass ......................................................................................... 3-6
3-4. COMPRESSOR LOADING AND UNLOADING ............................................................ 3-6
3-4.1. Loading/Unloading Procedure – Bypass and Discharge Valve Method .................. 3-9
3-4.2. Loading/Unloading Procedure – Vent Valve Method............................................... 3-9
3-5. INITIAL START-UP ....................................................................................................... 3-9
3-6 BREAK-IN AND OPERATION....................................................................................... 3-11
3-7. SUGGESTED ROUTINE STARTING PRACTICES...................................................... 3-11
3-8. ROUTINE STOPPING................................................................................................... 3-13
3-9. EMERGENCY OR NON-SCHEDULED SHUTDOWN .................................................. 3-13
3-10. SHUTDOWN FOR AN EXTENDED PERIOD ............................................................... 3-14
3-11. ROUTINE OPERATION AND MAINTENANCE ............................................................ 3-14
3-11.1. Daily ..................................................................................................................... 3-15
3-11.2. Weekly .................................................................................................................. 3-16
3-11.3. Monthly….. .............................................................................................................. 3-16
3-11.4. Every Three Months ................................................................................................ 3-16
3-11.5. Every Six Months..................................................................................................... 3-17
3-11.6. Annually….. ............................................................................................................. 3-17
3-12 TROUBLESHOOTING BY SYMPTON.......................................................................... 3-18

2
PG-1028-E (HOS) Table of Contents

CHAPTER 4 –MAINTENANCE

Paragraph Page

4-1. GENERAL ..................................................................................................................... 4-3

4-2. SAFETY PRECAUTIONS ............................................................................................. 4-4
4-3. FRAME ....................................................................................................................... 4-4
4-4. CRANKSHAFT.............................................................................................................. 4-7
4-5. CRANKSHAFT OIL SEAL............................................................................................. 4-7
4-6. ACCESSORY EQUIPMENT ......................................................................................... 4-7
4-7. MAIN BEARINGS.......................................................................................................... 4-7
4-7.1. Checking Bearing Clearance .................................................................................. 4-8
4-7.2. Replacing a Main Bearing ....................................................................................... 4-8
4-7.3. Bearing Crush ......................................................................................................... 4-10
4-7.4. Checking Crankshaft Thrust ................................................................................... 4-10
4-8. CROSSHEAD / CONNECTING ROD ASSEMBLY....................................................... 4-11
4-8.1. Crosshead............................................................................................................... 4-12
4-8.2. Connecting Rods..................................................................................................... 4-12
4-8.3. Connecting Rod Bearings ....................................................................................... 4-12
A. Stretch Micrometer Procedure .................................................................... 4-13
4-8.4. Replacing Connecting Rod Bearings ...................................................................... 4-15
4-8.5. Crossheads and Pins .............................................................................................. 4-16
4-8.6. Removing Crosshead and Connecting Rod ........................................................... 4-16
4-8.7. Replacing Small End Bushing................................................................................. 4-18
4-8.8. Replacing Crosshead Pin and Bushing................................................................... 4-20
4-8.9. Crosshead Shoe Replacement and Piston Rod Runout Adjustment...................... 4-20
A. Crosshead Shoe Replacement .................................................................. 4-22
B. Piston Rod Runout Adjustment .................................................................. 4-22
4-9. COMPRESSOR CYLINDERS....................................................................................... 4-23
4-9.1. Removing and Installing Compressor Cylinders ..................................................... 4-25
A. Removing Compressor Cylinder ................................................................. 4-26
B. Installing Compressor Cylinder ................................................................... 4-26
4-9.2. Disassembly and Assembly of Pistons & Piston Rods ........................................... 4-27
A. Piston and Rod Disassembly ...................................................................... 4-28
B. Piston and Rod Assembly ........................................................................... 4-28
4-10. INSTALLING PISTON ROD AND ADJUSTING END CLEARANCE............................ 4-32
4-11. INSPECTION / MAINTENANCE OF CYLINDER BORES ........................................... 4-35
A. Honing ......................................................................................................... 4-36
4-12. NON-METALLIC COMBINATION PISTON & RIDER RINGS ...................................... 4-36
4-12.1. Handling Instructions .............................................................................................. 4-36
4-12.2. Establishing Ring Wear Rate ................................................................................. 4-36
4-12.3. Replacing Rings ..................................................................................................... 4-37
4-12.4. Installing Rings ....................................................................................................... 4-38
4-12.5. Breaking-in Combination Rings .............................................................................. 4-40
4-13. PISTON ROD PRESSURE PACKING.......................................................................... 4-40
4-13.1. Packing Rings ......................................................................................................... 4-41
4-13.2. Packing Gasket....................................................................................................... 4-43
4-13.3. Packing Cases ........................................................................................................ 4-44
4-13.4. Installing the Packing .............................................................................................. 4-44
4-13.5. Packing Operation and Maintenance ...................................................................... 4-46
4-13.6. Inspecting the Packing ............................................................................................ 4-46
4-13.7. Replacing the Packing ............................................................................................ 4-47
4-14. PISTON ROD OIL SCRAPER RINGS .......................................................................... 4-47
4-15. BALANCE CYLINDER (If Used) ................................................................................... 4-49
4-16. COMPRESSOR VALVES ............................................................................................. 4-50
4-16.1. Description of Operation......................................................................................... 4-51
4-16.2. Valve Maintenance Recommendations .................................................................. 4-52
3
Table of Contents PG-1028-E (HOS)

CHAPTER 4 –MAINTENANCE (Continued)

Paragraph Page

4-16.3. Removing the Valves – O-Ring Valve Cover .......................................................... 4-55

4-16.4. Disassembling & Servicing the Valve...................................................................... 4-57
4-16.5. Refacing Valve Seats.............................................................................................. 4-58
4-16.6. Reconditioning the Stop Plate................................................................................. 4-60
4-16.7. Assembling the Valve.............................................................................................. 4-60
4-16.8. Installing the Valves – O-Ring Valve Cover ............................................................ 4-62
4-17. REGULATION DEVICES .............................................................................................. 4-64
4-17.1. Inlet Valve Unloaders .............................................................................................. 4-65
A. Control and Vent Piping............................................................................... 4-65
B. Unloader Cleanliness................................................................................... 4-67
C. Removing Operator, Unloader and Valve Assembly ................................... 4-67
D. Disassembling Cage and Plunger ............................................................... 4-68
E. Installing Valve, Cage and Plunger.............................................................. 4-68
F. Disassembling Unloader Cover and Operator............................................. 4-69
G. Installing the Unloader ................................................................................. 4-70
H. Adjusting the Stroke..................................................................................... 4-71
4-17.2. Variable Volume Clearance Pockets ...................................................................... 4-71
A. Construction................................................................................................. 4-71
B. Maintenance ................................................................................................ 4-71
4-17.3. Fixed Volume Clearance Pockets........................................................................... 4-73
A. Control and Vent Piping............................................................................... 4-74
B. Clearance Pocket Cleanliness..................................................................... 4-75
C. Removing the Clearance Pocket Assembly ................................................ 4-75
D. Disassembling Actuating Piston Housing .................................................... 4-76
E. Disassembling Clearance Valve Sleeve ...................................................... 4-76
F. Servicing the Gland Seal ............................................................................. 4-77
G. Assembling Actuating Piston Housing ......................................................... 4-78
H. Assembling Clearance Valve Sleeve........................................................... 4-78
I. Installing Clearance Pocket Assembly......................................................... 4-78

CHAPTER 5 –GENERAL DATA & SPECIFICATIONS

Paragraph Page

5-1. GENERAL AND OPERATING DATA............................................................................ 5-2

Table 5-1. HOS Compressor General Data ...................................................... 5-2
5-2. ASSEMBLY FITS AND CLEARANCES ........................................................................ 5-4
Table 5-2. Running Gear Part Fits and Tolerances (Inches) .......................... 5-4
Table 5-2A. Running Gear Part Fits and Tolerances (Metric)........................... 5-5
5-3. TIGHTENING REQUIREMENTS .................................................................................. 5-6
5-3.1. Preparation of Thread & Seating Surfaces.............................................................. 5-6
5-3.2. Tightening Sequence............................................................................................... 5-6
5-3.3. Closely Observe ...................................................................................................... 5-6
5-3.4. Checking Fastener Tightness.................................................................................. 5-7
5-3.4.1. When To Check Fastener Tightness ................................................................. 5-7
5-3.4.2. How To Check Fastener Tightness.................................................................... 5-7
5-3.5. Fastener Pre-Stress ................................................................................................ 5-8
5-3.6. Compressor Cylinder Bolting ................................................................................... 5-9
Table 5-3. Pre-Stress Levels For HOS ............................................................. 5-9
5-3.4. Torque Values ......................................................................................................... 5-10
Table 5-4. Torque Values (k = 0.13) Anti-Seize Thread Lubricant.................... 5-10
Table 5-5. Torque Values (k = 0.20) Common Mineral Lubricant..................... 5-11
5-3.5. Frame & Running Gear Bolting ............................................................................... 5-12
Table 5-6. Frame & Running Gear Bolting........................................................ 5-12
4
 Form PG-1028-E

DRESSER-RAND INTRODUCTION

HOS
CHAPTER 1

Paragraph Page
1-1. GENERAL INFORMATION ...................................................................................... 1-2
1-1.1. Ratings and Performance Characteristics ......................................................... 1-2
1-1.2. Design Improvements ........................................................................................ 1-2
1-2. SERIAL NUMBERS.................................................................................................. 1-3
1-3. CYLINDER NAMEPLATE INFORMATION .............................................................. 1-4
1-3.1. Cylinder Type, Serial Number, Bore & Stroke ................................................... 1-4
1-3.2. Rated Discharge Pressure................................................................................. 1-4
1-3.3. Maximum Allowable Working Pressure ............................................................. 1-5
1-3.4. Hydrostatic Test Pressure.................................................................................. 1-5
1-3.5. Maximum Cooling Water Pressure.................................................................... 1-5
1-3.6. Maximum Allowable Discharge Gas Temperature ............................................ 1-5
1-3.7. Maximum Speed ................................................................................................ 1-5
1-3.8. Base Clearance ................................................................................................. 1-5
1-3.9. Normal Lineal Clearance ................................................................................... 1-5
1-3.10. Added Fixed Clearance ..................................................................................... 1-5

1-1
Introduction PG-1028-E (HOS)

1-1. GENERAL INFORMATION

The first HOS ever built came out in the form of a 2 throw in late 1980 (YRH101). Approximately a
year and a half later, the first 4 throw emerged (YRH113), and in early 1984 the 6 throw made its debut
(YRH174). Since the first HOS was introduced back in 1980, over 650 (and counting) frames have made
their way into the gas field market. Within this time, there have been numerous design improvements, both in
the frame and respective cylinders. The following sections center on these improvements and the
performance capability of the HOS compressor.

1-1.1. Ratings and Performance Characteristics

Maximum Allowable Operating Rod load: 60,000 lbs compression and tension

Stroke: 6.00” STROKE 7.00” STROKE

Maximum Speed 1200 PRM 1000 RPM

Minimum Loaded Speed: 500 RPM 500 RPM

Maximum BHP/Throw: 1000 HP 1100 HP*

Piston Rod Diameter: 2.50 in. 2.50 in.

Cylinder Sizes Available: 3.50” - 26.50” 3.50” – 26.50”

Maximum Cylinder Working Pressures: 130 –8800 psig 130 – 8800 psig

Direction of Rotation: Counter-clockwise from pump end view

* Applies to 2 & 4 throw; 1000 for 6 throw

1-1.2. Design Improvements

1985 - Increased radii and wall thickness within frame access windows: This area was determined to be
a weak link on some frames due to a casting cooling phenomenon known as “shrink”.
Incorporating this change insured a proper cooling rate and eliminated the potential for any
shrinkage to develop, thus maintaining the integrity of the frame casting itself.

1987 - Combined piston rings: These rings replaced the moly micarta type rings. This type of non-
metallic ring supports the piston off the bore thus increasing bore life and reducing the potential for
scuffing.

1988 - PF valving: This D-R ported valve replaced the I-R channel type and Hoerbiger plate valve. It’s
unique valve plate design and material improved efficiency and reliability substantially.
®
Pistons: All aluminum pistons are now anodized and teflon coated to reduce ring groove wear.

1994 - Plug unloaders and partial PF inlet valves: As a result of the number of problems the recip industry
has encountered with finger type valve unloaders, D-R developed a partial valve and plug unloader
design to replace the old finger type. This greatly improved the reliability on unloading devices
while improving cylinder loaded and unloaded efficiencies.

1-2
PG-1028-E (HOS) Introduction

1994 - Internal crankshaft counter weight: On 2 and 4 throw frames, an internal counterweight was
added onto the oil pump end of the crankshaft. Another weight was then mounted externally
onto the coupling hub or flywheel. In conjunction, these weights considerably reduced the
horizontal moments on these frames. The 6 throw frame due to its cylinder phasing is inherently
balanced and does not have a need for counterweights.

1995 - Gas cooled HOS cylinders: With the introduction of the gas cooled cylinder line-up, this enabled
the customer to make a competitive choice for the application at hand.

1996 - Nodular iron crossheads: Due to the poor casting quality associated with the cast steel
crosshead, the switch to a high strength nodular iron material was made. Not only did this
dramatically improve the casting quality, but this material has better strength characteristics for
reversing loads than the previously supplied cast steel.

1998 - Precision type main bearings: This replaced the shim adjustable type bearing thus making them
much easier to service. Since this involved a physical change with the frame itself, all frames
with this upgrade have a serial number greater than 799 (ex: 6HF800 or 6HF1045).

1998 - Internal counterweighted crankshaft: This design improvement takes 1994’s improvement one
step further by eliminating the need for an external weight. The crankshaft now has a weight
assembled onto both ends. This required a crankshaft change and once again, all frames that
are supplied with this upgrade will have a serial number of 800 or larger.

1999 - Frame oil filter: The standard single frame oil filter is now mounted on the frame and piped to
the oil header to ease packaging costs and ensure cleanliness downstream of the filter.

2001 - Piston Rings: All aluminum pistons are now equipped with combination rings made from a
special filled PTFE material which provides longer ring groove life.

2002 - Oil Pump Relief Valve: All frames are now equipped with an external relief valve that allows
adjustment of oil pressure without having to shut down the compressor.
- Crankshaft oil slingers were added to all 2 and 4 throw HOS compressors to reduce any chance
of oil leakage past the oil seal. They were already available on 6 throw HOS compressors.

1-2. Serial Numbers

Correspondence concerning your compressor and related equipment must include the serial
numbers of the equipment about which you are writing. A complete record of serial numbers
and other data on your Dresser-Rand compressor is kept at the factory; giving the serial
numbers in your correspondence and parts orders helps us in providing prompt service.

1. The compressor frame serial number applies to the frame and running gear parts. It is
located on a nameplate that is attached to the side of the frame at the oil pump end. The
serial number is also permanently stamped directly below the nameplate in the frame
metal. It consists of several letters and numbers. Always give the complete serial
number (for example; 6HF751, Y6H108) when requesting specific information.

2. Each compressor cylinder has its own serial number that is stamped on a nameplate
attached to the cylinder. The cylinder nameplate also includes other data; this is
described in the section that follows. Always give the complete serial number (for
example; 6HC2400, Y6H775) when requesting specific information.

1-3
Introduction PG-1028-E (HOS)

1-3 Cylinder Nameplate Information

The nameplate (Figure 1) attached to the compressor cylinder contains information that allows
both the customer and Dresser-Rand to identify a particular cylinder. The following is an
explanation of some of the terms used on nameplates.

TP-4609B
Figure 1-1. Cylinder Nameplate

1-3.1. Cylinder Type, Serial Number, Bore & Stroke

The first block describes the compressor type. Following this is the block for the serial
number. The cylinder serial number is the most important item stamped on the nameplate. It
allows the customer, the distributor and the manufacturer to identify a particular cylinder, its
specifications, the parts used to build it and the performance conditions for which it was
designed. This is important in that it allows tracking of a particular cylinder throughout its
history, no matter what frame it may be installed on in later years. Always give this serial
number when ordering spare parts. This will expedite the handling of your order and helps
prevent shipment of incorrect parts.

The cylinder bore is the inside diameter of the cylinder. If there is a liner present, the cylinder
bore is the inside diameter of the liner. This is also the nominal piston diameter. Liners of
different thicknesses may be installed in a given cylinder to vary the bore diameter. The stroke
is the distance the piston and rod travels (forward or backwards) for every 1/2 revolution of the
crank.

1-3.2. Rated Discharge Pressure

The rated discharge pressure, or RDP, is the maximum pressure the cylinder is allowed to see
under normal continuous operating conditions.

1-4
PG-1028-E (HOS) Introduction

1-3.3. Maximum Allowable Working Pressure

The maximum allowable working pressure, or MAWP, is the maximum gas pressure permitted
in the cylinder period. The cylinder may be operated for short periods of time at pressures up
to this figure provided that other factors (such as driver horsepower, maximum bearing loads,
and piping and vessel limitations) do not prohibit this. Safety valve settings are usually much
lower than this figure, and may never exceed it in any case.

1-3.4. Hydrostatic Test Pressure

The pressure at which the cylinder has been hydrotested. Hydrostatic tests are always
performed at pressures at least 1.5 times that of the MAWP.

1-3.5. Maximum Cooling Water Pressure

This pressure limitation applies not only to jacketed cylinders, but to internally water cooled
packing cases as well.

1-3.6. Maximum Allowable Discharge Gas Temperature

This is the highest temperature to which any compressor cylinder parts should be exposed to.

1-3.7. Maximum Speed

This is the maximum design speed of the cylinder. Certain cylinders, mainly the large ones
with high reciprocating weights, may have speed limits that are lower than that of the frame.
This is uncommon and always addressed in the early states of any potential application.

1-3.8. Base Clearance

This is the inherent clearance that lies within and/or built within the cylinder. It is in the form of
a percent of the swept volume for a given end of the cylinder. It cannot be changed without
physically altering the internals of the cylinder.

1-3.9. Normal Lineal Clearance

The clearance between the piston and the head when the piston is at the end of the stroke
(each end). It is required to allow for the thermal expansion of the piston and rod when
temperatures increase through compression.

1-3.10. Added Fixed Clearance

The clearance added by some physical means to meet the required operating condition(s). It
is typically added in the form of valve spacers or a shorter than normal head or piston.

1-5
 Form PG-1028-E

DRESSER-RAND LUBRICATION
HOS
Chapter 2

Paragraph Page

2-1. GENERAL....................................................................................................................... 2-2

2-2. FRAME AND RUNNING GEAR LUBRICATION SYSTEM ............................................ 2-2
2-2.1. Main Oil Pump.......................................................................................................... 2-3
A. Main Oil Pump Removal & Disassembly..................................................... 2-3
B. Main Oil Pump Assembly & Installation ...................................................... 2-5
2-2.2. Oil Pressure Regulation Valve ................................................................................. 2-6
2-2.3. Oil Pressure Safety Relief Valve .............................................................................. 2-7
2-2.4. Hand Oil Priming Pump............................................................................................ 2-7
A. Hand Oil Priming Pump Removal & Disassembly ...................................... 2-8
B. Hand Oil Priming Pump Assembly & Installation ........................................ 2-9
2-2.5. Oil Pressure Gauges................................................................................................ 2-9
2-2.6. Low Oil Pressure Shutdown Protection.................................................................... 2-10
2-2.7. Oil Cooler (Heat Exchanger) .................................................................................... 2-10
2-2.8. Oil Filter .................................................................................................................... 2-11
2-2.9. Frame Oil Recommendations ................................................................................. 2-11
A. General Requirements ................................................................................ 2-12
B. Viscosity Requirements............................................................................... 2-12
C. Inspection ................................................................................................... 2-12
D. Oil Change Schedule .................................................................................. 2-12
2-2.10. Frame Oil Level ....................................................................................................... 2-13
2-2.11. Frame Breather ....................................................................................................... 2-13
2-3. CYLINDER LUBRICATION SYSTEM............................................................................. 2-14
2-3.1. Block-type Lubrication System ................................................................................. 2-14
A. Filling and Purging the System.................................................................... 2-16
B. Maintenance and Troubleshooting.............................................................. 2-18
2-3.2. Pump-to-Point Lubrication System .......................................................................... 2-19
A. Lubricator Operation ................................................................................... 2-19
B. Lubricator Adjustment ................................................................................. 2-20
2-3.3. Cylinder Oil Recommendations................................................................................ 2-22
A. General Requirements ................................................................................ 2-22
B. Service Considerations ............................................................................... 2-23
C. Inspection.................................................................................................... 2-24
D. Synthetic Lubricants .................................................................................... 2-24
2-3.4. Break-in and Operation ............................................................................................ 2-24
2-3.5. Extended Shutdown ................................................................................................. 2-26
2-3.6. System Malfunctions and their Causes.................................................................... 2-27
Lubrication PG-1028-E (HOS)

2-1. GENERAL

The importance of selecting the correct lubricating oil and then properly maintaining the
lubricating system cannot be over-emphasized. Using a lubricating oil not suited to the application can
shorten the service life of the compressor and lessen its efficiency, as will a poorly maintained lubricating
system. Use only a high grade of oil that meets the general, physical and chemical requirements as
specified in this section.

Do not wait for lubrication difficulties to appear. If there is some question as to the correct
lubricant to use for a particular application, consult a reputable oil supplier.

Lubrication of contact surfaces is intended not only to reduce friction and wear between parts
but also to carry away any heat developed where high speeds and loads are encountered. If the
compressor lubricating system is to accomplish these purposes, it is essential that the correct oil is used
and that the following recommendations for maintaining the lubricating system are closely observed.

2-2. FRAME AND RUNNING GEAR LUBRICATION SYSTEM

The standard lubrication systems are diagrammed in Figure 2-1A&B. The oil is drawn into the
crankshaft-driven gear type oil pump from the frame sump. The pump forces the oil first through a cooler
and then through a filter before it is delivered to the main bearing oil header, which is a pipe cast into the
frame. The oil is delivered to each main bearing through holes drilled in the bearing saddles to the oil
header. From the main bearings, oil passes through drilled passages in the crankshaft to the crankpin
bearing. A rifle-drilled hole in the connecting rod conducts oil from the crankpin to the connecting rod
pin in the small end of the rod. The pin then feeds oil to the connecting rod bushing and to the crosshead
which then feeds oil to the guides. After passing through and lubricating the various parts, the oil drains
back into the sump area.

LEGEND
PS – LOW OIL PRESSURE SWITCH; (Supplied by Packager)
SET AT 35 PSIG (159 kPa)
RV – REGULATION VALVE;
SET AT 70 PSIG (414 kPa)
SV – SAFETY RELIEF VALVE (NON ADJUSTABLE);
SET AT 90 PSIG (621 kPa)

Figure 2-1A. Typical Old Style Frame and Running Gear Lubrication Schematic With Internal
Relief Valve

2-2
PG-1028-E (HOS) Lubrication

LEGEND
PS – LOW OIL PRESSURE SWITCH; (Supplied by Packager)
SET AT 35 PSIG (159 kPa)
RV – REGULATION VALVE;
SET AT 70 PSIG (414 kPa)
SV – SAFETY RELIEF VALVE (NON ADJUSTABLE);
SET AT 90 PSIG (621 kPa)

Figure 2-1B. Typical New Style Frame and Running Gear Lubrication Schematic With External
Relief Valve

Relief valves, a differential pressure gauge and a low oil pressure shutdown switch are
incorporated into the standard system. These items are described in greater detail in the text that follows.

In addition to the standard equipment, optional equipment may be incorporated into the system
for a particular application.

A hand-operated priming pump is included in the standard system to permit pre-lubrication of

the bearings and to build up a slight pressure in the lubricating system prior to start-up. There is a check
valve built into the pump to prevent the reverse flow of oil through the priming pump circuit when the main
pump is operating.

An optional motor-driven auxiliary oil pump can be used instead of the hand-operated priming
pump. When the auxiliary pump is used, a check valve must be located in the priming pump discharge
line to the main oil pump discharge.

2-2.1. Main Oil Pump

The main oil pump supplies oil under pressure to the frame and running gear lubrication
system. This pump is internally mounted inside the frame, as shown in Figure 2-2, and is direct-driven
off the end of the crankshaft by a dowel and hub drive arrangement. The oil pump should not be
dismantled unless it has lost capacity.

A. Main Oil Pump Removal & Disassembly

The main oil pump is internally mounted in the frame and is directly driven off the end of the
crankshaft by a pin and hub drive arrangement. The oil pump should not be dismantled unless it is
suspected that it has lost capacity.

2-3
Lubrication PG-1028-E (HOS)

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

Deposits of hard lacquer in the pump assembly are not usually objectionable unless they are
extensive enough to cause binding. Deposits of this nature in the pump can often be removed by flushing
the pump with a safety solvent, without disassembling it.

1. Disconnect the oil pump discharge pipe and the hand oil pump piping (if used) from the frame
end cover at the oil pump end of the unit.

2. Remove the shaft-driven lubricator unit (if used) from the end cover by disconnecting the lube
lines and taking out capscrews (A) as shown in Figure 2-2. Use a straight pull to disengage the
drive.

3. Remove the frame end cover and oil pump assembly by first removing capscrews (B) and then
carefully pulling the assembly away from the frame.

4. Take the drive hub (C) off the pump drive shaft by removing the setscrews (J).

Figure 2-2. Main Oil Pump and Lubricator Drive Assembly

5. The oil pump head (E) and pump body (F) are both removed by taking out the long capscrews
(D) that fasten the parts to the frame end cover. These parts are also doweled together. Work
carefully when separating the parts so that the plastic gaskets (G) and (H) are not damaged.

6. The pump gears and their shafts can now be removed from the frame end cover. Before
removing the gears, mark them so that they can be re-meshed in the same relative position.

2-4
PG-1028-E (HOS) Lubrication

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

7. Clean the pump parts in a safety solvent and examine the gears, shafts, and bushings for
excessive wear. If these parts are badly worn they can be replaced, but it is generally more
economical to install a new pump.

B. Main Oil Pump Assembly & Installation

1. If new shaft bushings are to be installed, they must be shrink fitted (by freezing) into the frame
end cover and pump head.

2. Reassemble the pump body and head over the gears and shafts, being sure to place the plastic
gaskets (G) and (H) on each end of the pump body (F). Orient the end cover, pump body and
pump head with the dowels, then insert and tighten capscrews (D) evenly. The total end
clearance in the pump gears should be 0.006 to 0.009 inch (0.15 to 0.23 mm). Turn the pump
shaft by hand to check for any binding in the pump.

3. Slide the drive hub onto the pump shaft with the key in place, but do not fasten it in place at this
time. Snug one of the hub setscrews against the shaft just tight enough to hold the hub in place
during installation.

4. Install the end cover and pump assembly on the frame, being careful to align the slot in the drive
hub with the pin in the end of the crankshaft. Replace the capscrews (B) and tighten them
evenly.

5. Replace the shaft-driven lubricator (if used) on the frame end cover. An O-ring seal is placed
between the parts. Be sure the drive shafts are engaged properly, then tighten the capscrews
(A).

SERVICE NOTE

Access to the hub can be gained through the top inspection opening in the
frame.

6. Position the drive hub on the pump shaft to obtain end clearance of about 1/16 inch (1.6 mm)
between the hub and crankshaft. It is important that this end clearance be established to
prevent end thrust on the pump gears. Lock the drive hub in this position with the setscrews (J).
There is a tapped hole in the hub and the setscrews must be inserted into this hole. Tighten the
first screw firmly against the shaft, then run a second one on top of it and tighten it to keep it
from working loose. Rotate the crankshaft through 360° to ensure the crankshaft dowel pin
does not bind in the hub slot in any position.

7. Replace any piping and frame covers that were removed. Check the piping connections for
leaks after all piping is installed.

2-5
Lubrication PG-1028-E (HOS)

2-2.2. Oil Pressure Regulation Valve

The oil pressure regulation valve, illustrated in Figure 2-3, controls the oil pressure to the frame
lubrication system. Any excess capacity is then bypassed to the main oil pump suction. The valve is
preset to relieve at approximately 55-60 PSIG (378-413 kPa). However, field adjustment may be
performed to compensate for differences in oil viscosity. To increase oil pressure, remove the valve cap
and turn the screw clockwise. Under normal operating conditions oil pressure should be kept as near 55-
60 PSIG (378-413 kPa) as possible.

Figure 2-3. Oil Pressure Regulation Valve

If the regulating valve can no longer maintain system pressure it must be inspected as follows:

To disassemble the valve, remove the valve cap (see Figure 2-3) and its gasket, then remove
the locknut, the adjusting screw, retainer, spring and piston in that order. It is not necessary to remove
the stop ring under the piston. Examine the parts for wear and/or scoring. Replace any defective parts,
after cleaning all parts to be reused. Assembly is the reverse of the disassembly procedure.

2-6
PG-1028-E (HOS) Lubrication

2-2.3. Oil Pressure Safety Relief Valve

The oil pressure safety relief valve, illustrated in Figure 2-4, is set to relieve when excessive
pressures results. This can happen during cold oil starting, when the oil is viscous and pressures are
consequently higher, or in the case of a major blockage in the oil system. The currently installed valve is
not field adjustable, nor is it field repairable. If the valve malfunctions, order a new valve using the part
number contained in the compressor parts list. This valve is set at 90 PSIG (620 kPa).

Figure 2-4. Frame Oil Pressure Relief Valves

2-2.4. Hand Oil Priming Pump

The standard hand-operated pump or optional motor-driven auxiliary pump is used to pre-
lubricate bearing surfaces and build up a slight pressure in the lubricating system before start-up. This
pump should require little service.

On electric motor driven machines a prelube pump is required. See

CHAPTER 5, GENERAL DATA & SPECIFICATIONS for recommended
minimum prelube capacities.

The hand oil priming pump, Figure 2-5, may be serviced easily by first closing all connecting
valves to isolate it from the system, then by disconnecting its piping and removing the mounting
capscrews.

2-7
Lubrication PG-1028-E (HOS)

Figure 2-5. Hand Oil Priming Pump

A. Hand Oil Priming Pump Removal & Disassembly

1. Loosen the capscrew (4), then slide the pump lever (7) from the shaft.

2. Remove capscrews (6), then pull the lid (10), wing and shaft assembly (8) and oil seal (9) out
of the housing as an assembly.

NOTE

Note the inlet and discharge connections and the relationship of these to
the internal valves. The fill plug (5) will be correctly located at the three
o'clock position upon assembly.

3. Remove the housing gasket (11) and clean the mating surfaces.

4. Slide the wing and shaft assembly out of the lid. Using a hook or screwdriver, pry the oil seal
(9) from the lid. Note the orientation of the seal lips.

5. Lift the suction deck assembly (13) and discharge deck assembly (3) out of the housing (1).

6. Check the locating pins (12) for damage and replace as required.

2-8
PG-1028-E (HOS) Lubrication

B. Hand Oil Priming Pump Assembly & Installation

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

1. Clean all components using safety solvent.

2. Inspect all parts for wear or damage. Suction decks, discharge decks and shaft and wing
assemblies are sold only as complete assemblies.

3. Install locating pins (12), if removed, then install the suction deck assembly (13) with its valves
pointing towards the center of the pump. Install the discharge deck assembly (3) with its valves
pointing away from the center of the pump.

4. Lightly lubricate the oil seal assembly (9) and press the oil seal into the lid using an arbor press
or hydraulic press and a suitable seal driver. The oil seal lips must face the oil to be sealed.

5. Slide the wing and shaft assembly (8) into the lid.

NOTE
Be careful not to roll the seal lips during this operation. The raised bosses
on the wing should be pointing towards the suction deck so that the lever
can be properly connected.

6. Install the housing gasket set (11), slide the lid over the shaft and secure the lid using capscrews
(6).

7. Check the shaft end-play. If the end-play exceeds 0.008 inch (0.20 mm) remove the lid and
discard one of the housing gaskets.

8. Install the hand lever (7) and secure it with capscrew (4).

2-2.5. Oil Pressure Gauges

The standard lubrication comes with a differential pressure gauge that is installed across the oil
filter inlet and outlet to enable the operator to constantly monitor the condition of the filter elements. The
drop across a new filter with oil at operating temperature is usually less than 5 PSIG (35 kPa). Cold oil
or a dirty filter will increase the pressure differential across the filter. The oil pressure on the discharge
side of the filter is the approximate pressure to the main bearings.

2-2.6. Low Oil Pressure Shutdown Protection

Low oil pressure protection is required and should come in the form of a switch that monitors
the pressure at the end of the main bearing oil header away from the oil pump. The minimum switch
shutdown setting is 35 PSIG (243 kPa) decreasing oil pressure. This switch is typically supplied by the
packager.

2-9
Lubrication PG-1028-E (HOS)

With the crankshaft-driven main oil pump, it is necessary to keep the low oil pressure shutdown
device inoperative during compressor start-up to allow the unit to start and build up the oil pressure.

Whenever the compressor is started, visually check the frame oil

gauge to ensure adequate system pressure. This is necessary as
most control systems have the oil pressure shutdown bypassed for
approximately 60 seconds to allow the unit to start and build up the
oil pressure. During this time there is no protection against low oil
pressure.

2-2.7. Oil Cooler (Heat Exchanger)

The standard oil cooler is a shell and tube type heat exchanger with oil in the shell and water in
the tubes. The oil temperature in the frame sump should be maintained within the range given in
CHAPTER 5, GENERAL DATA & SPECIFICATIONS under normal conditions. The oil temperature out
of the cooler is controlled by regulating the flow of water through the cooler. The oil cooler must be
periodically inspected and cleaned if necessary.

A regular periodic maintenance schedule should be established and followed with any heat
exchanger. The following is recommended:

1. Drain the coolant and oil from the cooler.

2. Remove the bonnets from the heat exchanger and inspect the tubes for erosion or oxide
deposits. Scrape the pencils to expose a bright, clean surface. If the pencils are eroded to one-
half their original diameter, replace them.

3. Carefully examine the tube bundles for scale or other build-up and clean as required. After
cleaning, always inspect the tubes for corrosion or erosion.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

4. Clean all interior surfaces. This can be done several ways. Many deposits can be removed by
flushing with high-velocity steam or water. For more stubborn deposits, wire brushing and
rodding can be employed. Both shell and tube sides can also be chemically cleaned. Make
sure any cleaning chemicals are thoroughly flushed from the heat exchanger before putting it
back in service.

