L SERIES

RECIPROCATING COMPRESSOR
INSTRUCTION MANUAL

MAYEKAWA MFG. CO., LTD.

TOKYO, JAPAN

1
 Safety Information

This manual has been prepared to protect engineers, system operators and maintenance
personnel from any potential risks during operation and maintenance of L Series
Reciprocating and to assure effective utilization of the unit. Before commencing
disassembly and reassembly service work on the compressor, read carefully and
understand the contents of this manual, which explains the structure of and work methods
appropriate for L Series Reciprocating. If any service work is performed which disregards
the instructions given in this manual, there is a risk of accident. Most accidents and
problems encountered during operation are a result of negligence in following basic safety
precautions, insufficient understanding of and failure to observe proper operating
principles and procedures and failure to implement appropriate inspection and
maintenance procedures and precautions.
Safety and signal warnings provided in this instruction manual are classified into the
following four categories.

„DANGER“ indicates a hazardous situation in

! DANGER which failure to observe all safety precautions will
lead to death or serious injury and major damage
to the compressor system.

„WARNING“ indicates a hazardous situation in

! WARNING which failure to observe all safety precautions
may lead to death or injury and major damage to
the compressor system.

“CAUTION“ indicates a hazardous situation in

! CAUTION which failure to observe all safety precautions
could lead to injury or damage to the
compressor.

The safety and signal warnings contained in this instruction manual establish the minimum
level of safety required to perform maintenance work on the compressor. System
operators and maintenance personnel are advised to implement at their own responsibility
and further safety activities in line with the particular environment or location of the
compressor system.

2
Table of Contents
Page
1. Safety……………………………………………………………………………………….. 6
1.1 Basic Precautions………………………………………………………………….. 6
1.2 Safety information…………………………………………………………………..7
1.3 Safety and Signal Warning Label Locations……………………………………. 7

2. Component Parts List………………………………………………………………………9

3. Introduction………………………………………………………………………………...15

4. Mechanisms………………………………………………………………………………. 15
4.1 Gas compression mechanism and gas flow……………………………………15
4.2 Suction and discharge valve mechanisms…………………………………….. 15
4.3 Capacity control mechanism……………………………………………………..16
4.4 Oil supply mechanism…………………………………………………………….17
4.4.1 Oil flow…………………………………………………………………….18
4.4.2 Crankcase oil quantity………………………………………………….. 19
4.5 Mechanical shaft seal……………………………………………………………. 19
4.6 Safety valve, built-in type………………………………………………………... 20
4.7 Oil cooler…………………………………………………………………………...20
4.8 Accessories……………………………………………………………………….. 20
4.8.1 Direct coupling (Formflex type)………………………………………... 21
4.8.2 Flywheel for V-belt drive…………………………………………………. 21
4.8.3 Pressure gauges and instruments……………………………………… 21

5. Installation and Operation……………………………………………………………….. 23

5.1 Compressor Unit Centering……………………………………………………... 23
5.1.1 For belt drive operation………………………………………………….23
5.1.2 For direct coupling (Formflex type) operation………………………...23
a. Securing hub…………………………………………………………. 23
b. Centering………………………………………………………………23
1. Eccentricity……………………………………………………...23
2. Shaft declination………………………………………………..24
c. Coupling assembly…………………………………………………... 24
5.2 Piping……………………………………………………………………………….25
5.2.1 Refrigerant piping……………………………………………………….. 25
5.2.2 Pressure gauge and protection switch piping…………………………. 25
5.2.3 Protection switches………………………………………………………. 26
5.2.4 Oil heater and thermostatic switch……………………………………. 26
5.2.5 Oil separator……………………………………………………………...27
5.3 Precautions during Operation…………………………………………………… 28
(1) Initial start-up……………………………………………………………..28
(2) Operations records and inspection items…………………………….. 29
a. Suction pressure and discharge pressure………………………… 29
b. Discharge pressure and temperature……………………………… 29
c. Oil supply pressure…………………………………………………...30
d. Oil quantity (oil level)………………………………………………… 30
e. Oil temperature………………………………………………………. 30
f. Dirty oil…………………………………………………………………30
g. Shaft seal oil leakage………………………………………………...30
h. Power transmission status………………………………………….. 30

3
 i. Electric motor……………………………………………………………. 30
j. Others……………………………………………………………………. 30
* Liquid hammer…………………………………………………... 31
* Refrigerant leakage……………………………………………...31
(3) Decline in compressor capacity……………………………………….. 31
(4) Oil consumption…………………………………………………………. 31
5.4 Service limits……………………………………………………………………… 32

6. Maintenance and Inspection……………………………………………………………..33

6.1 Daily inspection…………………………………………………………………… 33
6.2 Monthly inspection………………………………………………………………...34
6.3 Periodic inspection……………………………………………………………….. 34
a. First periodic inspection…………………………………………………34
b. Second periodic inspection……………………………………………..35
c. Filter inspection…………………………………………………………..35
d. Pressure gauge (or pressure sensor) inspection……………………. 35

7. Compressor Lubricating Oil……………………………………………………………... 36

7.1 Lubricating oil characteristics and functions……………………………………36
7.2 Compressor oil selection………………………………………………………… 36
7.3 Changing compressor oil brand………………………………………………… 36
7.4 Oil supply to the compressor……………………………………………………. 36
7.5 Compressor oil brands……………………………………………………………37

8. Disassembly and Reassembly………………………………………………………….. 38

8.1 Disassembly………………………………………………………………………. 38
8.1.1 Refrigerant recovery……………………………………………………. 38
1. When compressor operable………………………………………… 38
2. When compressor inoperable……………………………………… 39
8.1.2 Precautions during disassembly………………………………………. 39
8.2 Disassembly Methods…………………………………………………………….39
8.2.1 Compressor oil discharge……………………………………………… 39
8.2.2 Disassembly of drive connections…………………………………….. 40
8.2.3 Removing head cover…………………………………………………...40
8.2.4 Discharge valve assembly and valve plate…………………………... 41
a. Discharge valve assembly…………………………………………...41
b. Valve plate……………………………………………………………. 42
8.2.5 Hand hole cover………………………………………………………….42
8.2.6 Cylinder assembly………………………………………………………. 43
a. Drawing out cylinder assembly……………………………………...43
b. Piston and connecting rod removal………………………………... 44
c. Cylinder sleeve disassembly……………………………………….. 44
d. Piston and connecting rod…………………………………………...45
e. Piston ring and oil ring………………………………………………. 45
8.2.7 Unloader mechanism disassembly…………………………………….46
8.2.8 Shaft seal cover removal………………………………………………..47
8.2.9 Mechanical shaft seal disassembly…………………………………… 48
8.2.10 Bearing housing disassembly…………………………………………..48
8.2.11 Pump side main bushing and thrust washer…………………………. 49
8.2.12 Oil pump assembly ……………………………………………………...50
8.2.13 Crankshaft……………………………………………………………….. 51
8.2.14 Seal side thrust bearing and thrust washer……………………………. 52

4
 8.2.15 Oil filter…………………………………………………………………… 52
8.2.16 Suction filter………………………………………………………………53
8.2.17 Built-in safety valve……………………………………………………... 53
8.2.18 Oil pressure regulating valve…………………………………………...53
8.2.19 Pressure equalizer……………………………………………………… 53
8.3 Reassembly………………………………………………………………54
8.3.1 Precautions during reassembly………………………………………...54
8.3.2 Crankcase reassembly…………………………………………………. 55
8.3.3 Crankshaft reassembly………………………………………………….55
8.3.4 Oil pump, main bushing and bearing housing……………………….. 56
8.3.5 Mechanical seal reassembly……………………………………………57
8.3.6 Cylinder assembly reassembly…………………………………………59
a. Piston and pisting rings………………………………………………59
b. Piston and connecting rod………………………………………….. 59
c. Cylinder sleeve………………………………………………………..60
d. Cylinder sleeve and piston/connecting rod reassembly…………. 61
8.3.7 Mounting cylinder assembly in crankcase…………………………….62
8.3.8 Valve assembly reassembly…………………………………………… 64
a. Valve plate reassembly………………………………………………64
b. Discharge valve cage reassembly…………………………………. 65
8.3.9 Head cover reassembly…………………………………………………66
8.3.10 Hand hole cover reassembly…………………………………………...66
8.3.11 Unloader cover reassembly……………………………………………. 67
8.3.12 Suction filter reassembly……………………………………………….. 67
8.4 Parts inspection and replacement standards…………………………………..67
8.4.1 Compressor oil replacement……………………………………………68
8.4.2 Suction filter and oil filter……………………………………………….. 69
8.4.3 Crankshaft……………………………………………………………….. 69
8.4.4 Mechanical seal…………………………………………………………. 69
8.4.5 Piston, piston pin and piston rings……………………………………..69
8.4.6 Connecting rod…………………………………………………………...71
8.4.7 Cylinder sleeve………………………………………………………….. 71
8.4.8 Discharge plate valve assembly and suction plate valve……………72
8.4.9 Oil pump…………………………………………………………………..72
8.4.10 Main bushing and thrust washer ……………………………………… 72
8.4.11 Thrust bearing…………………………………………………………… 73
8.4.12 Springs…………………………………………………………………… 73
8.4.13 Built-in safety valve……………………………………………………... 73
8.4.14 Gaskets and O-rings……………………………………………………. 74
8.4.15 Gaskets (external view and dimensions)……………………………...75
8.4.16 Designed allowable clearances………………………………………...76

MYCOM World-wide Aftersales Network……………………………………………………… 77

5
1. Safety

1.1 Basic Safety Warnings

The L Series Reciprocating Compressor Instruction Manual has been prepared to

assure maximum effective operation of the equipment as well as to ensure the safety
of those involved in operating, maintaining and overhauling the compressor and
related parts.
Read this manual carefully in order to familiarize yourself with the structure and
operating principles and procedures before undertaking disassembly and reassembly
of this compressor. Failure to follow the instructions given in this manual may result in
possible personal injury and/or serious compressor damage.

! WARNING

Should this machine be operated carelessly and in disregard of the instructions given
in this manual, death or serious injury may result. This manual must therefore be kept
in a convenient, easily-accessible location near the system and should be studied
periodically by those working with the system.

• Maintenance work on this compressor should not be undertaken without a

thorough understanding of the instructions given in this manual.
• Prior to commencing any inspection or maintenance work on the compressor, read
the safety warnings provided.
• Keep this manual in a convenient, easily-accessible location near the system and
study frequently.
• If this manual is lost or damaged, a replacement should be obtained immediately
from Mayekawa Mfg. Co., Ltd. or the nearest representative in your area.
• If ownership of the compressor passes to another party, this instruction manual
should always accompany the compressor.
• Mayekawa Mfg. Co., Ltd. reserves the right to make changes or improvements to
its products without notice. It is possible, therefore, that some explanations given
in this manual may not apply a particular machine. If any uncenrtainty exists on the
part of the compressor operator, contact Mayekawa Mfg. Co., Ltd. or the nearest
representative in your area.
• Various warning labels are affixed to the compressor.

6
1.2 Safety information

Safety information indicates safety precautions described in this instruction manual.

Failure to follow any and all safety information instructions may result in possible
personal injury and/or serious compressor damage.

1.3 Safety and Signal Warning Label Locations

Safety and caution warning labels are affixed to the compressor at the points shown
below. These labels must be kept clean at all times and should never be removed from
the compressor. If any label is stained or lost, contanct your nearest MYCOM office for
a replacement.

“WARNING” label for high temperature

Air Cooled Type Head Cover (Discharge Service Valve)

“”WARNING” label for high “WARNING” label for high

temperature (Head cover) temperature (Head cover)

“WARNING” label for high “WARNING” label for high

temperature (Head cover) temperature (Head cover)

Water Cooled Type Head Cover “WARNING” label for high temperature
(Discharge service valve)

7
 Discharge
Suction

Fig. 1 Cross sectional view

8
 2. Component Parts List for Model L Compressor
Component Parts for NH3 Application Specifications

Quantity
No.* Part No Name Material Remarks
4L 6L 8L
1 1 Crankcase FC300 1 1 1
2 2 Crankshaft FCD600 1 1 1
3 3 Retainer drive pin SK5 1 1 1 Ø x 1.8 (spring pin)
4 4 Pulley key SK45C 1 1 1 20 x 12 x 90 (half round)
5 7 Pully set bolt SK45C 1 1 1 M27 x L50 (P=1.5)
6 5 Pully flat washer SS400 1 1 1 Ø 90
7 6 Pulley lock washer SS400 1 1 1 For M27
8 8 Housing, bearing FC250 1 1 1 Combined with oil pump
9 9 Gasket, bearing housing Non-asbestos 1 1 1 T=0.5
10 10 Bolt, bearing housing SCM435 10 10 10 M12 x L45
11 12 Main bushing WJ1 (F1) 1 1 1
12 29-4 Thrust washer LBC3 (F100) 2 2 2 Common use for main thust
13 13 Locking pin, thrust washer SK5 4 4 4 Ø4 x L8 (spring pin, half round)
14 29 Thurst bearing gvWJ2 2 1 1
15 31 Locking bolt, thrust bearing S45C 6 6 6 M10 x L30 (small size)
Washer, thrust bearing locking
16 30 S45C 6 6 6 M10 (small, round)
bolt
Oil pressure regulating valve
*17 -- 1 1 1
(assy.)
18 26 Shaft seal cover FC250 1 1 1
19 27 Gasket, shaft seal cover Non-asbestos 1 1 1 T=0.5
20 28 Bolt, shaft seal cover SCM435 10 10 10 10 x L35
21 Oil drain tube SK5 1 1 1 Ø 4 x L60 (spring pin)
22 32 Mechanical seal assembly -- 1 1 1
23 49&50 Head cover FC300 2 3 4
24 51 Gasket, head cover Non-asbestos 2 3 4 T=0.5
25 52 Bolt, head cover SCM435 40 60 80 M12 x L40
26 53 Head, jacket cover FC250 2 3 4
27 55 Gasket, head jacket cover Rubber 2 3 4 T=1.5
28 54 Bolt, head jacket coverr SUS304 24 36 48 M10 x L25
29 109 Cage, discharge valve FC300 4 6 8
30 75 Bolt, discharge valve cage S45C 16 24 32 M10 x L45 (P=1.0)
Positioning pin, discharge
31 75-2 S45C 8 12 16 Ø6 x L18 (parallel pin)
valve cage
32 110 Discharge plate valve SUS420J2-Mb 4 6 8
33 116 Spring, discharge valve SK5 32 48 64
34 111 Seat, discharge valve SNC631 4 6 8
35 112 Retainer, discharge valve seat SCM435 12 18 24 M8 x L30
Retainer, discharge valve seat
36 112-2 SPCC 4 6 8 T=0.8
bolt
Positioning pin, discharge
37 115 S45C 4 6 8 Ø6 x L18 (parallel pin)
valve seat
38 73 Valve plate FC300 4 6 8
39 73-2 Washer, valve plate bolt SCM435 14 21 28 M10 x L30 (P=1.0)
40 73-2 Washer, valve plate bolt S45c 14 21 28 M10 (small, round)
41 71 Suction plate valve SUS420J2Mb 4 6 8
Spring, suction valve (conical
42 72 SK5 24 36 48 Conical type
spring)
43 61 Cylinder sleeve FC250 4 6 8
Positioning pin, cylindersleeve
44 61-1 (for retaining pin, SK5 4 6 8 Ø3 x L8 (spring pin)
cylindersleeve)
45 66 Gasket, cylinder sleeve SPCM 4 6 8 T=0.1
46 62 Cam ring (leftward slant) FC250 4 4 6
47 65 Retaining ring, unloader SWC 4 6 8
48 68 Lift pin, unloader S50C-D 24 24 36
49 69 Spring, unloader lift pin SWC 24 24 36
Stop ring, unloader lift pin
50 70 S60CM 24 24 36 Also called „E“ locking ring
(E-ring)
51 85 Piston AC8A-T6 4 6 8
52 86 Pin, piston SCM415 4 6 8 Ø34 x L99

