PUMPS

OPERATIONS AND MAINTENANCE

Derleyen: Nejat ÖZTEZCAN

Chief Engineer
A Pump is a machine used to raise liquids from a low point to a high
point.(from point A to point B )

Pumps are used to move any substance which flows or which can be
made to flow.

As a general rule, all pumps are designed to move fluid substances from
one point to another by pulling, pushing or throwing or by some
combination of these three methods.

A pump is a device that adds energy to the fluid to enable it to move

from one point to another.

The additional energy can be used to increase

 Velocity (flow rate)

 Pressure
 Elevation
Pumps are divided into two fundamental types based on the
manner in which they transmit energy to the pumped media:

Kinetic or Positive displacement.

In kinetic displacement, a centrifugal force of the rotating element,

called an impeller, “impels” kinetic energy to the fluid, moving the
fluid from pump suction to the discharge.

On the other hand, positive displacement uses the reciprocating

action of one or several pistons, or a squeezing action of meshing
gears, lobes, or other moving bodies, to displace the media from
one area into another.
Sometimes the terms ‘inlet’ (for suction) and ‘exit’ or ‘outlet’ (for
discharge) are used.

The pumped medium is usually liquid; however, many designs can

handle solids in the forms of suspension, entrained or dissolved gas,
paper pulp, mud, slurries, tars, and other exotic substances, that, at
least by appearance, do not resemble liquids.
The main elements of a pumping system are:

1.Supply side (suction or inlet side)

2.Pump (with a driver)
3.Delivery side (discharge or process)

Energy input = Energy useful + Losses

Efficiency = Energy useful /Energy input

Losses = Mechanical + Volumetric + Hydraulic

bearings leakage (slip) friction
coupling entrance/exit
rubbing vortices
separation
disc friction
From the pump user viewpoint, there are two major parameters of
interest:

Flow and Pressure

Flow is a parameter that tells us how much of the fluid needs to

be moved (i.e., transferring from a large storage tank to smaller
drums for distribution and sale, adding chemicals to a process,
etc.).

Pressure tells us how much of the hydraulic resistance needs to

be overcome by the pumping element, in order to move the fluid.
 Driver

Coupling

Pump
Valve Valve
 PUMPS

POSITIVE DISPLACEMENT CENTRIFUGAL PUMS

PUMPS (KINETIC)

RECIPROCATING ROTARY

PISTON PUMPS GEAR PUMPS

PLUNGER PUMPS LOBE PUMPS

DIAPHRAM PUMPS SCREW PUMPS

CAM PUMPS

VANE PUMPS
Pump Efficiency

Pump efficiency is defined as the ratio of water horsepower output

from the pump to the shaft horsepower input for the pump.

Water horsepower is determined by the flow rate and pressure

delivered from the pump.

The shaft horsepower is delivered to the pump from the power unit,
which usually is an electric motor or internal combustion engine.

The efficiency of a particular pump is estimated by determining two

values. These values are pump flow rate and total head.
Positive displacement pumps

Positive Displacement pumps perform work by expanding and then

compressing a cavity, space, or moveable boundary within the pump.

In most cases, these pumps actually capture the liquid and physically
transport it through the pump to the discharge nozzle.

Inside the pump where the cavity expands, a zone of low pressure, or
vacuum, is generated that causes the liquid to enter through the suction
nozzle.

Then the pump captures and transports the liquid toward the discharge
nozzle where the expanded cavity compresses.

In this sense, because the available volume of space at any point inside
the pump is a constant, we can say that in theory, these pumps are
considered a ‘constant volume device’ with every revolution or
reciprocating cycle.
Simple Hand Pump Operation
The Simple Pump is a positive
displacement progressive lift
pump...sometimes referred to as a
"sucker rod" pump.

SELF PRIMING
Self-priming pumps have to be
capable of evacuating air from the
pump suction line without any
external auxiliary devices.
 Positive Displacement I I I F T leciprocating \
Rotary. Simplex Gear. screw. Vane. Lobe.