5. Reassemble the oil cooler. Assembly is the reverse of the disassembly procedure.

NOTE

At start-up or after a maintenance inspection both shell and tube sides

should be carefully vented and must be completely filled.

2-10
PG-1028-E (HOS) Lubrication

2-2.8. Oil Filter

The standard oil filter is frame mounted. This filter is a canister type with replaceable element.
A pipe plug is provided at the bottom of the filter housing to allow it to be drained.

The oil pressure drop through the filter is monitored by the differential pressure gauge and the
filter element should be replaced whenever the pressure drop exceeds 13 to 15 PSIG (91 to 105 kPa) with
the oil at operating temperature. Pressure drop with clean oil at operating temperature is approximately
3-5 PSID (21-35 kPa Differential); flow rate varies depending upon the viscosity of the oil.
On early units the oil filter is not frame mounted and uses a different style filter arrangement. The
oil pressure drop through the filter is monitored by the differential pressure gauge and the filter element
should be replaced whenever the pressure drop exceeds 8 to 10 PSIG (55 to 70 kPa) with the oil at
operating temperature. Pressure drop with clean oil at operating temperature is approximately 3-5 PSID
(21-35 kPa Differential); flow rate varies depending upon the viscosity of the oil.

To ensure maximum protection for the compressor, check the filter element frequently for
clogging or channeling. The filter element should be replaced whenever the frame oil is changed.

Duplex filters can be supplied by Dresser-Rand as optional equipment. If these are installed,
a transfer valve enables one filter to be switched "on line" while the other is serviced or placed in the
"standby" mode. Service is similar to that for the single filter element described later.

Oil filter element replacement is as follows:

1. Stop the compressor, following procedures found in the appropriate section of this Instruction
Book.

2. Drain the filter by removing the drain plug.

3. Remove the canister by loosening the lock ring until the canister becomes free.

4. Remove the element and canister together. Then wash the canister with safety solvent.
Agitating the solvent during the process will assist in removing loose dirt. The canister should
be thoroughly dried before installing a new element.

5. Install the new element with the canister surrounding the element.

6. Tighten the lock ring.

7. Add oil to fill the canister by utilizing the hand oil priming pump until pressure is reached at the
gauge.

8. Run the unit, following standard start-up procedure, and observe the filter for leaks. We
recommend an observed run of at least ten minutes.

2-2.9. Frame Oil Recommendations

Use a good grade of highly refined oil as recommended by a reputable oil supplier or company. The oil
selected for use, as a frame lubricant must meet the following requirements.

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Lubrication PG-1028-E (HOS)

A. General Requirements

The oil must be well-refined petroleum product with low carbon residue. It should not contain
fats or fixed oil compounding. Oil containing rust and oxidation inhibitors and a foam depressant is
preferred. The oil selected must be substantially non-corrosive to the common bearing metals, with a pour
point at least 10°F (5.6°C) below ambient temperature when the unit is started for engine drives.

Multiviscosity lubricants may be used in the crankcase where widely variable ambient
temperatures are encountered, provided that the lubricant maintains a viscosity of 115 to 150 SSU
(23.7 to 31.8 cSt) at normal operating sump temperature.

When heavier lubricants are used to accommodate higher sump temperatures, crankcase
heaters may be required if ambient temperatures fall below 50°F (10°C) to maintain the sump temperature
above the pour point.

It is recognized that the oil recommended by the engine manufacturer (when an engine drive is
supplied) is normally heavier (in the SAE 40 viscosity range). When this is the case and the user desires
to stock only one oil for use in both the engine and compressor crankcases, the heavier weight oil
recommended for the engine may also be used in the compressor crankcase. Under cold ambient
starting conditions, it is recommended that the oil sump temperature be at least 10 to 20°F (5.6 to 11°C)
above the pour point prior to starting for engine drives. This may require the use of auxiliary crankcase
heaters.

If sump temperatures above 165°F (74°C) are experienced, the lubricant should be monitored
more closely for nitration effects and more frequent oil changes should be scheduled to prevent an
increase in long term maintenance problems.

B. Viscosity Requirements

The viscosity requirements for the crankcase oil are as shown in Table 2-1.

C. Inspection

Conduct all testing of the lubricating oil in accordance with the Standard Methods (latest edition)
of the American Society for Testing Materials (ASTM).

D. Oil Change Schedule

The oil should be changed every 2000 to 4000 hours, or every 6 months, depending on local
conditions, or as indicated by oil analysis. Most reputable oil companies offer laboratory analysis services
of oil samples on request. We highly recommend the use of this type service. A once-a-month analysis
schedule is recommended when the compressor is operated under severe conditions.

Where the compressor is operated in an extremely dirty atmosphere, installed outdoors,

operated intermittently, handling foul gas, or where the oil reaches high temperatures in a very hot
atmosphere, it may be necessary to change the oil more often.

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PG-1028-E (HOS) Lubrication

Table 2-1. Crankcase Oil Viscosity Requirements

SUMP OIL TEMPERATURE

Below 145°F 145-165°F 165-180°F

(63°C) (63-74°C) (74-92°C)
SAE 20 SAE 30 SAE 40

VISCOSITY AT 100°F
(38°C)
Saybolt Universal, SSU 420 600 750
Kinematic Viscosity, cSt 90.5 129.5 162.5

VISCOSITY AT 210°F
(99°C)
Saybolt Universal, SSU 50 60 70
Kinematic Viscosity, cSt 7.3 10.5 13

2-2.10. Frame Oil Level

The amount of oil required may vary slightly from the values listed in Chapter 5 (GENERAL
DATA & SPECIFICATIONS). There is a gauge glass located at the oil pump end of the frame, which
should be checked periodically, and the oil level maintained as follows:

1. When the unit is running under normal operating conditions, the oil level should be maintained
to the line in the center of the sight glass. A filler connection is provided in the frame for adding
oil to the sump.

NOTE
Do not fill to a point where the rotating parts will strike the oil surface; this
will cause foaming and loss of oil pressure from the main pump. If the oil
level is allowed to drop below the gauge glass, air may be introduced in the
oil or oil pump and cause a fluctuating or total loss of oil pressure to the
bearings.

2-2.11. Frame Breather

The breather, which is mounted on the frame, vents the frames interior to atmosphere while
condensing oil vapors and returning the condensed oil to the frame sump. Examine the element at
regular intervals and service it as required.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

To service the element, remove the breather's cover. Clean the element by washing it in a
safety solvent and allowing it to dry.

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Lubrication PG-1028-E (HOS)

2-3. CYLINDER LUBRICATION SYSTEM

A mechanical lubricator provides lubrication of the compressor cylinder bores, and pressure
piston rod packings. For some applications, "pump-to-point" lubrication is supplied where each lubrication
point is fed from an individual lubricator pumping unit. Normally, a metered "Block-type" oil distribution
system is furnished with the oil supply coming from the frame. With either method, a check valve is
required at the cylinder connection of each oil line to prevent compressed has from passing back through
the lubrication system. Both systems are described below.

Recommendations are given to enable selection of suitable oil for a particular application and
to determine an optimum feed rate. For external suction lubricator reservoirs, you must maintain a good
grade of lubricant to lubricate internal components within the box. It must be a viscosity grade of ISO 680
compounded with acidless tallow AGMA-8. This provides a high degree of sliding motion under pressure
and minimizes wear. It is recommended that the oil be changed at least every 6 months.

2-3.1. Block-type Lubrication System

In a metered block-type system, the compressor cylinders are lubricated by a completely

integrated unit, which is mounted at the pump end of the frame, and directly driven by the compressor
drive shaft, utilizing a chain and sprockets to drive the oil pump drive shaft. One or more conventional
mechanical “force-feed” lubricator pumping elements pumps oil under pressure in measured quantities.
The system operates as follows: (See Figure 2-6 for a typical installation.) Oil is pumped into a single
main line through a filter and a flow switch. The oil is then discharged into the divider valve assembly and
from there to various points on the cylinder(s). (The number of lubricator pumping elements varies with
the number of cylinders on the frame.)

Figure 2-6. Typical Block-Type System Schematic

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PG-1028-E (HOS) Lubrication

The typical divider block lubrication system will have the secondary blocks mount somewhere
near or on each cylinder. These blocks are then feed from the primary block located near the lubricator
itself. Cycle pin indicators are supplied on each secondary block. The main metering device is then
mounted on the primary block and typically comes in the form of a switch.

A no-flow switch can be used to sound an alarm, or it can be connected to a shutdown device
on the driver. If a proximity switch is used, the PLC within the panel must then be programmed for an
alarm and automatic shutdown. The lubrication system is a single-line, progressive, positive displacement
system which divides pump output into pre-determined, proportional amounts. It then distributes these
amounts to the points of lubrication. In this type system, the pistons within each divider block assembly
are cycled by input flow, continuously dividing and distributing lubricant until input flow ceases. By varying
piston diameters, the amount of lubricant received by one point can be changed relative to the amount
received by other points in the assembly. The piston not only divides the flow, but also proportions the
flow. Due to the valve arrangement, this dividing and proportioning action starts again when input flow
is resumed. This assures positive lubricant delivery to each point. Figure 2-7 shows how each piston is
"valved" by the completion of a full stroke of a previous piston.

Each divider valve assembly consists of anywhere from 3 to 8 valve blocks mounted to a base
block. O-ring seals between the base and valve blocks provide leak-proof sealing to pressures as high
as 7000 PSIG (48.3 Mpa). Lubricant outlets are located in the base block, thus providing easy removal
and replacement of worn or contaminated valve blocks without disturbing the base mounting or lubrication
lines. All valve blocks are interchangeable in any position on the base block.

One divider valve assembly is capable of serving up to 16 points of lubrication. When more than
16 points of lubrication are to be served, or when good design dictates, a two-stage system is employed.
The first stage (the master block) proportions the pump flow, which is subdivided at the second stage
(secondary blocks) into the required volumes. In this manner, a multiple number of points can be properly
lubricated from one pump supply.

NOTE

Since the block-type system is based on positive displacement, never block

a point intended to be used or try to feed two points from one outlet.

L U B R I C A T IO N
P O IN T

L U B R I C A T IO N
P O IN T

L U B R I C A T IO N
P O IN T

Figure 2-7. Divider Valve Piston Operation

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Lubrication PG-1028-E (HOS)

The SMX Metering Elements are available in a wide range of deliveries (See Table 2-2). Cycle
indicator pins are available on most size elements. A by-pass element is also available which allows an
addition or reduction of lubrication points at any time without having to disconnect any piping or tubing.
Bridge Elements (Internally Cross Ported) are available. These interconnect and discharge into the next
element. The Metering Elements are supplied with either one or two outlets. Conversion plugs are
available for field conversion from one to two outlets. All metering elements are fully interchangeable in
various positions on the base.

Table 2-2. Oil Output Per Cycle

METERING ELEMENT DELIVERY In3 DELIVERY In3
SIZE (TWIN OUTLET) (SINGLE OUTLET)
SMX-08 .005 .010

SMX-12 .0075 .015

SMX-16 .010 .020

SMX-25 .015 .030

SMX-35 .020 .040

SMX-40 .025 .050

SMX-50 .030 .060

SMX-60 .035 .070

SMX-65 .040 .080

SMX-00 By-Pass . By-Pass

The output per cycle of each proportioning piston in any given divider block assembly and its relative value
to other proportioning pistons in the same divider block assembly is shown in Table 2-2. Valve blocks are
marked "T" for twin and "S" for single.

Keep in mind that while the divider block assemblies supply the relative proportions to points of
lubrication, the total volume of oil to all points of the system for any given time period is governed by the
lubricator pump supply volume.

In some installations, the output from two adjacent valve blocks may be internally combined and
discharged from one outlet. This is called cross-porting. Newer blocks are externally cross-ported.

A. Filling and Purging the System

To ensure proper operation of the lubrication system before start-up or after an overhaul, it is
imperative that all tubing and components be filled with oil and free air.

To properly fill and purge the system:

1. Loosen the tube nuts at all injection points. Loosen the tube nuts at the inlets of all secondary
divider valves and loosen the four sockethead setscrews at the inlet end of the block. Loosen
all alternate outlet plugs on the face of the master divider valve.

2. Remove one alternate outlet plug from the master and connect a manual oil pump to the
alternate outlet. (This pump is available from Dresser-Rand. See Figure 2-8.)
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PG-1028-E (HOS) Lubrication

3. Operate the manual pump until clear, air-free oil appears at the inlet of the secondary, then
tighten the secondary inlet connection. After tightening the inlet connection, continue to pump
until clear oil emerges from the four sockethead setscrews, then tighten the setscrews.

Figure 2-8. Purging Air From Divider Block

4. Continue to pump until air-free oil is discharge at all injection points served by the secondary
divider, then tighten the tube nuts at these points. After all lines to the injection points have been
filled and tightened, operate the pump for a few strokes while checking for leaks.

5. Remove the manual pump from the master divider alternate outlet, replace the plug (fingertight),
connect the pump to another alternate outlet in the master and repeat the procedure outlined
above.

6. After all alternate outlets have been purged, and all alternate plugs replaced (fingertight),
connect the manual pump to the check valve on top of the manifold bar.

7. Proceed to loosen the following connections: cap of the atmospheric indicator in manifold bar,
inlet connection at the flow-meter, no-flow valve, high-pressure switch and master divider valve.
Also loosen the four sockethead setscrews and the inlet end of the master.

8. Operate the manual pump, filing the system from the manifold bar until clear, air-free oil appears
at each disconnected point in turn. Tighten loose connections, starting from the atmospheric
indicator in sequence to the master divider inlet and sockethead setscrews. Continue pumping
until clear oil appears at all master alternate outlets. Tighten all alternate plugs in the master
so that the entire system is now completely sealed and oil-tight.

9. Operate the manual pump for a few more strokes to finally check for leads or malfunction.
Remove the manual pump and plug the check valve.

10. Disconnect the fittings that connect the lubricator pumps to the manifold and operate each pump
manually until a steady flow of oil emerges at the top of the pump line.

11. Connect the pumps to the manifold; the system is now ready to operate. Use the correct, clean,
and filtered oil at all stems and be sure the reservoir is adequately filled at all times.

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B. Maintenance and Troubleshooting

Performance indicators are sometimes used to signal excessive system pressure and localize
problem areas. Pin type indicators use a rupture disc, which bursts at a predetermined pressure, and
causes an indicator pin will remain out until the disc is replaced and the pin is manually reset. Controls,
such as proximity switches, can be installed to sense a pressure signal caused by blockage. This signal
can be used to shutdown the compressor or ring an alarm. The rupture disc must be replaced to restore
normal operation.
A blockage in the lubrication system may be caused by any of the following:

• Crushed tube line in the system

• Blocked or carboned infection point
• Blocked divider valve assembly
• Divider valve assembly bound up

If blockage occurs anywhere in the divider valve system, proceed as follows:

Handle all parts with great care and ensure complete cleanliness.
These parts are manufactured to very close tolerances and any nick,
scratch, or dirt left on them will interfere with proper operation of the
divider block.

1. Connect a manual oil pump, with gauge, to the inlet of the master divider valve and try to cycle
the system by pumping oil into the master. If the master divider is equipped with indicators and
the blockage is downstream of the master, one of the indicator pins in the master will protrude.
Blockage is then down stream of the discharge line common to the protruding pin. If the system
will not cycle and no indicator pin is "up" in the master divider, blockage is then within the master
divider.

2. If the master divider valve is not equipped with pin-type indicators, remove (one at a time) each
alternate outlet plug in the master, which is common to a discharge port. (When plugs are
removed, trapped lubricant will usually surge out of the alternate outlet hole which is common to
the blocked out-going line). Pump oil into the inlet of the master after each plug is removed; if
pressure drops, the blockage is downstream of the last outlet so tested. While pumping oil into
the master, (with all alternate plugs removed), if no oil is discharged at any open port the
blockage is within the master divider valve.

3. Proceed to the secondary divider valve, which is downstream from the blocked port, and remove
each alternate plug, which is common to a discharge port. Insert the manual pump into the
alternate outlet port back at the master divider valve, which serves as a lubricant to this
secondary assembly. Pump oil into the master alternate outlet; if lubricant is discharged freely
through each of the alternate outlets in the secondary, blockage is not in the secondary divider
valve but is downstream of it.

4. Connect the manual pump into each alternate outlet (one at a time) of the secondary block. If,
while pumping oil into one of the secondary alternate outlets, pressure builds up, the blockage
has been located. Look for crushed lines, or a blocked injection point.

5. If the secondary divider valve will not cycle or discharge lubricant through the open alternate ports,
blockage is within the divider valve. If the divider is blocked internally, it must be removed,
disassembled and cleaned.

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PG-1028-E (HOS) Lubrication

6. Before disassembling the divider valve, remove only the piston enclosure plugs and with strong
finger pressure, work the piston back and forth without removing it. If all pistons are moveable,
replace the enclosure plugs and retest the assembly by pumping oil in the inlet. (The particle of
dirt, which may have caused the internal blockage, may now be dislodged and the assembly may
be back in working condition with no further service to be performed.)

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complicated with when storing,
handling, or using solvents.

7. If piston is jammed, proceed with further disassembly, first making a note of valve block positions
on the base(for example: Inlet-355-165-125). With individual valve blocks on the bench remove
the piston enclosure screws. Working with one block at a time, remove the piston. If it appears
to be stuck, try removing it from the other direction. The piston may have to be forced out of the
block by tapping it with a brass rod. When the piston is removed, flush the piston and block with
a suitable solvent. Blow out all ports thoroughly and use a small piece of soft wire to probe the
passageways. Inspect the cylinder bore for scratches or score marks. Inspect the piston in the
same manner. If either of these parts is damaged, replace the valve block. If the block and
piston both appear to be in good condition, reassemble the parts, making sure the piston slides
smoothly and snugly in the bore. The final step is to disassemble and clean the base block.

8. After the entire assembly has been cleaned, blown-out, inspected and found to be in working
condition, assemble the divider valve, positioning the valve blocks on the base in their original
order. Test the operation of the assembly with a manual oil pump. If it now functions properly,
replace the divider assembly in the system and test for proper system operation.

2-3.2 Pump-to-Point Lubrication System

HOS compressor cylinders are lubricated by a mechanical lubricator mounted on the frame end
cover. The lubricator is directly driven by the oil pump drive shaft by a chain and sprockets. The
lubricator drive is shown in Figure 2-2. The main difference between this system and the block type
is that each lubrication point is individually supplied oil with its own pump. These types of pumps come
with sight glasses to allow for monitoring, as opposed to feed rate monitoring via divider block cycle time.

A. Lubricator Operation

The oil in the lubricator sump is forced by action of the individual pumping units through tubing
and check valves to the cylinder bores and piston rod packing. Each pumping unit in the lubricator is
adjustable to permit regulation of the oil feed to the various points. Each pump unit is actuated by a
rocker or roller type cam follower and cam assembly (see Figure 2-9), causing a plunger piston within the
pump body to reciprocate. The pump stroke, thus the pump output, can be varied by adjusting the
adjusting sleeve shown in the drawing. Maximum output is achieved with the sleeve fully extended from
the pump body.

As the plunger moves downward in stroke, oil is drawn through the suction check valve into the
plunger bore from the sight feed reservoir. Removing this volume of oil from the sight feed reservoir
creates a vacuum, which causes more oil to be drawn into the reservoir via the suction tube. A small
quantity of oil then enters the sight feed nozzle and drips into the reservoir below. The quantity of oil can
be determined by counting the drops as they fall. As the plunger moves upward, oil is forced from the
plunger bore through the outlet check valve into the feed line to the lubrication point.

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Lubrication PG-1028-E (HOS)

B. Lubricator Adjustment

When starting the unit for the first time, prime each lubricator pump as follows:

1. Remove the sight feed plug and fill the sight feed about one-third full of oil.

2. Manually operate the pump, using the priming stem, until air-free oil is discharged from the pump
outlet.

3. Connect the lube feed line to the outlet and continue to hand prime until the line is filled.
Connect the other end of the line to the discharge check valve (one at each lube point) and
pump a few more strokes to fill the check valve.

4. Refill the sight feed to the one-third full mark, then check the reservoir to make sure it is filled
and adjust the pump output (Step 5).

5. With the lubricator in operation, observe the number of drops falling through the sight feed glass
over the course of one minute. Adjust the adjusting sleeve to achieve the required number of
drops per minute. See Table 2-3. On a good, airtight assembly it is normal for the air in the
sight glass to be dissolved in, and gradually replaced by, the oil. This is of no consequence so
long as the lubricator reservoir is maintained full and there are no suction side leads in the
pumping unit.

Figure 2-9. Lubricator Pump Assembly

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PG-1028-E (HOS) Lubrication

If the oil level in the sight glass constantly decreases during

operation, it indicates that the vacuum created in the sight feed is
pulling entrained air from the oil as it passes through. If this
continues for any period of time, an air lock in the system can result.
When this occurs, the drops normally seen falling in the sight glass
will cease. Because no oil is getting to the lubrication point, this can
cause serious damage to the compressor. Air lock can be eliminated
by refilling the lubricator reservoir, loosening the lube feed line at the
pump outlet and manually pumping the unit with the priming stem
until no air bubbles are visible in the oil stream. Note that if a fairly
rapid loss of oil occurs, the cause is often a leak on the suction side
of the pump.

Table 2-3. Oil Feed Drops per Minute (dpm) Total to Cylinder

CYLINDER DISCHARGE PRESSURE (PSIG)

Cylinder
Diameter 25-150 150-300 300-600 600-1500 1500-3000 3000-7500
(inches)
3–6 26-35 dpm
4–8 5-14 dpm 11-18 dpm 12-21 dpm 16-28 dpm 21-32 dpm
8 – 10 7-16 dpm 14-21 dpm 18-26 dpm 21-35 dpm
10 – 12 9-19 dpm 16-25 dpm 21-32 dpm
12 – 14 11-23 dpm 19-30 dpm 25-37 dpm
14 – 16 12-26 dpm 23-35 dpm
16 – 18 14-30 dpm 25-37 dpm
18 – 20 16-33 dpm
20 – 22½ 18-37 dpm
22½ – 26 19-40 dpm
Approximately 14,000 drops = 1 pint.

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Lubrication PG-1028-E (HOS)

2-3.3. Cylinder Oil Recommendations

Four classifications of lubricating oil have been developed to cover the normal lubrication
requirements of compressor cylinders. The physical and chemical properties of the four oil types
generally recommended for these units are listed in Table 2-4. (This table is general in nature and covers
conditions and pressures not necessarily applicable to HOS compressors.)

Selection of the proper type of oil for your particular application normally will be determined by
the discharge pressure and also by the gas quality with respect to "wetness". Consideration also must
be given to the local operating conditions. Review this set of oil selection instructions with your oil supplier
and compare your particular operating conditions with those listed in Table 2-4 for the various type
cylinder oils.

In addition to the operating conditions given in Table 2-4, the following information also must be
considered when selecting the type of oil to be used in a particular application.

For Type 2 and 3 oils, the gases handled must be dry; that is, gases which do not carry
suspended liquid, contain water vapor or other condensables which remain in the super-heated vapor
state throughout the compression cycle. For Type 2X and 3X oils, the gases handled occasionally may
carry small quantities of suspended liquid into the cylinder or may deposit some condensation in the
cylinder. type 2 oils are generally used when the operator wishes to use internal-combustion engine
lubricating oil.

A. General Requirements

These oils are well-refined petroleum products of the general types listed. They should be
prepared from selected stacks of either naphthionic or paraffinic type, processed to minimize deposit
formation. Superior rust-preventative properties also are desired. The pour point must be consistent with
the lowest ambient gas intake and cylinder temperatures to be encountered. The pour point always must
be sufficiently lower than ambient temperature to permit the proper rate of oil feed by the lubricator. In
handling low-temperature gases, select oil of suitably low pour point, on the basis of intake and cylinder
temperatures, to maintain a fluid of lubricant in the cylinder.

This oil must be capable of providing an improved state of boundary lubrication and must resist
the washing effect of the particular condensate involved.

Type 2 - Internal-combustion engine lubricating oil of the following classes:

• Straight mineral oil.

• Additive-treated, non-detergent oil.
• Detergent engine oil.

Type 2X- Compounded compressor cylinder oil with 5% compounding is recommended. This oil must
be capable of providing an improved state of boundary lubrication and must resist the
washing effect of the particular condensate involved.

Type 3- Rust and/or oxidation-inhibited oil or straight mineral oil is acceptable.

Type 3X- Compound compressor cylinder oil with 5 to 10% compounding is recommended.

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PG-1028-E (HOS) Lubrication

Table 2-4. Standard Cylinder Oil Recommendations

Operating Conditions Type 2 Type 2X Type 3 Type 3X

Discharge Temp.
(°F) Max. 350° Max. 350° > 350° > 350°
(°C) Max. 177° Max. 177° > 177° > 177°

Condensed water vapor NO POSSIBLE NO POSSIBLE

present

Suspended liquid present NO POSSIBLE NO POSSIBLE

Special Requirements:
Cylinder with discharge
pressure of 2000 to 7000 NO NO REQUIRED REQUIRED
PSIG (13.8 to 48.27 Mpa)

Flash Point (°F) 380° Min. 380° Min. 410° Min. 410° Min.
(Open Cup) (°C) 193° Min. 193° Min. 210° Min. 210° Min.

Viscosity @ 100°F (38°C)

Saybolt Universal SSU --- 780 Max. --- ---
Kinematic Viscosity cSt --- 168.4 Max. --- ---

Viscosity @ 210°F (99°C)

Saybolt Universal SSU 60 Min. 72 Min. 105 Min. 105 Min.
Kinematic Viscosity cSt 10.2 Min. 13.3 Min. 21.5 Min. 21.5 Min.

Sulfated Ash 0.50 Max. --- --- ---

Neutralization Value (color);

Total Acid Number --- --- --- ---
Strong Acid Number 0.00 Max 0.00 Max 0.00 Max 0.00 Max

Carbon Residue 0.45 0.45 0.65 0.65

(Conradson) Max. ¹ Max. ¹ Max. Max.
NOTES: ¹ = Ash-free basis

B. Service Considerations

1. On multi-stage and circular type compressors, or other applications involving high cylinder
discharge temperatures, it is necessary to use higher viscosity oil than is normal.

2. When a gas being compressed is saturated with water or hydrocarbons, it is mandatory that a
3X oil be used.

3. Certain lubricating oil additives will cloud the glycerin-water often used in lubricator sight feeds,
necessitating frequent changes of the mixture.

4. On services that are compressing air, it is recommend that a synthetic type lubricant is used.

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Lubrication PG-1028-E (HOS)

The continuous or intermittent carry-over of liquid to compressor

cylinders requires the installation of efficient separators.

C. Inspection

All tests of cylinder lubricants should be conducted in accordance with the Standard Methods
(latest edition) of the American Society for Testing Materials (ASTM).

D. Synthetic Lubricants

In general, our experience with synthetic lubricants indicates that they will do a commendable
lubrication job when the compressor is correctly prepared, the lubricant properly selected, and the
lubricant is supplied in sufficient quantity.

Past experience has shown that it is difficult to properly break in new compressor cylinders,
particularly larger sizes, on synthetic lubricants. Therefore, we recommend that cylinders first be broken
in (at least 150 hours of running time or until the bore surfaces have taken on a glazed appearance) using
a 3X oil. After the break-in period, switch to a grade of synthetic lubricant per the lubricant manufacturer's
recommendation.

In those few cases where it is absolutely impossible to break in the compressor cylinders on a
mineral oil due to system contamination, note that the danger of cylinder scuffing does exist. Extreme
cleanliness of suction piping is absolutely mandatory if scuffing is to be avoided because the film
thickness of a synthetic lubricant is generally less than with mineral oil. We further recommend that the
particular grade of synthetic lubricant be on the higher side of the available viscosity range.

It is important that the quantity of synthetic lubricant fed to the cylinder be ample to wet the entire
bore surface and that actual inspections be carried out within a few hours after switching to synthetic
lubrication to determine that the feed rate is adequate. We recommend that the lubricator be adjusted
to provide approximately double the flow of synthetic lubricant as opposed to mineral base oil during initial
start-up and break-in.

Occasionally, units must be started and broken in during low ambient temperatures. Due to the
extremely high viscosity index of most synthetic lubricants, take precautions to ensure that the lubricant
is warm enough to flow properly.

It must be again pointed out that synthetic lubricants should not be used in the compressor
unless the unit has been correctly prepared.

2-3.4. Break-in and Operation

Because of the wide range of compressor cylinder sizes and designs, as well as the varying
operating conditions encountered at different compressor installations, it is not practical to specify a rigid
break-in schedule for the compressor cylinders. On compressor units the break-in of compressor and
cylinder end parts is done concurrently, with the load and speed gradually being increased during the
break-in period.

2-24
PG-1028-E (HOS) Lubrication

The compressor cylinders must be broken in gradually because it is necessary that mating parts
establish a satisfactory running fit with each other. To do this, there must be a certain amount of wear
between the mating parts. Also, during this break-in period, the cylinders may be exposed to dirt, welding
beads and other foreign material. This is normally the most critical period in the service life of the cylinder
and the demands on the cylinder lubricant are the most extreme at this time.

During the break-in runs, it is also necessary to feed the maximum amount of lubricant in order
to help flush out wear particles and foreign material.

Prior to starting the unit for the first time, check to see how many compartments in the
compressor cylinder lubricator are used to lubricate the cylinder bores and the piston rod packings. Fill
these particular compartments with the break-in oil selected and adjust each of the pump units in these
compartments for maximum oil feed. Disconnect all lubricator lines at the cylinders and packing glands;
then, operate the lubricator pump(s) manually until oil appears at each broken connection. This may
required the compressor to be rotated in order to manually pump each plunger. Reconnect the piping and
operate the pump(s) several strokes to assure an initial supply of oil at each point of lubrication when the
machine is started. Also, during the priming period check lubricator piping and connections for possible
leaks; any leads found should be corrected at this time.

NOTE

If the compressor cylinders are being lubricated by a block-type oil

distribution system, all piping and components in that system must be filled
with oil and purged of air; this must be done manually, following the
instructions found later in this chapter.

The following time schedule is generally applicable for lubricating the compressor cylinders
during the break-in period, when the cylinders will ultimately be lubricated with a petroleum based product:

For the first full week of operation the lubricator pumping units should be adjusted for maximum
feed rate. As the cylinder wears in, occasional inspections should be made to the cylinder bore to see
if it is taking on a glazed appearance. Should any trouble develop (usually in the form of increased
temperatures) as the oil is being diluted, increase the pumping rate until a glaze is formed on the cylinder
walls.

It is usually desirable to reduce to a minimum the quantity of oil from the lubricator to the
compressor cylinders and rod packing from the standpoint of oil economy, coupled with the need to avoid
excessive oil in the discharge and carbon build up in the packing. Because of the widely differing
conditions under which these units operate (the variety of cylinder sizes, pressures, temperatures, and
types of gas handled) it is impossible to establish any ironclad rule for the quantity of oil required for
cylinder and piston rod lubrication. The ideal condition is to feed the minimum quantity that will adequately
lubricate the surfaces. This minimum quantity can be established only after several weeks of operation
and experience.

We offer as guidelines the following:

· Under normal operating conditions, the amount of cylinder oil required for the various
cylinder sizes and pressures are displayed in Table 2-3. These feed rates are
approximate and are based on an empirical formula that varies to suit the particular
conditions of service of the compressor cylinders and the gas compressed. The figures
given are the suggested normal feed rates when clean and dry conditions prevail in the
compressor cylinder. Wet and dirty air or compressed gas may require increased feeds
as conditions dictate.

2-25
Lubrication PG-1028-E (HOS)

· The feed rates given are the totals for the cylinder bore and packing, and are based on
an average sized drop (with 14,000 drops equaling one pint of oil at 75°F). Any variation
in drop size will require recalculation. To determine the feed rate for each individual
feed, divide the drops given in the table by the number of lubricator lines (feeds) to the
cylinder. Adjusting the oil feed rate at the lubricator will increase or decrease the flow rate
the same amount to each lubrication point. Check all lubrication points to determine the
optimum amount. Again, the figures given are only an approximation. For a more
detailed lubrication rate requirement refer to the packager guidelines and/or compressor
lubrication schematic. Good judgement is required whenever the particular conditions
of service are out of the ordinary.

NOTE

The figures given in Table 2-3 are for gravity and vacuum type sight feed
lubrication. Feeds to cylinder bores never should be less than two drops
per feed per minute, under any circumstances.

Oil feed rates to the piston rod packing also will depend upon the condition of the air or gas
compressed. Under normal clean and dry conditions, four to five drops of oil per feed per minute should
be satisfactory. During the first few weeks, it is better to feed too much oil than too little, After the packing
rings have seated themselves on the rod, the lubrication to the packing should be just enough to maintain
a very light film of oil on the rod.

The compressor cylinder bores, valves, and gas passages should be carefully examined each
time before and shortly after any reduction is made is cylinder lubrication, and the reduction must be made
in small steps. The correct oil feed is that which will just maintain a light film on the cylinder walls. a
puddle of oil in the counterbore at the end of the cylinder or in the discharge passage can be evidence
of over-lubrication or unsuitable oil. The appearance of any dry spots on the cylinder walls is definite
evidence of inadequate lubrication or an improper combination of temperature, gas characteristics and
oil.

2-3.5. Extended Shutdown

When the compressor is shut down for more than a few days, it is recommended that
precautions be taken to keep the cylinders in good condition during the shutdown period. An extra
quantity of oil should be pumped to the cylinder bore and piston rod packing, by manually operating the
mechanical lubricator pumping units, just prior to shutting down the compressor when an extended
shutdown is planned. Periodically thereafter, oil should be manually pumped to the cylinders while barring
the unit one and quarter revolutions.

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to bottom-
dead-center as an equilibrium condition due to the difference in
piston surface area (by piston rod cross sectional area) exposed to
the process gas pressure. Failure to depressurize the compressor
cylinders prior to barring may result in unexpected rollover that can
cause personal injury.

2-26
PG-1028-E (HOS) Lubrication

The operator must ensure that the driver will not start, by grounding
the ignition and closing the fuel gas valve on engine driven units or
by ensuring that the power cannot be turned on with electric motor
driven units, before barring the unit over.