9
 Quantity
No.* Part No Name Material Remarks
4L 6L 8L
53 87 Lock spring, piston pin SWC 8 12 16
54 89 Piston ring (fc-PC-BF-G1) FC250 4 6 8 Top ring
nd
55 90 Piston ring (FC-T) FC250 4 6 8 2 ring
Bottom ring, complete with coil
56 100 Oil control ring (FC-PC-CB3) FC250 4 6 8
expander
57 77 Connecting rod AC4D 4 6 8 T31-T6
58 78 Bolt, connecting rod SCM435 8 12 16 M10 (small, round)
59 80&81 Nut, connecting rod S45C 16 24 32 M10 (P=1.5)
60 79 Washer, connecting rod S45C 8 12 16 M10 (small, round)
Wrapped bearing, LBC3
61 82 4 6 8
Connecting rod (F100)
Bearing half (upper),
62 84U WJ1 (F1) 4 6 8
Connecting rod
Bearing half (lower),
63 84U WJ1 (F1) 4 6 8
Connecting rod
64 45 Hand hole cover (with window) FC250 1 1 1
65 46 Hand hole cover (blind) FC250 1 1 1
66 47 Gasket hand hole cover Non-asbestos 2 2 2 T=0.5
67 48 Bolt, hand hole cover SCM435 32 32 32 M12 x L40
68 164 Oil sight glass BH54 1 1 1
69 165 O-ring, oil sight glass NBR 2 2 2 JIS W1516 P35
70 166 Gland, oil sight glass FC250 1 1 1
71 167 Bolt, oil sight glass gland S45C 4 4 4 M10 x L30 (small)
Unloader cover (built-in
72 146 -- 2 2 3 120V, 240V
solenoid valve)
73 147 Gasket, unloader cover Non-asbestos 2 2 3 T=0.5
74 149 Bolt, unloader cover SCM435 8 8 12 M8 x L35
75 145 Unloader piston S25C 2 2 3
76 135 Push rod, unloader (1) AC2B-F 1 1 1 L=371
77 136 Push rod, unloader (2) AC2B-F 1 1 1 L=401
78 137 Push rod, unloader (3) AC2B-F -- -- 1 L=431
79 143 Washer, unloader push rod S25C 2 2 3
80 144 Stop ring, unloader push rod SK5 2 2 3
81 142 Spring, unloader device SWC 2 2 3
100A (common to 6A, 8LO, also
82 175 Scale trap FC250 -- 1 1
called „Suction Filter Case“)
Gasket, suction filter case
83 176 Non-asbestos -- 1 1 100A MYC Flange, t=2.5
(Crankcase side)
84 177 Bolt, suction filter case SCM435 -- 4 4 M22 x L55
Washer, suction filter case
85 177-1 SK5-7 -- 4 4 For M22
locking bolt
86 178 Suction filter SUS316 1 1 1 4L = 80A, 6L & 8L = 100A
87 179 Suction filter cover FC250 1 1 1
88 180 Gasket, suction filter cover Non-asbestos 1 1 1 T=1.0
89 181 Bolt, suction filter cover SCM435 4 8 8 M12 x L40
90 168 Discharge elbow FC250 -- 1 1 6L = 80A, 8L=100A t=1.5
Gasket, discharge elbow
91 169 Non-asbestos -- 1 1 6L=80A, 8L=100A t=1.5
(crankcase side)
92 170 Bolt, discharge elbow SCM435 -- 4 4 M20 x L55
Washer, discharge elbow
93 170-1 SK5-7 -- 4 4 M20
locking nut
94 119 Oil filter SUS316 1 1 1 #200
95 118 Hexhead nipple S25C 1 1 1 R1/2 x R1/2
96 214 Built-in safety valve -- 1 2 2 R1“ (Working D.P.=250Psi)
97 173-1 Companion flange, suction S25C 1 1 1 4L=80A, 6L & 8L=100A
Gasket, suction companion
98 173-2 Non-asbestos 1 1 1 4L=80A, 6L & 8L=100A t=1.5
flange
99 182-3 Companion flange, discharge S25C 1 1 1 4L=65A, 6L=80A, 8L=100A
Gasket, discharge companion
100 182-2 Non-asbestos 1 1 1 4L=65A, 6L=80a, 8L=100a t=1.5
flange
101 173-B Bolt, suction companion flange SCM435 4 4 4 M20 x L50
Bolt, discharge companion 4L=M16 x L45,
102 182-B SCM435 4 4 4
flange 6L & 8L=M20 x L50
103 173 Service valve, suction -- 1 1 1 4L=80A, 6L & 8L=100A
104 184 Gasket, suction service valve Non-asbestos 1 1 1 4L=80A, 6L & 8L=100A t=1.5

10
No.* Part No Name Material Quantity Remarks
4L 6L 8L
105 182 Service valve, discharge -- 1 1 1 4L=65A, 6L=80A, 8L=100A
106 172 Gasket, discharge service Non-asbestos 1 1 1 4L=65A, 6L=80A, 8L=100A t=1.5
valve
107 174 Bolt, suction service valve SCM435 4 4 4 4L=M16 x L140
108 183 Bolt, discharge service valve SCM435 4 4 4 4L & 6L=M16 x L140,
8L=M20 x L190
109 185 Oil cooler assembly -- 1 1 1 TCF-0.3-0.613P
(water-cooled type)
110 186-1 Set bolt, oil cooler assembly SCM435 4 4 4 Hexhead socket bolt, M8 x L25
111 186-2 Nut, oil cooler SS400 4 4 4 M8
*112 Heaxhead bushing SS400 2 2 2
(R1 x RC 1/2)
*113 Hexhead nipple (R 1/2) SS400 1 1 1
*114 Double-headed nipple STPG38 1 1 1 Sch-40
(R 1/2 x L50)
*115 Elbow (Rc 1/2) SF390 1 1 1
*116 Cheese (Rc 1/2) SF390 1 1 1
*117 Straight half union S45C 2 2 2
(R 1/2 x R 1/2)
*118 „L“ type half union S45C 2 2 2
(R 1/2 x R 1/2)
*119 High pressure pipe (15A) STPG38 -- -- -- Sch-40
*120 Oval flange (HEF-150) SS400 5
*121 Oval flange (HEF-70) SS400 2
*122 Oval flange (HEF-38) SS400 1 1
*123 Gasket, oval flange Gummi 5 6 8
*124 Bolt, oval flange SUS304 8 12 16 M10 x L25
*125 Straight elbow SUS304 1 1 1
*126 Hose nipple (R ¾) FC150 1 1 1
*127 Hose band (R 3/4) FC150 1 1 1
Blade hose, pressure-tight (R
*128 -- - - -
3/4)
*131 Hose nipple (R 3/8 x L50) STPG48 1 1 1 For oil feeding, draining
*132 Hose nipple (R 3 x L50) STPG38 1 1 1 For gas purging
Thermometer assembly „L“ Type (R 3/8)
133 199 -- 1 1 1
(-50 ~ +50°C) Complete with casing
Thermometer assembly „L“ Type (R 3/8)
134 197 -- 1 1 1
(0 ~ 200°C) Complete with casing
*135 Eye bolt SF390 1 2 2 4L=M20, 6L & 8L=M116
Oil heater mounting portion and outer
*136 Hexhead socket plug, R1“ S25C 2 2 2
safety valve seat
*137 Hexhead socket plug R ¾ S25C 1 1 1 Outer safety valve retyrb
*138 Hexhead socket plug R ½ S25C 1 1 1
*139 Hexhead socket plug R 3/8 S25C 4 4 4 Oil passage, etc.
*140 Hexhead socket plug R ¼ S25C 2 2 2 Oil passage, etc. (Crankshaft)
*141 Hexhead socket plug R 1/8 S25C 2 2 3 Oil passage (Unloader)
*142 Square plug, R 1/2 S25C 1 1 1 Oil filter mounting portion
*143 Square plug, R 1/4 S25C 1 1 1 For initial oil charging valve
*144 Pressure equalizing tube -- 1 1 1
Rubber packing, pressure
*145 NBR 1 1 1 T=3
equalizing
*146 Nut, pressure equalizing tube SS400 1 1 1 M12

11
Fig. 3 Exploded view of Model 8L reciprocating compressor

12
Fig. 3-A Exploded view of compressor cylinder section

13
 Fig. 3-B Exploded views of Model 4L and 8L compressors

Regarding other models, refer to Figs. 3 and 3-A as parts are common to these
models. Number shown in the above figure are part numbers given in the parts
list.

14
3. Introduction

The Model L is a newly designed compressor based on MYCOM A, B, C, J, WA, WS

and K series reciprocating compressors. The Model L is well suited for the WB
capacity range and is capable of being direct-coupled to a 4-pole motor or diesel
engine to create a small, light weight, high speed unit. Either R22 or NH3 refrigerant
can be used in the Model L. This compressor design incorporates the best of
MYCOM’s technical know-how. For instance, the unloader oil pressure piping and the
lubricating oil piping are all built into the machine body, eliminating the need for
external piping and resulting in a neat external appearance and easier maintenance.
The component parts are all machined under the highest quality control standards
using the latest NC lathe equipment and assembled and inspected by skilled workers.
While initial performance of the compressor after installation is superlative, unless the
system is properly maintained, performance deterioration may result. Periodic
maintenance should be diligently performed in order maintain the Model L compressor
in the best condition for the longest period of time.

4. Mechanisms

4.1 Gas compression mechanism and fas flow

Refer to the cross-sectional drawing (Fig. 1). Suction and discharge service stop
valves are provided on the gas inlet and outlet ports of the compressor, respectively.
Refrigerant gasified in the evaporator is fed to the compressor through the piping and
enters the suction gas chamber in the crankcase through the suction elbow after
passing through the suction service stop valve. At this pont the gasified refrigerant is
filtered through the suction filter.
A suction gas chamber and crankshaft chamber are provided in the crankcase and
cylinders are provided in the suction gas chamber. Pistons in the cylinders are
connected to the crankshaft by connecting rods and reciprocate up and down as the
crankshaft rotates.
A suction/discharge valve mechanism actuated by the pressure differential which
exists before and after the valve is provided at the top of each cylinder. Internal
pressure drops as the piston descends in the cylinder and gas in the suction chamber
pushes up the suction valve and flows into the cylinder. Gas continues to flow into the
cylinder until the piston reaches the bottom dead center and the suction valve is then
pressed against the seat by spring force to seal the cylinder. When the piston begins
to ascent, the internal volume of the cylinder is reduced and the pressure rises,
compressing the gas in the cylinder. When the cylinder internal pressure becomes
higher than the discharge side pressure, the gas pushes up the discharge valve and is
discharged to the high pressure side from the cylinder. This high prtessure gas is fed
to the condensor through the discharge elbow and the discharge service stop valve,
then is supplied to the evaporator to circulate onside the refrigeration system.
The compressor, in essence, functions to transform heat from the low to the high side.

4.2 Suction and discharge valve mechanisms

The design of the suction and discharge valve mechanism of Model L is the same as
that found on all other MYCOM reciprocating compressor. The head spring is
eliminated by incorporating a valve plate on each cylinder and securing the discharge
valve assemblies with bolts. Other mechanisms include a ring valve to minimize the

15
 top clearance between the discharge valve seat of the piston head and the top of the
piston in order to absorb impact on the back face with a gas damper.
Experience with other models has led to the use of a conical spring force which
provides changing spring force.