POSITIVE DISPLACEMENT
PUMPS

T leciprocating
RECIPROCATING ROTARY

Plunger Gear
Piston Screw
Diaphragm Vane
Lobe
Positive displacement pumps normally are preferred over
centrifugal pumps in applications of:

Viscous liquids,
Precise metering, (dosification, pharmaceutical chemistry)
Where pressures are high with little flow.

The positive displacement pumps differ from centrifugal pumps,

which deliver contunious flow for any given pump speed and
discharge resistance.
When positive-displacement pumps are used, the system must be
protected from excessive pressures.

Because of their ability to generate almost unlimited pressure, all

positive-displacement pumps systems must be fitted with relief
valves on the downstream side of the discharge valve.

This is required to protect the pump and its discharge piping from
over-pressurization.

Some designs include a relief valve that is integral to the pump’s

housing. Others use a separate valve installed in the discharge
piping
RECIPROCATING PUMP•Pressure can be controlled without
affecting flow rate.

Piston Pump
Plancer Pump
Diaphgram Pump

A. PISTON PUMP

• Based on two stroke principles

• High pressure, high efficiency
• Self-priming

• Small quantity, vibration, physical dimension, uneven flow

• Used mainly for handling slurries in plant processes and

pipeline applications
Piston pumps, also called reciprocating pumps, can be powered by
an electric motor, steam or a turbine, hydraulic drive mechanism.

Function

A piston pump uses the reciprocating motion of a piston rod to

move fluid along an axis through a cylinder chamber. As the piston
moves through the cylinder, pressure builds up and forces the fluid
through the pump.
Advantages

Piston pumps have a wide pressure range, can reach high pressures
and the pressure can be controlled without an impact on the rate of
flow.
Piston pumps have a continuous rate of discharge. Pressure changes
and discharge rate have minimal effect on performance. Piston pumps
can be used viscous fluids, high gas volumes and solids, only if the
valves are correctly designed.
They are self priming.

Disadvantages

Piston pumps cost more per unit to run compared to centrifugal and
roller pumps. The mechanical parts are prone to wear, so the
maintenance costs can be high. Piston pumps are heavy due to their
large size and the weight of the crankshaft that drives the pump.
Types

There are many types of piston pumps , but they all employ at least
one piston moving in an enclosed cylinder. Specific types of designs
include axial and radial piston pumps.

Axial piston pumps contain a number of pistons attached to a

cylindrical block which move in the same direction as the block's
centerline (axially).
Radial piston pumps contain pistons arranged like wheel spokes
around a cylindrical block.

A drive shaft rotates this cylindrical block which pushes or slings the
pistons, causing compression and expansion. The eccentricity
between the piston housing and cylinder block centerlines
determines the piston stroke.

These pumps have a low noise level, very high loads at the lowest
speeds, and high efficiency.
Pump Action

Pump action determines what directions the piston moves to perform

fluid suction and discharge.
B. PLUNGER PUMP

Plunger pump or also known as positive displacement pump is used

to pump small amount of liquid at high pressure.

The main components of plunger pump are the plunger and the inlet
and outlet with two valves where they can open only in one
direction.
 Main pump advantages:
1. Small size
2. Operation reliability
3. Long life
4. Have high efficiency.
5. Capable of developing very
high pressures.
6. Low and easy maintenance

Plunger pump (single acting)

What is the difference between a plunger and a piston?

A piston pump is a type of positive displacement pump where the

high-pressure seal reciprocates with the piston.

A plunger pump is a type of positive displacement pump where the

high-pressure seal is stationary and a smooth cylindrical plunger
slides through the seal. This makes them different from piston
pumps and allows them to be used at higher pressures.