2-3.6. System Malfunctions And Their Causes

1. Pump does not discharge lubricant:

· Empty reservoir

· Air entrainment

2. Pump repeatedly ruptures disc:

· Clogged filter

· Blocked main line, divider valve or injection point

· Disc pressure rating incorrect for the system

3. Divider valve does not cycle:

· Contaminated or stuck piston

· High pressure downstream; broken tube line serving this valve

4. Divider valve leaks:

· Valve block screws loose

· O-ring not installed

· O-ring damaged

2-27
Lubrication PG-1028-E (HOS)

5. Divider valve repeatedly ruptures disc:

· Blocked line downstream

· Blocked injection point

· Improperly drilled tube fitting

· Rupture disc pressure rating incorrect for system

· Divider block bound up

6. Flow meter does not register counts:

· Loss of lube supply

· Broken line

· Inoperative divider valve in flow meter

· Damaged linkage

· Loss of air supply

· Inoperative air valve

· Inoperative air cylinder or counter

7. No-flow valve fails to properly shut down:

· Incorrect adjustment

· Valve improperly installed

· Stuck or contaminated piston

2-28
 Form PG-1028-E

DRESSER-RAND OPERATION & TROUBLESHOOTING

HOS
Chapter 3

Paragraph Page

3-1. GENERAL ..................................................................................................................... 3-2

3-2. PREPARATION FOR INITIAL START ......................................................................... 3-2
3-2.1. Alignment Check ..................................................................................................... 3-2
3-2.2. Lubrication Systems................................................................................................ 3-4
3-2.3. Compressor Cylinders............................................................................................. 3-4
3-2.4. General Inspections and Adjustments .................................................................... 3-5
3-2.5. Compressor Cooling System .................................................................................. 3-5
3-3. CAPACITY CONTROL ................................................................................................ 3-5
3-3.1. Cylinder Clearance Volume .................................................................................... 3-6
3-3.2. Cylinder Unloading. ................................................................................................. 3-6
3-3.3. Suction Pressure Control ........................................................................................ 3-6
3-3.4. Capacity Control Bypass ......................................................................................... 3-6
3-4. COMPRESSOR LOADING AND UNLOADING............................................................ 3-6
3-4.1. Loading/Unloading Procedure – Bypass and Discharge Valve Method.................. 3-9
3-4.2. Loading/Unloading Procedure – Vent Valve Method .............................................. 3-9
3-5. INITIAL START-UP....................................................................................................... 3-9
3-6 BREAK-IN AND OPERATION ...................................................................................... 3-11
3-7. SUGGESTED ROUTINE STARTING PRACTICES ..................................................... 3-11
3-8. ROUTINE STOPPING .................................................................................................. 3-13
3-9. EMERGENCY OR NON-SCHEDULED SHUTDOWN.................................................. 3-13
3-10. SHUTDOWN FOR AN EXTENDED PERIOD .............................................................. 3-14
3-11. ROUTINE OPERATION AND MAINTENANCE............................................................ 3-14
3-11.1. Daily .................................................................................................................... 3-15
3-11.2. Weekly ................................................................................................................. 3-16
3-11.3. Monthly….. .............................................................................................................. 3-16
3-11.4. Every Three Months................................................................................................ 3-16
3-11.5. Every Six Months .................................................................................................... 3-17
3-11.6. Annually….. ............................................................................................................ 3-17
3-12 TROUBLESHOOTING BY SYMPTOM......................................................................... 3-18
Operation and Troubleshooting PG-1028-E (HOS)

3-1. GENERAL

The operator should carefully read this section before the unit is prepared for its initial start. The
purpose of this section is threefold; first, to familiarize the operators with the requirements of the unit; second,
to outline the recommended procedures for starting, loading and stopping the unit; and third, to assist the
operator in setting up an efficient inspection and maintenance schedule. Optimum performance can be
obtained by closely adhering to the instructions in this section.

After the operators have started the machine a number of times, and have received experience in
caring for it, starting will become a routine procedure. However, there are a number of special precautions
that must be taken when starting a compressor for the first time. Carelessness or lack of knowledge can
result in serious damage to the equipment and to personal injury. If possible, an experienced erection
engineer should supervise the initial start of the unit; even then, the regular operators should be well
acquainted with the details of the machine, the precautions to be taken when starting, and the reasons for
them.

When the unit is checked out prior to initial start-up, it is an excellent idea to log important
clearances and runout figures. This will establish benchmark readings for these clearances, which will allow
calculation of wear rates and establish a meaningful maintenance schedule. It is equally important to log
these same clearances after any major overhaul.

3-2. PREPARATION FOR INITIAL START

NOTE

On a new compressor no internal inspections are required. (If the machine

has set for over 6 months refer to Section 3.2.3)

Refer to the instructions supplied by the manufacturer of the

compressor driver when preparing the unit for start-up; carefully
follow the manufacturer’s recommendations. This also applies when
placing into operation accessory equipment items such as coolers,
filters, pumps, and similar equipment.

Thoroughly inspect the entire machine to be certain there are no loose parts or tools where they
can cause damage or interfere with start-up.

3-2.1 Alignment Check

It is extremely important that the driver-to-compressor alignment be

checked before start-up.

3-2
PG-1028-E (HOS) Operation and Troubleshooting

NOTE

The following procedure is designed for a standard flex type coupling

alignment.

A check of the drive alignment is required before starting the unit. The purpose of this drive
alignment is to verify that, during positioning of the skid, the alignment of the driver crankshaft to the
compressor crankshaft has not shifted. The following procedure applies to the coupling drive
arrangement normally supplied:

1. Make a suitable fixture to mount two dial indicators at the coupling hub.

2. After the fixture is securely fastened to the coupling hub, mount a dial indicator to read on
the outer rim of the compressor coupling hub and another indicator to read on the face of
the hub.

3. Rotate the driver through one complete revolution and bring both indicators to the top
vertical position with the respect to the driver flywheel; then, using a marking pencil or
chalk, place reference marks on the flywheel and flywheel housing. These will be the zero
reference marks.

4. Mark the flywheel housing at the 90º, 180º and 270º positions. These marks will be used
as reference points to take the dial indicator readings.

5. Using a bar, shift both crankshafts against their stops in the same direction.

6. Zero the dial indicators, with the driver flywheel at the top vertical reference marks, then
rotate the driver to the 90º mark and take an indicator reading; repeat at the 180º and 270º
marks and then return to the starting point. Recheck the zero settings at the starting point.
Be sure the driver and compressor crankshafts are first shifted per Step 5 before recording
the indicator reading at each reference point.

7. Compare the dial indicator readings to determine the main point of misalignment. If readings
taken at the 180º reference point indicate that the driver is high or low at the drive-coupling
end, this will, in most cases, indicate that the driver end of the skid is not properly leveled
with respect to the compressor end. Correct this misalignment by raising or lowering the
driver by readjusting the shimming at the driver mounting points.

8. When it has been determined that a any possible misalignment has been corrected by
raising or lowering the driver, take a final set of indicator readings at each of the reference
points. The coupling misalignment should be as close to zero as possible and must not
exceed 0.005 inch (0.13 mm) Total Indicator Reading when the equipment is up to operating
temperature. Therefore a tolerance for thermal growth should be considered when
performing this cold alignment procedure. (See CHAPTER 5 for specifications). If further
alignment adjustments are necessary, do this by adding or removing shims from the driver
mounting points and by moving the driver sideways, if required, using jack screws against
the sides of the driver base.

NOTE

In most cases, Dresser-Rand specifies coupling misalignment limits that

are much tighter than those allowed by the coupling manufacturers. Always
adhere to the Dresser-Rand limits.

3-3
Operation and Troubleshooting PG-1028-E (HOS)

3-2.2. Lubrication System

1. Refer to CHAPTER 2, LUBRICATION for a detailed description of the compressor frame and
running gear lubrication system, and the compressor cylinder lubrication system.
Recommendations for selecting the proper oils for frame and cylinder lubrication will also be found
in CHAPTER 2. The operator should be thoroughly familiar with the lubrication requirements of the
compressor before starting the machine.

2. The following procedure should be used to check the entire frame lubricating system prior to starting
the compressor for the first time:

A. The rust preventative coating applied to the lube system at the factory is soluble with the
recommended lubricating oils and need not be removed.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when starting,
handling, or using solvents.

B. Check all oil piping for tight connections.

C. Fill the frame oil sump to the level indicator on the oil level gauge. Refer to CHAPTER 2,
LUBRICATION for the grade and quantity.

D. We recommend the operator use a manual or motor-driven priming pump to circulate the
oil and fill the lubricating system (vent air from oil filter while circulating). The bearings may
suffer from a “dry” start. Add oil to the frame sump as required. Do not fill above the level
mark on the level gauge because the rotating compressor parts may strike the oil surface,
causing foaming and loss of oil pressure.

E. Continue to operate the priming pump until pressure indication is seen at the gauge. Check
external oil piping during this period for tight connections.

3-2.3 Compressor Cylinders

NOTE

The compressor is normally shipped from the factory with externally fed
lube pumps with oil supplied from the frame oil system. Should special oil
lubricant be required, please consult with the factory.

1. Fill the lubricator box with high-grade lubricating oil. The same oil selected for the frame can be
used in the lubricator box. This oil is for lubrication of the camshaft, pump rocker arms and the
gears inside the lubricator box.

2. Disconnect all lubrication lines and prime until all air is forced out of the lines and oil appears.
Reconnect the lines and cycle the lubricator pumps a short time so the cylinders will be lubricated
as soon as the compressor is started. The lubricator feed(s) should be initially set for maximum
flow. Once the compressor is started, the oil lines will remain full of oil. After a few days of
operation, as the cylinders wear in and the bores become glazed, the oil feed rate can gradually be
reduced. This is described in more detail in the break-in instructions, which are found in CHAPTER
2, LUBRICATION.

3-4
PG-1028-E (HOS) Operation and Troubleshooting

If the machine has set for over 6 months proceed with the following:

3. Remove the outer head and inboard suction valve assembly from each compressor cylinder and
inspect the cylinder bores.

4. Reassemble the cylinders using adequate lubricating oil.

NOTE

For cylinders operating in non-lube service, re-assemble cylinders dry.

3-2.4 General Inspections and Adjustments

1. Check, and tighten as required, all bolts and nuts to be sure that all is ready to start. Refer to
CHAPTER 5, GENERAL DATA & SPECIFICATIONS for specific tightening recommendations.

2. The piston rod runout has been checked and piston end clearances have been set at the factory.
However, if an outboard cylinder support has been installed in the field, then the rod runout must
be checked prior to starting the unit. Refer to CHAPTER 4, MAINTENANCE for detailed procedures
for checking the piston rod runout and piston end clearances. The final settings should be recorded
for future reference.

3. Prepare the compressor driver and any accessory equipment for initial starting and operation per
the manufacturer’s recommendations.

3-2.5 Compressor Cooling System

1. Run coolant through the shell and tube type compressor oil cooler to be sure the cooling system
is operative and that all connections are tight. Vent the waterside of the cooler and all high points
in the piping to remove trapped air.

3-3. CAPACITY CONTROL

Capacity control, as used in this context, is any means of varying the capacity of the unit to meet
the conditions under which the unit is applied. For most engine driven compressors, the simplest method
of capacity control is varying the speed of the driver. Another, more long-term adjustment, involves
changing cylinder sizes. This section covers four of the more common methods used to vary capacity for
shorter durations. The first is by adding clearance volume to the cylinder to reduce volumetric efficiency
of the cylinder. The second is by cylinder unloading. The third is by varying the suction pressure through
use of a suction pressure control valve. A fourth method is through use of a bypass system. Each will be
discussed more fully in the following sections.

3-5
Operation and Troubleshooting PG-1028-E (HOS)

3-3.1. Cylinder Clearance Volume

The standard compressor cylinder may provide for the addition of clearance volume to
outboard end of the cylinder. The outer head may contain either a variable volume clearance
pocket or a fixed volume clearance plug. Fixed volume clearance pockets are operated by
pneumatic pressure from an external source. Variable volume pockets are generally operated
manually by means of a handwheel or wrench, and may be adjusted ONLY when the machine
is shut down.

When clearance volume is added, cylinder performance should be checked for adequate
rod reversal and volumetric efficiencies. This method of capacity control reduces the horsepower
requirements proportionally to the reduction of flow.

3-3.2. Cylinder Unloading

Unloading of a cylinder end is done by retracting the suction valve from the unloaded end.
This has the effect of reducing the capacity of the machine by the amount of flow the unloaded
end is capable of generating. This method of capacity control reduces the horsepower
requirements by approximately 50 percent. Unloading sequences not initially approved or
reviewed can lead to overloads, non-reversal, overheating, and/or valve reliability problems.
Consult with a Dresser-Rand representative if such unloading sequences have not been
approved.

3-3.3. Suction Pressure Control

Controlling the suction pressure to the compressor can also be used to control capacity. This
is most often used when horsepower is limited and the flow rate is higher than the unit can handle.
A suction control valve is used to hold the suction pressure to a preset limit, thereby limiting flow.
Performance must be run at the desired set point to ensure that temperature and rod load limits of
the compressor are not exceeded. This method of capacity control offers the advantage of a stable
operating condition for the unit.

3-3.4. Capacity Control Bypass

A unit bypass system may be used to control capacity, particularly when the unit is
oversized, or when the suction pressure is not stable and has a tendency to fall below a desirable
limit. This method utilizes a pressure control valve in the bypass system around the unit, set to
operate at the minimum operating point for the compressor. When this method is used, it is
important that the bypass gas stream be taken downstream of a process aftercooler. This will avoid
an uncontrolled temperature rise during continuous operation. Figure 3-1 illustrates a typical bypass
system.

3-4. COMPRESSOR LOADING AND UNLOADING

It is important that the compressor be unloaded prior to and during startup. There are two basic
methods to loading and unloading a HOS compressor. Which of the two is best suited for a particular
installation depends on site conditions. The following should be considered prior to designing the piping
system:

3-6
PG-1028-E (HOS) Operation and Troubleshooting

Figure 3-1. Bypass Capacity Control

The two methods are as follows:

· Bypass and discharge check valve method

· Vent valve method

Probably the simplest, most reliable and safest method, is by use of a bypass and discharge
check valve. This is illustrated in Figure 3-2. With this set-up, there is little danger of exceeding rated rod
load and the rate of loading can be controlled by the rate of closing the bypass valve. On multiple-stage
units, this set-up works well for sequence loading because each bock valve is opened or closed
separately. It should be noted that with this method, when the compressor cylinders and piping are
pressurized to suction gas pressure, the load on the unit will be dependent on the sizing of the bypass
valve and associated piping, Also, the sizing of the bypass valve and piping will be the limiting factor on
the period of time the unit can be bypassed without excessive gas heating.

The other method of loading and unloading is the vent valve method. This is illustrated in Figure
3-3. This method results in the venting of excess gas during loading which may not be acceptable in
certain situations at particular sites. Also, during idling periods the compressor will pull partial vacuum on
the suction piping downstream of the suction valve, and it is extremely important that the unit is purged
prior to loading. Additionally, the suction valve must be fully open prior to closing the vent valve to prevent
the possibility of generating excessive rod loads.

3-7
Operation and Troubleshooting PG-1028-E (HOS)

Figure 3-2. Bypass and Discharge Check Valve Method

Figure 3-3. Vent Valve Method

3-8
PG-1028-E (HOS) Operation and Troubleshooting

3-4.1. Loading/Unloading Procedure – Bypass and Discharge Check Valve Method

1. Prior to starting the unit, ensure the suction and discharge valves are closed. Then, open the
bypass valve and the vent valve to de-pressurize the compressor cylinders and piping to
atmosphere.

2. Start the driver and allow it to idle and warm up; after ten minutes of warm-up, bring it up to fast
idle.

3. Open the discharge valve, which will allow discharge pressure to back up against the discharge
check valve.

4. Partially open the suction valve to purge the compressor cylinders and piping.

5. Pressurize the compressor cylinders and piping by closing the vent valve and opening the
suction valve.

6. Load the unit by closing the bypass valve.

7. Reverse the preceding steps to UNLOAD.

3-4.2 Loading/Unloading Procedure – Vent Valve Method

1. Prior to starting the unit, ensure the suction and discharge valves are closed. Then, open the
vent valve to pressurize the compressor cylinders and piping to atmospheric pressure.

2. Start the driver and allow it to idle and warm up; after ten minutes of warm-up, bring it up to fast
idle.

3. Open the discharge valve, which will allow discharge pressure to back up against the discharge
check valve.

4. Partially open the suction valve to purge the compressor cylinders and piping.

5. Load the unit by opening the suction valve fully, then by closing the vent valve.

6. Reverse the preceding steps to UNLOAD.

3-5. INITIAL START-UP

1. When starting the compressor for the first time, it is extremely important that the operators are
alert for unusual or abnormal pressures, temperatures, noises and other conditions. Indicating
gauges and thermometers should be closely monitored during this initial starting period.

2. Read the following break-in instructions before starting the compressor. The procedure, which
follows, applies generally to the initial start of the unit; some modifications to this procedure may
be required when starting a particular machine.

A. As far as is practical, check the inlet and discharge lines for foreign objects. Check all
line valves for proper location, flow direction and position.

3-9
Operation and Troubleshooting PG-1028-E (HOS)

B. Operating the priming oil pump to pre-lubricate the compressor bearings and to build up
a slight pressure in the frame and running gear lubrication system.

On electric motor driven machines a prelube pump is required. See

CHAPTER 5, GENERAL DATA & SPECIFICATIONS for recommended
minimum prelube capacities.

C. Manually operating each lubricator pumping unit, by pushing down the plunger cap, to
ensure that oil is being fed into the cylinder bores and piston rod packing. This can be
confirmed by motion of the cycle indicator pin in the distribution blocks. This may require
the compressor to be rotated in order to manually pump each plunger.

D. Walk around the machine to double check that all equipment is ready for start-up and that
all personnel in the areas are aware that the unit will be started.

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to
bottom-dead-center as an equilibrium condition due to the
difference in piston surface area (by piston rod cross sectional
area) exposed to the process gas pressure. Failure to
depressurize the compressor cylinders prior to barring may result
in unexpected rollover that can cause personal injury.

The operator must ensure that the driver will not start, by
grounding the ignition and closing the fuel gas valve on engine
driven units or by ensuring that the power cannot be turned on
with electric motor driven units, before barring the unit over.

E. Release the driver flywheel lock, if fitted. Bar the compressor over a few times to be sure
moving parts are clear and also to ensure that lubricating oil is distributed to all running
surfaces. Disengage the barring device prior to start-up,

F. Turn on the cooling water to the frame oil cooler.

G. Start the driver according to the manufacturer’s instructions.

The machine must be immediately shut down if an abnormal

condition exists, and the cause found and corrected before restarting
the unit.

H. After the compressor is started observe the frame oil pressure and check the cooling water
temperature. Watch for signs of excessive heating, unusual noises or other abnormal
conditions.

3-10
PG-1028-E (HOS) Operation and Troubleshooting

I. If everything appears normal, operate the machine continuously for 30 minutes at no load.
On engine driven units, the engine speed can be varied from idle to mid-range speed
during this period.

Never operate any compressor at maximum speed with no load. The

piston rod load may be exceeded at this condition.

J. At the end of the 30-minute period, if no problems are identified, the compressor is ready
to purge and load for the operation and service that the unit is intended for. When placing
the unit in service, pay particular attention to the break-in considerations that are given
in the following instructions.

NOTE

Verification of proper bore lubrication is not final until the bore has been
checked after the unit has been shut down under load. Lubrication rates
vary depending on load conditions.

3-6. BREAK-IN AND OPERATION

1. The normal procedure for “breaking-in” a new compressor involves several short runs at
gradually increasing speed and load. The type of driver and the particular operating conditions
will dictate the break-in requirements and procedures.

Compressor cylinders should be set up according to performance

data sheets before loading.

2. Sometime during the break-in period, while the unit is not in operation, tighten the cylinder
mounting flange nuts, packing gland nuts and all other exposed nuts and bolts. When first
subjected to full load and temperature conditions, gasket material will crush; if joints are not
tightened up at this time, oil, water, or gas leaks may start later or stud breakage may occur.
Check all foundation bolts to ensure they are tight. Tightening requirements are given in
CHAPTER 5, GENERAL DATA & SPECIFICATIONS.

3. Because of the wide range of operating conditions, it is not practical to give specific break-in
recommendations for the cylinders. The instructions in CHAPTER 4, MAINTENANCE are general
and should be modified as required to suit a particular situation.

3-7. SUGGESTED ROUTINE STARTING PRACTICES

The routine starting procedure, which follows, is for a typical compressor equipped for manual
starting. Some modifications to this procedure may be required to suit a particular compressor and drive
arrangement; however, it is important that a standard starting sequence be established and followed
consistently by the operators.

3-11
Operation and Troubleshooting PG-1028-E (HOS)

1. Check the oil level in the frame sump and add oil as required to bring the level to the mark on
the oil level gauge.

2. Operate the priming oil pump to pre-lubricate the compressor bearings and to build up a slight
pressure in the frame and running gear lubrication system.

On electric motor driven machines a prelube pump is required. See

CHAPTER 5, GENERAL DATA & SPECIFICATIONS for recommended
minimum prelube capacities.

3. Manually operate each lubricator-pumping unit, by pushing down the plunger cap to ensure that
oil is being fed into the cylinder bores and piston rod packing. This can be confirmed by motion
of the cycle indicator pin in the distribution blocks. This may require the compressor to be rotated
in order to manually pump each plunger.

NOTE

If the compressor has been opened to the atmosphere, it should be purged

with process gas before being put on line to ensure that no oxygen is
present in the cylinders or piping.

4. Unload the compressor. The method of starting-unloading must be established for each
compressor, but is generally accomplished by use of a manual bypass system. Blow down the
unit prior to starting.

Never operate any compressor at maximum speed with no load. The

piston rod load may be exceeded at this condition.

5. Check to ensure all equipment is ready for start-up and that all personnel in the area are aware
that the unit will be started.

6. Bar the unit over once to be sure all moving parts are clear. This is especially important when
the unit has just been serviced.

7. Turn on the cooling water and check to be sure that the cooling system is operative.

8. Prepare the driver for start-up according to the manufacturer’s instructions.

9. Start the driver and run the compressor at no load for 10 minutes or until the frame oil warms
to 90ºF (32ºC). Refer also to the driver instructions for warm-up requirements. (When starting
an engine driven compressor, the unit is normally warmed up at 800 to 900 RPM and the load
then applied before bringing the machine up to operating speed.)

3-12
PG-1028-E (HOS) Operation and Troubleshooting

Do not operate the compressor at a speed less than 500RPM.

10. When the unit is warmed up and determined to be operating satisfactorily, without any unusual
noises, the compressors can be loaded. Build up the discharge pressure gradually, by slowly
closing the manual bypass valve. Note the gas temperatures while loading (abnormal
temperatures are often the first indications of trouble).

11. Adjust cooling water flow, if required.

12. When temperatures and pressures have stabilized, record for future reference as operation and
maintenance guidelines.

3-8. ROUTINE STOPPING

1. When the compressor drive is an engine, it should be slowed to idle speed.

Do not operate the compressor at a speed less than 500RPM.

2. Unload the compressor by slowly opening the bypass valve. A standard unloading procedure
should be set up for each compressor application as they may not all be manual.

NOTE

During normal operations cylinder o-rings may become saturated with gas,
especially at pressures above 1000 PSIG. When a compressor is blown
down too rapidly, the o-rings may blister due to the rapid escape of the gas
from the o-rings. This is known as explosive decompression. To avoid this,
a compressor should be blown down at a moderate rate allowing the gas
to escape the o-rings without blistering. If this situation should arise, consult
your nearest Dresser-Rand Distributor.

3. Allow the compressor to operate at idle speed at no load for several minutes to cool.

4. Stop the driver according to the manufacturer’s instructions.

5. Prepare the compressor so that it can be restarted on short notice.

3-9. EMERGENCY OR NON-SCHEDULED SHUTDOWN

1. If any emergency occurs requiring immediate shutdown of the compressor, the compressor can
be shut down under load.

3-13
Operation and Troubleshooting PG-1028-E (HOS)

2. In the event of an automatic safety shutdown, the operator should immediately check to find the
cause of the shutdown. If the problem is not readily apparent, the operator should relieve the
system of pressure before making a more thorough examination.

3. If it appears that the compressor will not be operating again within ten minutes, turn off the water
flow to the cooler and cylinders.

3-10. SHUTDOWN FOR AN EXTENDED PERIOD

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to
bottom-dead-center as an equilibrium condition due to the
difference in piston surface area (by piston rod cross sectional
area) exposed to the process gas pressure. Failure to
depressurize the compressor cylinders prior to barring may result
in unexpected rollover that can cause personal injury.

The operator must ensure that the driver will not start, by grounding
the ignition and closing the fuel gas valve on engine driven units or
by ensuring that the power cannot be turned on with electric motor
driven units, before barring the unit over.

1. If the compressor is to be shut down for less than a month, the manual frame oil priming pump
and the cylinder lubricator pumps should be operated every two (2) weeks and the unit barred
one and a quarter revolution.

2. If the compressor is to be shutdown more than a month, the compressor frame and cylinders
should be preserved.

3. Refer to the manufacturer’s recommendations for the driver and other accessory equipment
when planning an extended shutdown of these items.

3-11. ROUTINE OPERATION AND MAINTENANCE

The HOS compressor is designed and built for long periods of continuous full-load operation and
should be equipped with automatic safety switches to shut it down in case of low frame oil pressure,
vibration, or lack of cylinder lubrication. It can be equipped with additional safety devices to obtain
practically any degree of protection desired.

When the unit is first placed in operation and the machine is operating at normal speed and load
and with stable operating pressures and temperatures, all safety alarm and shutdown controls should be
carefully checked for correct operation. Never disconnect the safety shutdown devices and allow the unit
to run unprotected.

3-14
PG-1028-E (HOS) Operation and Troubleshooting

Every compressor requires a certain amount of supervision and care if it is to give continued
satisfactory performance and long service life. A time schedule of duties for the operator must be subject
to alteration by experience to fit the actual conditions. The following minimum schedule is suggested,
based on continuous duty of 720 hours per month.

NOTE

The time schedule of routine inspections and maintenance for the

compressor must be used in conjunction with the schedule and duties
recommended by the driver manufacturer. This also applies to other
accessory equipment.

3-11.1. Daily

1. Check the oil level in the frame sump and add oil as required to maintain the level at the line on
the oil level gauge. Check that the oil tank (if so equipped) is filled.

2. Check the oil level in the lubricator drive box and add as necessary. If oil level has increased,
check the pumps for leakage past the plungers. Make sure all pumping units are working and
inspect distribution blocks for leakage, indicator pins “popped up”, or other problems.

3. Keep an hourly log of all gas temperatures, water temperatures and gauge pressures. One of
the principal means of keeping track of the physical condition of a compressor and its equipment
is by these hourly readings. Watch carefully for any marked changes which indicate further
attention is warranted. Use interstage pressures and temperatures to detect abnormal
conditions. A decrease in the interstage pressure and temperature means that the lower
pressure cylinder has reduced capacity. An increase in interstage pressure and temperature
means that the next higher stage cylinder has reduced capacity. These effects can be attributed
to leaking valves, worn piston rings or broken parts.

4. If separators are used in the compressor system, a schedule must be established whereby they
are periodically drained to prevent a liquid carryover into the compressor cylinders, which can
cause serious damage. If automatic drains are furnished, check them for proper operation and
to be sure that no liquid has accumulated in the level gauge.

NOTE

In every case, because of variable operating conditions, the operator

should establish the frequency of draining off the various drains. This will
be determined by the amount of liquid that collects at each point.

5. Listen for any unusual noises while the machine is operating. These should be investigated
immediately.

6. Drain all low points in the discharge piping.

7. Keep the exterior of the compressor and the compressor room floor clean.

3-15
Operation and Troubleshooting PG-1028-E (HOS)

3-11.2 Weekly

1. One week after start up check fasteners for joints with gaskets and all cylinder frame bolting.
Take note of any fasteners that have loosened any pay close attention to these fasteners;
increase periodic checking of those fasteners.

2. Inspect all loaded joints for motion across the joint during operation. Tighten as required.

3. After the first week, check the runout of the compressor piston rods. Make sure the piston rod
is not scored. Check every three months thereafter.

4. Check scraper packing, piston rod packing and distance piece vents for excessive blowby and/or
oil leakage.

3-11.3 Monthly (ALL WEEKLY checks plus:)

1. Take a sample of the frame oil for analysis. Compare the analysis to one made on a fresh
sample straight from the drum. Change oil and filter per analysis or compressor manufacturer's
recommendations.

2. Lubricate clearance packing grease fittings (see CHAPTER 4, Paragraph 4-13.) and check for
free motion by moving the pocket in and out with the unit not operating.

3. Check all safety shutdowns and operation of loading and unloading devices for proper operation.

4. Check crankshaft breather and clean or replace as needed.

5. Clean the lubricator reservoir and pumping units as necessary or according to the
manufacturer’s instructions.

3-11.4. Every three Months (ALL WEEKLY and MONTHLY checks plus:)

1. Check the crosshead-to-guide clearance by feeler gauge. Check the runout of the compressor
piston rods.

2. The frame lubricating oil should be changed after 2000 to 4000 operating hours or as monthly
analysis indicates. Always clean the filter housing and install new filter elements when the oil is
changed.

NOTE

When the compressor is being operated in an extremely dirty atmosphere,

or where it is installed outdoors, operated intermittently, handling foul gas
in the cylinders, or operating with high oil temperatures in a very hot
atmosphere, it may be necessary to change the oil more often. Most
reputable oil companies offer laboratory analysis of oil samples, the use of
this type service is recommended.

3. Check the compressor piston rings and piston rod for wear and the cylinder bore for scoring, and
remove any accumulation of foreign material. Replace piston rings if they are worn to their limit.
See Chapter (Paragraph 4-14.) for checking the wear rate of, and renewing, TFE piston and
rider rings.

4. Check the accuracy of compressor pressure gauges on a dead weight tester; recalibrate them
as required.

3-16
PG-1028-E (HOS) Operation and Troubleshooting

5. Remove all inlet and discharge valves; clean and inspect the valves for excessive wear and
broken parts. Lap seats and guards. Refer to the compressor cylinder instructions.

6. Clean the separator sight glasses (if so equipped).

7. Inspect Beta drive shaft seal (if so equipped) and replace if required.

8. Check anchor bolts for tightness. Tighten as required to the torque valves given in CHAPTER
5, GENERAL DATA & SPECIFICATIONS.

9. Inspect drive coupling; tighten as required.

3-11.5. Every Six Months (ALL QUARTERLY checks plus:)

1. Check crankshaft end play.

2. Check piston end clearances.

3. Remove, clean and inspect the piston rod pressure packing rings and oil scraper; renew the
rings as required.

3-11.6. Annually (ALL SIX MONTH checks plus:)

1. Check all running gear clearances and compare to benchmark readings. If a change is detected,
disassemble and inspect those affected parts.

2. Clean and flush the oil cooler and any other heat exchanger supplied.

3. Remove the compressor pistons and inspect the rings. Record cylinder bore diameters.
Inspections of this nature will indicate the replacement schedule for parts that are subject to
wear.

4. Safety valves used in the compressor gas system should have their settings tested at lest once
a year, and more often under extreme conditions, by a hydraulic test.

5. Examine any separators, bottles, dampers and similar equipment that may be used in the
compressor system for accumulation of dirt, rust and other foreign material. Remove the vessel
from the system and clean it if necessary.

6. Visually inspect the packing cups; re-lap as required.

7. Remove and inspect main bearings and connecting rod bearings.

3-17
Operation and Troubleshooting PG-1028-E (HOS)

3-12. TROUBLESHOOTING BY SYMPTOM

Table 3-1. Compressor Troubleshooting Chart

TROUBLE PROBABLY CAUSE(S) REMEDIES

FRAME KNOCKS 1. Loose, worn main, crankpin 1. Check clearances and

or crosshead bearings. replace bearings accordingly.

2. Low oil pressure. 2. Increase oil pressure; repair

leaks.

3. Cold oil. 3. Warm oil before loading unit;

reduce coolant supply to oil
cooler.

4. Incorrect oil. 4. Use proper oil per

specifications.

5. Knock is actually from 5. Tighten piston nut, etc. refer

cylinder. to “Noise in Cylinder”.

COMPRESSOR WILL NOT 1. Power supply failure. 1. Restore power supply.

START (Motor Drive Only)

2. Switch gear or starting panel. 2. Check circuitry, interlocks,

(Motor Drive Only) relays. See vendor literature.

3. Oil pressure permissive to 3. Check oil pressure at header

start switch. using aux. pump; adjust or
replace switch.

4. Control panel. 4. Check electrical connections

and settings.

5. Cylinders pressurized. 5. Unload cylinders.

6. Running gear blocked. 6. Unblock to allow rotation.

7. Barring device/lock engaged. 7. Disengage barring rig or lock.

CRANKSHAFT OIL SEAL 1. Faulty seal installation. 1. Reset seal per instruction
LEAKS book.

2. Clogged drain hole. 2. Clear obstruction.

3-18
PG-1028-E (HOS) Operation and Troubleshooting

Table 3-1. Compressor Troubleshooting Chart

TROUBLE PROBABLY CAUSE(S) REMEDIES

OIL SCRAPER LEAKAGE 1. Worn scraper rings. 1. Replace rings.

2. Scraper rings incorrectly 2. Assemble per Instruction

assembled. Book.

3. Worn or scored piston rod. 3. Replace piston rod.

4. Ring side clearance 4. Replace rings.

excessive.

LOW OIL PRESSURE 1. Oil pump cavitation. 1. Replace worn oil pump.
1a. Oil Level too low in sump.

2. Oil foaming from rotating 2. Reduce oil level in sump.

parts hitting oil surface.

3. Cold oil. 3. Utilize frame oil immersion

heater or steam-trace piping.

4. Dirty oil filter. 4. Replace elements; clean filter

can.

5. Oil pressure valve (PCV) 5. Set to specifications.

incorrectly set.

6. Low relief valve setting. 6. Replace valve.

7. Defective gauge. 7. Replace Gauge.

8. Plugged sump suction 8. Clean suction strainer.

strainer.

NOISE IN CYLINDER 1. Loose piston 1. Tighten piston assembly to

piston rod per instructions.

2. Piston hitting outer head or 2. Adjust end clearance to

frame head. specifications.