4.3 Capacity control mechanism

Capacity control is achieved by controlling operation of the suction valves using an oil
pressurized piston cylinder. The mechanism controls the number of cylinders
compressing gas. Each suction valve seat is provided with a flange on the top of the
cylinder sleeve. Gas flows into the cylinder through the intermediate space. A lift pin,
which moves up and down, is provided at the center of the suction valve seat. The top
of the pin contacts the suction valve and the bottom mounted on an inclined portion of
the cam ring, which rotates around the cylinder sleeve. The cam ring is designed to
rotate when activated by a rod driven by oil pressure and the lift pin moves up and
down as the cam ring rotates. When the top of the lift pin is lower than the seat face,
the suction valve operates freely on the seat due to the differential pressure of the gas
before and after the valve. When the lift pin pushed up the suction valve due to
rotation of the cam, the suction valve does not operate, even in and out of the suction
port even if the piston moves up and down, so the pressure does not rise. The cylinder
is therefore in a „no-load“ condition. Compressor capacity is controlled by changing the
number of cylinders actually compressing gas.
The cam rings of the cylinders are activated by oil and spring pressure. When oil
pressure is acting on the cam of a particular cylinder, that cylinder is in a „no-
load“condition. Consequently, capacity control during the operation is effected by
shutting off oil pressure to particular cylinders. This is accomplished by a three-way
solenoid valve. Since no oil pressure is available when the compressor is stopped, the
system starts up in a „no-load“ condition and compression is not commenced until the
oil pump begins operating due to rotation of the crankshaft and oil pressure rises.
The unloader mechanism thus serves to ensure that the system is unloaded during
start-up. Since a three-way solenoid valve is used to control oil reduction during
operation, load on the oil pump is decreased, unlike with conventional methods which
require oil flow during unloading.
Capacity control is effected by two cylinders at a time in successive steps.

16
4L Compressor
Cylinder number

0% 50 % 100 %
Positioning pin,
Stop | ~ | ~ Cylinder sleeve (61-1)
Or No. of push rod
run Unloader (136-137)
{ } Unloader working order

6L Compressor

0% 33 % 66 % 100 %
} € } € } €
Stop { ~ { ~
| 

8L Compressor

0% 25 % 50 % 75 % 100 %
~ ‚ ~ ‚ ~ ‚ ~ ‚
}  }  } 
Stop Note1) Unloader fuctions when power on and
| € | € unloads when power off.
2) Unloader working order is same as loading
{  order and revers order when unloading.

Fig. 4 Unloader and solenoid valve for Model L

4.4 Oil supply mechanism

Oil cooler piping and control pressure connecting piping are incorporated into Model L
Compressors as standard specifications. A fine mesh oil filter is provided on the
suction side. Sufficient passing area is provided and is durable for use of standard
cleaning equipment. Since a trochoid gear and reversible mechanism are used for the
pump, the direction of discharges constant irrespective of the direction of rotation of
the crankshaft. The relief valve presses against the seat by spring force and is

17
 designed to automatically maintain oil pressure in a specific range and to act as a
safety relief valve in case of abnormally high pressure.

4.4.1 Oil flow

The botom of the crankshaft chamber in the crankcase serves as an oil reservoir.
Oil is sucked into the crankshaft-driven pump through an oil filter (#200 mesh) and
is pressurized. The pump is a reversible trochoid type which discharges oil in a
specific direction irrespective of the direction of rotation of the shaft. Oil discharged
from the pump is fed to the oil coller through piping.
Oil is then fed from above the hand hole (seal side) on the crankcase and branches
to the main bushing side and the thrust bearing mechenical seal side for lubrication
purposes. Oil fed to the main bushing passes from an oil groove on the crankshaft
lubricates and cools the inner wall of the piston pin, passing through a hole in the
connecting rod. Oil supplied to the thrust bearing side further branches along two
paths in order to lubricate the thrust bearing and the mechanical seal. Oil lubricating
and cooling the mechanical seal returns to the oil reservoir in the crankshaft
chamber. Oil supplied to the thrust bearing is fed to an oil hole in the crankshaft
through the oil groove on the crank on the crankshaft and then flows to the seal side
crank pin to lubricate and cool the pin and the cylinder inner walls, as in the case of
oil supplied to the pump side.
Oil fed to the bearing housing is supplied to each unloader cover solenoid valve
through holes in the crankcase. When the solenoid valve is turned ON, oil is fed to
the unloader cylinder to create a loaded condition by pushing up the piston. Oil does
not flow along this path any longer to maintain the position of the pin.
When the solenoid valve is turned OFF, oil supplied from the pump is shut off and
the pressure in the cylinder conforms to the internal pressure of the crankcase. Oil
in the cylinder is then pushed out by spring force to create a no-load condition.

Oil Cooler

Three-way solenoid valve,

unloader

Oil pressure regulating valve

Crankshaft
Shaft seal
Reversible trochoild pump

Main bushing
Thrust bearing
Thrust washer Thrust washer

Oil filter
Fig. 5 Oil flow diagram for Model L compressor (standard)

18
 Fig. 6 Bearing housing oil passageway

4.4.2 Quantity of oil inside crankcase

Model No. 4L 6L 8L
Upper limit
Normal level 25
Lower limit
Unit: Liters
45 166

45 Hand hole cover

164 167 164 Oil signt glass
165 O-ring, oil signt glass
166 Gland, oil signt glass
167 Bolt, oil signt glass gland

165 165
Fig. 7 Sectional view of oil sight glass

4.5 Mechanical shaft seal

The mechanical shaft seal incorporated into the Model L compressor was selected
taking into consideration the most reliable yet simple design. The rolling portion of
contact face of the shaft seal is finished with a special combination of cast steel and
carbon.
O-ring packing is utilized on both sides of the oil sight glass, as shown in Fig. 7.

19
 Fig. 8 Oblique sectional view of Fig. 9 Safety valve (214)
Mechanical shaft seal (Internal built-in type)

4.6 Safety valve, built-in type (214)

The Model L compressor is furnished with an internal built-in safety valve in the head,
i.e., at the partition wall between the high and low pressure sides of the casing inside
the head coveer. If the differential pressure between the discharge and the suction
sides reaches or exceeds 1.77MPa (18kg/cm² or 250PSI), the safety valve is
activated.

4.7 Oil cooler (185)

The Model L compressor is furnished with an oil cooler as a standard component. It is

a shell and tube type water-cooled oil cooleer. Optional selection of another type of oil
cooler is possible, subject to conformance with the specified heat exchange capacity.
For details of heat exchange capacity requirements, contact the nearest MYCOM
subsidary or liaison office.

4.8 Accessories

Accessories differ according to the kind of compressor package required.

Fig. 10 Crankshaft end portion

20
4.8.1 Direct coupling (Formflex type)

The form-flex, double flexing type coupling consists of three major components, i.e.,
a hub, a spacer and an element made of laminated square flexible plate, as shown
in Fig. 11. Because the function of the couplins is maximum power transmission, a
coupling element made of thin laminated stainless steel is utilized to ensure
maximum power transmission capacity and superior flexibility characteristics. Due
to the simplicity of the design, which does not utilize any frictional parts such as
rubber, the durability of the coupling is unsurpassed. By utilizing a double flexible
mechanism with the spacer, inspection of the seal portion can be easily carried out
without removing the motor.

Fig. 11 Flexible coupling

4.8.2 Flywheel for V-belt drive

The flywheel for V-belt drive system is complete with a JIS C-grooves as standard.
For Model 4L compressor four (4) V-belts are required whereas for Model 6L, six (6)
belts are necessary and for Model 8L, eight (8) belts.
Red colored belts are standard.

Fig. 13 Sectional view of flywheel

4.8.3 Pressure gauges and instruments

Piping connection work must be carried out for the components attached to the
respective pressure outlet ports shown in Fig. 14.

21
 Component Connecting port
4L: Crankcase on pump side
Suction pressure gauge 6L/8L Suction filter case Rc 3/8
Discharge pressure gauge 4L: Crankcase on discharge side
High pressure cutout switch (LP) 6L/8L Discharge elbow Rc 3/8
Oil pressure failure protection switch 4L: Crankcase on pump side
(OP) 6L/8L Discharge elbow Rc 3/8
Oil pressure gauge
Adjacent to bearing housing
Oil pressure failure protection switch
On pump side Rc 3/8
(OP)
Oil separator (for oil return) Hand hole cover (with window) Rc 3/8

Fig. 14 Connecting port locations

22
5. Installation and Operation

5.1 Compressor Unit Centering

! DANGER

Turn off or disconnect the main power supply to the motor and the control power supply
before commencing centering work for the compressor and driving apparatus. The
power supply should never be connected or turned on during centering work. If
energized, the compressor may commence operation, posing the threat of physical
harm to anyone in the vicinity of the belt drive or shaft.

! WARNING

Care should be taken when turning any power supply on or off to prevent electric
shock.

! CAUTION

When performing centering work on the compressor and prime mover, use only those
tools which are designated in this manual. If worn, damaged or inappropriate tools are
utilized, accident or injury may result.

5.1.1 For belt drive operation

a. Confirm that the compressor is parallel with the centerline of the motor using a
steel wire or string stretched across the face of the flywheel. If the compressor
and motor are not aligned, the V-belts will wear rapidly and the durability of the
compressor will be reduced due to the excessive force acting on the crankshaft
bearings.
b. When fitting the V-belts on the pulleys, do not force into the grooves; loosen the
motor adjusting bolts and slide the motor closer to the compressor. Confirm that
the V-belts are properly seated in the pulley grooves, then adjust tension using
the motor adjusting bolts. Tension is correct when the belts can be depressed
midway between the pulleys by an amount equal to the thickness of the belt.
Remember that excessive tension on the belts will shorten belt life.

5.1.2 For direct coupling (Formflex type) operation (Ref. Fig. 16)

a. Securing the hub

The distance between the compressor side hub end face and the motor side hub
end face should be set to the specified dimension.

b. Centering
1) Eccentricity

23
 Eccentricity can be detemined by mounting a dial gauge on the motor side hub
with the sensor in contact with the driven side hub periphery. Determine the
eccentricity value by rotating the motor side shaft. Eccentricity tolerance
should not exceed 0.05mm (relative eccentricity under 0.1 mm).

Fig. 15 V-belt centering alignment

Fig. 16 Shaft eccentricity Fig. 17 Shaft declination

2) Shaft declination
Shaft declination can be measured using a dial indicator mounted as shown in
Fig. 17. Attach the dial indicator to the hub flange and measure the declination
of the opposite side hub while turning the hub flange. The allowable tolerance
is 0.05mm or less per 100mm radius.

c. Coupling assembly
Assemble the coupling referring to Fig. 11, Flexible coupling. The coupling
element can easily be assembled by securing the coupling bolts.
* Coupling bolt torque value: 1600 kg-cm

24
 Fig. 18 Washer orientation Fig. 19 Coupling bolt set

Cautions during assembly

Shaft eccentricity and declination should be rechecked 1~2 hours after starting
operation. At the same time, all bolts and nuts should be retightened to the specified
torque values shown in section 8.3.1 of this manual. According to test results, the
nylon nuts can be secured/removed a maximum of 15 times, but it is preferable to
renew them after ten times. If it becomes necessary to remove and refit a nylon nut
10 times, spare nuts should be made available.
The convex face of the washer should face the flex element. When inserting the
bolt, do not apply an excessive power. All nylon nuts should be tightened to the
specified torque. The bolts need not be inserted in a particular direction; insert from
the side most convenient for servicing.

5.2 Piping

5.2.1 Refrigerant piping

a. The compressor is one of the few components in the refrigeration system with
reciprocating and rotating parts. These need to be protected from any foreign
matter circulating in the piping system. When the piping is being installed,
extreme care should be taken to prevent rust and welding debris from remaining
inside.
b. When the compressor is shipped from the factory, it is usually charged with
nitrogen gas as a rust prevention measure. The suction and discharge valves
should never be opened until installation on site.
c. Moisture contamination of the piping system must be carefully avoided,
otherwise, problems may develop with the compressor after the commencement
of operation. Piping work should therefore be carried out under completely dry
conditions.
d. Dust guard plates are fitted to the pipe joints of the compressor. These must be
removed when the piping is connected to the compressor.
e. Suction gas piping must be arranged so that any oil which enters the pipes is
returned to the compressor. If a trap is incorporated or the routing includes
bends, attention must be paid to ensuring the necessary gas flow rate and oil
return.

5.2.2 Pressure gauge and protection switch piping

Piping work between the compressor and the pressure gauges or protection
switches shall be carried out referring to Fig. 14, Connecting port locations.
Unlike with pressure switches, pressure gauges and thermometers are not directly
for evaluating operating conditions. The following devices are usually mounted for
this purpose.
a) Oil pressure gauge
b) Suction pressure gauge

25
 c) Discharge pressure gauge
d) Suction gas thermometer
e) Discharge gas thermometer
* Any questions concerning piping and auxiliary devices should
be directed to the nearest Mycom office.

When installing piping between the compressor and the oil pressure gauge,
discharge/suction pressure gauges and thermometers, refer to Fig. 14. When small
diameter, e.g., 6mmOD, pipe is used, care must be taken when installing to prevent
possible clogging with welding butts, spatter, etc.

5.2.3 Protection switches

The surface temperature of the compressor stabilizes within a specific range during
operation under normal conditions. If an abnormality develops within the
compressor, unusual symptoms are usually evident in advance. Constant and
proper management of the discharge gas temperature as well as oil temperature is,
therefore, essential in order to protect the compressor from vital mechanical failure.
The oil temperature and the discharge gas temperature are also related. Especially,
abnormal symptoms are usually reflected in the discharge gas temperature at an
early stage. Careful supervision and management of the discharge gas temperature
is therefore an essential aspect of system management.
Pressures throughout the system stabilize within a specific range during operation
under normal conditions. If any abnormal change in pressure is observed, the
compressor must be stopped immediately and the cause determined in order to
prevent accident or damage to the compressor.
Model L series compressors are equipped with the following protection switches to
ensure that system pressures do not exceed normal levels.
a. Oil pressure failure proterction switch (OP)
b. High pressure cutout switch (HP)
c. Low pressure control switch (LP)

5.2.4 Oil heater and thermostatic switch

The oil heater is a cartridge type, incorporating an insulated heating wire sealed
in a pressure-tight stainless tube with a maximum heat transfer surface.
Fluorcarbon refrigerant has a propensity to mix with the lubricating oil under
certain temperature conditions and the lubricating oil in the compressor
crankcase may foam or bubble with small changes in pressure or when starting
operation, resulting in insufficient oil pressure, a shortage of lubricating oil,
seizure, etc. For this reason installation of an oil heater is essential.