Pistons have rings cut in to it to

accommodate rings and plungers has
no rings
C. DIAPHGRAM PUMP

The diaphragm pump is composed of the following:

• A chamber used to pump the fluid

• A diaphragm operated by either electric or
mechanical means
• Two valve assemblies: a suction valve
assembly and a discharge valve assembly
 Diaphragm Pump
1.flexible diaphragm is used
(rubber, thermo-plastic, metal).

2. Can be used to make artificial

hearts.

3. Can handle highly viscous

liquids.

4.Can handle toxic or corrosive

liquids.

5. 97% efficient.

Diaphragm Pump (single acting)

ROTARY PUMPS
GEAR PUMPS
A. Internal Gear.
Internal gear pumps carry fluid between the gear teeth from the inlet
to outlet ports. The outer gear (rotor) drives the inner or idler gear
on a stationary pin. The gears create voids as they come out of mesh
and liquid flows into the cavities. As the gears come back into mesh,
the volume is reduced and the liquid is forced out of the discharge
port.
b. External Gear.
External gear pumps also use gears which come in and out of mesh.
As the teeth come out of mesh, liquid flows into the pump and is
carried between the teeth and the casing to the discharge side of the
pump. The teeth come back into mesh and the liquid is forced out
the discharge port. External gear pumps rotate two identical gears
against each other. Both gears are on a shaft with bearings on either
side of the gears.
The most common type of positive-displacement pump uses a
combination of gears and configurations to provide the liquid
pressure and volume required by the application.

Variations of gear pumps are:

Spur
Helical
Herringbone

Spur : The simple spur-gear pump consists of two spur gears

meshing and revolving in opposite directions within a casing.

Only a few thousandths-of-an-inch clearance exists between the

case, gear faces, and teeth extremities.
In all simple-gear pumps, power is applied to one of the gear shafts,
which transmits power to the driven gear through their meshing teeth.

There are no valves in the gear pump to cause friction losses as in

the reciprocating pump.

Gear pumps well suited for viscous fluids, such as fuel and lubricating
oils.

Helical: The helical-gear pump is a modification of the spur-gear pump

and has certain advantages. With a spur gear, the entire length of the
tooth engages at the same time.

Herringbone. The herringbone-gear pump is also a modification of the

simple-gear pump. The principal difference in operation from the
simple-gear pump is that the pointed center section of the space
between two teeth begins discharging fluid before the divergent outer
ends of the preceding space complete discharging.
 Gear Pump
Delivery
Drive Gear
Driven Gear

Inlet Cam
Positive displacement gear pumps are well suited for pumping oil
because they are essentialy self priming and capable of high suction
lift.
External Gear Pump

RELIEF VALVE

İf the positive displacement pump works efficiency but

pump is not transferring any liquid ; pump relief valve
might be leaking.
Can a worn-out gear pump life be doubled with no new parts and
modifications?
If a gear pump casing is turned around, for example, as discharge and
suction ports are swapped, the worn-out part of the casing would now
face the discharge end, and the non-worn section would face toward
the suction end. When the casing is turned around, the non-worn part
of the casing will actually restore the radial clearance between the gears
and casing, thereby reducing the slip, and restoring the pump flow.
Certainly, this solution is not a permanent fix,
LOBE PUMP

Fluid is carried between the rotor teeth and the pumping chamber.
The rotor surfaces create continuous sealing. Both gears are driven
and are synchronized by timing gears.

Advantages Disadvantages

•Pass medium solids •Requires timing gears

•No metal-to-metal contact •Requires two seals
•Superior CIP/SIP capabilities •Reduced lift with thin liquids
•Long term dry run (with
lubrication to seals)
•Non-pulsating discharge
 Screw Pump
Screw pumps carry fluid in the spaces between the screw threads.
The fluid is displaced axially as the screws mesh.
Single Screw Rotor

Elastomer Stator Universal Coupling

NEVER RUN DRY

 Rotary Screw Pump

A screw pump is a type of positive displacement pump that uses two

or more screws that intermesh to pressurize fluids and move them in a
system. The screws take in fluid then push it out from the other side
while increasing its pressure.
VANE PUMP

Vane pumps can handle moderate viscosity liquids, they excel at

handling low viscosity liquids such as LP gas (propane), ammonia,
solvents, alcohol, fuel oils, gasoline, and refrigerants.