3. Loose crosshead jam nut. 3. Tighten jam nut.

4. Broken or leaking valve. 4. Repair or replace valves.

5. Piston rings broken. 5. Replace piston rings.

6. Liquids. 6. Remove liquids.

3-19
Operation and Troubleshooting PG-1028-E (HOS)

Table 3-1. Compressor Troubleshooting Chart

TROUBLE PROBABLY CAUSE(S) REMEDIES

PACKING OVERHEATING 1. Lubrication failure. 1. Replace lubrication check

valve or lubricator pump.

2. Improper lube oil or feed 2. Use correct oil; increase feed

rate. rate.

3. Insufficient cooling. 3. Clean coolant passages,

(Especially with water-cooled install water filter, increase
packing.) supply pressure or rate.
Reduce coolant temperature
at inlet.

4. Inadequate side clearance. 4. Replace packing rings.

PACKING LEAKAGE 1. Worn packing rings. 1. Replace packing rings.

AND/OR BLOWBY
2. Improper lube oil or lube oil 2. Use correct oil or increase
feed rate. (Blue Hot) feed rate.

3. Dirt in packing. 3. Clean packing, piping and

ensure gas supply is clean.

4. Pressure increase too fast. 4. Reduce pressure and

increase at lower rate.

5. Rings incorrectly assembled. 5. Reassemble per Instruction

Book.

6. Improper end or side 6. Check and adjust clearances.

clearance.

7. Packing vent plugged. 7. Unlock and provide low-point

drains.

8. Scored piston rod. 8. Replace piston rod.

9. Excessive rod runout. 9. Check crosshead clearances

and piston to bore clearances.

3-20
PG-1028-E (HOS) Operation and Troubleshooting

Table 3-1. Compressor Troubleshooting Chart

TROUBLE PROBABLY CAUSE(S) REMEDIES

EXCESSIVE CARBON ON 1. Too much cylinder lube oil. 1. Adjust supply rate.
VALVES
2. Wrong cylinder lube oil, too 2. Use correct oil for application.
light; high carbon residue. See chart in Instruction
Manual.

3. Oil carryover from inlet or 3. Install separator/drain system.

previous stage.

4. Broken or leaking valves; 4. Replace or repair valves.

high temperature.

5. Excessive pressure ratio 5. Clean intercoolers; valves.

across cylinder, high Look for failed valve in
temperature. cylinder, upstream or down-
stream.

HIGH DISCHARGE 1. Excessive ratio across 1. Replace leaking inlet valves or

TEMPERATURE cylinder. Rings leaking on piston rings.
next higher stage.

2. Fouled intercooler or piping. 2. Clean intercooler or piping;

reduce lube feed rate.

3. Leaking discharge valves or 3. Repair/replace parts as

piston rings. necessary.

4. High inlet gas temperature. 4. Clean intercooler.

5. Fouled cylinder water 5. Clean water jackets.

jackets.

6. Improper cylinder lube oil or 6. Use correct lube oil and

lube feed rate. correct the feed rate.

RELIEF VALVE POPPING 1. Faulty relief valve. 1. Test valve and reset per
manufacturer’s instructions.

2. Leaking inlet valves or piston 2. Repair/replace defective

rings on next higher stage. parts.

3. Obstruction, blind flange or 3. Relieve obstruction; open

valve closed in discharge valve.
line.

3-21
Operation and Troubleshooting PG-1028-E (HOS)

Table 3-2. Valve Troubleshooting Chart

TROUBLE REASON OR ACTION TO BE TAKEN

VALVE FAILURE – INLET VALVES 1. Make certain that correct parts are being used. In many
cases, inlet springs are lighter than discharge springs.

2. Investigate the possibility of liquid carryover.

3. Consider the possibility of intake pulsations.

4. Flutter – Incorrect spring action.

VALVE FAILURE – DISCHARGE 1. Make certain that correct parts are being used. In many
VALVES cases, discharge springs are stiffer than inlet springs.

2. Check log of failures to see if failures occur only when a

clearance pocket is open. If this is the case, report the
situation to Dresser-Rand.

3. Consider the possibility of discharge pulsations.

VALVE FAILURE – BOTH INLET AND 1. Make certain correct parts are installed.
DISCHARGE
2. Check to see if discharge failures are caused by broken
pieces of other valves.

3. Check for rust, scale or other foreign matter.

4. Check for excessive wear of parts caused by grit or

insufficient lubrication.

5. Consider the possibility of pulsations.

6. Stiction – Incorrect lube rate or varnish.

FAILURE FOLLOWING 1. Check reconditioning procedures to make sure valve lift

RECONDITIONING was not changed.

2. Verify correct parts were installed.

SEASONAL FAILURES 1. Winter failures caused by liquid slugs.

A. Piping should be insulated.
B. Piping should be steam traced.
C. Separators should be installed.

3-22
PG-1028-E (HOS) Operation and Troubleshooting

Table 3-2. Valve Troubleshooting Chart Continued)

TROUBLE REASON OR ACTION TO BE TAKEN

RAPID WEAR – 1. Insufficient lubrication rate or incorrect cylinder lube oil.

INLET VALVES ONLY
2. Wet gas washing lubrication from valves.

3. Cylinder water temperature lower than incoming gas

temperature.

4. Dirty process gas; install scrubbers.

RAPID WEAR – 1. Insufficient lubrication rate or incorrect cylinder lube oil.

DISCHARGE VALVES ONLY
2. Dirty process gas; install scrubbers.

3. Flutter – Incorrect spring selection,

BROKEN SPRINGS 1. Investigate possibility of gas contaminants causing

corrosion; send samples of broken parts to Dresser-
Rand

2. Check for grit or other solid matter, which can lodge

between coils of compression springs to cause failure.

3. Stiction – Incorrect lube rate or varnish.

BROKEN PLATES 1. Check valve plates for wear resulting in sharp corners at
(BUT NOT SPRINGS) O.D. or I.D.

3-23
 Form PG-1028-E

DRESSER-RAND MAINTENANCE
HOS
Chapter 4

Paragraph Page

4-1. GENERAL ..................................................................................................................... 4-3

4-2. SAFETY PRECAUTIONS ............................................................................................. 4-4
4-3. FRAME ....................................................................................................................... 4-4
4-4. CRANKSHAFT.............................................................................................................. 4-7
4-5. CRANKSHAFT OIL SEAL............................................................................................. 4-7
4-6. ACCESSORY EQUIPMENT ......................................................................................... 4-7
4-7. MAIN BEARINGS.......................................................................................................... 4-7
4-7.1. Checking Bearing Clearance .................................................................................. 4-8
4-7.2. Replacing a Main Bearing ....................................................................................... 4-8
4-7.3. Bearing Crush ......................................................................................................... 4-10
4-7.4. Checking Crankshaft Thrust ................................................................................... 4-10
4-8. CROSSHEAD / CONNECTING ROD ASSEMBLY....................................................... 4-11
4-8.1. Crosshead............................................................................................................... 4-12
4-8.2. Connecting Rods..................................................................................................... 4-12
4-8.3. Connecting Rod Bearings ....................................................................................... 4-12
A. Stretch Micrometer Procedure .................................................................... 4-13
4-8.4. Replacing Connecting Rod Bearings ...................................................................... 4-15
4-8.5. Crossheads and Pins .............................................................................................. 4-16
4-8.6. Removing Crosshead and Connecting Rod ........................................................... 4-16
4-8.7. Replacing Small End Bushing................................................................................. 4-18
4-8.8. Replacing Crosshead Pin and Bushing................................................................... 4-20
4-8.9. Crosshead Shoe Replacement and Piston Rod Runout Adjustment...................... 4-20
A. Crosshead Shoe Replacement .................................................................. 4-22
B. Piston Rod Runout Adjustment .................................................................. 4-22
4-9. COMPRESSOR CYLINDERS....................................................................................... 4-23
4-9.1. Removing and Installing Compressor Cylinders ..................................................... 4-25
A. Removing Compressor Cylinder ................................................................. 4-26
B. Installing Compressor Cylinder ................................................................... 4-26
4-9.2. Disassembly and Assembly of Pistons & Piston Rods ........................................... 4-27
A. Piston and Rod Disassembly ...................................................................... 4-28
B. Piston and Rod Assembly ........................................................................... 4-28
4-10. INSTALLING PISTON ROD AND ADJUSTING END CLEARANCE............................ 4-32
4-11. INSPECTION / MAINTENANCE OF CYLINDER BORES ........................................... 4-35
A. Honing ......................................................................................................... 4-36
4-12. NON-METALLIC COMBINATION PISTON & RIDER RINGS ...................................... 4-36
4-12.1. Handling Instructions .............................................................................................. 4-36
4-12.2. Establishing Ring Wear Rate ................................................................................. 4-36
4-12.3. Replacing Rings ..................................................................................................... 4-37
4-12.4. Installing Rings ....................................................................................................... 4-38
4-12.5. Breaking-in Combination Rings .............................................................................. 4-40
4-13. PISTON ROD PRESSURE PACKING.......................................................................... 4-40
4-13.1. Packing Rings ......................................................................................................... 4-41
4-13.2. Packing Gasket....................................................................................................... 4-43
4-13.3. Packing Cases ........................................................................................................ 4-44
4-13.4. Installing the Packing .............................................................................................. 4-44
4-13.5. Packing Operation and Maintenance ...................................................................... 4-46
4-13.6. Inspecting the Packing ............................................................................................ 4-46
Maintenance PG-1028-E (HOS)

Paragraph Page
4-13.7. Replacing the Packing ............................................................................................. 4-47
4-14. PISTON ROD OIL SCRAPER RINGS .......................................................................... 4-47
4-15. BALANCE CYLINDER (If Used).................................................................................... 4-49
4-16. COMPRESSOR VALVES.............................................................................................. 4-50
4-16.1. Description of Operation ......................................................................................... 4-51
4-16.2. Valve Maintenance Recommendations .................................................................. 4-52
4-16.3. Removing the Valves – O-Ring Valve Cover .......................................................... 4-55
4-16.4. Disassembling & Servicing the Valve...................................................................... 4-57
4-16.5. Refacing Valve Seats.............................................................................................. 4-58
4-16.6. Reconditioning the Stop Plate................................................................................. 4-60
4-16.7. Assembling the Valve.............................................................................................. 4-60
4-16.8. Installing the Valves – O-Ring Valve Cover ............................................................ 4-62
4-17. REGULATION DEVICES .............................................................................................. 4-64
4-17.1. Inlet Valve Unloaders .............................................................................................. 4-65
A. Control and Vent Piping............................................................................... 4-65
B. Unloader Cleanliness................................................................................... 4-67
C. Removing Operator, Unloader and Valve Assembly ................................... 4-67
D. Disassembling Cage and Plunger ............................................................... 4-68
E. Installing Valve, Cage and Plunger.............................................................. 4-68
F. Disassembling Unloader Cover and Operator............................................. 4-69
G. Installing the Unloader ................................................................................. 4-70
H. Adjusting the Stroke..................................................................................... 4-71
4-17.2. Variable Volume Clearance Pockets ...................................................................... 4-71
A. Construction................................................................................................. 4-71
B. Maintenance ................................................................................................ 4-71
4-17.3. Fixed Volume Clearance Pockets........................................................................... 4-73
A. Control and Vent Piping............................................................................... 4-74
B. Clearance Pocket Cleanliness..................................................................... 4-75
C. Removing the Clearance Pocket Assembly ................................................ 4-75
D. Disassembling Actuating Piston Housing .................................................... 4-76
E. Disassembling Clearance Valve Sleeve ...................................................... 4-76
F. Servicing the Gland Seal ............................................................................. 4-77
G. Assembling Actuating Piston Housing ......................................................... 4-78
H. Assembling Clearance Valve Sleeve........................................................... 4-78
I. Installing Clearance Pocket Assembly......................................................... 4-78

4-2
PG-1028-E (HOS) Maintenance

4-1. GENERAL

This portion of the Instruction Book describes the recommended procedures for disassembling,
servicing or replacement, and reassembly of the compressor running gear and cylinders. Service notes
have been placed in the text to assist the mechanic. Separate instructions are furnished to cover special
or optional equipment.

Good working habits are essential to the performance of satisfactory maintenance work on the
compressor. When disassembling a unit, use every available means to keep dirt away from the
compressor internals. Cover exposed openings with cloth, kraft paper, cardboard or other suitable
material to keep dirt from falling into the frame interior or into the compressor cylinders. Scratches, nicks
and rough areas must be removed from machined surfaces. This can be done with fine emery cloth, a
fine hone or a mill file. (Do not use emery cloth, or any other finishing method employing abrasives, when
working on soft bearing surfaces; such material can become embedded in the bearing metal.)

Mark or tag parts as they are disassembled so that they can be replaced in their original
positions. Replace all composition gaskets that are torn, dried or cracked with ones of similar material
and thickness. Shims should be marked so that they will be reassembled in their original positions or so
that replacement shims can be accurately sized.

Original parts should be thoroughly cleaned in a solvent compatible to the process and to the
material of the parts to be cleaned. Inspect parts for wear and other visible defects before re-using them.
Generally, unless otherwise stated, parts should be covered with a thin coating of clean lubricant before
reassembling.

All precautionary measures specified by the Occupational Safety

and Health Act of 1970 (OSHA) must be complied with when
storing, handling, or using solvents.

After removal cotter pins, lockwashers, lock wires and other locking devices must be replaced
to prevent the loosening of parts during operation. Always advance a nut in the tightening direction to
align cotter pin openings once the required torque or bolt stretch is obtained. Lockwire must always be
arranged so that it pulls on the bolt head in the tightening direction.

Running gear clearances and fits and tightening requirements are summarized at the back of
this book in CHAPTER 5, GENERAL DATA & SPECIFICATIONS. The specified clearance limits and fits
are those to which the parts are originally assembled. Unless otherwise stated, they are for parts that are
at room temperature and are generally referred to as "cold" clearances. Some slight changes in
clearance can be expected when parts are hot.

Generally, the clearances and fits listed should be checked during maintenance work involving
those parts. It is recommended that running clearances be checked with the parts in their assembled
positions, wherever possible, since bearing crush, interference fits and other factors can affect the
clearance measurement.

Logging important clearances can be of considerable help in determining the wear of parts. It
can also be of some benefit in estimating the time interval between scheduled overhauls.

Varying operating conditions at different installations make it impractical to specify maximum

acceptable clearances. Careful observation of the unit by the operator and good judgment by the
mechanic are often the most effective means of determining when clearances have become excessive
and adjustment of parts is required.

4-3
Maintenance PG-1028-E (HOS)

4-2. SAFETY PRECAUTIONS

Observe every safety precaution when working on the compressor frame, cylinders and drive
arrangement, especially when making repairs or adjustments inside the frame or cylinders. The following
minimum precautions should be taken before working on the compressor.

1. Be certain the main driver is locked out so that there is no possibility of the driver starting. In
addition, a warning sign bearing the legend "WORK IN PROGRESS - DO NOT START" must
be attached to the starting equipment.

2. Close suction and discharge line valves and bleed off any pressure that may be in the
compressor cylinders.

3. Block or brace under a crankshaft web, or block the crossheads, so that the shaft cannot turn
while working inside the unit.

4. Service on a machine should always start with cleaning the floor and the outside of the
machinery to remove oil which could cause maintenance personnel to slip and injure
themselves.

5. Never open a compressor cylinder or any other part of the compression system without first
completely relieving all pressure within the unit and taking all necessary precautions to prevent
accidental re-pressurizing of the system.

6. Compressors handling toxic or flammable gases must be isolated from the process piping by
means of blinds, or double valves and bleed valves, when major maintenance is required.
Before opening such compressors the equipment should be purged or evacuated. Minor
adjustments may be performed without blinding provided that adequate precautions, such as
de-pressurizing the system, are taken to protect personnel. Check valves must not be relied
upon for isolating the compressor.

7. Consult OSHA regulations covering cleaning materials and their use. Volatile flammable liquids
must not be used as cleaning agents for engine or compressor parts. A safety solvent should
be used and the parts dried thoroughly before assembly. CARBON TETRACHLORIDE MUST
NEVER BE USED AS A CLEANING SOLVENT. Appropriate provisions for ventilation should
be made when using other halogenated solvents.

4-3. FRAME

1. The compressor frame (Figure 4-1) is a rigid, cast iron structure designed to provide a suitable
mounting for compressor cylinders, crankshaft and other running gear, and to hold all parts in
accurate alignment under the stresses and strains involved in operation. Suitable ribs and
partitions are incorporated in the frame design to provide maximum strength compatible with
reasonable weight.

2. The lower part of the frame forms a sump for the lubricating oil, and a pipe tap connection is
located on the end of the frame at the bottom of the oil sump to permit sump draining. An oil
level gauge is also located at one end of the frame so that the frame oil level can be checked
at all times.

3. The frame contains the crankshaft, main bearings, connecting rods and crossheads, which
comprise the "running gear".

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PG-1028-E (HOS) Maintenance

FIGURE 4-1. TYPICAL HOS FRAME

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Maintenance PG-1028-E (HOS)

0.94” (24 mm)

Crankshaft Oil Seal for 6 Throw

Crankshaft Oil Seal for 2 Throw and 4

2.94” (75 mm)

FIGURE 4-2. CRANKSHAFT OIL SEAL

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PG-1028-E (HOS) Maintenance

4-4. CRANKSHAFT

The crankshaft is a single-piece, heavy steel forging and is designed to avoid torsional criticals
within the operating speed range. There is a separate crank throw to carry the connecting rod for each
compressor cylinder. Oil holes are drilled in the shaft from the main journals to the adjacent crank pins
so that lubricating oil under pressure at the main bearings is fed to the connecting rod bearings. It is
essential to the proper lubrication of the compressor that the oil passages in the crankshaft are kept clear
of any obstruction. They should be inspected during any compressor overhaul for sludge or other
obstructions

4-5. CRANKSHAFT OIL SEAL

The crankshaft oil seal, located at the drive end of the unit as shown in Figure 4-2. A correctly
installed oil seal should require little or no attention.

Should leakage occur past the crankshaft oil seal, do not, under
any circumstances, reduce the bearing oil pressure in an effort to
control the leakage. Reduced oil pressure can result in serious
compressor damage, which might not be immediately apparent.

The following procedure is recommended to properly install the crankshaft oil seal:

1. Install the front cover gasket on the frame. Install front cover by sliding it over the alignment
dowels. Secure the cover by tightening the capscrews to their proper torque value.

2. Coat the oil seal with grease on only that portion that contacts the crankshaft. Orient the seal
so that the seal lips are pointing toward the frame and then press the seal into the recess in the
end cover.

4-6. ACCESSORY EQUIPMENT

Items not manufactured by Dresser-Rand Company include the lubricator, oil cooler, drive
engine or motor, coupling, filters, coolers, scrubbers and control devices. Additional equipment supplied
by the packager of the compressor must be supported by accessory literature supplied by the various
manufacturers of the components. This literature, generally including engine or drive motor
manufacturer's bulletins, coupling manufacturer's bulletins and control panel manuals, is found in the
overall manual prepared by the packager for the complete compressor package.

4-7. MAIN BEARINGS

Main bearing arrangement is shown in Figure 4-3. The main bearings are horizontally split
precision aluminum shells that are accurately sized to fit the bearing caps and the support saddles in the
frame.

Whenever a main bearing cap is removed from the machine, it is important that it is returned
to its original position in the frame or serious damage can result. The bearing caps are match-stamped
in an off center location to agree with the nearest stamping on the top of the frame partition. Always
check the stamping on a bearing cap when installing it to be sure that it matches the nearest stamping
on the frame partition.

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Maintenance PG-1028-E (HOS)

FIGURE 4-3. MAIN BEARING ARRANGEMENT

4-7.1. Checking Bearing Clearance

The clearance of each main bearing can be determined by the use of Plastigage® at point "A"
shown in Figure 4-3. Lay a piece of Plastigage® across the crankshaft journal, install cap and torque to
specifications. Remove the cap and measure the Plastigage® to ensure you have proper clearance.
Refer to CHAPTER 5, GENERAL DATA & SPECIFICATIONS, which gives the bearing clearance limits
of machines as originally built. Remove Plastigage® from crankshaft and/or bearing before reassembly.
These clearance limits, although only guidelines, can be helpful in determining when a bearing requires
replacement. The only proper way to determine if a bearing replacement is required is to perform a visual
check. It should be noted, however, that a bearing will give much longer service when the proper oil
clearance is maintained. After a bearing change always recheck the actual bearing-to-shaft clearance
with Plastigage® before operating the machine.

PlastigageÒ is the preferred method of checking bearing clearances. If PlastigageÒ is not

available, another acceptable method is doing a lift check.

Mount a dial indicator on top of the connecting rod as close to the center of the split line as
possible. Lift the connecting rod up until the clearance is removed, and note the dial indicator reading.
Ensure that the crankshaft does not rotate while checking bearing clearances using the left check method.

4-7.2. Replacing a Main Bearing

If replacement of a main bearing becomes necessary, use these recommended steps:

Be certain the main driver is blocked out so that there is no

possibility of the driver starting. In addition, a warning sign
bearing the legend "WORK IN PROGRESS - DO NOT START" must
be attached to the starting equipment.

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PG-1028-E (HOS) Maintenance

1. Remove the top covers from the frame.

2. Loosen all frame spacer tie rods.

3. Remove the frame spacer and tie rod that corresponds to the bearing being serviced.

4. Remove the capscrews from each side of the main bearing cap.

5. Install a 1/2-inch eyebolt into the tapped hole in the top of the bearing cap. Carefully remove the
bearing cap and upper bearing half.

6. Remove the lower half of the bearing by rotating it 180°. If the lower shell cannot be pushed out
by hand, use a copper or soft metal "roll-out" plug in the crankshaft and "roll out" the lower shell.
The plug is placed in the oil hole in the crankshaft so that it protrudes about 1/4-inch (6 mm)
from the shaft; it must be flanged to prevent it from dropping into the oil hole.

SERVICE NOTE
If more than one adjacent lower shell is removed; blocking must support
the crankshaft. Always support the crankshaft on two cylinder frames.

7. Replacement bearing shells must fit the support saddle and bearing cap perfectly so that they
will be uniformly supported at all points. An imperfect fit, burrs, nicks or dirt between the shells
and support saddle or cap will result in stress concentration due to flexing of the shell and
subsequent premature failure of the bearing.

Never scrape the bore nor file or attempt to build up the ends of these
precision bearing shells. To do so will result in a ruined bearing and
possible major damage to the crankshaft.

8. Place a lock plate under the head of each bearing cap bolt and tighten the bolts evenly to the
torque value specified in CHAPTER 5, GENERAL DATA & SPECIFICATIONS. Bend the edge
of the lock against the flat on the head of each cap bolt.

9. Check the installed bearing clearance with Plastigage® as described in Paragraph 4-7.1. before
continuing with further assembly.

10. When one or more replacement bearings are installed, check the crankshaft alignment by
checking for clearance under the bottom of the crankshaft journal at each main bearing. A
0.0015 inch (0.04 mm) feeler should not start. Any bearings found to be low must be replaced.
®
11. Replace the main bearing tie rod and spacer, using Teflon pipe thread sealer under the nut
heads and on the tie rod threads. The spacer is sized for an interference fit with the frame
opening. Position the tie rod in the frame and spacer so that it is centered with respect to the
frame. Place a washer over each end of the tie rod and then assemble and snug up the cap
nuts evenly. Tighten one of the nuts until the measured distance in the spacer opening is not
less than, and no more than 0.002 inch (0.05 mm) greater than, the dimension stamped in the
frame adjacent to the spacer. See Figure 4-1 for stamping location.

12. Install the frame top cover and any other parts that may have been removed.

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Maintenance PG-1028-E (HOS)

4-7.3. Bearing Crush

Bearing crush is the difference in height between the bearing and its housing at the parting line.
This crush is actually an interference fit between the bearing and its housing. It is necessary to assure
full contact between the bearing and housing to prevent flexing of the bearing shell and to aid in
transferring heat from the bearing. Because both bearings and housings are precision-made parts, there
is no reason to measure the bearing crush in the field. If a problem with bearing crush is suspected,
contact your Dresser-Rand customer service representative.

NOTE
Bearing crush has no relation to bearing clearance and it is important that
the two are not confused.

4-7.4. Checking Crankshaft Thrust

End thrust of the crankshaft is limited by bronze shoes fastened to the faces of two of the main
bearing caps. On two-cylinder frames, there is a main bearing at each end of the frame, and the thrust
shoes are attached to the inboard faces of the bearing caps; the shoes bear against the thrust collars of
the number 1 and number 2 crank webs. On the four- and six-cylinder frames, the thrust shoes are bolted
to the faces of the second and third main bearing caps from the drive end of the unit; the shoes bear
against the thrust collars of the number 2 and number 3 crank webs, counting from the driver end.

FIGURE 4-4. CRANKSHAFT THRUST ARRANGEMENT

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PG-1028-E (HOS) Maintenance

Crankshaft end thrust, or end play, is totally controlled by the position of the driver unit, whether
it is a motor or a gas engine. The thrust shoes cannot in any way "control" the end thrust and the shoes
are installed primarily to position the shaft axially in the frame. Normally, end thrust is negligible if the
compressor and driver have been properly installed.

If wear on the thrust surfaces is observed, the only way to correct it

is moving the driver. If this isn't done, serious damage to the
compressor crankshaft or frame can result.

The compressor is originally built with a total crankshaft thrust clearance within the limits given
in CHAPTER 5, GENERAL DATA & SPECIFICATIONS. The clearance can be measured by totaling the
feeler clearances taken between each thrust shoe and the adjacent crank web (Figure 4-4). The
manufacturing process controls the thrust and cannot be field adjusted.

4-8. CROSSHEAD / CONNECTING ROD ASSEMBLY

Figure 4-5. Crosshead

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Maintenance PG-1028-E (HOS)

4-8.1 Crosshead

The compressor crosshead, Figure 4-5, is a box type with shim-adjustable shoes. The
crosshead pin is full floating and is carried on two steel-backed bronze bushings that are shrunk into the
crosshead. A single steel-backed bronze bushing is shrunk into the eye of the connecting rod. The
compressor piston rod screws into the crosshead and is secured by a crosshead locknut.

4-8.2. Connecting Rods

The compressor connecting rods are made of forged steel and incorporate a one-piece, shrink-
fitted bronze bushing with a light babbitted coating in the small end and two-piece bearing shells in the
large (crankpin) end. The rods are rifle drilled from the connecting rod journal bearing-end to the
crosshead pin-end, providing a passageway for the lubricating oil between the two points.

Figure 4-6. Connecting Rod & Bearing Assembly

4-8.3. Connecting Rod Bearings

The connecting rod bearing is a split steel-backed bronze design with a babbitt overlay. See
Figure 4-6, which shows the assembled position of the bearing in the connecting rod. This is a precision
bearing, which requires no adjustment. If the bearing-to-shaft clearance becomes excessive and the
bearing is noisy, the bearing shells must be replaced.

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PG-1028-E (HOS) Maintenance

When the connecting rod cap is removed from the rod, it must be reassembled in exactly the
same position it held during factory assembly or serious damage to the machine can result. The cap and
its rod are stamped with identical letter and number markings as shown in Figure 4-6.

NOTE
While checking bearing clearances with Plastigage® make sure crankshaft
does not rotate.

At the factory the bolts are stretched per specifications in CHAPTER 5, GENERAL DATA AND
SPECIFICATIONS. Once the proper stretch has been achieved, the end of the bolt and the face of the
nut are stamped with three corresponding letters. (See Figure 4 -7).

If a new connecting rod is being installed or if the existing components become mixed up during
disassembly, please use the following bolt stretch procedure. The following procedure may be done while
the connecting rod is installed in the frame, but the preferred method is with the connecting rod on a
workbench.

"A" "A"

"A"
PRICK PUNCH MARK USED
FOR ALIGNING AND HOLDING
THE STRETCH MIC TO THE
ENDS OF THE CONNECTING
ROD BOLT.

“A” REPRESENTS THE ALIGNMENT MARK THAT IS PUNCHED INTO THE END OF
THE CONNECTING ROD NUT. IT IS NOT NECESSARILY A LETTER, IT MAY BE A
PUNCH MARK OR A NUMBER.

Figure 4-7. Identification of Connecting Rod Bolt Markings

A. Stretch Micrometer Procedure

NOTE
Before removing connecting rod nuts make note of the match mark
stampings on the face of the nut and the end of the bolt as shown in Figure
4-7. Ensure all components (nuts, washers, bolts) are reassembled in the
same position as they were removed. It is extremely important that these
components are not mixed up. If this happens refer to the connecting rod
bolt stretch procedure.

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Maintenance PG-1028-E (HOS)

1. Prior to assembly, thoroughly degrease with solvent and dry all contact surfaces of rod, nut and
washer.

2. Thoroughly lubricate bolt threads with an anti-seize lubricant after placing it in the hole.

NOTE
When using anti-seize lubricants, care should be taken not to use
excessive amounts. Excessive amounts could contaminate oil samples.

3. Lubricate the contact surface between the nut face and the washer with anti-seize. The surface
between the washer face and rod must remain dry, so washer does not rotate.

4. Bolts should be prick (center) punched on each end, before assembly, to ensure that micrometer
reading is taken in the same place before and after elongation.

5. The micrometer reading of the bolt length should be taken before the nut is tightened (see Figure
4-8). This dimension should be recorded for future reference. (This should be done on both
bolts prior to any tightening.)
6. Bolts shall be tightened in a cross pattern ensuring that all bolts are tightened in equal
increments.

7. Each nut should be tightened in small increments until the micrometer reading indicates the bolt
has been elongated (stretched) the specified amount. For proper stretch dimensions refer to
CHAPTER 5, GENERAL DATA & SPECIFICATIONS.

8. After proper elongation (stretch) is attained the face of the nut and the end of the bolt should be
match marked as shown in Figure 4-7.

CONNECTING CONNECTING
ROD NUT ROD BOLT
KNURLED NUT STARRETT MIC

KNURLED HEAD
SCREW

Figure 4-8. Stretch Micrometer

Connecting rod bearing-to-shaft clearance can be checked by using Plastigage®. Lay a piece
of Plastigage® across the crankshaft journal, install cap and tighten to connecting rod bolt stretching
procedure. Remove the cap and measure the Plastigage® to ensure you have proper clearance. The
assembly clearance specifications are given in the list of part fits and tolerances in CHAPTER 5,
GENERAL DATA & SPECIFICATIONS. Remove Plastigage® from crankshaft and/or bearing before
reassembly.

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PG-1028-E (HOS) Maintenance

4-8.4. Replacing Connecting Rod Bearings

1. Remove the frame top cover that will give access to the connecting rod.

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to
bottom-dead-center as an equilibrium condition due to the
difference in piston surface area (by piston rod cross sectional
area) exposed to the process gas pressure. Failure to
depressurize the compressor cylinders prior to barring may result
in unexpected rollover that can cause personal injury.

Before barring the unit over, the operator must ensure that the driver
will not start either by grounding the ignition and closing the fuel gas
valve on gas engine-driven units or by ensuring that power cannot be
turned on with electric motor-driven units. Failure to heed this
WARNING can result in a fatal accident if the unit rolls over
unexpectedly.

2. Rotate the crankshaft to place the connecting rod in a convenient position to remove the cap.

NOTE
Before removing connecting rod nuts make note of the match mark
stampings on the face of the nut and the end of the bolt as shown in Figure
4-7. Ensure all components (nuts, washers, bolts) are reassembled in the
same position as they were removed. It is extremely important that these
components are not mixed up. If this happens refer to the connecting rod
bolt stretch procedure.

3. Pull the cotter pins and remove the nuts and washers from the connecting rod bolts.

4. Carefully lift the connecting rod cap and cap bearing half out of the frame.

5. Support the connecting rod and then rotate the crankshaft to move the crankpin away from the
rod so that the rod bearing half can be removed.

6. Clean the replacement bearing shells, being certain that the oil holes and grooves are clear, and
also clean the bore in the connecting rod and cap before assembling the new bearing. It is
essential that there be no dirt or foreign particles between the bearing shells and the rod, and
that the shells fit their housing perfectly so that they are supported uniformly at all points. It is
normally not required to check bearing crush since these are precision made and inspected
parts. If a bearing crush problem is suspected, contact your Dresser-Rand service
representative.

7. Install the bearing shell halves in the rod and cap. Each shell half has a tab on its outer edge
at the parting line. The tabs fit into slots which are machined into the rod and cap and accurately
position each shell half and lock the bearings to prevent rotation in the bore.

8. Assemble the rod and cap on the crankpin. Work carefully to assure correct assembly and to
prevent damaging the parts.

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Maintenance PG-1028-E (HOS)

9. Tighten the nuts on the connecting rod bolts uniformly until the bolts are elongated (stretched)
the amount given in CHAPTER 5, GENERAL DATA & SPECIFICATIONS. Bolt elongation is
determined by measuring the length of the bolt both before and after tightening.

10. Check the connecting rod bearing-to-crankpin clearance as described previously.

11. Insert and bend a cotter pin to lock each nut on the rod bolt. When it is necessary to reposition
the nut to install the cotter pin, always turn the nut in the tightening direction.

12. Check to be sure no tools have been left inside the frame and replace the top cover on the
frame.

4-8.5. Crossheads and Pins

The conventional crosshead, figure 4-9, is the box type with shim adjustable shoes. The
crosshead pin is full floating and is carried on two steel-backed bronze bushings that are shrunk into the
crosshead. A single steel-backed bronze bushing is shrunk into the eye of the connecting rod. The
compressor piston rod screws into the crosshead and is secured by a crosshead jam nut.

Normal running clearance of the crosshead in the guide is specified in CHAPTER 5.

4-8.6. Removing Crosshead and Connecting Rod

The connecting rod should be removed from the frame if it is necessary to replace the
crosshead pin bushing that is shrunk into the small end of the rod. To remove the connecting rod:

1. Remove the top frame cover, tie bar(s), and frame extension cover that will give access to the
connecting rod.

Figure 4-9. Lockwire Crosshead Balance Weights as Shown

2. All crosshead balance weights must be removed from the nose of the crosshead by removing
the lockwire and cap bolts. (See Figure 4-9.)

3. Unscrew the piston rod from the crosshead using a strap wrench or a piston removal tool as
shown in Figure 4-10. As the piston rod thread disengages from the crosshead, unscrew the
crosshead jam nut and remove balance weights (if required) and lay them aside. Pull the piston
rod away from the crosshead being careful not to pull the threads into the scraper rings.