26
 Component Activation Set value
(1) Oil pressure failure OFF LP + 0.12Mpa
2
Protection switch (OP) (LP + 1.2kg/cm )

ONS – C106Q ON LP + 0.7±0.2Mpa

2
TIMER (LP + 0.7±0.2kg/cm )
Man. Return 45 ± 20 Sek.

(2) Built-in safety valve Pressure difference 1.77Mpa

2
between HP & LP (18kg/cm )

0.25±0.02Mpa
2
(3) Low pressure control switch OFF 2.5±0.2kg/cm )
(LP)

SNS-C106Q ON 0.15±0.02Mpa
2
(1.5±0.2kg/cm )

Note: The setting values shown above are based on MYCOM standards.

The preset values for all devices must be confirmed before starting operation.
Except for the built-in safety valve, the function of all devices should be confirmed
during test operation.

Note: OP Switch Testing

Performance testing of the high pressure cutout switch should be carried out
by of lowering the activation value to the standard pressure level. If the
actuation pressure level of the HP is equal to the pressure level read on the
High Pressure Gauge, the high pressure cutout switch is considered able to
actuate at the preset pressure level, and can therefore be judged as
functioning satisfactorily.
Under no circumstances should the switch be tested by raising operating
pressure to the HP preset value as this is extremely dangerous.

5.2.5 Oil separator

(Various types of oil separator are available according to the particular installation)
Oil mist is mixed in the refrigerant gas discharged from the compressor.
Consequently, an oil separator is necessary to separate this oil from the refrigerant
gas. Regarding to the structure of the oil separator, refer to Fig. 20.
Refrigerant gas discharged from the compressor is fed to the oil separator through
the gas inlet port on the top of the separator. The gas/oil mix swirls around the inner
wall of the oil separator and oil particles entrained in the gas are separated out by
centrifugal force, adhering to the wall and then falling into the oil reservoir due to
gravity.
When sufficient oil accumulates in the oil reservoir, the float valve opens to return
the oil to the compressor crankcase automatically.

27
 G as outlet port
(to condenser

G as inlet port
(from compressor

O il return
(to com pressor crankcase)

Float valve, autom atic oil return

Fig. 20 Oil separator Fig. 21 Float valve

5.3 Precautions during operation

(1) Initial start-up

The refrigeration equipment is expected to provide maximum performance for a
long time after installation. Precuations during initial start-up operation of the
compressor are, therefore, essential in assuring the durability and performance of
the compressor.
During the first 10~24 hours of operation, any dust, scale, rust or sand
contaminating the piping system will be carried into the compressor by the
circulating gas. Very fine dust which can not be removed by the suction filter
becomes entrained in the oil causing accelerated wear and eventual failure. While
various foreign contaminants are sucked into the compressor over a long period of
time after initial start-up, most accumulated foreign matter is sucked into the
compressor just after starting initial operation.
Determine the presence of foreign matter by checking the suction filter and the oil
color. Since deterioration of the oil in the crankcase is the probable result of
system contamination, the system can be regarded as clean if the oil remains
clear for an extended period of operation. On the other hand, if the oil color turns
black or muddy brown, contamination by foreign ,matter in the piping system is the
most probable cause. In such a case the oil should be replaced as soon as
possible. When replacing the oil, care must be taken to prevent further
contamination.

a. Filter cleaning and oil change

Frequency Oil filter cleaning and oil change Frequency Suction filter cleaning
Initial After refrigerant charging
st
2nd After test running 1 After test running
3rd 100 hrs. after initial start-up 2nd 100 hrs. after initial start-up
4th 300 hrs. after initial start-up 3rd 300 hrs. after initial start-up
5th 700 hrs. after initial start-up 4th 700 hrs. after initial start-up
6th 5th
Every 1,000 hrs. Every 1,000 hrs.
& thereafter & thereafter
Note: Regardless the above, if any symptoms of a problem are observed regarding the compressor
lubrication oil or the filters are becoming clogged, replace the oil and clean the filters
immediately.
If the refrigerant cycle remains clean, periodic filter cleaning may be ignored.

b. There should be no abnormally high temperature or abnormal sound generated

by the compressor.

28
(2) Operations records and inspection items
Records of refrigeration equipment operating conditions should be maintained
using a log book. Accurate records are essential not only for ensuring safe,
effective operation of the equipment but also in quickly determining the cause of
any problem that might be encountered so that proper countermeasures can be
taken.
All personnel involved in operating the system should be prepared to implement
countermeasures not only for future conceivable problems and accidents.
Machine room cleaning, management of spare parts, maintenance and
arrangement of the hand tools should all be considered part of the daily routine.

a. Suction pressure and temperature

In theory, the ideal suction pressure is saturation pressure equivalent to the
evaporative temperature. In pracctice, however, there is a small pressure drop
(loss) due to piping resistance. If a large pressure drop is identified,
countermeasures should be taken, e.g., cleaning a clogged suction filter. The
suction pressure, the evaporative pressure as well as the temperature are
determined when the equipment is being designed. If the compressor is
operated outside of the specified operating parameters, for example, below the
specified values, refrigeration capacity will be reduced, resulting in poor
operating conditions. On the other hand, if the compressor is operated at higher
than the specified values, refrigeration capacity will increase but the power
requirement will also increase, resulting in motor overload.
Maintaining the appropriate suction pressure is essential to assuring
satisfactory compressor capacity for a long period of time.
Usually, the most suitable suction temperature is the saturation temperature
equivalent to the suction pressure plus 10~15°C (that is, the superheat degree
is 10~15°C), assuming that there is no liquid flow back to the compressor at this
superheat value.
Continuous operation at a superheat degree exceeding 10~15°C is not
recommended because the discharge temperature will increase to an abnormal
level.
b. Discharge pressure and temperature
The criteria for discharge pressure can be simply states as „Condensing
pressure + Piping resistance.“
When the discharge pressure rises excessively, various problems develop.
These include as drop in refrigeration capacity, motor overload or malfunction
and, most importantly, dangerous conditions due to abnormally high pressure.
A shortage of cooling water, contamination of the suction gas by non-
condensable gas (air) and a decline in the performance of the heat-exchanger
can lead to an abnormally high compressor discharge pressure.
Since the above factors change from moment to moment, a check of the
operating records can facilitate determination of the cause.
On the other hand, a drop in the discharge pressure (condensation pressure)
can lead to favorable results such as an increase in refrigeration capacity, a
reduction in motor power consumption, etc. In any case, if the power
consumption of the water pump, the circulation rate of the cooling water, etc.
are neglected, economic operation cannot be achieved.
Discharge temperatures differ according to the kind of refrigerant and the
superheat degree of the suction gas, but care must be taken never to exceed
135°C. If the discharge temperature is excessively high, the cause may be

29
 excessively high degree of suction gas superheat or recompression superheat
due to discharge or suction valve damage.
c. Oil supply pressure
The most suitable oil pressure is equivalent to the suction pressure +
0.2~0.3MPa (2~3kg/cm²). A drop observed in the oil pressure may be due to oil
filter clogging or to oil foaming inside the crankcase (which may occur if a large
amount of liquid refrigerant flows back to the crankcase.
d. Oil quantity (Oil level)
The oil level in the crankcase can be detemined by observing the oil level
gauge. Confirm that the oil level is within the specified oil range. Usually, the oil
level in the crankcase gradually drops during initial start-up. If the oil level is not
visible in the level gauge, add oil. If refrigerant is dissolved in the oil, care must
be taken because the apparent oil level will appear to be higher than the actual
level.
e. Oil temperature
The oil temperature will vary according to operating conditions. Generally, the
oil temperature is between ambient temperature and 55°C. Operation which
raises the temperature of the crankcase hand hole above 50°C should be
avoided.
f. Dirty oil
Clear, transparent oil similar in appearance to fresh new oil is desirable.
Generally, oil deterioration can be determined by observing the change in color,
i.e., brown to black and finally to a muddy appearance, which is a sign of
contamination by foreign solids. Such should be immediately replaced.
Imagine, for example, the engine oil of a car. Assuming that the oil must be
changed every 10,000 km, if the car ran at a steady 50 km/h, the oil would have
to be changed every 200 hours, or every 8 days. When you think about the
steady operation of a compressor, the effectiveness and durability of the
compressor lubricating oil is truly amazing. Operating the compressor for half a
day per year is equivalent to some 4,500 hours of operation annually.
Obviously, diligent oil maintenance is vital to the long life of the compressor.
g. Oil leakage from shaft seal portion
Oil leakage from the shaft seal is determined by the estimated quantity of oil
which leaks from the cylinder. The factory standard is 3cc per hour. This
amount of leakage is not considered abnormal.
h. Power transmission
If the compressor uses a V-belt drive, care must be taken to ensure proper belt
tension. If the tension is to great, excessive load is applied on the compressor
crankshaft bearings, the motor and the V-belts. On the other hand, excessive
slack lead to heat generation and belt wear due to slippage, resulting in a
reduction in the durability of the V-belts as well as the generation of abnormal
vibration. Periodic inspection and adjustement of V-belt tension is an important
part of regular maintenance (refer to Section 5.1, Compressor unit centering).
For a direct coupling, confirm that there is no abnormal vibration due to
loosening of the bolts and nuts. Generally, a rhythmical operating sound should
be heard.
i. Elektric motor
Confirm that the electric current and voltage remain steady within the ranged
recommended by the motor manufacturer. The temperature of the bearing
casing should also be remain within normal parameters.
j. Others
* Temperature of refrigerant piping (during the time of normal operation)

30
 The refrigerant piping between the receiver and the expansion valve should
be warmish to the touch. If the piping is excessively hot, a condenser
malfunction may have developed or gas is flowing through the pipe instead of
liquid due to a shortage of refrigerant.
On the other hand, if the refrigerant piping is cold, the liquid refrigerant is
expanding inside the piping. This may be due to clogging of the dryer,
excessively lean refrigerant, a bent in as the piping, a closed valve, etc.
Determine the cause and remedy it to return the system to normal.
* Liquid hammer and oil hammer
If a large quantity of oil or non-gasified refrigerant is sucked into a
compressor cylinder, a clanking sound is heard and the discharge piping
becomes frosted (instantaneous drop in temperature). This commonly called
„liquid hammer“ and is very dangerous, posing the threat of a serious
accident. If this phenomenon is encountered, even if every so slightly, adjust
the expansion valve after throttling the suction valve to control the quantity of
refrigerant flow into the cylinders. When the sound of liquid hammer ceases
and the discharge piping becomes warm again, open the suction valve
gradually to return to normal operation.
Oil hammer, a similar phenomenon, occurs when the oil level in the
crankcase is too high. In this case, the excessive oil should be drained off.
* Refrigerant leakage
The refrigeration system incorporates a considerable number of connection
joints. Periodic inspection and retightening to the proper torque value is
essential.
Bolts securing components under high pressure, high temperature and
vibration become loose over time, resulting in refrigerant leakage.
Periodic retightening of the joints and confirmation of torque values are
essential
Torsionswerte ist wesentlich.

(3) Decline in compressor capacity

A significant decline in the capacity of the compressor may result from refrigerant
leakage from the discharge or suction plate valves and the piston rings due to
breakage or excessive wear.
Refrigerant leakage from the safety valve or the oil return float valve mounted
inside the oil separator may also occur.

(4) Oil consumption

Lubricating oil mixed in the refrigerant gas passes the piston and is discharged
from the compressor, flowing into the receiver through the oil separator and
condenser. With fluorcarbon refrigeration equipment, an oil separator fitted with an
automatic oil return mechanism stops most of this oil passing downstream.
Lubrication oil is also returned from the evaporator.
Oil consumption is rather large during initial start-up operation but it stabilisez after
a certain period of time and the quantity of oil returned from the evaporator and
actual oil consumption reach a near balance as apparent oil consumption
(requiring additional oil charging) decreases.

31
5.4 Service limits

Model Single-stage
No
Item compressor
1 Refrigerant R-22 NH3
Evaporative temperature (°C) Max. 14 13
2
Min. -30 -30
3 Maximum suction pressure (kg/cm2) 6
4 Condensing temperature (°C) Max. 50 50
5 Maximum discharge gas pressure (kg/cm2) 20
6 Maximum discharge gas temperature (°C) 135 140
7 Oil temperature (°C) Under 55
8 Superheat degree (°C) Under 15 Under 30
Revolution speed (RPM) Max. 1750
9
Min. 970
2
10 Oil pressure (Low pressure +) ~ Mpa (Cm G) 0.2 ~ 0.3 (2 ~ 3)
Cautions: * Superheat degree (°C)
Discharge temperature rises as the superheat degree of the suction gas
rises.
Since oil temperature also rises, care must be taken not to exceed the
specified limit.
Never operate the compressor by any means under conditions exceeding
the above limits, otherwise mecahnical failure will result.

32
6. Maintenance and inspection
! DANGER

Turn off or disconnect the main power supply to the motor and the control power
supply before commencing inspection and maintenance work. The power supply
should never be connected or turned on when working on the system. If energized,
the compressor may commence operation, posing the threat of electrical shock or
physical harm to anyone in the vicinity of the belt drive or shaft

! WARNING

Turn off or disconnect the main power supply to the heater and all other electrical
equipment before commencing inspection and maintenance work. The power supply
should never be connected or turned on when working on the system. If energized,
electrical shock, burns or other physical harm may result.

! DANGER

When carrying out inspection or service work in control valves while the compressor
is operating, special care must be taken to assure absolute safety.
Because of the complexity of the refrigeration system, various hazards exist if all
safety measure and precautions are not taken, posing the threat of death, serious
injury, electric shock, burns, etc.

6.1 Daily inspection

The following should be inspected every 2 ~ 3 hours and inspection data recorded in
the operation log book.
a) Suction pressure
b) Discharge pressure
c) Oil pressure
d) Suction temperature
e) Discharge temperature
f) Liquid level in receiver and oil level in crankcase
g) Any abnormal sound or vibration
h) others
- Motor current
- Cooling water flow to condenser
- System moisture contamination
- Machine room temperature
In addition, the following data should be recorded
1. Oil supply
2. Refrigerant charging
3. Filter cleaning
4. Periodic inspection and maintenance
5. Total operating hours

33
6.2 Monthly inspection

a) V-belt tension
Check V-belt tension of the belt by pushing down one of the belt midway between
the pulleys. Tension is satisfactory if the belt can be displaced by an amount equal
to the thickness of the belt.
b) Confirm that the flywheel (or coupling) is securely fastened.
c) Determine if the protection devices such as the pressure gauges and pressure
sensors are actuating correctly.
Pressure sensor performance testing should be carried out and adjustments made,
if necessary.
d) Confirm that oil leakage from the shaft seal is within allowable limits.
e) Visually or, preferably using a halide torch, confirm that all joints, flare joints and
flanges for gas leakage.
f) Check the cooling water system and cleaning if necessary.
The cooling coils of the condensor should be carefully cleaned.

6.3 Periodic inspection

Generally, periodic inspection is carried out every one year or 6,000 hours after the
previous inspection, whichever comes first.

a. First periodic inspection (overhoal)µ

The first periodic inspection should be carried out one year after initial start-up or
6,000 hours operation. Remove the shaft seal cover, the head cover and the hand
hole cover, and draw out the pistons and connecting rods. The crankshaft and the
main bearing need not be removed.
(1) Replace the plate valves and plate valve springs with new parts.
(2) Renew the bearing halves of the connecting rods.
(3) Check the mechanical seal assembly. If any abnormality is found, replace the
seal assembly with a new one.
(4) Replace the piston rings and oil control rings.
(5) Replace the gaskets and the o-rings.
(6) Inspect the connecting rods.
(7) Inspect the piston pins. If any abnormal wear is found, replace the piston pins
with new ones.
(8) Inspect the cylinder sleeves and the pistons.
(9) Inspect the crankshaft pins.
(10) Inspect the filters for abnormal wear or damage and clean thoroughly (Refer
to Section 5.3, Precautions during operation).
(11) Clean the inside of the crankcase thoroughly.
(12) Replace the lubrication oil (Refer to Section 5.3, Precautions during
operation).
(13) Inspect the V-belts for excessive wear and replace if any abnormality is
found.
(14) Others
If the built-in type safety valve has actuated it should immediately be
replaced with a new one

34
b. Second periodic inspection
The second periodic inspection should be carried out two years or 12,000 hours
after the first periodic inspection. In addition to the items listed for the first periodic
inspection, the following additional inspections should be carried out.
Remove the crankshaft and the main bearing head.
(1) Inspect the main bearing and the thrust bearing. If abnormal wear or damage
is found, replace the main and thrust bearings with new ones.
(2) Inspect the thrust washer. If any abnormality is found, replace the thrust
washer with a new one.
(3) Inspect the crankshaft. If abnormal wear is found, replace the crankshaft with
a new one.
(4) Others. Check all parts, and carry out replacement as necessary or any
abnormal symptom is found.

c. Filter inspection
(1) Refer to Section 5.3, Precautions during operation, and Section 5.3(1) a.
(2) Clean the dryer filter and the water piping filter.

d. Pressure gauge (or pressure sensor) inspection

Calibration adjustment should be carried out every six months referring to a
standard pressure gauge. If an error exceeding the minimum graduation unit is
found, replace the pressure gauge with a new one.

Notes:
(1) The times mentioned in above sections a) and b), i.e., 6,000 and 12,000 hours are
standard values. In practice, the life of various parts differs according to model,
type of refrigerant, revolution speed, operating conditions, status of equipment,
type of oil, etc.
MYCOM therefore does not guarantee free replacement parts if the components
experience wear requiring replacement earlier than specified.
(2) Usually, expendable parts for MYCOM Model L compressor are replaced during
periodic inspection.

35
7. Compressor Lubricating Oil

7.1 Functions and characteristics of lubricating oil

The compressor lubricating oil fuctions to lubricate the surfaces of moving parts in
order to assure smooth operation without damage and/or seizure over a long period of
time.
The essential requirements of lubricating oil are:
1. Maintaining appropriate viscosity under the respective temperature conditions
within the specified operating range.
2. Maintaining appropriate fluidity even under low temperature conditions (within the
applicable temperature range of the refrigeration equipment).
3. Chemical stability with no influence on metal or rubber such asd corrosion,
deterioration or chemical change.
4. Free of wax separation from the lubricating oil or hardening under low temperature
conditions.
5. Free from development of sludge and carbonization of the oil even under high
temperature conditions.
6. Moisture-free.
7. Maintaining sufficiently lubricous characteristics.

7.2 Compressor oil selection

a. First of all, consider the importance of refrigeration compressor lubrication.

Maintaining the viscosity of the lubricating oil is essential when supplying oil to the
surfaces of moving.
b. Next, consider oil circulation throughout the entire refrigeration system. While low
oil viscosity in the evaporator is preferable, high oil viscosity is better in the
compressor. The lubricating oil must satisfy these two opposing demands.
c. In the case of the fluorocarbon refrigerant, toil viscosity decreases considerably
when refrigerant is mixed in the oil. As oil classified as ISO-VG32 or equivalent
expedites surface wear, oil classified as ISO-VG46 or higher viscosity oil should
be used.

7.3 Changing compressor oil brand

When changing from one brand to another, unexpected problems may occur as a
result of mixing the old and the new oil. Care should be taken, therefore, when
changing the oil brands.
sollte die Sorge dazu widmen besonders bei der Veraenderung der Oelmarke.
a. When the oil manufacturer is different from the previous oil maker, confirm with
both manuafacturers whether the change in brand is advisable. Also when
changing from one type of oil to another, both of which are made by the same
manufacturer, confirm the suitability of the new oil.
b. There should be no problem with changing the grade of oil if it is the same brand,
e.g.,
SUNISO 4GS Î SUNISO 5GS

7.4 Oil supply to the compressor

The oil level in the compressor decreases gradually when the system is operated
continuously.

36
 Oil replenishment should be carried out when the oil level remains visible within the
yellow circle of the sight glass. To replenish the oil:
a. Close the suction valve on the compressor gradually so that the suction pressure
approached a vacuum state (approx. –0.026MPa or –20cmHg).
b. Attach the oil hose to the oil supply/discharge valve and draw oil into the
compressor gradually.
c. Close the oil supply/discharge valve securily after supplying the required amount
of oil.
d. Open the suction stop valve gradually to return to normal operation.

Note: Special care should be taken not prevent air and moisture contamination of
the system when supply oil.
Only fresh clean oil from a sealed container should be used.
Oil should be supplied gradually to the compressor in order to prevent foaming
in the crankcase.
Compressor lubricating oil should be stored under air tight conditions until
used in order to prevent the absorption of moisture in the air.

7.5 Compressor oil brands

Oil standard ISO-VG46 or equivalent

Manufacturer Brand Name Class

Nippon Sun Oil Suniso 4GS
Idemitsu Kosan Daphne CR45
Nippon Oil Lefoil 4GS
Nippon Oil Atmos 46
Showa Shell Cravas 46
Cosmo Oil Super Freeze 56
Mitsubishi Oil Diamond Freeze 46
Kyodo Oil Freole U-46
Mobil Oil Gagoil Arctic 300ID
Esso Standard Zerice R46

37
8. Disassembly and Reassembly

! DANGER

Turn off or disconnect the main power supply to the motor and the control power
supply before commencing inspection and maintenance work. The power supply
should never be connected or turned on when working on the system. If energized,
the compressor may commence operation, posing the threat of electrical shock or
physical harm to anyone in the vicinity of the belt drive or shaft.

! WARNING

Turn off or disconnect the main power supply to the motor and all other electrical
equipment before commencing inspection and maintenance work. The power
supply should never be connected or turned on when working on the system. If
energized, electrical shock, burns or other physical harm may result.

8.1 Disassembly

Disassembly of the compressor is divided broadly into two categories, namely,

periodic inspection, and failure repair.
Disassembly should be carried out following the procedures given below.

8.1.1 Refrigerant recovery

Start compressor overhaul only after confirming that the internal pressure has
reached the ambient pressure level. High pressure gas and oil remaining in the
compressor are purged when the system is opened and could cause shock,
suffoction or unconsciousness.
1. When compressor operable
a. Close the compressor auction valve.
Close the oil separator return valve.
b. Prepare to close the discharge stop valve.
c. Release the low pressure controller, if installed, so that it does not activate if
the pressure drops.
If the system is equipped with an automatic control device, operation may not
be possible without short circuiting the other temperature controller. Implement
the necessary procedures to gain manual control of the system.
d. Start the compressor and stop operation when the low pressure reaches
0 MPa (0kg/cm G).
e. Leave the compressor as it is for a while to allow any refrigerant dissolved in
the oil to evaporate. As this occurs, the pressure will gradually rise. Start the
compressor again and stop operation when the low pressure reaches 0 MPa
(0kg/cm²G).
f. Repeat the above operation two or three times and close the discharge stop
valve when low pressure does not rise over 0.02MPa (0.2kg/cm²G). Now open
the gas discharge valve gradually to make the pressure inside the compressor

38
 equal to ambient air pressure. If the pressure inside the compressor is lower
than the ambient air pressure, moisutre is liable to enter the system.
The fluorocarbon refrigerant should not be released directly into the air as it
contributes to destruction of the ozone layer.
g. Turn off the main power supply in order to ensure that the system does not
start up accidentally.

2. When compressor inoperable

a. Close the suction valve, discharge valve and oil separator return valve to
isolate the compressor.
b. Connect the appropriate piping to another compressor and recover the
refrigerant.
If another compressor is not available, recover the refrigerant using a
reclaimer. Fluorocarbon refrigerant should never be discharged directly into
the atmospere as it contributes to destruction of the ozone layer.

8.1.2 Precautions during disassembly

! CAUTION

Only designated tools should be used when working on the refrigerant system.
Use of inappropriate, worn or damaged tools may lead to serious injury. Handle
all heavy objects with care, using auxiliary tools such as safety bolts, etc. to
ensure that they do not fall and cause injury.

a. Remove parts carefully to prevent damage.

b. Store removed parts on a clean work bench in good order.
c. Clean all parts with anhydrous alcohol, gasoline or light oil.
Warm (40~50°C) compressor lubricating oil can also be used.
d. Blow the parts dry with compressed air, or dry with a sponge or clean, lint-free
cloth, then coat the parts with fresh compressor lubricating oil.
e. Disassembled cylinders should be arranged in good order with the components
of each cylinder grouped together. This is particularly important for the
connecting rods as each is assembled with a unique combination of rod and rod
cap.
f. Bolts holding the components together should be removed carefully, confirming
the positions for future assembly.

8.2 Disassembly methods

8.2.1 Compressor oil discharge

After refrigerant gas recovery from the compressor is completed, lubricatin goil
inside the compressor crankcase should be removed. Connect a pipe to the oil
supply/drain valve located on the left side below the oil pump and drain the oil into a
container of sufficient size.

39
 Fig. 23 oil charge/drain valve

8.2.2 Disassembly of drive connections

Remove the V-belts or the coupling and pull off the flywheel or coupling flange using
a pulley remover.

8.2.3 Removing head cover (49 & 50)

a. In the case of a model with several cylinder banks, remove the head covers of
the top banks first so that the lower cylinders and valves are not damaged if the
cover drops. Take care to prevent dirt entering the crankcase during head cover
removal.
b. Remove the upper bolts first, insert a safety bolt, then remove the remaining
bolts.
c. If the gasket adheres to the head and head cover faces and cannot be removed,
tap the side of the cover with a plastic mallet to free.
d. Unlike other models such as the A, B, C, J, WA, WB and SF types, L series
compressors are not equipped with head springs.

Fig. 24 Removing head cover

40
 Fig. 25 Head cover Fig. 26 View after head cover removed

8.2.4 Valve assembly and valve plate

a. Discharge valve assembly

1. The discharge valve is incorporated into the discharge valve assembly and
affixed to the valve plate with 2 positioning pins and 4 screw bolts. The screw
bolts are partly common with the valve plate locking bolts.
2. Remove the locking bolt for the discharge valve cage (109) by lifting it up. The
positioning pin (75.2) may sometimes be too tight to draw out. In such case,
raise the discharge valve horizontally taking care not to bent the positioning
pin.
3. The top surface of the valve plate after removing the cage forms the outer seat
of the discharge valve (111). Take care not to damage the seat surface.
4. The discharge valve cage (109) and the valve seat are secured together with
three discharge seat bolts (112). Straighten the claws of the lock washers and
remove these bolts. The discharge valve seat is located in place with a
positioning pin (115). If the discharge valve seat (111) is removed, the
discharge plate valve (110) can easily be removed. The discharge valve
springs (116) are inserted in the spring holes on the discharge valve cage.

Fig. 27 Removing discharge valve plate (109) Fig. 28 Valve plate (73)

41
 Fig. 29 Discharge valve cage (109) Fig. 30 Discharge valve cage, disassembled

b. Valve plate (73)

1. The valve plate is affixed to the crankcase with a bolt (73-1). It is positioned
between the crankcase and the periphery of the cylinder sleeve flare fitting
hole.
2. Raise the valve plate perpendicularly against the mounting face.

8.2.5 Hand hole cover (45 & 46)

a. Replace the bolt (48) in the top center position with a safety bolt. Now remove all
other bolts and separate the gasket (47) from the crankcase.
b. The hand hole cover complete with oil sight glass (45) secures the oil sight glass
from outside with an O-ring (165). When replacing the O-ring, be sure to secure
the bolts to the specified torque during reassembly.