4-16
PG-1028-E (HOS) Maintenance

Figure 4-10. Piston Removal Tool

4. Remove the crosshead pin bolt lock and unscrew the crosshead pin bolt. The pin end caps are
doweled to the pin. Remove the pin end caps. A steel chisel of appropriate length wedged
between the bottom of the crosshead extension and pin bolt slot will aid in removing the pin bolt.

5. Use pieces of 2 X 4 lumber to wedge the crosshead end of the connecting rod upward enough
to take the weight of the rod off the pin. Block the rod and remove the pin.

6. Rotate the crosshead 90° in the guide to place it on its side and remove the crosshead from
the frame.

7. Immediately mark the crosshead to identify which cylinder it is associated with and which face
is positioned at the top.

8. Bar the compressor over until the cylinder is at mid-stroke and the connecting rod being
worked on is positioned at the top of the frame. Break the connecting rod cap bolts loose.

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to
bottom-dead-center as an equilibrium condition due to the
difference in piston surface area (by piston rod cross sectional
area) exposed to the process gas pressure. Failure to
depressurize the compressor cylinders prior to barring may result
in unexpected rollover that can cause personal injury.

Before barring the unit over, the operator must insure the driver will
not start; either by grounding the ignition and closing the fuel gas
valve on engine driven units, or by insuring that power cannot be
turned on with electric motor driven units. Failure to heed this
WARNING can result in a fatal accident if the unit rolls over
unexpectedly.

4-17
Maintenance PG-1028-E (HOS)

NOTE
Before removing connecting rod nuts make note of the match mark
stampings on the face of the nut and the end of the bolt as shown in Figure
4-7. Ensure all components (nuts, washers, bolts) are reassembled in the
same position as they were removed. It is extremely important that these
components are not mixed up. If this happens refer to the connecting rod
bolt stretch procedure.

9. Remove the connecting rod cap.

10. Move the connecting rod and crankshaft to gain space for removing the rod. Ensure the
crosshead guides are protected from damage. Ease the large end of the connecting rod past
the crankshaft with care to prevent damage to the crosshead guide or the crankpin. Continue
to rotate the crankshaft until the webs are positioned such that the small end of the connecting
rod will pass.

4-8.7. Replacing Small End Bushing

The small end bushing-to-crosshead pin clearance can be checked by comparing micrometer
measurements of the pin O.D. and bushing I.D. The bushing is non-adjustable; it must be replaced with
a new one when the clearance becomes excessive or if the bushing is otherwise defective.

1. Press or machine the old bushing out of the connecting rod. If a machining operation is
used, be careful not to cut into the connecting rod.

2. Clean the rod and check to make sure it is not bent or twisted. Maximum allowable bend and/or
twist is 0.003 inch (0.076 mm).

Always use liquid nitrogen in a well ventilated area and protect the
eyes and skin from contact. Improper use may result in frostbite,
respiratory ailments or asphyxia.

3. The replacement bushing must be chilled (using liquid nitrogen) to reduce its outer dimension
sufficiently so that it can be pressed into the eye of the connecting rod without applying an
appreciable amount of force. The back of the bushing and connecting rod eye must be wiped
clean before installing the bushing.

There is a hole in the connecting rod bushing, which must align

with the rifle-drilled hole in the rod to ensure sufficient lubrication
of the crosshead. If the hole is not aligned properly, the crosshead
bushings will be quickly destroyed.

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PG-1028-E (HOS) Maintenance

4. Use an insertion tool as shown in Figure 4-11 to press the chilled bushing into the rod. The tool
will aid in keeping the bushing square as it enters the rod. Do not allow the bushing to warm up
during this procedure. Excessive force on these thin-walled bushings will cause distortion.

Figure 4-11. Bushing Insertion Tool

5. Be sure to align the hole in the bushing with the rifle-drilled hole in the rod. Check the pin-to-
bushing clearance of the new parts. Refer to CHAPTER 5, GENERAL DATA &
SPECIFICATIONS for assembly fits and tolerances.

6. Install the connecting rod in the compressor using the reverse of the removal procedure. Be
sure the rifle-drilled oil passage in the rod is clear of any obstruction before installing the rod.
Refer to the appropriate instructions when assembling the rod on the crankshaft and when
installing the crosshead pin.

7. If new parts are being used, check for sufficient side clearance between the connecting rod and
adjacent crank webs. This clearance can be measured with feelers and compared with the
listed assembly clearance limits. As a final check of proper connecting rod installation, it is
suggested that the unit be barred through one complete revolution while watching the connecting
rod to see that it runs true on the crankpin. Replace the top cover on the frame.

The connecting rod bolts must be kept tight at all times. If they are
allowed to loosen, broken bolts and considerable damage will occur.
If these connecting rod bolts have been allowed to run in a loosened
conditioned, as noted upon inspection, they should be replaced to
prevent future fatigue failure no matter what their visual appearance.
New bolts must be securely tightened to the proper torque specified
in CHAPTER 5, GENERAL DATA & SPECIFICATIONS.

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Maintenance PG-1028-E (HOS)

4-8-8. Replacing Crosshead Pin and Bushing

To replace the crosshead bushings, the crosshead must be removed from the machine as
previously described.

1. Use a puller to remove the shrink fitted bushings from the crosshead. It is also possible to drive
out the bushings.

There is a hole drilled in each crosshead pin bushing. This hole must
align with the oil hole in the crosshead to ensure adequate lubrication
of the crosshead shoes. Improper installation will result in a scored
crosshead guide and ruined shoes.

2. Clean the bore in the crosshead and wipe off the replacement bushings. Chill the bushings in
liquid nitrogen to reduce the diameters so they can be pressed into the crosshead without
applying appreciable force. Insert the bushings into the bore. When inserting the bushing use
a tool as shown in Figure 4-9 to keep the bushing square to the bore. Do not allow the bushing
to warm up. Excessive insertion force on these thin wall bushings will cause distortion. Bushings
must be flush with the edge of the crosshead.

Always use liquid nitrogen in a well ventilated area and protect the
eyes and skin from contact. Improper use may result in frostbite,
respiratory ailments or asphyxia.

3. Mic the I.D. of the bushing and the O.D. of the crosshead pin. Refer to CHAPTER 5, GENERAL
DATA & SPECIFICATIONS for the proper clearance.

4. Install the crosshead into the crosshead guide using the opposite procedure as previously
described for removal in Paragraph 4-8.6.

5. Oil the crosshead pin and slide it into place in the crosshead and connecting rod. Assemble the
end covers (the end covers are doweled to the pin) and replace the bolt to fasten the covers to
the pin.

6. Check to see that the lock is in place under the head of the bolt and then tighten the bolt to
the torque given in CHAPTER 5, GENERAL DATA & SPECIFICATIONS. Bend up the lock
tabs to secure the bolt.

7. Remove any blocking device used and replace the frame extension cover.

4-8.9. Crosshead Shoe Replacement and Piston Rod Runout Adjustment

The crosshead shoes are fitted at the factory with the clearance listed in CHAPTER 5,
GENERAL DATA & SPECIFICATIONS between the top shoe and upper crosshead guide. However, this
clearance as well as the compressor piston rod alignment must be checked before starting a new unit and
also after any replacement of compressor cylinder, piston, piston rod or crosshead shoes. Adjustment
or replacement of the crosshead shoes is indicated when the shoes become noisy or when the
compressor piston rod runout exceeds the specified limits.

With the compressor cylinder correctly installed and the piston rod crosshead locknut tightened,
check the crosshead to be sure it is resting squarely on the lower guide. Do this by checking for
clearance under the bottom crosshead shoe; a 0.0015 inch (0.04 mm) feeler should not enter between
the center of the bottom shoe and guide at either end of the shoe. Measure the clearance between the
top shoe and the upper guide at all four corners. Record these clearances for later reference.

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PG-1028-E (HOS) Maintenance

The compressor piston rod runout (alignment) must be checked before starting a new unit or after
any replacement of compressor cylinder, piston, piston rod or crosshead. Be sure the crosshead locknut
has been properly tightened against the crosshead before checking the piston rod runout.

One of the primary reasons to keep rod runout within limits is to keep the rod running true
through the piston rod packing, thus ensuring the longest possible packing life with the least leakage.

Piston rod runout is usually checked with the unit "cold". Vertical rod runout under these
conditions is mainly influenced by the crosshead-to-crosshead guide cold clearance and the compressor
piston-to-cylinder bore clearance. Because the compressor piston "grows" as it heats up during
operation, it is normal to see a cold vertical runout much larger than what it will be when the unit is
operating.

Runout limits are given in Table 4-1. All runout figures assume that the piston end of the rod is
"low" to compensate for thermal growth of the piston. After running for four hours under full load and
temperature conditions, check the "hot" runout. Runout should be as close to zero as possible.

There is no adjustment for horizontal piston rod runout, and it should not exceed 0.003 inch
(0.08 mm) if everything is fitted properly.

Factors that can influence piston rod runout are as follows:

A. Lack of proper supports, particularly on larger cylinders where excessive cylinder "droop" can
occur.

B. Excessive piping strain on the cylinder, or distorted cylinder supports pulling the cylinder out of
alignment.

C. Cylinder-to-frame joint burrs or debris in the joint, causing the cylinder to be misaligned.

D. Excessive piston or cylinder bore wear. This can be checked by measuring the piston and bore
with the appropriate micrometers.

E. Worn crosshead shoes. Crosshead shoes are adjustable on conventional crossheads only and
may be shimmed if worn.

Table 4-1. Normal Cold Vertical Piston Rod Runout

Cylinder Bore Approximate Cold Runout

Diameter (Inches) (Inches)

4.75 – 8.00 Less Than - 0.0020

9.50 – 11.50 Less Than - 0.0025
13.00 - 15.00 Less Than - 0.0035
17.50 – 20.50 Less Than - 0.0055
23.00 – 26.50 Less Than - 0.0065

NOTE: All rod runouts are to be negative. No positive rod runouts allowed.

F. A worn (or bent) piston rod. Check rod diameters along the full length of the rod if this is
suspected. Also, check for bending. A worn or bent rod should be replaced.

G. A crosshead jam nut not seating squarely against the crosshead nose. Improperly machined
parts or debris can cause this situation.

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Maintenance PG-1028-E (HOS)

A. Crosshead Shoe Replacement

1. To remove the crosshead shoes pull the crosshead pin and remove the crosshead as described
in Paragraph 4-8.6.

NOTE
Ensure the shims, which are removed, are reinstalled in the same position.
It is recommended (but not required) that all lock nuts be replaced after
initial use.

2. Remove the lock nuts, which secure the shoes to the crosshead.

3. Install new crosshead shoes and torque to the proper specifications listed in CHAPTER 5,
GENERAL DATA & SPECIFICATIONS.

4. Mic the I.D. of the crosshead guide and the O.D. of the crosshead to ensure you have the proper
running clearances per CHAPTER 5, GENERAL DATA & SPECIFICATIONS.

5. Reinstall the crosshead into the crosshead guide.

B. Piston Rod Runout Adjustment

The following instructions describe the recommended procedure for checking and adjusting the
compressor piston rod runout:

1. Mount a dial indicator in the distance piece so that it will read on the top of the piston rod. Be
sure the indicator is securely mounted and depress the indicator button, rotating the pointer one
revolution on the dial to preload the indicator. Set the dial to the zero mark.

2. Bar the compressor through 180°, starting from the maximum outboard stroke. The largest
reading seen during this 180° traverse to the inboard stroke position, whether plus or minus, is
the total runout and is to be recorded on the frame record card using the proper sign (±) for the
number. In order to check the accuracy of the reading, continue to bar the compressor an
additional 180° (in the same direction of rotation) to the maximum outboard stroke position. The
dial indicator should now be pointing to zero; if not, the indicator has moved.

SERVICE NOTE
If the indicator needle "jumps" at the extreme ends of the stroke it is an
indication of either a loose crosshead jam nut or a nut face that is not
square to the crosshead nose.

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PG-1028-E (HOS) Maintenance

3. The piston rod runout is adjusted in the vertical direction by adding or removing shims between
the crosshead and its bottom shoe. If the piston rod is high at the piston end, shims must be
added under the bottom shoe. If the rod is high at the crosshead end, shims must be removed
from under the bottom shoe. If there is some confusion as to which end of the rod is high, a
machinist's level can be placed on the piston rod to tell whether the crosshead must be raised
or lowered. Always remember that the shim thickness removed or added to one shoe must then
be either added or removed from the other shoe if the required top shoe-to-guide clearance is
to be maintained.

4. Since the piston rod runout is initially checked and adjusted with the parts cold, the rod should
normally be set slightly lower at the piston end to compensate for piston expansion when running
at design load and temperature conditions. The amount the piston is set lower than the
crosshead is determined by both the size and material of the piston. (Larger piston sizes should
be set slightly lower to compensate for increased expansion.) See Table 4-1.

5. It is necessary to remove the shim from under the crosshead shoe to adjust the shim thickness.
To remove the shoe, pull the crosshead pin as described in the instructions which follow; the
crosshead shoe bolt nuts can then be removed and the crosshead rotated 90° in its guides to
allow the shoe to be removed through the side inspection opening in the frame extension. Take
off the shim and add or remove laminations as required. Generally, adding or removing one
shim lamination will change the indicated rod runout about 0.001 inch (0.03 mm); therefore, to
raise the indicated rod runout 0.002 inch (0.05 mm) at the crosshead end, it would be necessary
to add two laminations to the shim used under the bottom shoe. Always remove or add a like
number of laminations to the upper shoe to maintain the required top shoe-to-guide clearance.

6. Re-check the piston rod runout with a dial indicator, as described in Steps 1 and 2, after each
shoe adjustment. Always check rod runout with the piston rod crosshead jam nut firmly
tightened as a loose nut can alter the runout reading.

7. After setting the rod runout initially, and before operating the compressor, check that there is
running clearance between the piston rod and piston rod packing glands.

8. There is no adjustment for horizontal piston rod runout. It is important, however, that the rod
runout is checked in the horizontal direction by arranging the dial indicator to read on the side
of the rod. If the horizontal indicated rod runout exceeds 0.003 inch (0.08 mm), the cause must
be located and corrected. Check the cylinder, yoke and frame mating surfaces for dirt, nicks
or burrs. Another possible cause of misalignment is an improperly tightened crosshead locknut
or a nut that is not seating squarely against the crosshead. The possibility of cylinder supports
or piping pulling the cylinder out of alignment should also be explored.

9. Both the piston rod alignment and the crosshead top shoe-to-guide clearance should be checked
after operating the compressor for at least four hours under full load and temperature conditions.
These checks must be made immediately after shutting down before the parts have had a
chance to cool. Piston rod runout should be as close to zero as possible and must not exceed
the limits given in Table 4-1 in any plane. The minimum acceptable clearance between the top
crosshead shoe and guide with the parts at operating temperature is given in CHAPTER 5,
GENERAL DATA & SPECIFICATIONS. If it is necessary to remove the shims to obtain this
minimum clearance, be sure they are removed from under the top shoe. Record the hot
clearance for future reference.

4-9. COMPRESSOR CYLINDERS

A wide variety of cylinder types are used on the 6-inch stroke HOS compressor. These can be
divided into two major families – water cooled and gas cooled. Examples of these two families of cylinder
are illustrated in Figure 4-12.

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Maintenance PG-1028-E (HOS)

Figure 4-12. Typical HOS Cylinders

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PG-1028-E (HOS) Maintenance

Water-cooled cylinders are available in standard bore sizes from 4-3/4 inches to 26-1/2 inches
in diameter in cast iron, while gas-cooled cylinders with bores ranging from 6 inches to 15 inches in
diameter are available in nodular iron as standard. (The cylinder line-up is shown in Table 4-4.)

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

The cylinder bores, valves, valve passages, piston rod packings and any regulation equipment
supplied should be inspected at regular intervals (refer to the routine maintenance schedule in Chapter
3), and any accumulations of foreign matter should be removed. Valves must be dismantled, soaked in
safety solvent and physically brushed to soften and remove any deposits; a light scraping usually will
suffice to clean the cylinder valve passages.

Dresser-Rand Type PF valves are used as standard in HOS cylinders. Detailed instructions for
servicing the valves can be found in this chapter, Paragraph 4-17.4.

With water-cooled cylinders, mud will be deposited in the cylinder jackets, water heads and
packing cooling sleeves if the circulating coolant (usually a mixture of 50-50 ethylene glycol and water)
is dirty. This will eventually obstruct the flow of coolant unless care is used to prevent such an
accumulation. Clogged passages will interfere with proper cooling, which will result in possible damage
to the cylinder, pistons and packing.

The cylinder water jacket cover plate or hand hole covers (depending on design) should be
removed occasionally and the water jackets and passages inspected. If any mud deposit is found, clean
it out thoroughly and flush the jackets with water.

Piston and ring clearances for standard water-cooled and gas-cooled HOS cylinders are given
in Table 4-4. Clearances for non-standard bore diameter cylinders will be given in a separate addendum
sheet prepared for your unit. The specified clearance limits are those to which the parts are originally
assembled. Varying operating conditions at different installations make it generally impractical to specify
maximum acceptable clearances. Careful observation by the operator and good judgment by the
mechanic are often the most effective means of determining when clearances have become excessive
and adjustment or replacement of parts is required.

Before doing any maintenance work on the cylinders, closely observe the minimum safety
precautions described previously in Paragraph 4-2. To protect personnel, it is imperative that all
pressure be bled from the cylinder passages before attempting to open the cylinder.

Also, before servicing the cylinders, review the Parts List illustrations thoroughly to become
familiar with the particular assemblies involved. There may be slight design differences on a particular
assembly that can require a modification to the recommended maintenance procedures.

4-9.1. Removing and Installing Compressor Cylinders

The compressor cylinder can be opened and the various cylinder components serviced as
described in the maintenance instructions that follow. If the complete cylinder is to be removed from the
compressor frame, it is first necessary to disconnect all piping from the cylinder, as applicable. Also, the
compressor piston rod assembly should be removed from the cylinder as explained in the instructions,
which follow. To remove the cylinder from the frame, support the weight of the cylinder with rigging from
an overhead hoist, or other means, and then unbolt the cylinder from the main frame and carefully lower
the cylinder assembly to the floor.

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Maintenance PG-1028-E (HOS)

Normally, the cylinders are mounted on the compressor frame when it is shipped to the
installation site. However, in some instances, usually because of shipping and packaging restrictions, the
cylinder as shipped separately and must be installed at the compressor site. Refer to the installation plans
prepared for the compressor to determine the position in which each cylinder is to be mounted.

Before doing any maintenance work on the cylinders, closely observe the minimum safety
precautions described previously in Paragraph 4-2.

To protect personnel, it is imperative that all pressure be bled from

the cylinder passages before attempting to open the cylinder.

Also, before servicing the cylinders, review the Parts List illustrations thoroughly to become
familiar with the particular assemblies involved. There may be slight design differences on a particular
assembly that can require a modification to the recommended maintenance procedures.

The compressor cylinder can be opened and the various cylinder components serviced as
described in the maintenance instructions that follow.

A. Removing Compressor Cylinder

Remove the compressor cylinder from the compressor frame as follows:

1. If the complete cylinder is to be removed from the compressor frame, it is first necessary to
disconnect all of the gas, oil, water and control piping from the cylinder, as applicable.

2. The compressor piston and rod should next be removed from the cylinder as explained in the
instructions that follow in Paragraph 4-9.2.

3. To remove the cylinder from the frame, support the weight of the cylinder with rigging from an
overhead hoist, or other means, then unbolt the cylinder yoke from the main frame and carefully
lower the cylinder assembly to the floor.

NOTE
Cylinders must be returned to their original locations on the frame.
Never change cylinder mounting locations without first consulting the
nearest Dresser-Rand office.

Instructions for installing and aligning the compressor cylinder are described below. Install one
cylinder at a time on the unit. Where supports are used, insert leveling screws in the support bases being
sure the threads are greased and free in their holes.

B. Installing Compressor Cylinder

Install and align the cylinder on the compressor frame as follows:

1. Thoroughly clean the mating surfaces on the cylinder and yoke. Coat both surfaces with gasket
shellac, but do not use a gasket.

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PG-1028-E (HOS) Maintenance

NOTE
Mating surfaces must be checked for flatness. Flatness of both mating
components should be within .002”.

2. Using capscrews, bolt the cylinder and yoke together. Insert the four cylinder-to-frame tie rods
through the yokes and into the cylinder.

3. Thoroughly clean the mating surfaces on the frame extension and yoke. Coat both surfaces with
gasket shellac, but do not use a gasket.

4. Mount the cylinder and yoke assembly on the frame. The cylinder yoke is centered on the frame
extension by a shoulder which fits closely into the frame extension bore. Support the cylinder
and then snug down the two top tie rod nuts.

5. Clean the gasket surface for the inlet (flange) on top of the cylinder and place a level on this
surface parallel to the crankshaft. Rotate the cylinder until the gasket surface is level with the
top of the frame; then, secure the cylinder.

6. Depending on the particular compressor, the cylinder may be equipped with a yoke support, or
outer end support, or a combination of both. With either support location, the support must be
adjusted so that it is supporting the weight of the cylinder but not placing an upward strain on
the cylinder-to-frame bolting. The following procedure is recommended when an outer end
support is used:

A. Loosen the cylinder-to-frame tie rod nuts and capscrews, leaving the two top tie rod nuts
snugged down lightly.

B. Raise the cylinder with the support leveling setscrews until a 0.0015 inch (0.04 mm)
feeler gauge can just be started at the bottom cylinder-to-frame joint.

C. Lower the cylinder to just close the joint, then tighten the cylinder to frame tie rod nuts
using a torque wrench to obtain 40,000 PSI (276 Mpa) pre-stress. See CHAPTER 5,
GENERAL DATA & SPECIFICATIONS for torque value.

7. Remove the outer head from the cylinder. Using a machinist's level having a cross level, check
that the cylinder bore in the piston travel area is level. Locate the cause of any misalignment.
Do not use the support leveling setscrews to force the cylinder into alignment.

8. Check the level of the crosshead guide. The cylinder bore and the crosshead guide need not
be perfectly level, but both should be in the same plane. Do not use the cylinder inlet (or
discharge) connection as an alternate to the cylinder bore. If the crosshead guides are level but
one or more cylinders is not, the most likely cause is dirt or raised material in the joint where the
cylinder fits the yoke or where the yoke mates with the frame extension.

Assembly of the compressor cylinders, including installation of valves and rod, piston rod
packing, alignment of the piston rod and adjustment of piston and clearances, is completed by following
the appropriate assembly procedures outlined in this manual.

4-9.2. Disassembly and Assembly of Pistons & Piston Rods

1. Observe all possible safety precautions as described previously in Paragraph 4-2.

2. Block the crosshead by jamming wooden blocks between the crosshead and frame extension
to prevent twisting the crosshead and/or connecting rod when removing the locknut.

3. Loosen the crosshead locknut on the piston rod.

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Maintenance PG-1028-E (HOS)

NOTE

If a balance weight or weights are present, depending on the size of the

weights, it may be necessary to remove them first. Slide the weight(s)
out toward the stuffer plate to get access to the jam nut. In very rare
instances the stuffer plate may have to be removed to make additional
room.

4. Remove the piston rod pressure packing and oil scraper rings as explained later in these
instructions in Paragraphs 4-13. and 4-14. Always remove the packing rings before pulling or
installing the piston rod; never slide these rings over the end of the rod.

Never use a pipe wrench on the piston rod. Take every precaution
to avoid scratching or nicking the piston rod surface. Even a
slight nick in the rod can ruin the packing rings.

5. Remove the outer head and then unscrew the piston rod from the crosshead using a strap
wrench or piston removal tool (Figure 4-10).

6. Pull the piston and rod assembly through the outer end of the cylinder. Be careful to support the
piston until the rod is clear to prevent bending or scratching it. Mark the assembly so that it can
be installed in the same cylinder.

7. If the packing cup and gland assemblies are removed from the cylinder at this time, be sure the
parts are marked or tagged to facilitate proper reassembly.

8. Set the piston and rod in a safe place and protect the finished surfaces from damage. If the
piston and rod are not integral, and if the piston is to be separated from the piston rod, refer to
piston & rod disassembly and reassembly steps.

A. Piston and Rod Disassembly

1. Install the piston rod assembly in a clamping fixture as shown in Figure 4-13 or a similar device
that will keep the piston rod from turning while loosening and/or tightening the piston rod nut.
Use a soft bearing material next to the rod surface to prevent scoring or scratching.

2. Remove the piston nut locking setscrew. Remove the piston rod nut using the wrench adapter
provided. If available, a suitable size impact wrench is ideal for loosening the nut. If necessary
to sledge or use a cheater on the wrench, support the piston to prevent bending of the piston
rod.

3. Remove the piston from the rod.

B. Piston and Rod Assembly

1. To assemble a piston and rod, install the rod in a clamping fixture as shown in Figure 4-13.

2. Inspect the mating surfaces of the piston rod collar, piston faces and piston rod nut for dirt, burrs
and general condition. Clean up the parts as required.

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PG-1028-E (HOS) Maintenance

Figure 4-13. Suggested Piston Rod Clamping Fixture

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Maintenance PG-1028-E (HOS)

3. Place the collar on the rod and check the mating surfaces between the rod shoulder and collar
by "blueing" to assure that at least 75% bearing contact is made. Repeat for collar contact on
piston. Check that the mating area is uniform completely around the circumference and across
the mating face. Lap the faces, if necessary, using a valve grinding compound. Remove all
traces of compound using soap and water.

SERVICE NOTE
With step cylinders, both an inboard and outboard piston and piston spacer
as well as piston collars and nut must be blued to 75% contact in the
appropriate order.

4. Check the mating surface between the piston nut and the piston for adequate contact as in Step
3. If the bearing area is insufficient, check the squareness of the nut face with the nut threads.
Scrape or lap faces, if necessary, using valve grinding compound until adequate bearing area
is obtained. Remove all traces of compound using soap and water.

5. Coat the piston rod and piston nut threads with a suitable anti-galling compound, such as Felpro
C-100 (distributed by Felpro, Inc., Skokie, IL 60776) or Jet Lube #20 (distributed by Marlon
Supply Co., 5016 Edgewood Rd., Crystal Lake, IL 60014). Apply a thin film on the face of the
piston nut and piston. Tighten the nut to 150 ft. lb. (203 NAm) to ensure adequate metal-to-
metal contact.

6. Scribe a line (A) through the centerline of the rod and extend it out onto the piston as shown in
Figure 4-14.

7. Refer to Table 4-2 to determine the number of degrees the nut must be turned with relation to
the piston rod. The use of torque is strongly discouraged because of the variations obtained
with small changes in lubrication and surface condition of the mating parts.

8. Measure from the original scribe line (A) the number of degrees that the piston nut must be
turned. Prick punch point (B) on the piston and scribe a line through this point (B) and the
centerline of the piston rod.

9. Install the piston nut adapter. Mark the adapter (or socket, if an impact wrench is used) adjacent
to the first scribe line (A) as in Figure 4-14.

10. Tighten the piston nut until the mark on the adapter (or socket) coincides with the second scribe
line (B).

SERVICE NOTE
With the wrench socket on the adapter, it will be impossible to see the scribe
mark on the piston nut. It is essential that the scribe marks between the piston
rod and nut line up. It is therefore recommended that the scribe mark on the
socket be turned slightly beyond the second scribe mark on the piston, as the
piston may rotate slightly on the rod due to friction.

11. If a new piston, piston rod or piston nut is being installed, tighten the assembly at least twice to
the full pre-stress as described in Steps 6 through 10. Then, loosen the assembly again and
repeat Steps 18 through 23 (for at least the third time) to secure the piston on the rod.

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PG-1028-E (HOS) Maintenance

NOTE
It is anticipated that the piston will go beyond the original scribe mark;
therefore, it is imperative to re-scribe each time the nut is tightened.

12. After completing the piston nut tightening procedure, drill and tap the piston rod and nut for the
locking setscrew. (Facing the end of the piston, half of the tapped hole should be in the piston
rod and half in the nut.)

Figure 4-14. Marking Piston Nut and Adapter or Socket

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Maintenance PG-1028-E (HOS)

Table 4-2. Piston Nut Tightening Angles for Standard Cylinders

Tightening Cylinder Configuration

Angle Size

Two Valves per Corner

40° 9.5", 10.5", 11.5" & 13" Cast Iron Piston

45° 6.0" Linered, 7.0" & 8.0" One Valve per Corner
Slant Design

45° All 15", 17.5" & 20.5" Cast Aluminum Pistons

Smaller Sizes

50° All 23" & 26" Cast Aluminum Pistons

Larger Sizes

60° 4.75", 5.0" Linered & 6.0" Cast Iron Billet

70° 6.0" F.S. Forged Steel Billet

120° Step Pistons Step (Tandem) Cylinder

Note: Table 4-2 covers both water-cooled and gas-cooled designs.

Table 4-2A. Piston Nut Tightening Angles for HOS Balanced Pistons

Stroke Tightening Piston Rod Piston

Angle Reference Reference

6” HOS 40° R72014 H50029

7” HOS 52° IAUM0001 JGUM0001

Note: Table 4-2A covers both water-cooled and gas-cooled designs.

13. Lock the piston nut to the rod using the setscrew.

NOTE
Some piston tightening angles are found printed on the piston parts lists. If
there is a discrepancy between this chart and any such figure, use the figure
on the parts list.

This completes the assembly of the compressor piston and rod. Install the piston and rod into
the cylinder as outlined in the following steps.

4-10. INSTALLING PISTON ROD AND ADJUSTING END CLEARANCE

When adjusting piston end clearance, it is desirable to have more clearance at the outer end
than at the frame end. This is because expansion from operating heat tends to increase the frame end
clearance and decrease the outer end clearance. For this reason, when setting piston end clearance, the
outer end is usually given about 50% more lineal clearance than the frame end. Specific end clearances
are shown on the cylinder nameplate. Standard HOS cylinder clearance is as follows:

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PG-1028-E (HOS) Maintenance

Frame End = 0.043-0.082 inch (1.09-2.08 mm)

Outer End = 0.064-0.123 inch (1.63-3.12 mm)

Compressor cylinders must be depressurized to atmospheric

pressure before barring. Compressor pistons will move to bottom-
dead-center as an equilibrium condition due to the difference in
piston surface area (by piston rod cross sectional area) exposed
to the process gas pressure. Failure to depressurize the
compressor cylinders prior to barring may result in unexpected
rollover that can cause personal injury.

Before barring the unit over, the operator must ensure that the
driver will not start - either by grounding the ignition and closing
the fuel gas valve on engine driven units - or by ensuring that the
power cannot be turned on with electric motor driven units.
Failure to heed this WARNING can result in a fatal accident if the
unit rolls over unexpectedly.

The piston end clearance, after having been correctly set at the time of installation, should rarely
require adjustment. It should, however, be checked occasionally as follows: To measure the end
clearance, first remove the cylinder indicator plugs for each end. When the machine is cold, find the exact
clearance by barring over the compressor until the piston is at the innermost end of its stroke. Using feeler
gauges, measure the distance between the face of the piston and the inboard cylinder head. Note this
measurement and then bar the compressor 180° to bring the piston to the outermost end of its stroke.
Again using feeler gauges, measure the clearance between the face of the piston and the outboard
cylinder head. Note any difference in the clearances and then screw the piston rod in or out of the
crosshead to make the clearance about 50% more at the outer end than at the frame end.

If it is necessary to change the clearance at either end, loosen the locknut on the piston rod at
the crosshead. Turn the piston rod in or out of the crosshead as required. Each quarter turn of the rod
changes the end clearance by 0.031 inch (0.79 mm). After proper clearance in the cylinder is established,
tighten the crosshead locknut on the piston rod, as described later in the following steps.

1. Place an entering sleeve onto the end of the piston rod to protect the packing. Coat piston rod
and sleeve with oil, then push the piston assembly into the cylinder.

2. Remove the entering sleeve.

Never use a pipe wrench on the piston rod. Take every precaution
to avoid scratching or nicking the piston rod surface. Even a
slight nick in the rod can ruin the packing rings.

3. Install jam nut on the piston rod and balance weights (if required) making sure the machined
surface will contact the crosshead.

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Maintenance PG-1028-E (HOS)

4. Screw the piston rod into the crosshead until the required piston frame end clearance is
obtained. (Refer to the instructions above for a discussion of the piston end clearance.) A strap
wrench or a piston installation/removal tool ( see Figure 4-10) should be used to screw the
piston rod into the crosshead. Snug the piston rod locknut against the crosshead, but do not
tighten it at this time. Check to see that there is some clearance between the piston rod and the
connecting rod in the crosshead.

5. Check the seating surfaces between the crosshead and lock nut by "blueing" to ensure that at
least 80% seating contact is made. Check that seating area is uniform completely around the
circumference and across the seating face. If the seating is insufficient, check the squareness
of the nut face with the nut threads. Scrape or lap the faces, if necessary, using a grinding
compound until adequate seating area is obtained. Remove all traces of compound using soap
and water.

6. Tighten the crosshead lock nut as follows:

A. The crosshead should be blocked between the crosshead and frame extension to
prevent twisting the crosshead and/or connecting rod during tightening. A wooden block
may be used.

B. Coat the rod and nut threads with a suitable anti-galling compound or extreme pressure
lubricant. Apply a thin film on the seating faces of the nut and crosshead. Tighten the
nut to approximately 150-ft. lb. (203 N m) to ensure good metal-to-metal contact.

C. Refer to Figure 4-15. Match mark a flat on the nut with the face of the crosshead using
a punch, scribe, or other suitable instrument. To mark the proper nut-tightening angle,
measure clockwise 15 degrees from the first mark using a protractor and make a second
mark on the crosshead face.

NOTE

If a balance weight or weights are present, depending on the size of the

weights, it may be necessary to assemble weight(s) onto the crosshead
after the jam nut has been tightened.

Figure 4-15. Marking Crosshead and Crosshead Lock Nut Tightening Angle

D. Tighten the lock nut until the first mark (on the nut flat) is aligned with the second
mark (on the crosshead face).

7. Check the rod runout and adjust as required in Paragraph 4-8.9.

8. Install the outer head assembly onto the cylinder and tighten to the specified torque. Check the
piston end clearance at each end of the stroke as described in instructions above.