Fig. 31 Inside view after removal of valve Fig. 32 Removing handhole cover plate (46)
plate (73)

42
 Fig. 33 Hand hole cover (45) and oil sight glass (164)

8.2.6 Cylinder assembly

[Cylinder sleeve (61), piston (85), connecting rod (77) etc.]

a. Drawing out cylinder assembly

1. As the with of the connecting rod big end is greater than the diameter of the
cylinder sleeve (61), the cylinder sleeve must be removed from the crankcase
together with the piston (85) and connecting rod (77).
2. First turn the crankshaft so that the piston is positioned at bottom dead center.
3. Remove the No. 2 nut (81) and No. 1 nut (80) in order from the conrod locking
bolt (78) on the crankshaft pin portion. Care must be taken not to lose the
connecting rod washer (79) or drop it into the crankcase.
4. Remove the rod cap. Screw a hanger eye bolt into the tapered hole on the top
of the piston and pull up on the hanger bolt. The cylinder sleeve and piston will
come out together due to the tension of the piston rings (89 & 90) against the
cylinder wall.
5. If the piston only is pulled on forcibly, the piston rings will comes out and
disassembly work thereafter will be more difficult.
6. When removing the cylinder assembly from the crankcase, care must be taken
to prevent the lower portion of the connecting rod from striking the crankcase,
otherwise it may be scratched or scored.
7. Free and draw out all remaining cylinder assemblies in a like manner and
arrange each assembly together in a manner which will allow proper
installation in the correct order during reassembly. All rod caps, bolts and nuts
should be grouped with their respective cylinder assemblies.

43
Fig. 34 Loosening connecting rod bolt Fig. 35 Removing cylinder assembly

b. Piston (85) and connecting rod (77) removal

1. After removing the bolts from the big end, place the cylinder assembly on a
wood or plastic plate with the cylinder seat (flared end) facing down. The
connecting rod retainer bolt (78) should be drawn out before this is done.
2. Holding the cylinder sleeve with one hand, draw out the piston while
supporting the connecting rod big end with the other hand.

c. Cylinder sleeve (61) disassembly

1. It is usually unnecessary to disassemble the cylinder sleeve unless the sleeve
itself or the cam ring (62) must be replaced. If the retaining ring (65) fitted in
the lower groove on the sleeve is removed, the cam ring will drop.
2. The cam rings for L Series compressors are all processed as leftward slanted.
3. Remove the unloader lift pin stop (E ring) (70) from the lift pin (68) and remove
the lift pin from the cylinder sleeve. Be careful not to lose the spring (69).

Fig. 36 Removing lift pin stop ring (70)

(Also referred to as the „E-ring“)

44
 d. Piston (85) and connecting rod (77)

1. Position the piston with the crown facing down and the rod end facing up.
Remove the piston pin lock spring (87) using a pair of snap ring pliers.
2. Holding the piston and connecting rod securely, push the piston pin (86) out
with your finger to separate the piston and connecting rod.
3. Do not remove the connecting rod large end bearing metals (84U and 84L)
unless they must be replaced. The small end of the connecting rod is
furnished with a wrapped bearing (also referred to as the „Rod bushing“) (82).
4. Each set of connecting rod large end and cap is engraved with mating marks.
Be sure to keep the rod and cap pairs together.

Fig. 38 Connecting rod bearing Fig. 39 Connecting rod (77)

(84U & 84L)

e. Piston ring (89 & 90) and oil ring (100)

1. Do not remove the piston rings or oil ring unless replacement is necessary.
2. Utilize hooks or a pair of piston ring pliers to expand the ring end gap on the
same plane facilitate removal of the ring. A pair of thick copper loops can also
be used to expanding the rings (ref. Fig. 41)
3. Torsional expansion of the ring will deform the ring, resulting in oil leakage
after reassembly.

Fig. 40 Piston ring (89 & 90) and oil ring (100) Fig. 41 Removing piston ring

45
8.2.7 Unloader mechanism disassembly

a. Remove the coil portion of the unloader solenoid valve (remove the nut which
secures the coil) and take off the unloader cover bolt.
Since the cover will move outward due to the pressure of the unloader spring, be
sure to keep a good grip on the cover.

Cylinder
b
Positioning pin,
Cylinder sleeve (61-1)
No. of puh rod
Unloader (136-137)
Unloader working order

1) Unloader functions when power on and

Unloads when power off.
2) Unloader working order is same as loading
order and reverse order when unloading
Fig. 42 Push rod (135-137) and Fig. 43 Unloader push rod (135-137)
Cam ring (62)

Fig. 44 Built in solenoid valve with unloader Fig. 45 Unloader piston (145)
Cover (146)

46
 Fig. 46 Unloader push rod (135-137)

b. Remove the unloader cover so that the unloader piston, push rod and spring can
easily be removed. The length of push rod differs according to the number of the
cylinder it is mounted on. Keep a record of the cylinder number and the unloader
cover number as well as the direction.
c. The locking ring and the washer of the unloader push rod should never be
removed but left in place.

8.2.8 Shaft seal cover (26) removal

a. The shaft seal cover contains oil. Position an oil pan under the shaft seal cover to
catch any oil remaining in the seal.
b. Loosen alkl seal cover retainer bolts (28). If the gasket (27) is not stuck, a gap
will open between the cover and the case due to the pressure of the seal spring.
Remove all except two bolts on opposite sides. Loosen these two bolts
alternately and remove while holding the cover.
c. Remove the cover perpendicular to the crankshaft.
d. If the gasket has adhered to the cover, loose the bolts and rotate the cover right
and left to free the gasket (ref. Fig. 47).
e. The floating seat is secured in the seal cover by an O-ring. Remove the floating
seat by pushing the cover from the outside. Since the floating seat is easily
damaged, handle with care (ref. Fig. 49).

Fig. 47 Shaft seal cover (26) Fig. 48 Shaft seal cover removal

47
 Fig. 49 Removing shaft seal

8.2.9 Mechanical shaft seal disassembly

a. Remove the shaft seal cover to expose the mechanical seal assembly (32). The
mechanical shaft seal assembly is connected to the shaft by a spring retainer
positioned by a knock pin. It consists of the seal ring, O-ring, the drive collar and
the seal spring. The mechanical shaft seal assembly is furnished with a floating
seat and O-ring at the shaft seal cover side.
b. Grasp the shaft seal assembly with both hands and draw out while securing the
seal collar positioned inside.
c. Dismantle the seal assembly, arrange in an orderly fashion and store with care.
The seal ring frictional face should be protected to prevent damage.

Fig. 50 Mechanical shaft seal Fig. 51 Mechanical shaft seal assembly,

Exploded view

8.2.10 Bearing housing (8) disassembly

the clearance of the crankshaft in the thrust direction should be measured before
removing the bearing housing (8). Push the shaft in the crankcase close to the seal
side or the pump side and measure the clearance with a thickness gauge inserted
between the opposite shaft end face and the metal. Alternately, push the shaft to
the pump side and measure the distance moved in the thrust direction using a dial
gauge mounted on the end of the crankshaft.

48
 a. Remove all bearing housing retainer bolts (10). A tap hole is located on the
flange portion of the bearing housing. Screw one of the bolts removed into the
tap hole to force off the bearing housing. The gasket (9) should remain adhered
to the crankcase side (ref. Fig. 53).
b. After pulling the bearing housing off somewhat with the tap hole bolt, grasp with
both hands and pull off. The shaft fitting for the bearing inside the bearing
housing may sometimes come out together with the bearing housing. Secure the
crankshaft by hand through the hand hole or from the seal side to prevent the
crankshaft being pulled out together with the bearing housing.

Fig. 52 Bearing housing (8) Fig. 53 Removing bearing housing

8.2.11 Pump side main bushing (12) and thrust washer (29-4)

a. The main bushing is press fitted into the hole on the main bearing housing. In
appearance it resembles a thinly coiled bushing (Fig. 55). It is usually
unnrcessary to remove the bearing housing assembly unless replacement is
required.
b. The thrust washer (29-4) is a circular-shaped metal plate with a backing sheet. It
is fitted to the thrust face of the bearing housing with a lock pin.
c. When replacing the thrust washer, push out the metal with an L shaped pry bar.

Fig. 54 Bearing housing (8) and thrust Fig. 55 Main housing (12)
Washer (29-4)

49
 Fig. 56 Thrust washer (29-4) Fig. 57 Bearing housing (8)

8.2.12 Oil pump assembly

The oil pump assy. is mounted with the main bushing (12) on the bearing housing
(8). If the pump has experienced a drop in performance, replace as the bearing
housing assy.

Fig. 58 Oil pump

50
 Changing direction of rotation will result in
change of contact point between outer gear
and casing, thus eccentric position of casing
Rotation of crankshaft chagnes from
and outer gear changes and discharge
Schematic Drawing Reversible Trocoid Pump
xounterclockwise to clockwise direction direction remains constant.

Counterclockwise Clockwise rotation

rotation

Rotation of crankshaft changes from clockwise Rotation of crankshaft changes from

to counterclockwise direction counterclockwise to clockwise direction
Fig. 59 Reversible pump mechanism

8.2.13 Crankshaft (2)

a. After removing the bearing housing (8), the crankshaft is held in place only by the
seal side metal. With an assistant to support one end of the crankshaft, lift and
draw out the shaft until the bearing housing side balance weight can be rested on
the bearing housing mounting flange (Fig. 60).
b. Now place the center arm of the crankshaft on the bearing housing mounting
flange as shown in the photo (Fig. 61).
c. After the crankshaft has been removed, support on wood V-blocks to prevent
damage to the bearing journals.

Fig. 60 Removing crankshaft Fig. 61 Removing crankshaft

51
 Fig. 62 Removing crankshaft

8.2.14 Seal side thrust bearing (29) and thrust washer (29-4)

a. The seal side thrust bearing of the Model L compressor is mounted in the
crankcase with bolts (31). Remove the bolts from the crankcase when carrying
out replacement of the thrust bearing. If the thrust bearing is too tightly fitted
within the crankcase to withdraw, insert two bolts in the tap holes on the thrust
bearing and, twisting the thrust bearing left and right, draw out.
b. The seal side thrust washer is also fixed to the faucet of the thrust bearing with
locking pins (13).

Fig. 63 Thrust washer (29-4) and thrust bearing (29)

8.2.15 Oil filter (119)

The oil filter is mounted inside the crankcase with a hexhead nipple (118). Remove
the oil filter together with the nipple. Since the wire material of the filter element is
rather fragile, excessive force should not be applied (Fig. 64).

52
8.2.16 Suction filter (178)

The suction filter is mounted inside the suction filter case. This filter should always
be cleaned during periodic inspection (Fig. 65).

Fig. 64 Oil filter (119) Fig. 65 Suction filter (178)

8.2.17 Built-in type safety valve (214)

The plug-like safety valve (Fig. 66) is screwed into the boundary wall between the
high and low pressure sides of the crankcase, inside the head cover. If the safety
valve has once been activated during operation, it should be replaced with a new
one as the activation pressure of the activated safety valve may drop due to
deformation of the Teflon component (ref. Fig. 66 and 67).

Fig. 66 Built-in safety valve (214) Fig. 67 Mounting position of safety valve

8.2.18 Oil pressure regulating valve (*17)

The oil pressure regulating valve is screwed into the top of the bearing housing (8).
It is usually unnecessary to disassemble or adjust the valve unless a problem has
been encountered with oil pressure (Fig. 68).

8.2.19 Pressure equalizer (*144)

A hole is provided between the crankcase suction chamber and the crankshaft
chamber to equalize pressure between them and to prevent oil inside the crankshaft

53
 chamber from entering the suction chamber. It is usually unnecessary to carry out
disassembly (Fig. 69).

Fig. 68 Oil pressure regulating valve (*17) Fig. 69 Pressure equalizer (*144)

8.3 Reassembly

All parts disassembled from the compressor should be repaired or replaced according
to the inspection and replacement standards given later in this manual.
Reassembly work is essentially carried out in the reverse order of disassembly. When
ordering spare and replacement parts, specify the number of the part indicated in the
exploded view (Fig. 3) or parts list, the name of the part, the model and the serial
number of the compressor.

8.3.1 Cautions during reassembly

! CAUTION

Only designated tools should be used when working on the refrigeration system.
Use of inappropriate, worn or damaged tools may lead to serious injury. Handle
all heavy objects with care, using auxiliary tools such as safety bolts, etc. to
ensure that they do not fall and cause injury.

a. When replacing a part, confirm that the new part is in fact the correct one before
starting reassembly.
b. Clean all parts in kerosene, remove any visible rust with fine emery paper and,
finally, coat with lubricating oil before reassembling.
c. Prepare an oiler containing fresh lubricating oil and apply oil to all friction
surfacec just before reassembly.
d. Dry all washed parts with compressed air or wipe dry using a cotton or nonwoven
fabric cloth. Do not use cloth materials such as wool or synthetic fiber as these
do not absorb oil well and may leave fibers on the parts, causing later problems.
e. The gaskets used between mated surfaces should be coated with lubricating oil
on both sides before installation in order to assure airtight sealing. When
replacing a gasket, scrape all old gasket residue off of the mating surfaces before
mounting the new gasket.

54
 f. All hand tools used during disassembly should be cleaned before commencing
reassembly work.
g. When mounting a cover, take care to ensure that the gasket is properly
positioned. Be careful to avoid blocking oil ports when mounting gaskets.
h. Fasten all bolts lightly then retighten to the specified torque in a crisscross
pattern.

MYCOM L Series Compressor Bolt and nut tightening torque list

Fastening
Part No. Applicable
Bolt name Bolt size torque
Or * No. model
N-M (kg.cm)
112 Bolt, discharge valve seat M8xL30
186-1 Set bolt, oil cooler (water cooled & hex head) M8xL35 29.4 (300)
186-2 Nut, oil cooler (water-cooled) M8 (nut)
149 Bolt, unloader cover M8xL35
*124 Bolt, oval flange M10xL25
54 Bolt, head jacket cover M10xL25
31 Locking bolt, thrust bearing (small) M20xL30
73-1 Bolt, valve plate (P=1.0) M10xL30 39.2 (400)
167 Bolt, oil sight glass gland (small) M10xL30
All models
28 Bolt, shaft seal cover M10xL35
75 Bolt, discharge valve cage (P=1.0) M10xL45
78 Bolt, connecting rod (special) M10xL109
80 No. 1 nut, connecting rod (P=1.5) M10 58.9 (600)
81 No. 2 nut, connecting rod (P=1.5) M10 39.2 (400)
48 Bolt, hand hole cover M12xL40
52 Bolt, head cover M12xL40
78.5
181 Bolt, suction filter cover M12xL40
10 Bolt, bearing housing M12xL45
182-B Bolt, discharge companion flange (65A) M16xL45 4L 117.7 (1200)
174 & 183 Bolt, suction/discharge service valve (65A, 80A) M16xL140 4L, 6L
173-B&182-B Bolt, suction/discharge companion flange (80A, 100A) M20xL50 Al models
170 Bolt, discharge elbow (80A) M20xL50 6L 157.0 (1600)
170 Bolt, discharge elbow (100A) M20xL55 8L
174 & 183 Bolt, suction/discharge service valve (100A) M20xL190 6L, 8L
177 Bolt, suction filter case M22xL55 6L, 8L 294.3 (3000)
7 Pulley set bolt M27xL50 Al models 588.6 (6000)

8.3.2 Crankcase reassembly

a. Supply lubricating oil to all portions of the thrust bearing (29) of the shaft seal
side and thrust washer (29-4).
b. When replacing the thrust bearing, be sure to position the oil supply hole of the
bearing at the top.
c. The thrust bearing should be press-fitted into the clearance in the crankcase.
d. Mount the oil filter using the fitting. Do not push onn the filter element, otherwise
it may be deformed.

8.3.3 Crankshaft (2) reassembly

a. Apply a generous coating of lubricating oil to the crankcase journals. Place the
crankshaft balance weight on the flange portion of the bearing housing (ref. Fig.
71).
b. Insert the crankshaft into the crankcase until the center arm is balanced on the
bearing housing flange. When carrying out this work be careful not to damage the
bearing with the shaft end.

55
 c. When the balance weight of the crankshaft on the oil pump side passes the
flange portion, the crankshaft is ready to accept the bearing. The crankshaft end
is visible at the shaft seal side. Insert the shaft into the bearing while supporting
both ends of the crankshaft. Move the crankshaft parallel to the shaft core.
d. Push the shaft in until it contacts the thrust face. Vertically position the groove for
driving the oil pump.

8.3.4 Oil pump, main bushing (12), and bearing housing (8) reassembly

a. If the main bushing must be replaced, complete renewal of the bearing housing
assembly is generally carried out. If replacement of the main bushing must be
carried out due to unavoidable circumstances, pull out the main bushing after
scraping it somewhat.
b. When press fitting the main bushing, remove the oil pump and push the bushing
in manually. The bushing metal should not be tapped in forcibly, otherwise the
bearing metal may be deformed.
c. Fit the thrust washer (29-4) to mate with the thrust washer locking pin (13).
d. Mount the oil pump on the bearing housing (8) after fitting the gasket (9),
positioning it so that the suction port of the oil pump faces down. Improper
positioning of the gasket will lead to later oil pump malfunction. The pump shaft
must be mated with the crankshaft precisely in the vertical direction.
e. Apply a generous coating of lubricating oil to the journal and position the gasket
(9) on the flange of the bearing housing (8). Be careful not to block the oil port by
improperly positioning the gasket. Fit the bearing over the crankshaft and then,
raising the bearing housing slightly, push the crankshaft into the crankcase.
f. The pump shaft fits into crankshaft groove during the final 20mm of travel. Turn
the bearing housing left and right slightly to ensure a tight fit.
g. When the shaft fits into the groove properly, the shaft can easily be pushed into
the crankcase. Fasten the bolts lightly, confirm that the oil pump is a good fit
while rotating the crankshaft by hand, then tighten the bolts to the specified
torque.
h. Move the shaft in the axial direction and measure the thrust gap.

Fig. 70 Thrust bearing (29) Fig. 71 Mounting crankshaft (2)

56
Fig. 72 Preparations for mounting oil pump Fig. 73 Oil pump shaft

Fig. 74 Thrust washer locking pin (13) Fig. 75 Mounting pump shaft on crankshaft

8.3.5 Mechanical seal (32) reassembly

a. Fit the floating seat on the shaft seal cover (26). Apply oil to the O-ring and press
evently to seat. Care must be taken to prevent the friction surface of the ring from
being scratched.
b. When installing the shaft seal retainer, position the locking pin upward and push
in the shaft with the notch of the seal retainer of the assembly also pointing
upwards. Confirm that the locking pin engages with the notch.
c. Attach the gasket (27) to the inlay of the crankcase.
d. Apply oil to the seal, position the seal cover perpendicularly in front of the shaft
and slide over the shaft carefully.
e. While securing the shaft seal cover by hand, install the shaft seal cover on the
crankcase with the bolts (28) and tighten to the specified torque. Turn the
crankshaft by hand to confirm that the shaft seal cover is correctly positioned and
the shaft turns smoothly.

57
 Fig. 76 Reassembly of floating seat

Fig. 77 Shaft seal retainer Fig. 78 Mechanical seal assembly (32)

Fig. 79 Mechanical seal assembly Fig. 80 Mounting mechanical seal assembly

58
8.3.6 Cylinder assembly reassembly

a. Piston (85) and piston ring (89, 90 & 100)

1. Mounting the piston rings on the piston
The piston ring set consists of:
1st (top) ring: Barrel face groove type
(FC-PC-BF-GI)
2nd (middle) ring: Tapered piston ring
(FC-T)
3rd (bottom) ring: Oil ring complete with coil spring
(FC-PC-CB3)
The piston rings should be mounted starting with the oil ring (bottom) and
moving upward in order.
2. When installing the piston rings in the pistons, care should be taken to avoid
excessively widening or distorting the rings. After installing each ring into its
respective ring groove, confirm that the ring moves smoothly in the groove.
3. The ring end gaps of the three rings should be offset by 90° or 180°.

Fig. 81 Mounting oil ring Fig. 82 Mounting piston rings

b. Piston (85) and connecting rod (77)

1. Stand the piston upside down and attach the connecting rod small end using
the piston pin (86), as shown in Fig. 85. The piston pin should fit snugly.
2. Mount the piston pin lock spring (67) securily in the piston groove.
3. If the bearing halves 84U and 84L (commonly referred to collectively as the big
end connection rod plain bearing metal) are to be replaced, fit the bearing
metal locking claw into the notch in the connecting rod. Be sure to clean the
rod big end and the back of the plain bearing metal carefully before installing
to ensure they are completely free of foreign matter. As shown in Fig. 86, the
upper bearing half (84U) has a small hole in it while the lower bearing half
(84L) is plain.

59
 Fig. 85 Mounting piston pin (86) Fig. 86 Bearing half upper (84U)
(Big end upper bearing metal)

c. Cylinder sleeve (61)

1. If the cylinder sleeve is to be replaced, first drive the positioning pin (61-1),
also called the „Retaining pin,“ into the cylinder seat (flare side), as shown in
Fig. 87. Now mount the cam ring (62) on the cylinder sleeve and secure the
cam ring with the retaining ring (65), as shown in Fig. 88.
2. Mount the unloader lift pin (68), the lift pin spring (69), and finally install the
unloader lift pin stop ring (70), also called the „E locking ring“ or „E-ring“ (ref.
Fig. 90).
3. Turn the cam ring to adjust the engagement of the notch on the cam ring with
the positioning pin, referring to Figs. 91 and 92. The most suitable position of
the notch on the cam ring is the π/4 rad.(or 45°) turning counterclockwise from
the positioning pin (61-1) and looking from the top of the cylinder sleeve.

Fig. 87 Cylinder positioning pin (61-1) Fig. 88 Retaining ring (65)

60
 Fig. 89 Cam ring (62) Fig. 90 Lift pin (68), Spring (69) and
Stop ring (or E-ring) (170)

d. Cylinder sleeve (61) and piston/connecting rod assembly

1. Turn the cam ring to raise the lift pins out of the seat and position the sleeve
with the seat side facing down.
2. Apply lubricating oil to the piston while holding the connecting rod portion of
the piston/connecting rod assembly, then insert into the cylinder sleeve
approximately half-way. The piston ring section of the piston is inserted into
the cylinder from the tapered end of the cylinder sleeve while squeezing the
rings.
3. Stop insertion of the piston midway into the cylinder sleeve so the cal ring can
be positioned in the same location as before disassembly.
4. After fitting all of the cylinders with piston/connecting rod assemblies, arrange
in order for mounting each group of cylinders. Apply a generous coating of
lubricating oil to the cylinder sleeve gasket (66) and attach the gasket below
the brim of the cylinder sleeve. Care must be taken not to tear or otherwise
damage the gasket. Never use a damaged gasket.

Fig. 91 Cylinder sleeve (61), Cam ring (62) Fig. 92 Mounting piston (85) in cylinder
and Lift pin (68) sleeve (61)

61
 Fig. 93 Mounting piston in cylinder sleeve Fig. 94 Movement of lift pin (68)

8.3.7 Mounting cylinder assembly in crankcase (1)

a. The cylinder assemblies are mounted in the crankcase from the top, confirming
the position of notch and the direction of the positioning pin (61-1) of the cylinder
sleeve (61). Mount the bolts (78) to the connecting rods (77).
b. Adjust the unloader push rod (135 – 137) so that the protrusion of the connecting
rod at the center of the cylinder sleeve hole of the compressor crankcase is as
shown in Fig. 95B. Secure the unloader piston (145) temporarily by mounting the
unloader cover (146). Care must be taken during the final stage of mounting the
unloader piston because the unloader piston may protrude into the cover,
resulting in displacement when the unloader cover is finally tightened.

Fig. 95A Push rod positioning Fig. 95B Push rod positioning

Fig. 96 Push rod, free position Fig. 97 Mounting cylinder sleeve

62
 Fig. 98 Mounting cylinder sleevee Fig. 99 Pushing piston into cylinder sleeve

Fig. 100 Mounting connecting rod cap on crankshaft

c. Position the connecting rod with the crankshaft at the bottom dead point. Locate
the piston in the middle of the cylinder sleeve and insert the entire cylinder
assembly into the crankcase. When the notch on the cam ring (62) mates with
the pin portion of the push rod (135 – 137), push the cylinder sleeve deep into the
crankcase while aligning the retaining pin (or positioning pin) (61-1) with the
groove in the crankcase.
d. Push the piston down and fix the big end of the connecting rod with the bearing
metal on the crankshaft. Mount the big end bearing half (84U and 84L) with the
mounting position of the connecting rod on the crankshaft using the connecting
rod bolts (78). Care must be taken not to scratch the crankshaft with the bolt.
e. Confirm the rod cap fitting direction, mount, and install the washerr (79) and the
first nut (80) after confirming that the mating numbers of the big end and the rod
cap match. Tighten the bolts alternately to the specified torque. As the rod cap is
tightened to the specified torque, the inside diameter of the bearing halves
gradually becomes round. Now fit the second nut (81) on each bolt and tighten to
the specified torque.
f. Rotate the crankshaft after installing each assembly to confirm smooth
movement. At this time hold the cylinder by hand, otherwise, not yet being
secured, it will move somewhat with the piston due to the frictional force of the
piston rings. In this case, it is possible to retain the cylinder sleeve temporarily
using the washer (73-2) and bolt (73-1) for the valve plate

When turning the crankshaft, do so slowly and carefully, holding the cylinder firmly.
63
 Fig. 101 Mounting connecting rod nut (80) Fig. 102 Tightening rod cap

8.3.8 Valve assembly reassembly

a. Valve plate (73) reassembly

1.Mount the suction valve springs (72) in the spring holes on the valve plate (73).
As the outer diameter of the spring is somewhat larger than the spring hole, it
must be twisted into the hole.
2. When securing the unloader piston with the unloader cover (146), as shown in
Fig. 95, push down the lift pin (68).
3. Mount the suction plate valve (71) on the valve plate from inside using both
hands, now secure to the valve plate using the bolts (73-1). Confirm that the
suction valve is correctly located on the valve plate, then tighten the bolts.

Fig. 103 Valve plate (73) and Fig. 104 Suction valve spring (72)
Suction plate (71)

64
 Fig. 105 Mounting valve plate (73) Fig. 106 Tightening valve plate

b. Discharge valve cage reassembly

1. Mount the discharge valve springs (116) on the discharge valve cage (109).
Twist the springs into the holes.
2. Position the discharge plate valve (110) on the discharge valve cage (109) and
secure with the discharge valve seat (111). The discharge valve seat should
be aligned with the central discharge valve seat positioning ping (115).
3. Fasten the discharge valve seat (111) with the bolts (772). Be sure to install
the triangular retainer (112-2) with the discharge valve seat positioning pin
(115).
4. Tighten the bolts (112) to the specified torque, then remove the valve cage to
confirm that the discharge plate valve moves smoothly. Also confirm that the
bolt heads are approximately level with the valve seat face. If they are
significantly lower than the seat face with some threads exposed, the wrong
bolts may have been used but if the bolt heads protrude from the seat face,
they may interfere with the piston. Finally, bvend the corners of the lock
washers.
5. Remount the discharge valve cage in the specified position on the valve plate
(73). In this case, the bolts are set in the crankcase so as to jam the valve
plate between the discharge valve cage and the crankcase.

Fig. 107 Mounting discharge valve seat (111) Fig. 108 Checking discharge plate valve (110) activation

65
 Fig. 109 Bolt retainer, discharge valve seat Fig. 110 Discharge valve cage properly assembled

8.3.9 Head cover (49 & 50) reassembly

a. Mount the built-in safety valve (214) in the crankcase if an external mounted type
safety valve is used, employ hexagonal plugs to mount.
b. Screw a safety bolt into the tapered hole in the top of the crankcase and attach
the head cover gasket (51). Now mount the head cover while confirming that the
head cover bolt holes match with the safety valve. Tighten all bolts other than the
safety bolt by hand, withdraw the safety bolt, then tighten the locking bolt.
c. Tighten all head cover bolts alternately in a crisscross pattern to the specified
torque.
d. Turn the crankshaft by hand to confirm smooth movement.