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PG-1028-E (HOS) Maintenance

4-11. INSPECTION / MAINTENANCE OF CYLINDER BORES

1. Place the cylinder in a clean work area and wipe the bore with clean rags. It may be necessary
to use a safety solvent to remove some deposits.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

2. Shine a light down the cylinder bore and visually inspect for scratches, gouges and nicks.

3. Using an internal micrometer, measure each bore at its frame end, center portion and outer end
at the limits of piston travel, taking measurements 90° apart. Comparing the measurements will
give figures for taper (end-to-end in the same bore position) and out-of-round (same bore
position but 90° apart) for each bore. Maximum allowable taper is 0.0005 inch (0.013 mm) per
inch (25 mm) of stroke. Maximum allowable out-of-round is 0.0005 inch (0.013 mm) per inch
(25 mm) of bore diameter for TFE or thermoplastic rings.

4. A bore not worn to the limits (above) may be cleaned up using a glaze breaker or a rigid portable
hone and new piston rings may be fitted. See "Honing", later in this section, for a procedure.

NOTE
Generally, standard rings may be used in cylinders worn up to the limits
shown in Table 4-3. For cylinders with bore diameters greater than
specified, oversize piston rings should be used. The bore must be round.
Oversize rings are not the cure for an out-of-round or tapered bore
condition. When ordering oversize rings, furnish Dresser-Rand with the
cylinder bore measurements. Rings ordered through Dresser-Rand will be
tagged, indicating the proper side and end gap clearances. Use Table 4-3,
as a guide to determine what the maximum bore should be before oversize
piston rings are required.

Table 4-3. Cylinder Reconditioning Data

Original Maximum
Cylinder Size Bore Diameter Increase (Inches)
(Inches) Allowed

Nominal Bore Before Oversize Rings Required

Diameter

4.75 0.015
6.000 0.018
7.000 0.021
8.000 0.024
9.500 0.029
10.500 0.032
11.500 0.035
13.000 0.039
15.000 – 26.500 0.048

NOTE: Inch-to-millimeter conversion-multiply inches by 25.4 to obtain millimeters.

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Maintenance PG-1028-E (HOS)

A. Honing

In all cases where a bore is being field reconditioned, it is important to achieve a surface finish
at least as good as the factory finish to ensure adequate ring seating and longevity. Hone the cylinder
bore to restore surface finish. Bores should be at least 32 RMS Ra (0.8 um). Honing will polish scratches
and remove burrs, and will often restore a cylinder bore after minor scuffing. This can be achieved using
a glaze breaker or hone, finishing with extra fine hone stones. A crosshatch pattern can be used if
desired. ALWAYS WASH GRIT FROM HONING OUT OF THE BORE USING SOAP AND HOT WATER

NOTE
The major difference between a glaze breaker and a cylinder hone is
that the glaze breaker will follow the contour of the cylinder. If the bore
is out-of-round, the glaze breaker will only clean it up; it will not "true
up" the bore. The hone, on the other hand, will true up a slightly out-of-
round or tapered cylinder bore, although it too tends to follow the
existing bore contour.

4-12. NON-METALLIC COMBINATION PISTON & RIDER RINGS

These segmented, non-metallic combination piston/rider rings function as both piston and rider
rings. They are used as a standard on all HOS cylinders except the 26- and 26.5-inch (660 and 673 mm),
which uses glass - molydisulphide-filled TeflonÒ piston rings with band-type riders made of the same
material.

The combination piston and rider rings will hold the piston away from the cylinder bore during
operation, thus preventing piston-to-cylinder bore contact and the resultant scoring and wear. To promote
long ring life, cylinder bore surface finish is to be maintained at 32 Ra (0.8 micrometer).

Standard size rings may be used in oversized cylinder bores up to 0.003 inch (0.08 mm) for
each inch (25.4 mm) of bore diameter up to and including 0.045 inch (1.14 mm) maximum oversize. For
cylinders with bore diameters greater than specified for nominal bore size, oversized piston rings should
be used. Remember that the bore must be round. Oversize rings will not correct or compensate for out-
of-round or tapered bore conditions.

4-12.1. Handling Instructions

These piston rings are fragile (when compared to metallic parts) and can be easily damaged by
careless handling. Always use care during storage, handling, installation and removal.

During long shutdowns (over six months), the pistons and rods should be removed from the
compressor; coat the piston and rod assembly with a rust preventative that meets Military Specification
MIL-C-16173 latest revision. The rings are to be removed from the piston and stored flat. No special
covering or rust preventative is required. Do not lay the piston and rod assembly down with rings installed.

4-12.2. Establishing Ring Wear Rate

The combination piston/rider rings may wear more rapidly than other rings because of the
functions they are designed to perform. (These are sealing of the cylinder bore, and the prevention of
piston to cylinder bore contact.) Operating and maintenance personnel must take this factor into
consideration when scheduling inspections and normal part replacement.

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PG-1028-E (HOS) Maintenance

As wear occurs, piston rod runout will eventually exceed allowable limits. If oversized rings are
installed in an oversized bore the ring wear factor is more critical because the rod drop will be increased
by one-half the total oversize. For example, if the bore is 0.026 inch oversize (0.66 mm) the rod will drop
an additional 0.013 inch (0.33 mm) before the bottom clearance or ring radial thickness indicates
replacement is required. Therefore, the operator must keep in mind that the rings must be replaced when
their original radial thickness is reduced by one-half of the original (new radial) thickness. Also, note the
clearance between the piston rod and packing housing. DO NOT allow these items to come into contact
with each other.

Because of the many variables involved, it is impossible to accurately predict the rate of wear.
(Some of the variables are pressure, temperature, lubrication or lack thereof, piston weight, gas type, gas
wetness, gas cleanliness and cylinder bore finish.)

To prevent scoring of the cylinder bore, piston or the piston rod,

the amount of ring wear (clearance between the piston and
cylinder bore) must be checked on a regular basis. This action will
tell the operator if wear is excessive, allowing replacement before
damage is done.

The importance of frequently checking ring wear rate cannot be over-emphasized. The rate of
wear must be determined so that a replacement schedule can be established. Measurement of the piston
to cylinder bore clearance ("A", Figure 4-16) should be taken at intervals of 10, 100, 250, 500 and 1000
hours. Record these numbers for future reference, or plot a simple wear versus time curve that will
indicate both the rate of wear and the approximate number of hours running time before the combination
rings need to be replaced.
NOTE
When plotted, the wear rate curve will usually show a relatively rapid rate of
wear during the first few hours of operation. As the rings wear, the curve
should flatten out.

Figure 4-16. Points for Checking Clearance

(See Table 4-4 For Dimensions)

4-12.3. Replacing Rings

Rings are replaced when the bottom piston to cylinder bore clearance ("B" Figure 4-16) has
been reduced to the minimum allowable clearance or if the original radial thickness of the rings has been
reduced by one-half.

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Maintenance PG-1028-E (HOS)

Never measure piston-to-cylinder bore clearance through a valve

opening; always remove the outer head. Refer to the appropriate
instructions to remove and install the outer head. Failure to comply
with this warning may result in severe personal injury caused by
compressor roll.

4-12.4. Installing Rings

The rings must be assembled in the piston grooves as the piston is slid into the cylinder bore.
These rings will extend beyond the piston's outside diameter when installed. After the piston is installed,
measure the bottom clearance between the piston and cylinder bore (see "A" Figure 4-16). This is the
point of reference from which the amount of wear will be determined.

Table 4-4. Piston and Ring Clearance for Standard HOS Cylinders

Nominal Groove "C" "E" “F”

3
Cylinder Piston Width Running Side Total
Size G/C¹ W/C
2 Piston Ring (In.) Clear.(In.) Clear.(In.) Ring
Mat'l. +0.001 Top-New Between End Gap
Mat'l.
(Inches) -0.000 Rings Ring & New
Groove Parts (In.)

4.75 X X CI TFE 0.500 0.029/0.040 0.009/0.013 0.081/0.095

6.00 X X CI TFE 0.500 0.012/0.026 0.009/0.013 0.102/0.120

7.00 X X CI TFE 0.625 0.014/0.028 0.011/0.015 0.119/0.140

8.00 X X CI TFE 0.500 0.017/0.031 0.009/0.013 0.136/0.160

9.50 X X CI TFE 0.625 0.018/0.032 0.011/0.015 0.162/0.190

10.50 X X CI TFE 0.625 0.021/0.035 0.011/0.015 0.179/0.210

11.50 X X CI TFE 0.625 0.023/0.037 0.011/0.015 0.196/0.230

13.00 X X CI TFE 0.500 0.026/0.040 0.009/0.013 0.221/0.260

15.00 X X AL TFE 0.625 0.041/0.056 0.011/0.015 0.255/0.300

17.50 X AL TFE 0.625 0.050/0.065 0.011/0.015 0.298/0.350

20.50 X AL TFE 0.625 0.057/0.072 0.011/0.015 0.349/0.410

23.00 X AL TFE 0.625 0.065/0.080 0.011/0.015 0.391/0.460

26.00 X AL TFE 0.625 0.071/0.092 0.011/0.015 0.442/0.520

26.50 X AL TFE 0.625 0.071/0.092 0.011/0.015 0.451/0.530

NOTES FOR TABLE:
1
= Gas cooled
2
= Water cooled
3
= TFE = Filled Teflon

Multiply clearance dimension by 25.4 to obtain (soft converted) metric dimension.

· CI = Cast Iron; AL = Aluminum

· Metric groove width tolerance is +0.025/-0.000 mm.

(A 0.500" width is 12.7 mm; a 0.625" width is 15.88 mm.)

· Dimensions Refer to Figure 4-15. All dimensions are for new parts.

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PG-1028-E (HOS) Maintenance

To install the rings, follow these steps. Clearances are listed in Table 4-4.

1. Check the ring part number against the parts list to ensure the correct parts are being installed.

2. Manufacture a ring gauge that has the same nominal inside diameter as the cylinder bore. Insert
the rings, measure and record total ring end gap clearance; see Figure 4-17.

3. Measure radial thickness of the rings. Record this dimension for future reference.

4. Be sure the piston ring grooves are clean and smooth.

5. Install the packing entering sleeve on the piston rod.

6. Push the piston into the cylinder until the innermost groove is just outside the cylinder.

Figure 4-17. Taking End Gap Clearance

Figure 4-17.A. Taking End Gap Clearance (Angle Cut)

Figure 4-17.B. Taking End Gap Clearance (Step Cut)

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Maintenance PG-1028-E (HOS)

7. Make, from thin shim stock, a tool to hold the ring segments in the piston grooves.

8. Place the ring segments into the piston grooves and take side clearance as shown in "E" Figure
4-16; record these clearances.

9. LIFT the piston slightly and push it into the cylinder until the cylinder bore holds the ring
segments in place. Remove the shim stock.

10. Measure the clearance between the ring and cylinder bore at "C" Figure 4-16. Repeat Steps 8
and 9 until all rings have been installed.

11. After all rings are in place, push the piston all the way into the cylinder; remove the entering
sleeve and connect the piston rod to the crosshead and install the outer head following the
appropriate instructions.

4-12.5. Breaking-in Combination Rings

Full pressures normally can be applied to the rings when they are initially placed in service.
However, on new or overhauled units, consideration of the break-in requirements of the compressor
"running gear" must also be considered. Always watch operating temperatures for indications of
overheating, especially during break-in. Refer to CHAPTER 3, OPERATION AND TROUBLESHOOTING.
If possible (pump-to-point systems only) set the cylinder lubricator feed rate to provide maximum delivery
during the break-in period. At the end of the break-in period, the feed rate can be reduced to normal.

4-13. PISTON ROD PRESSURE PACKING

Generally, all piston rods are packed with floating type packing (see Figure 4- 18). There is no
adjustment or take-up for this type of packing. Tighten the flange stud nuts evenly and squarely to obtain
even crushing of the gasket at the bottom of the stuffer; this will prevent cocking of the packing cups and
ensure their being perpendicular with respect to the piston rod.

Figure 4-18. Piston Rod Pressure Packing Typical Construction

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PG-1028-E (HOS) Maintenance

4-13.1. Packing Rings

The packing rings are the most important part of the packing. They seal the pressure, take the
normal wear and must be serviced and lubricated. When sludge and carbon from poor or incorrect
lubricating oil have fouled them, they must be cleaned. When the rings (except backup rings) have worn
so that no end clearance exists between the segments, the rings should be replaced. The rings are the
working parts in any packing set and it is they that require the most attention. Usually these rings have
a long life, but it is a good policy to have a set of replacement rings on hand to meet emergencies.
Replacement rings may be ordered in sets, without ordering the flange or cups.

Packing ring material and type of packing is supplied to suit each application. While it is
possible that special, non-standard packing may be encountered in the field, Dresser-Rand currently
supplies only three basic types of packing, based on the pressure application. These are as follows:

Type I. 1750 PSI (12 Mpa) Packing

This type packing is used on 4.75-inch, 6.00-inch, 7.00-inch and 8.00-inch water-cooled cylinders and
on 6.00-inch, 7.00-inch and 8.00-inch gas-cooled cylinders.

1- Zero end gap, cast-iron pressure breaker (P-ring)

4- Sealing single-acting rings, glass - graphite-filled TFE with metallic back-up ring
1- Flange end double-acting packing ring, glass - graphite-filled TFE.

Type II. 1150 PSI (7.9 Mpa) Packing

This type packing is used on 9.50-inch and 10.50-inch water-cooled and gas-cooled cylinders. No P-
ring is used.

4- Sealing single-acting rings, glass - graphite-filled TFE with metallic back-up ring
1- Flange end double-acting packing ring, glass - graphite-filled TFE

Type III. 775 PSI (5.3 Mpa) Packing

This type packing is used on 11.50-inch, 13.00-inch, 15.00-inch, 17.50-inch, 20.50-inch, 23.00-inch and
26.00/26.50-inch water-cooled cylinders and on 11.50-inch, 13.00-inch and 15.00-inch gas-cooled
cylinders. No P-ring is used.

3- Sealing single-acting rings, glass - graphite-filled TFE with metallic back-up ring
1- Flange end double-acting packing ring, glass - graphite-filled TFE

The TFE ring joints are cut tangent to a diameter slightly smaller than the rod size. These joint
surfaces seal, so they must be in good condition. On some rings, the pressure side will have radial
notches. These notches must face toward the pressure when installed. The metallic backup ring is
designed to remove heat from the rod and prevent extrusion of the TFE rings. The backup ring has radial
joints, which butt, when the ring is assembled on the rod, leaving the ring slightly larger than the rod. No
end clearance should exist at the joints, which would permit the ring to pressure-load the rod. The joints
must be smooth and butt squarely to prevent leakage.

The outside edges only of any pair of rings should have approximately 1/16-inch (1.6 mm) radius
and are normally furnished this way. Do not radius the mating (inside) edges of any pair of rings. The
faces of the rings are usually lettered or numbered on each segment of each ring for easy identification
and assembly. These identification letters or numbers must face toward the pressure. The depth of the
cup in each packing flange and the axial width of each packing ring or ring pair should be measured using
depth and outside micrometers, or a straightedge and feelers.

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Maintenance PG-1028-E (HOS)

Figure 4-19. Zero End Gap Pressure Breaker

The pressure breaker, Figure 4-19, is installed in the first packing cup that faces the pressure.
Its purpose is to slow down, or "break", the effects of gas pressure without totally sealing. The type
pressure breaker used is "zero end gap" type design which has zero gap at the joints and a 0.002-0.006
inch (0.05-0.15 mm) clearance on diameter over the rod. This ring has pressure relief cuts in the face
that is towards the pressure. It is important that this newer design is not confused with the old-type
pressure breaker that had a significant end gap at the ring joints.

Both single acting (Figure 4-20) and double acting (Figure 4-21) rings are free to float (move
axially and vertically with the piston rod) in their respective cups.

Figure 4-20. Single-Acting TFE Ring with Metallic Back-Up

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PG-1028-E (HOS) Maintenance

Figure 4-21. Double-Acting Sealing Rings, Tangentially Cut

Clearance should be as listed in Table 4-4. If the measured clearance is outside of the
limits shown, refer the problem to the Dresser-Rand Gas Field Compressors Customer Service
Group Tulsa, OK before remachining either packing rings or flange cups.

Table 4-4. Packing Clearances

Ring Axial Clearance Axial Clearance Maximum

Material Cast-Iron Cups Steel Cups Radial Clearance
Inch (mm) Inch (mm) Inch (mm)

Filled TFE 0.011 - 0.015 0.020 - 0.024 0.060

(0.28 - 0.38) (0.51 - 0.61) (1.5)

NOTE
The total radial clearance for the metallic back-up rings used with 16A11
single-acting sealing rings should be 0.010-inch (0.25 mm) maximum
without regard to piston rod diameter.

4-13.2. Packing Gasket

Next in importance to the packing rings is the end gasket. Keep gasket surfaces clean and dry.
No matter how perfectly the packing rings seal around the rod, if the end gasket leaks, the pressure forces
the gas to bypass the rings by leaking around the case into the area between the case and the bore and
then to the atmosphere. The packing flange stud nuts must be tightened evenly to ensure a proper seal
of the gasket at the front end of the packing and to ensure closure of the ground joints on the packing.
The packing rings have been given sufficient side clearance so that normal tightening will not pinch the
rings in their grooves.

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Maintenance PG-1028-E (HOS)

After a short period of operation, soft gaskets should be retightened to take up any additional
deformation caused by the working pressure on the packing.

Spare gaskets should be carried in stock and a new gasket installed each time a packing is
disassembled. This prevents forced shutdowns due to leaks occurring after the cylinder is pressurized.

4-13.3. Packing Cases

The cases are made up of cup-like sections. The joints are ground or lapped. Each contacting
surface must be cleaned of dirt and lint and inspected for scratches and burrs before assembling. The
mating surfaces must occasionally be lapped to maintain a tight seal. To do this, lap the cup to a surface
plate after making sure that the surface plate is in good condition. On packing assemblies that are
designed for internal water cooling, small O-rings are used between the cups. See the instructions, which
follow concerning proper installation of these seal rings.

4-13.4. Installing the Packing

The packing should not be installed until the unit is ready to start, since the rings may corrode
the piston rod where they rest on it. The cup sections are held together by tie rods which are screwed into
tapped holes in the nose piece (end cup) of the packing, and are held on the outer end by nuts on the face
of the flange. Become acquainted with the construction of the packing you are about to install. Learn how
it will go into the cylinder, and know the proper location of each cup and ring set. Note the location of vent
cups, oil cups and cooling water cups and gaskets, if used. Pay particular attention to the rings located
in each cup and know how they are assembled and which side faces the pressure. Before any packing
is taken apart, it is recommended that each cup and the flange be stamped in numerical sequence so they
can be reassembled in their original positions.

1. If the compressor piston and rod have previously been installed in the cylinder, remove the
locking dowel (if so fitted), disconnect the piston rod from the crosshead and move the
crosshead away from the rod. If the oil scraper packing was previously installed, disassemble
and remove the scraper rings as described in instructions, which follow.

All precautionary measures specified by the Occupational Safety

and Health Act of 1970 (OSHA) must be complied with when
storing, handling, or using solvents.

2. After marking the outside of the packing cups (on a non-critical surface) in numerical sequence
as discussed previously, disassemble the packing cups and rings; be careful not to lose any
gaskets, ring segments or garter springs. Lay the packing components on a clean surface in
the order removed. Clean all parts with a safety solvent. Be sure that there is no dirt, chips or
other foreign matter in the oil or vent passages that can be carried into the packing during
operation or obstruct the flow of oil into the packing.

3. Thoroughly clean the piston rod and packing cavity in the frame end of the cylinder. Make
certain that the piston rod is not scratched, nicked or otherwise marred where it will operate in
the packing.

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PG-1028-E (HOS) Maintenance

4. On older cylinders where an external packing cooling sleeve is used, the sleeve should be
removed, inspected and flushed out whenever the packing is being serviced. The sleeve is
removed as follows:

A. Remove the packing following the reverse of the installation procedure.

B. Disconnect the cooling water piping and remove the two clamps which attach the sleeve to
the cylinder.

C. The sleeve can now be removed and inspected.

D. Flush the sleeve with clean water for several minutes. Dry the sleeve and replace it into the
cylinder.

E. Reconnect the cooling water piping and turn on the cooling water. Check for leaks.

5. The packing cups should be disassembled and the rings taken apart when the packing is
installed (this also applies when the packing is being removed or when it is necessary to pull the
piston rod). It is not a recommended practice to attempt to slide the packing rings over the end
of the piston rod, unless an entering sleeve is used, because the rod threads can nick or
otherwise damage the rings.

6. New packings come assembled with the correct type of rings in their proper grooves and in
proper relation to one another. All rings must be reassembled in their original positions or they
will not function correctly. Refer to the previous instructions in Paragraph 4-13.

7. Slide the end cup (or nose cone) over the end of the piston rod and assemble its packing ring(s)
over the rod by first fastening the garter spring around the rod and then inserting the ring
segments, one at a time, under the spring. Be sure the rings are assembled exactly in their
original positions with all segments in correct relation to each other and with the correct side
facing the pressure. Be sure dowels and dowel holes are lined up between ring pairs; then,
lubricate the rings generously with oil and slide them into their cups.

8. Continue with each packing cup and ring arrangement in sequence, sliding the cups together
over the tie rods. Slide the flange into position and tighten the tie rod nuts. Be certain all of the
cups are evenly centered around the piston rod.

NOTE
For packings having O-rings between the cups, as is the case with
water-cooled packing assemblies, be sure that the O-rings are correctly
located in their grooves before tightening the tie rod nuts. A thin coating of
grease on the O-rings aids in keeping them in the grooves prior to
tightening the assembly. As the O-rings can be easily damaged, it is a
good practice to carry sufficient spare sets and to replace them each time
the packing is dismantled.

9. Make certain the gasket on the end cup is in good condition and clean; then, oil the rod (if
lubricated packing is being used) and slide the packing assembly into place in the frame end of
the cylinder. Center the packing with respect to the piston rod and then assemble and tighten
the packing flange stud nuts evenly to assure the end gasket is evenly compressed. If this
gasket is not properly seated, leakage can occur around the end cup.

10. Recheck the gap between the piston rod and packing flange at several points around the
circumference of the rod; the possibility of the rod dropping slightly because of piston ring wear
must be given due consideration.

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Maintenance PG-1028-E (HOS)

Should the rod contact the packing flange or cups during

operation, damage to the rod is almost certain to result.

11. The packing rings are free to float in their cups (assuming they have proper side clearance)
regardless of stud tightening forces and the packing cups are designed to transmit uniform stud
pressure through the joints without deflection. Like any gasketed joints, the packing stud nuts
must be periodically tightened.

12. Install the oil scraper rings per Paragraph 4-14 and connect the piston rod at the crosshead per
Paragraph 4-10.

13. When the machine is started, oil the packing rings and piston rod generously until the rings wear
in. The packing may leak slightly while creating a satisfactory fit with the rod; however, the
packing should not blow oil profusely during break-in. Should severe leakage (blowing) occur,
the compressor must be immediately shut down and the packing dismantled to determine the
cause. Abnormal leakage can also be caused by dirt or chips cutting the rings, an improper
grade (or too much) lubricating oil in the sump, or inadequate side clearance of the rings in their
cups.

4-13.5. Packing Operation and Maintenance

After installing a new packing or set of renewal rings, start the compressor up with no load in the
same manner as breaking in a new unit. Feed two or three times the usual amount of oil to the packing
while it is wearing in. The oil that works out along the rod, or through the packing vent, should be checked
frequently. If the oil remains clear, it is a good indication that the packing is wearing in properly. During
break-in of higher pressure packings (over 1000 PSIG or 6900 kPa), the oil normally will become darker
and show some wear particles; however, the oil should not become black. Should the oil become black
(indicating premature wear), or should blow-by be excessive, the cause may be a too-rapid increase in
the load or pressure on the packing. Often, by reducing the load slightly and running for a short time, the
oil will clear up to the point where the load can be increased again.

Because there are many variables (such as temperature, pressure, type of lubricant,
material, gases being handled, etc.), there are no hard and fast rules for allowable rate of increase
in pressure while breaking in a new packing. With filled Teflon® packing rings, the break-in time is
normally much shorter than with metallic rings. Often, the break-in time with this ring material is a
matter of minutes, and the load may be increased rapidly. Watch piston rod and packing
temperatures carefully to avoid excessive heat buildup in the packing during rapid break-in.

During operation, the packing leakage may become progressively worse over a period of
time. This indicates the packing is faulty and it should be inspected as soon as possible. Operation
of the unit with excessive packing leakage will result in abnormal wear of the packing rings or piston
rods.

4-13.6. Inspecting the Packing

Periodically, the packing should be removed for cleaning and inspection. In cleaning
packing rings, wire edges may be found around the bore of the rings if considerable wear has
occurred. Remove these wire edges with a file. However, do not break corners where any two
surfaces of a packing ring match. In removing the packing for cleaning, take care to avoid damage
to the gasket or any surfaces that make pressure tight joints. Do not use a chisel or sharp instrument
to open any joint (between packing cups) and do not disturb the bore of the rings except to remove
the wire edges. Wash the springs clean of carbon and sludge. If they have lost their tension, replace
them. Observe the clearance between the ends of the segments of the wearing rings. As long as
some clearance is present, the rings may be used. However, when the rings have worn to the point
where the ends butt, they should be replaced.

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PG-1028-E (HOS) Maintenance

4-13.7. Replacing the Packing

In replacing the piston rod packing, take care to tighten the flange nuts evenly, while
checking with feelers in the space between the rod and the packing flange. Make sure the clearance
is equal all the way around the rod. Make sure the rod packing flange does not touch the piston rod,
as the rod and the packing can be seriously damaged. When ordering parts or inquiring for additional
information regarding packing, give the serial number stamped on the end of the case, along with the
cylinder size and serial number.

4-14. PISTON ROD OIL SCRAPER RINGS

A stuffer is bolted to the frame end of the cylinder yoke; it contains a set of oil scraper rings,
with flange, and prevents frame oil from being carried out of the frame along the piston rod. The rings
also reduce the possibility of cylinder gases or cylinder lubricating oil entering the frame and possibly
contaminating the frame lubricating oil.

Current stuffer and oil scraper ring arrangements are illustrated in Figure 4-22. Some
distance pieces are equipped with a set of double-acting (Type BD) seal rings located in the gland
closest to the cylinder. For those applications requiring a purged distance piece (2) standard sets of
(3) 3RWS rings are used. This helps to seal the distance piece.

Metallic oil scraper rings must be disassembled and the rings

taken apart when they are being removed or installed. Do not
attempt to slide the rings over the end of the piston rod
because the threads can nick the rings and permanently
damage them.

Before starting for the first time, wipe out the stuffers and clean the piston rods. Take care
to keep a smooth bearing on the rod, as nicks or dents in the rings or scores on the rod will prevent
a tight seal.

Oil scraper rings normally require little attention except for periodic cleaning, as determined
by the operating conditions. Inspect the rings for wear by checking the end clearance after slipping
the rings over a mandrel the same diameter as the piston rod. When the rings have worn sufficiently
to butt the ends, it is best to replace them.

Renewal oil scraper rings are furnished in sets. The ring segments are usually numbered
and adjacent segments must match. With the current design shown in Figure 4-22, the radially cut
grooves on the scraper rings should face the cylinder and the flat faces of the rings should face the
crosshead. The packing rings can face either direction.

Use the following steps to install replacement oil scraper rings in the unit:

1. Unscrew the piston rod from the crosshead, back the crosshead away from the rod and
remove the stuffer from the yoke.

All precautionary measures specified by the Occupational

Safety and Health Act of 1970 (OSHA) must be complied with
when storing, handling, or using solvents.

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Maintenance PG-1028-E (HOS)

Figure 4-22. Piston Rod Oil Scraper Packing

2. Disassemble the rings and lay the parts on a clean surface. Note the identification marking
on each segment of each ring. Clean the parts thoroughly with a safety solvent.

3. Make certain that the piston rod is clean and free of nicks or burrs; if found, these should
be carefully removed with a file and the rod polished using a fine emery cloth.

4. Clean the stuffer thoroughly and install it in the yoke. Be sure a gasket is placed between
the stuffer and yoke mounting surfaces. Bolt the stuffer securely in place.

5. Place the ring flange on the piston rod and then assemble the oil scraper rings over the rod;
the flat sides of the rings face the crosshead. First fasten the garter springs around the rod,
then place the ring segments under the springs, making sure to match the segments
according to the letters or numbers stamped on them.

6. Move the flange into position over the rings. The flange is designed to provide 0.002 to
0.004 inch (0.05 to 0.10 mm) total end clearance for the scraper rings. Check this clearance
before securing the flange. If the clearance is insufficient for the rings to "float" on the rod,
they will not function properly. Make sure the drain holes in the flange are at the bottom,
then attach the flange to the stuffer; tighten the flange capscrews evenly. Check to be sure
the flange is centered around the piston rod; avoid any possibility of the rod touching the
flange or stuffer as the rod, flange and rings may be damaged if this happens.

7. Liberally oil the scraper rings before starting the compressor when new rings have been
installed. The oil from within the frame will then keep the rings lubricated during normal
operation and subsequent starts.

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Compressor cylinders must be depressurized to atmospheric

pressure before barring. Failure to depressurize the compressor
cylinders prior to barring may result in unexpected rollover that
can cause personal injury.

Before barring the unit over, the operator must ensure that the
driver will not start-either by grounding the ignition and closing
the fuel gas valve on engine driven units-or by ensuring that the
power cannot be turned on with electric motor driven units.
Failure to heed this WARNING can result in a fatal accident if the
unit rolls over unexpectedly.

SERVICE NOTE
When the compressor is shut down for a long period and the piston
rod packing and the oil scraper rings are not removed, bar over the
compressor once every 24 hours to distribute any oil held in the
packing and to prevent localized corrosion of the rods.

4-15. BALANCE CYLINDER (If Used)

Figure 4-23. Balance Cylinder

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A balance cylinder (Figure 4-23) is supplied on those compressors where less than a full
complement of cylinders is required (for example, a four-throw unit using only three cylinders). The
balance cylinder mounts directly on the frame extension and utilizes a piston rod and balance piston that
are similar to a conventional compressor piston and rod for disassembly and assembly purposes.

To remove the balance cylinder, disconnect lube supply and drain piping. Take out the
capscrews that hold the end cover in place, then remove the cover to expose the cylinder bore. Unscrew
the balance piston rod from the crosshead and pull the piston and rod out through the bore. Take off the
cylinder to frame stud nuts and remove the cylinder. Replacement of the balance cylinder is the reverse
of the removal steps.

4-16. COMPRESSOR VALVES

Figure 4-24. Typical "PF" Inlet Valve With Metal Valve Plate

The "PF" valve, a high speed plate valve of Dresser-Rand design, is used as the standard valve
in HOS cylinders. These instructions cover only the PF valve; if other valves are used, supplemental
instructions must be consulted. The valve is furnished in two styles; one style has a metal valve plate with
two damping plates that is assembled as shown in Figures 4-24 and 4-25. The other style has a plastic
valve plate with one damping plate as shown in Figures 4-26 and 4-27. Both valve styles contain a seat,
stop plate, damping plate(s), ring guide, damping springs, closing springs and valve plate. The valve is
held together by a center stud and nut arrangement. A gasket is used under the stop plate on inlet valves
and the valve seat on discharge valves where they seat in the cylinder gas passage, preventing gas
leakage past the valve.

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4-16.1. Description of Operation

A compressor valve acts as a check valve in the inlet and discharge passages to the cylinder
bore. The inlet valve allows the gas to enter the cylinder on the suction stroke and then closes to prevent
back flow of the gas into the inlet gas passage on the discharge stroke. The discharge valve opens to
allow gas to leave the cylinder on the discharge stroke and then closes to prevent the gas in the discharge
passage from re-entering the cylinder on the suction stroke.

Compressor valves are opened by differential pressure across the valve. The damping and
valve plates move off their seat and are guided into the stop plate recess by the guide ring when opening.
Damping springs and damping plate(s) prevent slamming of the valve plate against the valve stop plate
when the valve opens. As the piston nears the end of its stroke, pressure across the valve starts to
equalize. At this point, the springs start to move the damping plate(s) away from stop plate and the valve
plate toward the seat. This is done to prevent the parts from slamming against the seat as the piston
changes its direction. If slamming were allowed to happen, severe damage would result to the valve. A
combination of spring load and differential pressure will hold the inlet valve closed on the discharge stroke
and the discharge valve closed on the suction stroke.

Figure 4-25. Typical "PF" Discharge Valve with Metal Valve Plate

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4-16.2. Valve Maintenance Recommendations

1. To obtain maximum efficiency from a compressor cylinder, the inlet and discharge valves must
be clean and tight. The valves and cylinder gas passages must be periodically examined and
thoroughly cleaned wherever dirt is evident. Operating experience will dictate both the length
of time between valve inspections and the valve maintenance cycle. At start-up, check the
valves during break-in at least once, then one week after start-up, or more frequently if the gas
being handled is known to be dirty. If the valves are found to be particularly dirty, locate and
eliminate the cause. See item 2 for a suggested MINIMUM maintenance schedule.

2. We recommend the following valve inspection and maintenance schedule as a MINIMUM:

· Prior to initial start-up and EVERY TIME valve or unloader maintenance is performed.
· At least ONCE during the break-in period.
· One week after start-up (including after valve or unloader maintenance or after
overhauls).
· Once a month thereafter for three months.
· Once every three months thereafter for a full year.
· Once each year thereafter, or as conditions dictate.

3. The center setscrews used with unloaders, and all other valve fasteners, particularly the stud
nuts that secure the valve cover, MUST be properly tightened to the torque values given in this
Chapter 5 of the form. DO NOT USE AN IMPACT WRENCH ON VALVE FASTENERS.

Figure 4-26. Typical "PF" Inlet Valve with Plastic Valve Plate

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4. Never attempt to tighten fasteners on a compressor cylinder, including the valve or unloader
setscrews, while the compressor is running or with the cylinder pressurized. This practice is
extremely hazardous, and can result in a life-threatening accident should a stud or bolt break
during the tightening process.

5. Always make sure there is no residual gas pressure in the cylinder bore or passages before
removing valve or unloader covers.

6. Venting of hazardous gases must be performed in accordance with established safety practices
at the installation site.

7. The importance of keeping accurate valve maintenance records cannot be overemphasized.

Record all valve failures, the cylinder and location on that cylinder, the type of damage and any
other data that may be helpful in finding a trend.

Figure 4-27. Typical "PF" Discharge Valve with Plastic Valve Plate

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8. To eliminate dirt found in the compressor valves, a suitable intake filter or scrubber should be
installed and properly maintained. Experience will dictate the filter or scrubber maintenance
cycle.

9. Cylinder lube oil in excess of the amount required to properly lubricate the cylinder bore and
valves is detrimental to valve life. The oil feed rate of the cylinder lubricator (with pump-to-point
systems) can be reduced to eliminate excess lubrication based on the condition of the cylinder
gas passages, valves and cylinder bore. On inspection, the valve should have a greasy
appearance, but not have oil droplets showing. Shortened valve life often results from using an
oil with improper viscosity or poor quality, or delivery at the improper feed rate.
Recommendations for selecting a cylinder lubricating oil are given in CHAPTER 2,
LUBRICATION; these recommendations should be reviewed with a reputable oil supplier to
determine the best oil for a particular application.

10. All compressor valves should be inspected for leakage (which may result in abnormally high
temperatures). In addition, the cylinder cooling water system (if used) should be examined for
general cleanliness and obstructions to ensure the proper quantity of coolant at the required
temperature is available. Periodic cleaning of the cylinder water passages may be required.

11. Liquids in the gas stream can wash or dilute cylinder bore lubricating oils, causing rapid wear
and early failure of the valve (and cylinder) parts. A slug of liquid can cause a failure of the valve
channels or plates or, in severe cases, the valve seat. Some "wetness" in the gas stream often
can be dealt with by the selection of a suitable lubricating oil. With very wet applications,
adequate separators should be located close to the cylinders. Also, it is important that the
cylinder inlet piping be arranged without low spots where liquid can accumulate.

12. Mark or tag valves with the following minimum information as they are being removed from the
cylinder. This information will be useful when troubleshooting valve problems and will help
prevent the intermixing of valve parts, when more than one valve is disassembled.

· Compressor Serial Number....

· Cylinder Serial Number....

· Inlet or Discharge Valve....

· Cylinder location - Frame or Outer end....

· Hours of Operation.

13. The reconditioning procedures given in these instructions are valid only when genuine Dresser-
Rand parts are used.

14. Carefully check the part number of new parts against those in the parts list.

15. Never change valve lift.

16. The valve seat may be reconditioned following instructions later in this chapter.

17. A new valve plate must be used if the valve seat has been reconditioned.

18. Never turn the valve or damping plate(s) over; always replace them and recondition the seat.

19. When handling assemblies or parts, take care not to contaminate the items.

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Observe the safety precautions (Paragraph 4-2) before attempting to

remove a compressor valve. It is particularly important that ALL
PRESSURE is released from the cylinder passages and piping before
pulling valve covers. CAREFULLY CRACKING OPEN drain valves on
inlet and discharge manifolds is a good method to determine if any
pressure exists in the cylinder bore, cylinder passages and piping;
INJURY TO PERSONNEL CAN OCCUR IF THESE PRECAUTIONS ARE
NOT STRICTLY OBSERVED. Whenever compressor valves are
removed, it is extremely important that the inlet and discharge valves
be correctly reinstalled in the cylinder. Incorrect assembly can cause
an extremely hazardous condition which can result in severe damage
to the compressor and INJURY OR DEATH TO THE OPERATING
PERSONNEL.

4-16.3. Removing the Valves - O-Ring Valve Cover

The current standard valve cover design used with HOS cylinders is the O-ring cover design,
illustrated in Figure 4-28. Only the O-ring cover design is covered by these instructions.

With the O-ring body seal used on this type valve cover, any pressure
that may be left in the cylinder will not be released when the cover
nuts are loosened, but will remain under the cover trapped by the
O-ring. To prevent the possibility of the valve cover being "blown off"
by residual pressure when the cover nuts are removed, two longer
studs are required to permit the safe removal of the cover. These
studs are either present (they are double-nutted if factory supplied)
or should be fabricated at the site. FAILURE TO OBSERVE THE
FOLLOWING VALVE REMOVAL STEPS CLOSELY CAN RESULT IN
POSSIBLE PROPERTY DAMAGE, INJURY TO THE MAINTENANCE
PERSONNEL OR DEATH.

1. Mark or tag the valves and valve holes as the valves are removed to ensure that they are
returned to their original locations.

2. Locate the two longer studs; these are diametrically opposed across the valve cover bolt pattern.
If such studs are not installed, fabricate two studs and install them (with nuts) 180 degrees apart
before removing or loosening any other stud nuts. Evenly loosen the valve cover stud nuts; note
that two nuts are used on the two longer factory-installed studs used with each valve cover.

3. Remove only those nuts on the short valve cover studs. At this point, the nuts on the long studs
are securing the valve cover.

4. Equally loosen the nuts on the long studs two turns at a time. As the stud nuts are loosened,
it may be necessary to tighten down the valve cover jackscrews (if equipped) or to carefully pry
under the valve cover to keep the cover in contact with the stud nuts. (This will prevent sudden
loosening or blowing off of the valve cover when the O-ring breaks free of the valve passage,
caused by any residual pressure.) As the O-ring is pulled free of the valve passage, any residual
pressure will be safely vented.

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5. Remove the valve cover.

SERVICE NOTE
A retaining setscrew in the side of the valve cage is used to hold the valve
and cage in a valve hole located in the bottom half of the cylinder.
However, care still must be exercised when removing the valve cover so
that the valve does not fall out should the setscrew not hold.

Figure 4-28. O-Ring Seal Type Valve Cover Arrangement

6. Larger valves have two tapped holes in the discharge seat, or inlet stop plate, on the face toward
the cylinder bore. To simplify valve removal when the valve is located in the bottom half of the
cylinder, first remove the top valve that is located 180 degrees opposite the bottom valve being
removed; then, working through the top valve port, (with the compressor piston must be
positioned so that it does not interfere with this operation) screw a threaded rod into the tapped
hole in the bottom valve. The valve and cage assembly then can be supported from above while
the valve cover and valve is removed.

7. Loosen the retaining setscrew from any valve cage so equipped, then remove the valve cage
and valve from the cylinder. Remove the valve seat gasket that is located under the valve. This
gasket should not be reused; install a new gasket when installing the valve. Most valves are
attached to the valve cage with two capscrews or machinescrews to facilitate handling; remove
these fasteners to separate.

SERVICE NOTE
If the compressor valve is stuck in the cylinder, it can be jarred free by
striking edgewise on the valve crab with a wood block or soft metal bar (to
prevent damage to the cage or valve). Do not use a hammer on the cage.

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PG-1028-E (HOS) Maintenance

4-16.4 Disassembling & Servicing the Valve

Care must be taken when disassembling these valves to ensure that

the damping and valve plate closing springs do not become mixed.
Failure to follow this caution will result in incorrect loading of the
various plates, resulting in premature valve failure. Even when the
valves are of the same type (inlet or discharge) and of the same size,
the components of the various valves must not be mixed. This is
because each valve has established its own wear pattern and sealing
surface which will not function in another valve. Failure to follow this
caution will result in valve leakage and premature valve failure.

1. Place the valve in a valve holder. (Figure 4-29 shows a suggested valve holder.)

If the valve must be held in a vise, do not clamp the valve tightly
enough to cause distortion. Distorting the valve will render it useless.

Figure 4-29. Suggested Valve Holder

2. Remove the stud nut that fastens the valve together. DO NOT allow the stop plate to turn in
relation to the valve seat; to do so may shear the locating pins.

NOTE
The closing and damping springs can be of the same height and wire
diameter (load), but more often they will be of different height and wire
diameter, resulting in different loads.

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3. Very carefully, separate the stop plate and valve seat. Note the position of all valve internals;
do not allow them to become mixed. Remove the closing springs and place them in a separate
location; do the same with the damping springs.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling or using solvents.

4. Clean the parts. (Soaking the valve parts overnight in safety solvent followed by a stiff brushing
or light scraping will aid in the removal of carbon.) Brush the parts with a soft wire brush to
remove deposits, but use a soft bristle brush on all seating surfaces.

5. Rinse the parts in clean solvent; dry thoroughly using clean, dry compressed air.

6. Inspect the valve and damping plate(s) for cracks, nicks, warpage, wear steps, leakage paths
and other signs of defects. On the valve plate there will be annular rings worn in by the valve
seat, these are normal. [Replace the valve plate if the ring depth is greater than 0.010 inch (0.25
mm) on plastic plates OR 0.005 inch (0.13 mm) for metal plates.] Check the rings for uniformity
of contact; any dull or uneven contact is an indication of improper seating. Do not grind or invert
valve plates to obtain a new seating surface; replace them.

7. Examine the valve seat for cracks, nicks, burrs, scoring, steps, leakage paths and other signs
of defects. The valve plate seating area (rings) on the valve seat should be very bright and
evenly polished. Check the rings for uniformity of contact; any dull or uneven contact is an
indication of improper seating.

8. Valve seats can be machined to correct for wear or minor defects to the seating surfaces.
Refacing operations are described in later instructions. Excessively worn or damaged seats must
be replaced.

When rebuilding a valve, always renew the seating surfaces. That is,
provide a new valve plate when a new or reconditioned valve seat is
used. Likewise, when a new valve plate is used a new or refaced
valve seat must be provided. Failure to follow this caution will result
in leakage and early valve failure.

9. Check valve springs for cracks, pits or set (set is determined by measuring free height of a used
spring against a new one). Also, check for weakness by comparing the used spring against a
new one with the same part number.

10. Examine the stop plate for wear and damage.

4-16.5. Refacing Valve Seats

Valve seats which have become worn or damaged can be refaced provided that certain
dimensional limits are not exceeded; these limits are given in subsequent instructions.

On discharge valves, the center stud is screwed into the valve seat. Around the center stud
shank, there is a recess in the seat (see Figure 4-30) which is approximately 0.080 inch (2 mm) larger
in diameter than the shank diameter. This recess permits machining of the valve seat without removing
the center stud. In some machining methods, it may be necessary to remove the center stud.

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PG-1028-E (HOS) Maintenance

1. To remove the center stud, heat the valve to between 500º and 600ºF (260º to 352ºC); remove
the stud while hot.

2. Using Loctite® "Chisel Gasket Remover", spray the residue left by the previously used Loctite®
and wipe it off.

A valve seat can be machined as indicated below without affecting the valve's
performance (see Figure 4-30):

TP-4265-A
Figure 4-30. Valve Seat Rework Dimensions

If the valve's outside diameter is less than 3 inches (76 mm), the seat rib root depth (c) of the
innermost port cannot be less than 0.100 inch (2.54 mm). For valves with an outside diameter larger than
3 inches (76 mm), the rib root depth of the innermost port cannot be less than 0.188 inch (4.78 mm).

The rib root depth (c) of the valve seat must not be machined to
maintain the minimum depth. Do not increase diameter of ports (b).
Machining the rib will weaken the valve seat. Also, be certain that any
facing extends over the entire seating surface.

When facing the valve seat, the land width (s) is to be maintained at 0.025 to 0.050 inch (0.63
to 1.2 mm). If the land width exceeds this value, the mud grooves between ports (b) must be machined
to obtain the original land width. In addition, the depth of the mud grooves (a) should be maintained at
0.031 inch (0.79 mm) and a full radius must be maintained where the mud groove meets the land.
Moreover, a 0.005 to 0.015 inch (0.13 to 0.39 mm) chamfer edge must be maintained on each land.

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4-16.6. Reconditioning the Stop plate

Machining of the stop plate is usually not required during valve overhaul. If an inspection reveals
minor damage to the stop plate, the defective part can be machined provided that certain dimensional
limits are not exceeded; these limits are given in subsequent instructions.

SERVICE NOTE
On suction valves, the center stud is screwed into the stop plate. In order
to machine the counterbore, it may be necessary to remove the center
stud.

TP-4266
Figure 4-31. Stop Plate Rework Dimensions

1. To remove the center stud heat the valve to between 500° and 600°F (260° to 352°C); remove
the stud while hot.

2. Using Loctite® "Chisel Gasket Remover" spray the residue left by the previously used Loctite®
and wipe it off.

3. If the locating pins are damaged, pull them out. If the locating pins cannot be pulled out, cut
them off and drill out the remainder of the pin. Since the locating pins are held in by an
interference fit, care must be taken not to drill the pin hole larger than its original diameter.

The stop plate can be reconditioned provided that the counterbore depth (T) is maintained (see
Figure 4-31). If the counterbore depth is not maintained, the valve lift will be altered. The counterbore
depth is equal to the guide ring height + 0.002 inch / - 0.000 inch (+0.05,-0.0 mm). Furthermore, spring
hole depth must be maintained at original depth "0.010 inch ("0.26 mm), and the maximum removal from
the stop plate is 0.031 inch (0.79 mm).

4-16.7. Assembling the Valve

SERVICE NOTE
When installing the center stud in the stop plate or seat, screw the stud in
only until it is flush with back side of the stop plate or seat. Furthermore,
some center studs have a tapped hole or a longer threaded section on one
side. This side of the center stud does not screw into the seat or stop plate.

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PG-1028-E (HOS) Maintenance

1. If the center stud was removed, apply a light coat of Loctite® primer "T" to the threaded area.
Apply a few drops of Loctite® #272 (item 27240) threadlocker and screw the stud into the valve
seat or stop plate.

2. If removed, reinstall the locating pins.

3. Place the stop plate on a clean, flat surface with the locating pins up.

4. Place the valve springs into the spring holes in the stop plate. Ensure the springs are inserted
into the same holes from which they were removed. (The damping springs must contact the
damping plate(s) and the closing springs must contact the valve plate.) If new springs are being
installed, refer to the parts list for identification.

5. Reinstall the damping plate(s). If the used plate(s) are being installed, ensure that they are the
plate(s) removed from that valve. In valves with a metal valve plate, the damping plate with the
smaller diameter is placed next to the stop plate.

6. Install the valve plate. If the used plate is being reinstalled, ensure that its seating surface
matches the valve seat.

7. Insert the ring guide, with its nose down.

8. Fit the valve seat to the stop plate; orient the locating pins with the holes in the valve seat. Clean
the internal threads of the nut and external threads of the center bolt, then apply anaerobic
adhesive primer to the threads and allow it to dry for 5 minutes. Apply Loctite® #242
threadlocker (two drops only) to the external threads and install the nut finger tight. On discharge
valves, it is necessary to carefully turn the valve over and install the nut.

SERVICE NOTE
Some valves utilize a self-locking nut. It is not necessary to use Loctite®
with this type nut.

9. Place the valve in a holding fixture. A typical fixture is shown in Figure 4-29.

When tightening the center stud nut in Step 10, DO NOT allow the
stop plate to rotate with relation to the valve seat. If this is allowed to
happen, it may shear the locating pins.

10. Torque the center stud nut to 25,000 PSI (172 Mpa) pre-stress, following the tightening
instructions in CHAPTER 5, GENERAL DATA & SPECIFICATIONS.

11. Check for free movement of the valve plate by pushing on it with a piece of plastic or wood that
will not scratch the valve plate.

12. Examine the valve seating surface in the cylinder. If it is marred, proceed as in Paragraph 4-
16.8, Steps 1-A and 1-B.

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4-16.8. Installing the Valves - O-Ring Valve Cover

When removing an inlet valve from a location where an unloading device is being used in
conjunction with the valve as a means of capacity regulation, refer to the applicable unloader instructions
before removing the valve.

Whenever compressor valves are removed, it is extremely important

that the inlet and discharge valves be correctly installed in the
cylinder. Incorrect placement of the inlet and discharge valves in
some cylinders which have no provision for polarization can cause an
extremely hazardous condition. INSTALLING AN INLET VALVE IN A
DISCHARGE VALVE HOLE, OR INSTALLING A DISCHARGE VALVE
UPSIDE DOWN, CAN CAUSE A LIFE-THREATENING EXPLOSION. The
type "PF" valve is always placed in the cylinder with the valve center
bolt and nut located AWAY from the cylinder bore. Fasten the valve
or unloader cage to the valve, when possible, to ensure the valve is
not reversed at installation. IF IN DOUBT as to whether a valve is inlet
or discharge or as to which cylinder holes receive an inlet or
discharge valve, CHECK WITH YOUR SUPERVISOR.

1. Prior to installing the valve, check to see that the seating surfaces on the valve assembly, valve
cover and in the cylinder valve hole are smooth and clean. If any evidence of defective seating
surfaces is found, use the following steps to ensure proper valve installation:

A. Place lapping compound on the gasket seating surface of the valve and place the valve
in the valve hole without using the seat gasket. Lap the valve and valve hole gasket
surfaces to obtain at least 95% contact area, as evidenced by bluing or an equivalent
method.

B. Remove the valve and clean both it and cylinder valve hole thoroughly with soap and
water to remove all traces of the lapping compound. Solvent will not remove the lapping
compound no matter how clean the surface appears to the eye.

2. Install a new valve seat gasket, then install the valve and cage in the cylinder valve hole. This
task is made easier if these parts are fastened together with machinescrews and lockwashers
before installation. Be certain the valve seats firmly on the ledge in the cylinder and rests
squarely on the valve seat gasket.

SERVICE NOTE
Valves and cages must be returned to the same valve holes from which they
were removed. The threaded rod used to facilitate handling large valves, as
described previously in the valve removal procedure, also may be used to
assist in valve and cage installation.

3. On the bottom half of the cylinder, the valve and cage assembly is held in the valve hole by a
retainer, normally a setscrew through the side of the valve cage on this valve design. Install the
setscrew with an Allen wrench to hold the valve and cage in place until the valve cover can be
installed.

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PG-1028-E (HOS) Maintenance

4. Place a new O-ring in the valve cover body groove. A light coat of a silicone lubricant or other
lubricant compatible with the O-ring material and process applied on the O-ring will facilitate its
entry into the cylinder valve hole.

Torquing of the valve cover stud nuts is critical. Under torquing will
result in loss of sealing capacity between the valve seat gasket and
the valve seat and the possible loosening of the valve cover during
operation with attendant process gas release. Over torquing will
result in excessive stresses and loads being imparted to the valve,
valve cage and cylinder seating ledge. It is imperative that when
using the "Tightening Requirements" instructions in CHAPTER 5,
GENERAL DATA & SPECIFICATIONS, the proper prestress column in
the chart is selected as follows: find the maximum allowable working
pressure (MAWP) as stamped on the cylinder nameplate and compare
the pressure to those listed to obtain the correct pre-stress for the
fastener. Go to the column headers in the torque table; then move
down the column to the correct fastener size to obtain the torque.

5. Place the valve cover over the valve hole. Watch the cover O-ring as it enters the valve hole
to be sure it is not rolled out of its groove. Install the stud nuts.

Never tighten the valve cover stud nuts while the compressor is in
operation or pressure exists within the cylinder. A life-threatening
release of gas or explosion can occur if a stud breaks during the
tightening operation.

6. Tighten the valve cover stud nuts alternately across the bolt circle to ensure that the cover is
drawn down squarely. We require that this tightening progress in stages rather than to the full
torque on the initial tightening. The required torques are listed in the in CHAPTER 5, GENERAL
DATA & SPECIFICATIONS.

7. After all of the valves are installed, bar the compressor through at least one complete revolution
to be certain there is no interference between moving parts.

8. The compressor now may be started in the normal manner.

9. After the cylinder has reached operating temperature and pressure, shut down the compressor
and relieve all pressure in the cylinders. Check the tightness of the valve cover stud nuts.
Torque the valve cover stud nuts as described previously.

Use extreme caution when checking the valve covers. The discharge
valve cover can experience temperatures in excess of 250°F (121°C).
Touching a valve cover with an unprotected hand can cause severe
burns. We recommend the use of a contact thermometer for checking
temperature and a stethoscope for checking noises.

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10. At regular and frequent intervals (as established by operating experience) check the valve covers
for looseness by using a stethoscope on the valve cover to listen for pounding or knocking of
the valve cage against the cover while the compressor is operating. Any pounding or knocking
indicates that the valve is loose. A loose valve may break apart and drop into the cylinder bore,
causing serious damage to the compressor.

4-17. REGULATION DEVICES

Regulation devices can be of two basic types: the inlet valve unloader or the clearance pocket
(either fixed volume or variable volume). Instructions for both basic types of device follow. These
instructions cover the basic, current type regulation devices. Some design differences are to be
expected due to operating requirements and these variants will undoubtedly be encountered in the field
from time to time. Refer any questions regarding unloaders or clearance pockets to your nearest Dresser-
Rand service representative.

Regulation devices when activated or adjusted affect the

performance of the compressor. Unloading sequences not initially
approved or reviewed can lead to overloads, non-reversal,
overheating, and/or valve reliability problems. Consult with a
Dresser-Rand representative if such unloading sequences have
not been approved.

An unloader is used on a compressor cylinder inlet valve to render the valve inoperative as a
way of unloading the cylinder for starting, or to control capacity of the compressor during operation. A
typical inlet valve unloader, mounted on the standard O-ring cover, is shown in Figure 4-32. Some later
unloaders have the plunger attached directly to the push rod and no return spring is used.

This unloader is "direct acting"; that is, operating pressure is applied to the top of the actuating
piston to unload the end of the cylinder containing an unloader. (Reverse-acting unloaders also are
available from Dresser-Rand.) In its normal position (when there is no operating pressure applied to the
top of the actuating piston) the piston spring located under the actuating piston forces the piston and
piston rod upwards; the plunger return spring moves the plunger assembly away from the valve plates.
With pressure applied to the top of the actuating piston, the piston spring and plunger return spring are
compressed allowing the plunger legs to hold the valve plates away from the valve seat. With the inlet
valve being held open by the unloader, the gas admitted to the compressor cylinder on the suction stroke
passes freely back through the open inlet valve on the discharge stroke without being compressed. An
indicator is fitted to the underside of the actuating piston. When the unloader is actuated (cylinder end
unloaded) the pin will protrude from the clearance hole in the lower housing cover. When the unloader
is in its normal position (cylinder end loaded) the indicator pin is retracted.

Clearance pockets (Paragraphs 4-17.2 and 4-17.3) are used on a compressor cylinder to add
either a fixed volume, or a volume that is variable, to the cylinder's normal clearance volume. The pocket
reduces the cylinder discharge capacity when it is in its normal deactivated (open) position. Fixed volume
clearance pockets are operated by pneumatic pressure from an external source. Variable volume
pockets are generally operated manually by means of a handwheel or wrench, and may be
adjusted ONLY when the machine is shut down.

With a fixed volume, pneumatically-operated pocket, when operating pressure is applied to the
top of the actuating piston the valve is forced closed, increasing the cylinder discharge capacity. In its
normal position, with no operating pressure applied to the actuating piston, the clearance valve is held
in the open position by the return spring. A variable volume pocket is positioned by turning the piston rod
(to which is attached a piston riding in a cylinder) in a clockwise direction to reduce volume or a
counterclockwise direction to increase volume.

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PG-1028-E (HOS) Maintenance

In its open position, the clearance pocket adds the volume of the clearance pocket to the end of
the cylinder in which it is installed. By adding volume to a cylinder end, a reduced quantity of gas is
discharged during the compression stroke because part of the gas being compressed is passed into the
added volume of the pocket instead of out through the discharge valves. On the expansion portion of the
stroke, the gas in the added volume pocket expands into the cylinder. As with the inlet valve unloader,
an indicator rod is extended with pneumatic pockets when the clearance valve is in the open (volume
added) position. When the device is actuated, closing the clearance pocket valve (no volume added), the
indicator rod is retracted. Manual pockets generally are equipped with some type of scale to allow
determination of how much of the pocket is open.

4-17.1. Inlet Valve Unloaders

The inlet valve unloader is operated by pneumatic pressure applied to the top of an actuating
piston. The actuating piston is located outside of the cylinder inlet passage in a separate housing, as
shown in Figure 4-32, which is mounted on the setscrew adapter as shown in the illustration. The
setscrew adapter is hollow so that actuating piston motion can be transmitted by the piston rod via a
pushrod to a plunger mechanism located inside the valve cage. The plunger utilizes "legs" to force the
valve plates off the valve seat to mechanically hold the inlet valve open.

An O-ring seal is installed around the actuating piston to seal against the leakage of operating pressure
past the piston. Also, an O-ring and an O-ring/backup ring combination is installed on the piston rod to
prevent process gas leakage past the rod. A vent is provided in the setscrew adapter, which prevents
pressure buildup between the O-ring and O-ring/backup ring combination.

The internal components of the unloader assembly are held in the valve hole by the O-ring-type
valve cover that presses against the valve cage. The internals consist of the valve cage, the plunger
assembly, the return spring, the extension bolt, and the inlet valve. Some later models have the pushrod
attached to the plunger and no plunger return spring is used. With these designs, the piston return spring
pulls the pushrod and plunger away from the valve plates when operating pressure is released.

If toxic, flammable, or narcotic gas is being compressed, observe

applicable safety precautions.

A. Control and Vent Piping

Operating pressure is applied to a 1/4-inch NPT tapped hole provided in the piston housing
cover. Drawings are furnished to show the arrangement of factory supplied piping and controls.
Recommended piping arrangements are usually furnished when the piping is being done by others.

The vent opening in the setscrew adapter must always be left open to
assure safe and effective operation of the unloader. When the
process gas is toxic, flammable, or in any other way objectionable in
the compressor building, the vent must be piped so that any leakage
can be carried away. Vent tubing must not be less than 3/8-inch
(9.5 mm) O.D. and, if combined with other vent systems, there must
not be any back pressure or vacuum in this piping.

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Maintenance PG-1028-E (HOS)

TP-4524

Figure 4-32. Inlet Valve Unloader with O-Ring Valve Cover

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PG-1028-E (HOS) Maintenance

B. Unloader Cleanliness
1. The inlet valve unloader must be clean and tight to operate satisfactorily. The unloader should
be examined during normally scheduled valve maintenance and/or inspection cycles. O-rings
used in the unloader must be replaced during these maintenance/ inspection cycles. Always
lubricate new O-rings. The use of a silicone type lubricant, or other lubricant, that is compatible
with the O-ring material and the process is recommended.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

2. To thoroughly clean the unloader assembly, it must be completely dismantled. Soaking the
unloader parts in a safety solvent, followed by a stiff brushing or light scraping, will aid in removal
of foreign material. Brush the parts carefully with a soft wire brush, but use a bristle brush for
all seating surfaces. Blow away all loose particles with compressed air. All components must
be thoroughly dried before reassembly.

C. Removing Operator, Unloader and Valve Assembly

Before performing any service on the unloader, including removal of

the upper housing cover for inspection purposes, be certain there is
no pressure in the compressor cylinder bore or passages.

1. Shut off and vent the operating pressure to the unloader.

2. Depressurize and vent the compressor cylinder.

3. Disconnect the vent and operating pressure lines.

With the O-ring body seal used on this type valve cover, any pressure
that may be left in the cylinder will not be released when the cover
nuts are loosened, but will remain under the cover trapped by the
O-ring. To prevent the possibility of the valve cover being "blown off"
by residual pressure when the cover nuts are removed, two longer
studs are required to permit the safe removal of the cover. These
studs are either present (they are double-nutted if factory supplied)
or should be fabricated at the site. FAILURE TO OBSERVE THE
FOLLOWING VALVE REMOVAL STEPS CLOSELY CAN RESULT IN
POSSIBLE PROPERTY DAMAGE, INJURY TO THE MAINTENANCE
PERSONNEL OR DEATH.

4. Evenly loosen the valve cover stud nuts; note that two nuts are used on the two longer studs
used with each valve cover.

5. Remove only those nuts on the short valve cover studs.

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6. Back off the nuts on the long studs evenly two turns at a time. As the stud nuts are loosened,
it may be necessary to tighten down the cylinder cover jackscrews (if installed) or pry under the
valve cover to keep the cover in contact with the stud nuts. (This will prevent sudden loosening
of the valve cover when the O-ring breaks free of the valve passage, caused by any pressure
present.) As the O-ring is pulled from the valve passage, any residual pressure will be safely
vented from under the cover.

7. Remove the operator and the valve cover.

8. Loosen the cage setscrew, then pull the valve cage assembly, the unloader assembly and the
inlet valve assembly from the valve hole.

NOTE
If two or more unloaders are removed; mark each one to be sure it is
reinstalled into the same valve passage from which it was removed.

D. Disassembling Cage and Plunger

SERVICE NOTE
Some valve cages may be attached to the valve with two small
machinescrews. If so, first remove the machinescrews.

1. Lift the valve cage off the inlet valve.

2. Remove the plunger assembly and the return spring (if present).

3. Thoroughly clean all pieces.

4. Service the Type PF inlet valve following the instructions in Paragraph 4-16 of this manual.

SERVICE NOTE
With some valves, it may be necessary to remove an extension bolt which
is attached to the valve center stud in order to disassemble the valve.
When unscrewing the extension bolt, be careful not to mar the surface of
the bolt.

E. Installing Valve, Cage and Plunger

1. If the extension bolt has been removed, reassemble it to the valve first. Do this by cleaning the
threads (internal and external), and applying primer for anaerobic adhesive. Allow the primer
to dry for 5 minutes. Apply Loctite® #242 removable threadlocker (35272657) or equivalent.
Screw the extension bolt into the valve.

2. Place the plunger return spring (if present) on the inlet valve over the extension bolt.

3. Set the plunger assembly over the extension bolt and onto the plunger; align the legs with the
plates in the valve.

4. Lower the valve cage onto the inlet valve. Attach capscrew, if applicable.

5. Check for free movement of the plunger assembly.

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PG-1028-E (HOS) Maintenance

6. Install a new valve seat gasket. Place the assembled inlet valve, valve cage, and plunger
assembly into the cylinder valve hole. Secure the cage with the setscrew.

F. Disassembling Unloader Cover and Operator

1. Loosen the locknut on the setscrew adapter.

2. Separate the unloader cover from the operator and setscrew adapter.

Do not allow the actuating piston to rotate in the piston housing.

Parts will be damaged by rotation.

3. Unscrew the pushrod from the bottom of the actuating piston rod by using the hole at the base
of the piston rod to secure the operator.

4. Remove and discard the Threadseal™, then remove the washer.

5. Separate the setscrew adapter from the operator. The setscrew adapter should have some drag
on it, caused by the piston rod O-rings.

6. Loosen the six piston housing cover bolts gradually, allowing the housing covers to separate
from the piston housing and relieve the spring pressure.

7. Remove the covers and gaskets. Clean the threads of the lower piston housing cover. Pull the
piston spring, actuating piston with indicator and piston rod out of the piston housing. Remove
and discard the piston and piston rod O-rings, and the backup ring.

8. The piston rod may be unscrewed from the actuating piston, if necessary, taking care not to mar
the surfaces of the piston rod and piston. Use the two tapped holes on the top of the piston and
the hole at the base of the piston rod to hold the piston and piston rod while turning.

SERVICE NOTE
It is good maintenance practice to replace all O-rings, seals and gaskets
during reassembly. Always lubricate the O-rings with a silicone lubricant
or other lubricant compatible with the O-ring and process.

9. The indicator may be unscrewed from the actuating piston, taking care not to mar the surface
of the piston.

10. If the piston rod was removed, clean the threads of the piston rod and the piston, then apply
aerobic adhesive primer and allow it to dry for five minutes. Apply Loctite® #242 threadlocker
(two drops) to the piston rod threads. Attach the piston rod to the piston.

11. Renew the O-rings and backup ring on the piston rod. (Note the order in which they are placed.)
A single O-ring is installed in the top groove. Install the backup ring first and then an O-ring in
the bottom groove. Make sure the O-rings and backup ring are lubricated with a lubricant
compatible with the process gas.

12. Install a new piston O-ring and lubricate it with O-ring lubricant.

13. Insert the piston spring, actuating piston, and piston rod into the piston housing. Be sure that
the O-ring is not rolled out of its groove when installing the actuating piston.

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14. Clean the threads (both internal and external) of the piston housing cover bolts, then apply
anaerobic adhesive primer and allow it to dry for five minutes. Apply Loctite® #242 threadlocker
(two drops) to each bolt and with new piston housing cover gaskets in place, secure the piston
housing covers to the piston housing. Tighten the housing cover bolts squarely by tightening
gradually, in several stages, working back and forth across the bolt circle.

15. If the indicator was removed, clean the threads (internal and external) of the indicator, then apply
anaerobic adhesive primer and allow to dry for five minutes. Apply Loctite® #242 threadlocker
(two drops) to the indicator threads. Screw the indicator into the piston until the bottom of the
indicator is flush with the lower piston housing cover.

16. Ensure that the setscrew adapter vent passage is clear.

17. Clean the threads of the setscrew adapter, then apply aerobic adhesive primer and allow to dry
for five minutes. Apply Loctite® #242 (two drops) to the setscrew adapter threads. Slide the
piston rod through the setscrew adapter and screw the setscrew adapter into the lower piston
housing cover.

18. Ensure that the setscrew adapter has the locknut, beveled washer and Threadseal™ in place
and in proper sequence. Insert the setscrew adapter into the unloader cover approximately 0.5
inch (12.7 mm) and tighten the locknut finger tight.

Do not allow the actuating piston to rotate in the piston housing.

Parts will be damaged by rotation.

19. Clean the threads (internal and external) of the piston rod and pushrod, and apply anaerobic
adhesive primer. Allow it to dry for five minutes. Apply Loctite® #242 removable threadlocker
(two drops) to the threads. Using the hole at the base of the piston rod to hold it steady, screw
the pushrod into the piston rod.

G. Installing the Unloader

1. Install a new O-ring onto the valve cover.

2. Install the assembled operator and valve cover assembly into the valve hole, sliding the pushrod
over the extension bolt (loose fit).

3. Clean the threads (both internal and external) of the valve cover stud nuts or capscrews, then
apply anaerobic adhesive primer and allow it to dry for five minutes. Apply Loctite® #242
threadlocker (two drops) to each capscrew. Tighten the valve cover squarely by tightening the
capscrews gradually, in several stages, working back and forth across the stud circle.

Valve cover stud nuts must be correctly tightened to the design pre-
stress to ensure safe and efficient operation of the compressor. Refer
to CHAPTER 5 of this manual for detailed tightening requirements.

4. Adjust the stroke of the unloader.

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H. Adjusting the Stroke

1. Loosen the setscrew adapter locknut.

2. Slowly rotate the operator assembly clockwise until rotation is resisted without the locknut,
washer, and Threadseal™ assembly contacting the valve cover.