Fig. 111 Before mounting head cover (49 & 50) Fig. 112 Tightening head cover bolts (52)

8.3.10 Hand hole cover (45 & 46) reassembly

a. Confirm that the cover with the sight glass (45) and the blind hand hole cover
(46) are in the appropriate sides. Attach the gasket to the cover and secure the
cover the bolts (48).
b. Screw the safety bolt into the tapered hole at the top of the crankcase, and mount
the hand hole cover, confirming that the hand hole cover bolt holes match the
safety bolt. Now screw in all the bolts (48) into the respective hand hole cover

66
 bolt holes by hand. Finally, withdraw the safety bolt, and tighten all bolts to the
specified torque.

Fig. 113 Hand hole cover with sight glass (45) Fig. 114 Installing hand hole cover bolts (48)

8.3.11 Unloader cover reassembly

a. Push on the unloader piston by hand to confirm smooth movement.

b. Confirm that the unloader cover gasket hole, the crankcase hole and the oil
passageway of the solenoid valve on the unloader cover are properly aligned,
then tighten the bolts.
c. Mount the solenoid valve coil.

8.3.12 Sunction filter (178) reassembly

a. Mount the suction filter (178) in the suction filteer case (175).
b. Mount the suction filter cover (179) and tighten the bolts (181) to the specified
torque.

8.4 Parts inspection and replacement standards

! WARNING

MYCOM genuine parts must always be used as replacements. If parts

manufactured by third parties are installed in the compressor, malfunctions,
electric shock and serious accidents may result, posing a risk to human life.

! CAUTION
MYCOM genuine parts must always be used as replacements. If parts
manufactured by third parties are installed in the compressor, serious damage to
the compressor and other refrigeration system equipment may result.

67
8.4.1 Compressor oil replacement

a. In addition to daily inspection of the quantity, contamination level, color, etc. of

the oil, an oil sample should be extracted every six months for analysis by the
manufacturer of the oil.
b. If the lubricating oil becomes extremely dirty, do not hesitate to replace it. If the
oil is light coffee brown in hue (ASTM-6 or more), replace the oil immediately.
c. Check the oil trap in the bottom of the crankcase periodically for metallic residue.
If any metal particles are found, determine the source. Residue found in the trap
may include dirt from the suction piping or particles from the frictional parts of the
compressor.
d. If foreign matter finds its way into the compressor, the moving parts of the system
may be subject to premature wear or damage. It is therefore vital that all
precautions be taken to prevent contamination.
e. When submitting oil samples to the oil manufacturer, ask them check the
following:
1. Oil analysis
In general, analysis of the oil should be carried out to evaluate the
characteristics indicated below. Normally, a 200ml (200cc) sample in a clear
plastic or glass bottle is sufficient for analysis.
1. Hue (ASTM)
2. Kinematic Viscosity (40°C cst)
3. Total oxidation (mg-KOH/g)
4. Moisture content (ppm oder vol/s)
5. Milli-bore filter (mg/100mil)
Note: terms 1) through 5) represent routine analysis.
6. Fluuidity (°C)
7. Wax fog point (°C)
8. Metallic content (WC, ppm)

2. Oil renewal standard

The oil should be replaced based on the following values:
(a) Hue: ASTM 6 or under
(b) Kinematic viskosity: Under new oil ±5%
(c) Total oxydation: 0.3 (mgKOH/g) or less
(d) Moisture: 100ppm or less
(e) Mill-bore filter: 15 (mg/100ml) or more
Deterioration of the oil can generally be determined by items (a) through (c)
above. If the moisture content or contamination by foreing matter is high,
however, the oil should be replaced immediately and the source of the
moisture or foreing matter traced to remove the source.
Abnormal moisture:
* The system is not properly sealed and moisture and/or air is passing into
the system.
* The original oil contains an excessive amount of moisture due to long-term
storage in an improperly sealed container.
Abnormal mill-bore:
* The interior of the system has not been adequately cleaned and residue
inside the piping has been flushed through to the compressor with the
refrigerant and oil, resulting the residue mixing with the oil.
* Abnormal abrasion of moving parts is also a potential source of residue
accumulation.

68
8.4.2 Suction filter (178) and oil filter (119)

a. After cleaning the wire mesh, check for mesh damage and weld failure. If any
faults are found, repair or replace with a new one. Note that a special flux is
required for welding stainless steel.
b. If any dirt remains in the fine mesh after cleaning, blown out with compressed air.
Aim the air blast in the opposite direction to fluid flow.
c. The oil filter is a corrugated cylindrical type. If the filter is clogged, blow out with
compresssed air from the inside.

8.4.3 Crankshaft (2)

a. Check the abrasion of the crankshaft journals. Abnormal abrasion can initially be
determined visually or by the simple touch of a finger as revealing a difference in
the height of friction and non-friction areas. Check each journal for wear using a
micrometer. If measurements exceed service limits, replace the crankshaft.
b. Frictional parts of the crankshaftmay be damaged during disassembly work. If
any scratches or scoring are found, polish using fine emery paper (#300 mesh or
more) or an oil stone.

Measurement Point Standard Dimensions Service Limit

Main bearing diameter 85.0mm 84.86mm

Thrust bearing diameter

Crank pin/bearing metal 82.0mm 81.83mm

c. Remove all plugs from the crankshaft and clean the oil ports thoroughly.
Especially, the plugs themselves are liable to accumulate dirt. Wash the plugs
thoroughly in kerosene and lubricate with oil repeatedly before reinstalling. If the
plugs are not reinstalled, oil pressure failure and compressor seizure will result.
d. Inspect the mechanical seal mounting face of the crankshaft for scratches or
scoring and repair using a fine oil stone or fine emery paper (#300 mesj or more).

8.4.4 Mechanical seal (32)

a. Check the frictional face of the shaft seal cover side floating seat and the
crankshaft side seal ring. If the frictional face of the mechanical seal exhibit a
lustrous finish, it is considered satisfactory. If not, replace the mechanical seal
assembly.
b. Check the frictional face of the floating seat for scratches or scoring and, if found
replace the seal assembly with a new one as soon as possible.
c. Two O-rings are used. If disassembly or inspection is carried out, replace these
O-rings with new ones (regarding the nominal number and standard, refer to
8.4.14, O-rings and gaskets).

8.4.5 Piston (85), piston pin (86) and piston rings (89, 90 & 100)

a. The circumference of each piston should be inspected carefully for damage. If

any damage is found, polish with fine emery paper, moving the paper
perpedicular to the direction of movement during operation.

69
b. If the outer diameter of the piston exceeds the service limit given below, replace
with a new one

Measurement Point Standard Dimensions Service Limit

Piston diameter 115.0mm 114.78mm

c. The piston pin hole and the piston pin are designed as floatable in relation to
each other. If the measured clearance exceeds the service limit given below,
replace the piston pin or the piston, whichever shows the greater degree of wear.

Measurement Point Standard Dimensions Service Limit

Clearance between
piston pin hole and 0.009~0.036mm 0.15mm
pistin pin

d. If the outer diameter of the piston pin exceeds the service limit given below,
replace the piston pin with a new one.

Measurement point Standard Dimensions Service Limit

Piston pin outer
34mm 33.9mm
diameter

e. Piston ring wear can be determined by measuring the ring end gap. Insert the
piston ring into the cylinder sleeve to a depth approx. 3mm from the top end and
measure the ring end gap as shown in the following figure. If the gap exceeds the
service limit given below, replace the ring with a new one.

Measurement Point Standard Dimensions Service Limit

Piston ring end gap
0.45~0.65mm 1.3mm
(top, 2nd & bottom)

Insert the piston ring at abrasion free

portion in the cylinder sleeve, and
measure the gap shown below.
Upper end of
cylinder sleeve

Fig. 115 Measuring piston ring gap

70
 f. If the clearance between the piston ring groove and the piston ring exceeds the
service limi given below, replace the piston ring or the piston.

Measurement Point Standard Dimensions Service Limit

Clearance between
piston ring groove and 0.02~0.06mm 0.15mm
piston ring

8.4.6 Connecting rod (77)

a. Inspect the surface of the metal bearing halves (84U & 84L) on the big end of
connecting rod. If the bearing metal shows signs of pitting by foreign particles,
wear or scoring of the crankshaft pin portion (or the bearing half mounting
location on the crankshaft) may result. Replace the bearing halves (84U & 84L).
b. If the clearance between the crankshaft pin portion and the bearing halves
exceeds the service limit goven below, replace the bearing halves.

Measurement Point Standard Dimensions Service Limit

Clearance between
crank pin (or bearing
half mounting location 0.05~0.071mm 0.20mm
on crankshaft) and
bearing halves

c. If the clearance between the piston pin (86) and the small end pin hole of the
connecting rod exceeds the following service limit, replace the piston pin.

Measurement Point Standard Dimensions Service Limit

Clearance between
piston pin and piston pin
0.025~0.071mm 0.20mm
hole in connecting rod
small end

8.4.7 Cylinder sleeve (61)

a. Check the seat of the suction plate valve on the top of the cylinder sleeve. If
scratches or scoring are found on the seat, polish the seat surface by lapping the
seat.
b. If the height of the seat portion on the cylinder sleeve exceeds the service limit
given below, replace the cylinder sleeve with a new one.

Measurement Point Standard Dimensions Service Limit

Height of seat portion of
0.5mm 0.2mm
cylinder sleeve

c. Check the inner wall of the cylinder sleeve and repair any scratches with fine
emery paper.
d. If the clearance between the inside diameter of the cylinder sleeve and the piston
skirt portion exceeds the service limit given below, replace the cylinder sleeve.

71
 Measurement Point Standard Dimensions Service Limit
Clearance between
cylinder inner surface 0.19~0;292mm 0.4mm
and piston skirt surface

e. If the inner diameter of the cylinder sleeve exceeds the service limit given below,
replace the sleeve. Measure the diameter of the cylinder sleeve at a point
10~20mm from the top of the cylinder, a point which is subject to the greater
wear.

Measurement Point Standard Dimensions Service Limit

Cylinder inner diameter 115.0mm 115.25mm

8.4.8 Discharge plate valve assembly and suction plate valve assembly

a. The discharge plate valve (110), suction plate valve (71) and valve springs (116
& 72) must be replaced every 6,000 hours. Durability of these components varies
according to operating conditions but the wear limit for the valve seat portion
should be less than 0.15mm from the standard thikness shown below.

Part name Standard thikness Service Limit

Discharge plate valve (110) 1.4mm 1.25mm
Suction plate valve (71) 1.4mm 1.25mm

b. Even if abrasion of the plate valve seat portion is within the service limit, if
scratches, scoring or other damage is found on the circumference, which can
lead to breakage due to metal fatigue, replace the plate valve with a new one.
c. The allowable wearing limit for the discharge valve seat (111) and the seat
portion of the valve plate (73) is 0.2mm.

8.4.9 Oil pump

If the oil pressure is too low even after closing the oil pressure regulating valve (*17)
and the filter is found not to be clogged, one possible cause is wearing of the pump
gear, metal and shaft. When carrying out inspection of the oil pump, detach the
pump from the compressor, check the play of the pump shaft by moving the shaft in
both the parallel direction and perpendicularly. If shaft play is felt, replace the
bearing assembly with a new one.

8.4.10 Main bushing (12) and thrust washer (29-4)

a. If the clearance between the main bushing and the crankshaft exceeds the
following service limit, replace the main bearing and thrust washer.

Measurement Point Standard Dimensions Service Limit

Space between main
0.035~0.20mm 0.43mm
bushing and crankshaft

72
 b. If the inner diameter of the main bushing exceeds the service limit given below,
replace the bushing with a new one.

Measurement Point Standard Dimensions Service Limit

Inner diameter of main
85.0mm 84.863mm
bushing

c. Measure the thikness of the thrust washer. If the thickness of the washer is less
than the service limit, replace with a new one.

Measurement Point Standard Dimensions Serivice Limit

Thrust washer thickness 2.70~2.77mm 2.55mm

8.4.11 Thrust bearing (29)

a. If the clearance between the thrust bearing and the crankshaft exceeds the
service limit given below, replace the thrust bearing with a new one.

Measurement Point Standard Dimensions Service Limit

Clearance between
thrust bearing and 0.06~0.115mm 0.27mm
crankshaft

b. If the inner diameter of the thrust bearing exceeds the service limit given below,
replace with a new one.

Measurement Point Standard Dimensions Service Limit

Thrust bearing ID 85.0mm 84.86mm

8.4.12 Springs

a. Measure the free length of each spring. If the free length of the spring is 10% or
more shorter than the standard value given below, replace the spring with a new
one.
b. The discharge valve spring (116) and the suction valve spring (72) should be
replaced every 6,000 hours.

Spring name
Discharge valve spring (116) 10 x 0.2t x ø6 (max dia.)

Suction valve spring (72)

Lift pin spring (69) 10 x ø0.4 x ø5.2
Unloader device spring (142) 72 x ø2.8 x ø32.3

8.4.13 Built-in safety valve (214)

a. If the built-in safety valve has actuated, the seat is liable to be clogged with
foreign matter, resulting in subsequent refrigerant leakage. In such case, replace
the safety valve as an assembly.

73
8.4.14 Gaskets and O-rings

a. After disassembly and inspection have been carried out, replace the gaskets with
new one. If a gasket shows signs of hardening due to extended continuous
operation, replace it.
b. Although the O-rings used are made of synthetic rubber, they may deteriorate
due to exposure to refrigerant and oil over a long period of time. Periodic
replacement is recommended. When ordering, specify the refrigerant used.

Standard
Nominal
O Ring name Standard Dimensions (mm)
No.
(OD x ID x T)
O-ring, mechanical seal
JIS.B2401 P75 5.7 x 74.6 x 86.0
(for seal ring)
O-ring, mechanical seal
JIS.B2401 P85 5.7 x 84.6 x 96.0
(for floating seat)
O-ring, oil sight glass JIS.W1516 P35 5.3 x 59.69 x 70.35

74
8.4.15 Gaskets

External views and dimensions of L Series compressor gaskets

75
8.4.16 Designed allowable clearances

76
 MYCOM World-wide Aftersales Network

30 international subsidiaries
72 domestic (Japan) subsidiaries

We reserve the right to change design specifications according to technical developments and improvements
without notice.

77