3. Slowly rotate the operator assembly counterclockwise 1-1/2 turns if the suction valve lift is
greater than 0.100 inch (2.54 mm), or 1 turn if the suction valve lift is less than or equal to 0.100
inch (2.54 mm).

4. Tighten the setscrew adapter locknut, pressing the washer and Threadseal™ firmly against the
valve cover. Be sure not to rotate the operator, setscrew adapter assembly.

5. Connect operating pressure line and cycle unloader several times to ensure that free movement
exists and that the unloader is functioning. Connect vent lines.

4-17.2. Variable Volume Clearance Pockets

The variable volume clearance pocket (Figure 4-33) is installed in the outer head of the
compressor cylinder. Within the limits of pocket capacity, the exact amount of clearance volume can be
added by turning the pocket's piston rod with a wrench. The compressor MUST be shut down and the
cylinders depressurized before making adjustments.

The volume is changed by means of a movable piston, which is shown in Figure 4-33. The
piston is sealed against leakage by two piston rings and is attached to the piston rod by a threaded
connection between the piston and rod. The clearance volume is increased by loosening the jam nut and
unscrewing the threaded rod, which will draw the piston outward away from the cylinder. Close control
over cylinder capacity can be accomplished by setting the piston at some intermediate position between
fully closed and fully open.

A. Construction

There are two designs of the variable volume pocket. One has a bonnet with a long neck
(illustrated in Figure 4-33), while the other has a flat bonnet (not illustrated). The long-necked version is
equipped with special seals, shown in the detail in Figure 4-33, which are installed on each side of a
lantern ring. This seal assembly is held in place by a flat washer and secured by a retaining ring. The
flat-bonnet version is equipped with a simple soft gasket under the piston rod sealing nut. Passage in the
bonnet neck is equipped with a grease fitting that allows the piston rod threads to be greased. In addition,
there are two plugged openings in the pocket that allow accumulated liquids to be drained (lower hole)
or a test gauge to be connected (upper hole).

B. Maintenance

Periodic maintenance consists of applying a small amount of grease, compatible with the
process gas, to the one grease fitting. It is suggested that the grease fitting be greased at least every
three months.

The condition of the piston rings can be determined by periodic testing with a simple pressure
gauge. With the compressor shut down and the cylinder vented, attach a test pressure gauge having a
capacity at least a third higher than discharge pressure to the upper hole in the pocket. With the
compressor again running, the gauge should read a steady pressure that falls somewhere between inlet
and discharge pressure. A fluctuation of the gauge indicates that piston rings are leaking badly.

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Maintenance PG-1028-E (HOS)

Figure 4-33. Current Design Variable Volume Clearance Pocket

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PG-1028-E (HOS) Maintenance

To remove and disassemble the pocket, use the following steps;

1. RELIEVE THE PRESSURE IN THE COMPRESSOR CYLINDER AND VENT THE CYLINDER.

2. Loosen and remove the stud nuts that secure the flange to the outer head.

3. Pull the clearance pocket assembly from the outer head, keeping it level until the piston clears
the bore. Be sure the assembly is fully supported at all times with a sling and hoist arrangement
capable of taking the weight.

4. Clean and examine the components of the variable volume pocket. Pay particular attention to
the piston rings.

5. On long-neck bonnet versions, remove the seal retaining ring by first prying one end out of the
groove, then by winding the ring completely out.

6. Continue with seal removal process by removing the washer, then by pulling the seals and
lantern using a shop-made wire hook.

7. Install new seals with the open cup side of the seals facing the pressure (towards the cylinder
bore).

8. Install the washer and retaining ring, making sure the ring is tight in its groove.

9. Install new piston rings on the piston. Normally it is more practical to replace the rings than to
attempt a judgement call on their condition. Stagger the ring end gaps.

10. Clean the gasket surfaces of the outer head and the flange.

11. Loosen the jam nut and unscrew the piston rod a few turns; this will ensure that the piston is not
"bottomed" during installation. If this is a flat-bonnet version, replace the sealing gasket at this
time.

12. Install a new flange gasket, then guide the piston into the outer head bore. Make sure the
assembly is kept level during this operation to prevent damaging the piston rings.

13. Install the stud nuts and tighten them in a criss-cross fashion, and in several stages, to the
25,000 psi (172 MPa) level found on the standard torque chart for the proper size fastener.
(This chart is found in CHAPTER 5, GENERAL DATA & SPECIFICATIONS of this manual.)

14. Adjust the piston to the desired position for operation. Make sure the jam nut is secure before
starting up the compressor.

4-17.3. Fixed Volume Clearance Pockets

The internal operating components of the clearance pocket are the indicator rod, actuating
piston, piston rod, return spring, crossbar and clearance valve itself. The crossbar, return spring (if
present), piston rod and clearance valve are assembled in the clearance valve sleeve which is in turn
bolted to the valve cover. The actuating piston and indicator rod are located in the piston housing.

Piston rings are installed around the clearance valve sleeve to prevent leakage of process gas
past the sleeve and clearance valve when the valve is seated. O-ring seals are used on the actuating
piston and indicator rod to seal the leakage of operating pressure past the piston and rod. A gland seal
arrangement is used to seal around the piston rod to prevent the leakage of process gas. Vent openings
are provided in the valve cover and piston housing to vent the piston rod gland seal arrangement and the
actuating piston housing.

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When operating pressure from an outside control source is applied to the top of the actuating
piston, the piston motion is transmitted through the piston rod to the clearance valve crossbar and to the
clearance valve, closing the valve. (The clearance valve sleeve is slotted for the travel of the crossbar.)
Piston rings in the valve sleeve prevent leakage past the clearance valve into the clearance pocket when
the valve is in its closed position. When operating pressure is shut off and vented, the valve returns to
its normal (open) position.

Figure 4-34. Typical Fixed Volume Clearance Pocket

A. Control and Vent Piping

Operating pressure is applied to a 1/4-inch NPT tapped hole provided in the piston housing
cover. Drawings are furnished to show the arrangement of factory supplied piping and controls.
Recommended piping arrangements are usually furnished when the piping is being done by others.

The vent opening(s) in the clearance pocket must always be left open
to assure safe and effective operation of the device. When the
process gas is toxic, flammable, or in any other way objectionable in
the compressor building, the vent must be piped so that any leakage
can be carried away. Vent tubing must not be less than 3/8-inch
(9.5 mm) O.D. and, if combined with other vent systems, there must
not be any back pressure or vacuum in this piping.

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PG-1028-E (HOS) Maintenance

B. Clearance Pocket Cleanliness

1. The clearance pocket and valve assembly must be clean and tight to operate satisfactorily. The
assembly should be examined during normal periodic maintenance inspections. O-rings and
backup rings (if used) in the assembly must be replaced and lubricated periodically; it is
suggested that this be accomplished during routine maintenance. The use of a silicone type
lubricant or other lubricant that is compatible with the O-ring material and the process is
recommended.

All precautionary measures specified by the Occupational Safety and

Health Act of 1970 (OSHA) must be complied with when storing,
handling, or using solvents.

2. To thoroughly clean the assembly, it must be completely dismantled. Soaking the parts in a
safety solvent, followed by a stiff brushing or light scraping, will aid in removal of foreign material.
Brush the parts carefully with a soft wire brush, but use a bristle brush for all seating surfaces.
Blow away all loose particles with compressed air. All components must be thoroughly dried
before reassembly.

C. Removing the Clearance Pocket Assembly

1. Shut down and vent ALL pressure from the unit.

2. Shut off and vent the operating pressure.

3. Disconnect the vent and operating pressure lines.

4. Mark or tag the clearance pockets before they are removed.

With the O-ring body seal used on this type valve cover, any pressure
that may be left in the cylinder will not be released when the cover
nuts are loosened, but will remain under the cover trapped by the
O-ring. To prevent the possibility of the valve cover being "blown off"
by residual pressure when the cover nuts are removed, two longer
studs are required to permit the safe removal of the cover. These
studs are either present (they are double-nutted if factory supplied)
or should be fabricated at the site. FAILURE TO OBSERVE THE
FOLLOWING VALVE REMOVAL STEPS CLOSELY CAN RESULT IN
POSSIBLE PROPERTY DAMAGE, INJURY TO THE MAINTENANCE
PERSONNEL OR DEATH.

5. Evenly loosen the valve cover stud nuts; note that two nuts are used on the two longer studs
used with each valve cover.

6. Remove only those nuts on the short valve cover studs.

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Maintenance PG-1028-E (HOS)

7. Back off the nuts on the long studs evenly two turns at a time. As the stud nuts are loosened,
it may be necessary to tighten down the cylinder cover jackscrews (if installed) or pry under the
valve cover to keep the cover in contact with the stud nuts. (This will prevent sudden loosening
of the valve cover when the O-ring breaks free of the valve passage, caused by any pressure
present.) As the O-ring is pulled from the valve passage, existing pressure will be safely vented
from under the cover.

8. Remove the assembly from the compressor.

9. Install temporary covers over the clearance pocket passage(s) to prevent entry of foreign
objects.

D. Disassembling Actuating Piston Housing

1. Remove the nuts that fasten the piston housing cover to the piston housing.

2. Carefully lift the piston cover over the indicator rod; remove and discard the cover gasket. Clean
the gasket surfaces in preparation for reassembly.

3. Lift the piston housing off the valve cover.

4. Remove the actuating piston and indicator rod from the piston rod. (The piston rod can only be
removed through the bottom of the body.) Remove and discard the actuating piston and
indicator rod O-rings.

SERVICE NOTE
It is good preventative maintenance practice to replace all O-rings and
gaskets during reassembly. Always lubricate the O-rings with a silicone
lubricant or other lubricant compatible with the O-ring and process.

E. Disassembling Clearance Valve Sleeve

1. Remove the fasteners and the lockwasher that connect the valve sleeve to the valve cover and
separate the two.

2. The piston rod may now be removed through the bottom of the valve cover.

3. Disassemble the crossbar by unscrewing the fasteners and lockwashers that fasten it to the
clearance valve.

4. Pull the crossbar out of the sleeve.

5. Pull the clearance valve off the sleeve.

6. Remove and discard the piston rings if they are chipped, cracked, broken or stuck to their lands.

7. Remove and clean the return spring; check for cracks or other visible defects.

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F. Servicing the Gland Seal

1. Remove the fasteners to permit removal of the gland seal. (See detail in Figure 4-35.)

2. If necessary, use a shop-made wire hook to pull the gland seal from the body.

3. Remove and discard the O-rings and backup rings.

SERVICE NOTE
It is good maintenance practice to replace all O-rings, backup rings, and
gaskets during reassembly. Always lubricate the O-rings with a silicone
lubricant or other lubricant compatible with the O-ring and process.

Figure 4-35. Gland Seal Detail

4. Renew the O-rings and backup rings on the gland seal. (Note the order in which they are
placed.) O-rings are installed in the top inner and outer groove. Install a backup ring and then
an O-ring in the bottom inner and outer grooves. (The concave surface of the backup ring faces
toward the O-ring.) Make sure the O-rings and backup rings are lubricated with a lubricant
compatible with the process gas.

5. Place the gland seal into the body; be careful not to roll or cut the O-rings.

6. Clean the threads (both internal and external) of the gland seal capscrews, then apply anaerobic
adhesive primer and allow it to dry for five minutes. Apply Loctite® #242 threadlocker (two
drops) to each capscrew; reattach the gland seal to the body.

7. Push the piston rod up through the gland seal.

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G. Assembling Actuating Piston Housing

1. If the piston rod was removed, clean the threads of the piston rod and the piston, then apply
aerobic adhesive primer and allow it to dry for five minutes. Apply Loctite® #242 threadlocker
(two drops) to the piston rod threads. Attach the piston rod to the piston.

2. Install new indicating rod and actuating piston O-rings and lubricate them with O-ring lubricant.

3. Insert the actuating piston and piston rod into the piston housing. Be sure that the O-ring is not
rolled out of its groove when installing the actuating piston.

4. Clean the threads (both internal and external) of the piston housing cover bolts, then apply
anaerobic adhesive primer and allow it to dry for five minutes. Apply Loctite® #242 threadlocker
(two drops) to each bolt and with new piston housing cover gaskets in place, secure the piston
housing covers to the piston housing. Tighten the housing cover bolts squarely by tightening
gradually, in several stages, working back and forth across the bolt circle.

5. With a new cover gasket in place, reinstall the piston housing cover over the indicator rod;
tighten the stud nuts evenly.

H. Assembling Clearance Valve Sleeve

1. Inspect the valve sleeve piston ring lands, ensuring they are clean. The lands can be cleaned
with a piece of carved hardwood. Do not use old rings to clean the lands because they may cut
into the lands and grooves damaging the sleeve.

2. Fit new rings to the sleeve (if they are required). Stagger the butt ends of the rings 120 degrees.

3. While carefully compressing each piston ring, push the clearance valve over the piston rings and
onto the valve sleeve. Do not push the clearance valve onto the valve sleeve far enough to
block the slots in the sleeve.

4. Place the return spring (if used) into the valve sleeve. Some models do not require a return
spring.

5. Insert the crossbar through slots in the valve sleeve. Fit the crossbar to the return spring then
connect the crossbar to the clearance valve using the lockwashers and fasteners provided.

6. Connect the valve sleeve to the valve cover using the fasteners and lockwashers removed.

I. Installing Clearance Pocket Assembly

1. Remove the temporary covers from the valve passage(s).

2. Install a new valve O-ring and backup ring seal around the valve cover. Place the unit in the
clearance pocket and align the operating pressure and vent piping connections with the installed
piping.

3. Reinstall the valve cover fasteners and hand tighten. Loosen all fasteners 1/4 turn.

4. Reconnect operating pressure and vent piping.

5. Apply operating pressure to the actuating port to seat the clearance valve. (This will align the
clearance valve with the cylinder.)

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PG-1028-E (HOS) Maintenance

6. Release the operating pressure.

7. Reapply operating pressure to the actuating port.

Valve cover stud nuts must be correctly tightened to the design pre-
stress to ensure safe and efficient operation of the compressor. Refer
to CHAPTER 5, GENERAL DATA & SPECIFICATIONS of this manual
for detailed tightening requirements.

8. While operating pressure is still applied, make several passes working back and forth across
the stud circle to ensure the valve cover is drawn down tightly and evenly.

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DRESSER-RAND GENERAL DATA & SPECIFICATIONS

HOS
Chapter 5

Paragraph Page

5-1. GENERAL AND OPERATING DATA ........................................................................... 5-2

Table 5-1. HOS Compressor General Data...................................................... 5-2
5-2. ASSEMBLY FITS AND CLEARANCES ........................................................................ 5-4
Table 5-2. Running Gear Part Fits and Tolerances (Inches).......................... 5-4
Table 5-2A. Running Gear Part Fits and Tolerances (Metric) .......................... 5-5
5-3. TIGHTENING REQUIREMENTS.................................................................................. 5-6
5-3.1. Preparation of Thread & Seating Surfaces ............................................................. 5-6
5-3.2. Tightening Sequence .............................................................................................. 5-6
5-3.3. Closely Observe...................................................................................................... 5-6
5-3.4. Checking Fastener Tightness ................................................................................. 5-7
5-3.4.1. When To Check Fastener Tightness................................................................. 5-7
5-3.4.2. How To Check Fastener Tightness ................................................................... 5-8
5-3.5. Fastener Pre-Stress ................................................................................................ 5-8
5-3.6. Compressor Cylinder Bolting .................................................................................. 5-9
Table 5-3. Pre-Stress Levels For HOS............................................................. 5-9
5-3.4. Torque Values......................................................................................................... 5-10
Table 5-4. Torque Values Anti-Seize Thread Lubricant ................................... 5-10
Table 5-5. Torque Values Common Mineral Oil Lubricant ............................... 5-11
5-3.5. Frame & Running Gear Bolting ............................................................................... 5-12
Table 5-6. Frame & Running Gear Bolting ....................................................... 5-12

5-1
General Data & Specifications PG-1028-E (HOS)

5-1. GENERAL AND OPERATING DATA

The specifications in this section apply to the standard 6-inch stroke HOS compressor, rated at
60,000 pounds (27 270 kg) rod load. Contact the nearest Dresser-Rand branch office when there is a
question about any specification or recommendation in this manual.

Table 5-1. HOS Compressor General Data

Number of Throws 8 2 4 6

No. Main Bearings 8 2 4 6

Oil Sump Capacity GAL. 21 57 96

L. 79 216 365
Main Oil Pump GPM 40 70 110
Output @ 1000RPM LPM 152 266 380
Maximum Speed 1200 1200 1200
RPM
Minimum Operating Speed 500 500 500
RPM

Lubricating Oil:

Normal Oil Pressure (at Header)..........................................50-65 PSIG (344-448 kPa)

Minimum Oil Pressure (at Header)...................................................40 PSIG (275 kPa)
Shutdown Oil Pressure (at Header) .................................................35 PSIG (240 kPa)
Minimum Start-up Oil Temperature (Electric Drive).................................... 80°F (27°C)
Minimum Load Oil Temperature (Engine and Electric Drives) ................... 90°F (32°C)
Normal Oil Operating Temperature ................................... 150 to 170°F (66° to 77°C)**
**NOTE: Not to exceed 180° for continuous operation

For units containing main bearing RTD’s:

Maximum Alarm Setting ............................................................................. 190°F (88°C)
Maximum Shutdown Setting....................................................................... 200°F (93°C)

Recommended minimum prelube capacity @ 35 psi (241 kPa) (on electric motor
driven machines only):

Frame Size Gallons per Minute (LPM)

2 Throw ...........................................................................................15 GPM (56.8 LPM)
4 Throw ...........................................................................................25 GPM (94.6 LPM)
6 Throw .........................................................................................50 GPM (189.3 LPM)

5-2
PG-1028-E (HOS) General Data & Specifications

Water-Cooled Cylinders:

Minimum Coolant Temperature (Outlet) ................................................... 110°F (43°C)

Minimum Coolant Temperature (Inlet) .........................................................100°F (38°C)
Water-Cooled Packing [gpm (L/min)] per packing ............................................ 2.5 (9.5)
Nominal Pressure ............................................................................. 35 PSIG (241 kPa)
Maximum Pressure .............................................................................75 PSIG (517 kPa)

Distance Pieces:

Maximum Internal Pressure ............................................................ 25 PSIG (172 kPa)

5-3
General Data & Specifications PG-1028-E (HOS)

5-2. ASSEMBLY FITS AND CLEARANCES

Table 5-2. Running Gear Fits and Tolerances

(ALL DIMENSIONS ARE GIVEN IN INCHES)

Location of Original Original

Clearance or Fit Clearance Clearance
Micrometer Feeler

Main Bearing (Vertical-measured

between top of crankshaft and main 0.008 to 0.011 0.007 to 0.010
bearing shell)
(Shim Type Aluminum)

Crankshaft Total Thrust ---- 0.018 to 0.023

Connecting Rod Bearing to

Crankpin (Diametral) 0.007 to 0.010 0.006 to 0.009
(Shimless Steel-Backed Aluminum)
Total Side Clearance between
Connecting Rod and Crank Webs ---- 0.015 to 0.023
Crosshead Pin to Connecting Rod
Bushing (Diametral) 0.002 to 0.006 0.001 to 0.005
Crosshead Pin Bushing to
Connecting Rod (Interference) (0.002 to 0.004) ----

Crosshead Shoe to Guide(Cold) 0.013 to 0.018 0.012 to 0.017

Minimum (Hot) ------- 0.007
Main Bearing Tie Rod Spacer to
Frame (Interference) (0.003 to 0.005) ----
[Spacer Length Less Opening
Stamped on Frame]

5-4
PG-1028-E (HOS) General Data & Specifications

Table 5-2A. Running Gear Fits and Tolerances

(ALL DIMENSIONS ARE GIVEN IN MILLIMETERS)

Location of Original Original

Clearance or Fit Clearance Clearance
Micrometer Feeler

Main Bearing (Vertical-measured

between top of crankshaft and 0.20 to 0.28 0.18 to 0.25
main bearing shell)
Crankshaft Total Thrust ---- 0.46 to 0.58
Connecting Rod Bearing to
Crankpin (Diametral) 0.18 to 0.25 0.15 to 0.23
Total Side Clearance between
Connecting Rod and Crank ---- 0.38 to 0.58
Webs
Crosshead Pin to Connecting
Rod Bushing (Diametral) 0.05 to 0.15 0.025 to 0.13
Crosshead Pin Bushing to
Connecting Rod (Interference) (0.05 to 0.10) ----
Crosshead Shoe to Guide (Cold)
1 - piece 0.33 to 0.46 0.30 to 0.43
3 - piece 0.43 to 0.56 0.41 to 0.53
Minimum (Hot) ------- 0.18
Main Bearing Tie Rod Spacer to
Frame (Interference) (0.08 to 0.13) ----
[Spacer Length Less Opening
Stamped on Frame]

5-5
General Data & Specifications PG-1028-E (HOS)

5.3 TIGHTENING REQUIREMENTS

5.3.1. Preparation Of Thread And Seating Surfaces:

Preparation of thread and seating surfaces is equally important. In most torque applica-
tions, more than 80% of the applied torque is used to overcome friction and the balance to
actually stress the fastener. It is therefore imperative that threads are clean and free of nicks
and burrs; that seating surfaces on the nut or bolt head and mating surface be smooth, flat and
parallel; and that the threads and contact surfaces be properly lubricated.

5.3.2. Recommended Tightening Sequence:

All fasteners used on multi-fastener joints require a tightening procedure that will allow
the fasteners to be evenly and sequentially tightened, in gradual increments, to the specified
torque. This prevents distortion of mating surfaces and "cocking" of flanged connections.

5.3.3. Closely observe the following:

1. All torque values are for clean, well-lubricated (see Item 3 below) threads free of nicks
and burrs. For stud (or bolt) and nut combinations, the nut should turn freely on the stud
threads. Capscrews should run in freely at least up to the final assembled depth. (Some
thread interference is normal on certain self-locking fasteners.) Lubricant should be
evenly applied to both internal and external threads, and seating surfaces.

2. Wrench torques can produce fastener pre-stress variations of ±35%, depending on the
degree of lubrication or non-lubrication, and also on the condition of seating surfaces.
A properly calibrated torque wrench is essential in obtaining satisfactory results. Under
no circumstances is an impact wrench to be used for tightening of any fastener.

3. Thread lubricants with a nut factor (k) of approximately 0.13 are recommended. The nut
factor (k) is derived by adding 0.04 to the coefficient of friction. This nut factor (k) is an
average value of a commercially available copper based anti-seize, known as FEL-
PRO® C5-A, and a commercially available molybdenum disulfide (MoS2) based lubricant,
known as Dow Corning® G-n. Using other lubricants having a different nut factor (k)
can result in increased or decreased fastener pre-stress when the torque values in the
Standard Torque Table for Anti-Seize Thread Lubricant are applied.

4. Geared head wrenches (torque multipliers) will not produce the full mechanical ad-
vantage from the reduction gears. There are mechanical and friction losses of about
10% in the tool head. The tool manufacturer's instructions should be observed to deter-
mine the exact reduction percentage for a particular torque multiplier. The required input
torque must then be increased by that percentage.

5. The torque values listed in either Standard Torque Table should be used only on
those fasteners for which a specific torque is not given.

5-6
PG-1028-E (HOS) General Data & Specifications

5-3.4. Checking Fastener Tightness

WARNING
The fasteners used in engines and compressors must be
correctly tightened to the design pre-stress to ensure safe
operation. After startup, fasteners that were properly tightened
can loosen due to operating temperatures and pressures,
gasket crush, fastener and joint relaxation. THEREFORE, IT IS
IMPORTANT THAT FASTENERS BE CHECKED FOR TIGHTNESS
TO ENSURE FULL MECHANICAL INTEGRITY. Particular
attention should be given to all bolts, studs and nuts on the
compressor cylinders and distance pieces and to the cylinder-
to-frame bolting.

WARNING
Never check fastener tightness or tighten fasteners with the
compressor in operation or pressurized. Potential equipment
damage and/or release of process gas could result, causing
severe personal injury or death. Always check and/or tighten
fasteners when the compressor is shut down and de-
pressurized.

5-3.4.1. When to Check Fastener Tightness

Maintaining fastener tightness is critical to fastener reliability. Dresser-Rand recommends

the following schedule for checking fastener tightness:

• Before start up check fasteners at all joints that have gaskets and any joints not assembled
at the Dresser-Rand factory. (Consult the job-specific instruction manual parts list section
to locate joints containing gaskets)

• One week after startup for joints with gaskets and all cylinder frame bolting. Take note of any
fasteners that have loosened and pay close attention to these fasteners; increase periodic
checking of those fasteners.

• Anytime a joint containing a gasket is opened, replace gasket, tighten fasteners as

prescribed and check again one week after start up.

• Periodically based on experience, but annually is considered a typical interval.

• Anytime there is an incident, slugging event (liquid ingestion) or excessive vibration, which
has caused a compressor overload to occur.

5-7
General Data & Specifications PG-1028-E (HOS)

5-3.4.2. How to Check Fastener Tightness

To check the tightness of a torqued fastener, first mark the position of the bolt head or
nut and then loosen it; clean and re-lubricate. The fastener should then be re-torqued to the
required value. Observe to see whether the bolt head or nut has advanced past its reference
position. If it has, then the fastener has loosened, or was not originally torqued correctly. Inspect
the fastener for fatigue or stress cracks; replace as required. Contact Dresser-Rand for
technical advice.

To check the tightness of a hydraulically tensioned fastener, install the appropriate

size bolt tensioner and hydraulically tension the fastener to the required level. Attempt to turn
the tension nut clockwise using the adjusting rod. If the nut does not turn, then the fastener is
properly tensioned; if the tension nut does turn, then the fastener has loosened, or was not
originally tensioned correctly. Inspect the fastener for fatigue or stress cracks; replace as
required. Contact Dresser-Rand for technical advice.

5-3.5. Fastener Pre-Stress

Fastener pre-stress (initial tightening) is calculated to prevent separation of the con-

nected members when they are subjected to operating forces and, in cases of cyclic loading,
to protect the fastener from the fatigue effects of the alternating tensile and compressive
stresses. Wrench torque is the most widely used method of applying fastener pre-stress. A
properly calibrated torque wrench is essential in obtaining satisfactory results. An accurate
torque cannot be applied to fasteners using a commercial impact wrench. Under no
circumstances is an impact wrench to be used for final tightening of any fastener.

NOTE

Refer to the job-specific Instruction Book for specific bolting

torque values before applying these general guidelines.

In general, unless otherwise specified, the pre-stress level for a particular bolting application
can be determined as follows.

· For connections with metal-to-metal contact, use 30,000 PSI (207 MPa) stress level.

· For connections with non-metallic gaskets, use 20,000 PSI (138 MPa) stress level.

· For foundation bolts of the J type or bent bar use 25 000 PSI (172 MPa) stress level. Note
this type of anchor bolt should NEVER be used for locations that have to withstand the
dynamic loads from the compressor frame or cylinders.

· For foundation bolts which use plate type anchors (recommended for frame and cylinder
anchor bolt locations) tighten to 30,000 psi (207 MPa) stress level.

5-8
PG-1028-E (HOS) General Data & Specifications

5-3.6. Compressor Cylinder Bolting

In many cases specific torque values are given in the job-specific instruction manual for
each fastener required for compressor cylinder bolting. If specific torque values are not given,
use the information in the following tables. Determine the application and fastener pre-stress
level, then apply the torque values listed in the appropriate Standard Torque Table.

Table 5-3. Pre-Stress Levels For HOS

Joint Fastener Pre-Stress

Cylinder To Head 25,000 psi (172 MPa)

Cylinder To Valve Cover 25,000 psi (172 MPa)

Cylinder To Packing 30,000 psi (207 MPa)

Inlet & Discharge Flange 20,000 psi (138 Mpa)

Cylinder Tie Rod 40,000 psi (276 MPa)

Clearance Device To Outer Head 25,000 psi (172 MPa)

5-9
General Data & Specifications PG-1028-E (HOS)

5-3.4. Standard Torque Values

Table 5-4 TORQUE VALUES BASED ON ANTI-SEIZE THREAD LUBRICANT

Torque Table for Nut Factor (k = 0.13)

20,000 psi 25,000 psi 30,000 psi 40,000 psi

Nominal (138 MPa) (172 MPa) (207 MPa) (276 MPa)
Thread Pre-Stress Pre-Stress Pre-Stress Pre-Stress
Size (in)
ft-lbs N·m ft-lbs N·m ft-lbs N·m ft-lbs N·m

0.250 1.7 2.3 2.2 2.9 2.6 3.5 3.4 4.7

0.312 3.5 4.8 4.4 6.0 5.3 7.2 7.1 10
0.375 6.3 8.5 7.9 11 9.4 13 13 17
0.438 10 14 13 17 15 21 20 27
0.500 15 21 19 26 23 31 31 42
0.562 22 30 28 37 33 45 44 60
0.625 31 41 38 52 46 62 61 83
0.750 54 74 68 92 82 111 109 147
0.875 88 119 109 148 131 178 175 237
1.000 131 178 164 222 197 267 262 356
1.125 193 261 241 327 289 392 385 522
1.250 271 367 338 459 406 551 542 734
1.375 367 498 459 623 551 747 735 996
1.500 485 657 606 822 727 986 970 1315
1.750 789 1070 987 1338 1184 1606 1579 2141
2.000 1201 1628 1501 2035 1801 2442 2401 3256
2.125 1451 1967 1814 2459 2177 2951 2902 3935
2.250 1734 2351 2168 2939 2601 3527 3468 4702
2.500 2406 3262 3008 4078 3609 4893 4812 6525
2.750 3232 4383 4041 5478 4849 6574 6465 8765
3.000 4229 5734 5286 7167 6344 8601 8458 11468
3.250 5412 7338 6765 9172 8118 11007 10824 14675
3.500 6797 9216 8496 11520 10196 13823 13594 18431
3.750 8400 11389 10500 14237 12601 17084 16801 22779
4.000 10238 13881 12797 17351 15357 20821 20476 27761
4.500 14679 19902 18348 24877 22018 29852 29357 39803
5.000 20248 27452 25309 34315 30371 41178 40495 54904
5.500 26665 36153 33331 45191 39997 54229 53330 72305
6.000 34794 47174 43493 58968 52191 70761 69588 94349
Observe the following when using this Torque Table [k = 0.13]:

• All information and instructions given under TIGHTENING REQUIREMENTS must be thoroughly
reviewed before applying specified wrench torques.

• Torque values are based on thread lubricants with a nut factor (k) of approximately 0.13. This
nut factor (k) is an average value of a commercially available copper based anti-seize, named
®
FEL-PRO C5-A, and a commercially available molybdenum disulfide (MoS2) based lubricant,
®
known as Dow Corning G-n. (Nut factor (k) is derived by adding 0.04 to the coefficient of
friction)

• The wrench torques are applicable to both National Fine and National Coarse thread series. Any
difference in the torque values because of thread series is within the normal variation of torque
wrench accuracy.

• When tightening fasteners incorporating a self-locking feature, a certain amount of the applied
torque is lost because of the additional friction of the locking feature. Use a torque wrench to
measure the "run-down" torque and then add it to the listed value.

5-10
PG-1028-E (HOS) General Data & Specifications

Table 5-5. TORQUE VALUES BASED ON A COMMON MINERAL OIL LUBRICANT

20,000 PSI 25,000 PSI 30,000 PSI 40,000 PSI

(138 Mpa) (172 Mpa) (207 Mpa) (276 Mpa)
Bolt Stress Bolt Stress Bolt Stress Bolt Stress
NOMINAL
BOLT SIZE Torque Torque Torque Torque
(inches)
Ft-lbs. N·m Ft-lbs. N·m Ft-lbs. N·m Ft-lbs. N·m
1/4 3 4 3 4 4 6 5 7
5/16 5 7 7 10 8 11 11 15
3/8 9 12 12 16 14 19 19 26
7/16 15 20 18 24 22 30 29 39
1/2 22 30 28 30 33 45 44 60
9/16 31 42 39 53 47 64 63 85
5/8 44 60 55 75 66 90 88 119
3/4 76 103 95 129 114 155 152 206
7/8 120 163 150 203 180 244 240 325
1 175 237 220 300 265 360 350 475
1-1/8 260 355 330 450 390 530 520 705
1-1/4 360 490 450 610 530 720 710 965
1-3/8 480 650 600 815 710 965 950 1290
1-1/2 620 840 770 1045 920 1250 1230 1670
1-3/4 950 1290 1190 1615 1420 1925 1890 2565
2 1470 1990 1830 2480 2200 2980 2930 3970
2-1/4 2130 2890 2670 3620 3200 4340 4270 5970
2-1/2 2950 4000 3650 4950 4400 5970 5850 7930
2-3/4 3950 5360 4900 6640 5900 8000 7850 10640
3 5150 6980 6400 8680 7700 10440 10250 13900

Observe the following when using this Torque Table:

• All information and instructions given under TIGHTENING REQUIREMENTS must be

thoroughly reviewed before applying specified wrench torques.

• Torque values are based on common mineral oil lubricants.

• The wrench torques are applicable to both National Fine and National Coarse thread
series. Any difference in the torque values because of thread series is within the normal
variation of torque wrench accuracy.

● When tightening fasteners incorporating a self-locking feature, a certain amount of the

applied torque is lost because of the additional friction of the locking feature. Use a
torque wrench to measure the "run-down" torque and then add it to the listed value.

5-11
General Data & Specifications PG-1028-E (HOS)

5-3.5. Frame & Running Gear Bolting

Table 5-6. Frame & Running Gear Bolting

Bolt or Stud Size Distance Bolt Pre- Torque Torque

Location & Pitch Across Stress
(Inches) Flats (PSI) (Ft-lbs) (N•m)
(Inches)

Main Bearing Cap 1-8 1-5/8 50 000 420 569

Bolt Nominal
1
Connecting Rod Bolt 1-¾ - 12 2-5/8 48 000 0.018 to 0.020 in.
Nut Nominal (0.46 to 0.51 mm)

Frame Tie Rod Nut 1-1/2 - 8UN 2-3/8 30 000 ² ²

Cylinder Tie Rod Nut 1-1/2 - 8 2-3/8 40 000 1230 1670

Crosshead Shoe Nut ¾ - 10UN 1-1/4 30 000 114 155

(3 Piece only)

NOTES:
1
= Stretch method required for this fastener.
2
= See Paragraph 4-7.2. Step 11 for frame tie rod nut tightening procedure.

5-12