Vane pumps have no internal metal-to-metal contact and self-

compensate for wear, enabling them to maintain peak performance
on these non-lubricating liquids.
SLIDING VANE PUMPS

These are mainly applied for low viscosity liquids.

However, pumping lube oils and gasoline is not uncommon.

Vanes slide (i.e., adjust) to compensate for wear and are easy to
replace. If not replaced on time, however, vanes can wear out to
the point of breakage, causing catastrophic failures.

Preventative maintenance, therefore, should include vane

replacement, and should be done at regular, established intervals.

These pumps can be extremely noisy at speeds over 300 RPM .

Performance
Positive-displacement pump performance is determined by three
primary factors:

Liquid viscosity

Rotating speed

Suction supply
Viscosity:

Positive-displacement pumps are designed to handle viscous liquids

such as oil, grease, and polymers. However, a change in viscosity has a
direct effect on its performance.

As the viscosity increases, the pump must work harder to deliver a

constant volume of fluid to the discharge. As a result, the brake
horsepower needed to drive the pump increases to keep the rotating
speed constant and prevent a marked reduction in the volume of liquid
delivered to the discharge.
Temperature variation is the major contributor to viscosity change.

The design specifications should define an acceptable range of both

viscosity and temperature for each application.

These two variables are closely linked and should be clearly

understood.
Rotating Speed.

With positive-displacement pumps, output is directly proportional to

the rotating speed. If the speed changes, from its normal design point,
the volume of liquid delivered also will change.

Suction Supply.

Positive-displacement pumps are self-priming. In other words, they

have the ability to draw liquid into their suction ports.
However, they must have a constant volume of liquid available.
Therefore, the suction-supply system should be designed to ensure that
a constant volume of nonturbulent liquid is available to each pump in
the system.

When the pumps are required to overcome suction lift, they must work
harder to deliver product to the discharge.
CAVITATION IN GEAR PUMPS

Cavitation is the formation of voids or bubbles in a liquid as the

pressure drops below the vapor pressure of the liquid in the pump’s
inlet.

These bubbles then collapse when they reach the high pressure side
of the pump. This collapse can, over time, damage the pump and
erode hard surfaces.

Cavitation causes a drop in output flow that can sometimes be

mistaken for slip, but cavitation can usually be identified by its
distinctive sound.
.
Significant cavitation will usually sound like gravel rattling around
inside the pump.

Therefore, pump suction pressure must be greater than the

minimum allowable value.

If this condition is not maintained, the pump flow will decrease,

accompanied by noise, vibrations, and possible damage to the
equipment
SHAFT ALIGNMENT
Motor-Pump alignment is the process of aligning shaft centerlines
between a motor and a pump.

The motor is the prime mover, transferring power to the pump by the
use of a coupling.

When speaking of a pumping system, proper alignment of two different

types is important: the alignment of the pump shaft and the drive shaft,
and the alignment of the pump flanges with the connecting piping.

The alignment of the pump shaft to the drive shaft of the motor, gear, or
engine driving the pump is called shaft alignment. The alignment of the
pump flanges to the connecting piping is called flange alignment.
Importance of Shaft Alignment

The shafts of the pump and drive unit must be closely aligned.
Failure to achieve proper alignment, a condition referred to as
misalignment, will result in increased pump vibration, decreased
bearing life, and has the potential to cause mechanical seal leakage
and issues with the coupling.

Importance of Flange Alignment

It is critical that the piping be carefully aligned to the pump flanges,

and that the piping not be forced into place when the pipe flanges
are bolted to the pump flanges. Poor flange alignment will place a
tremendous amount of force on the casing – a condition referred to
as flange loading – and may result in shaft misalignment as the
casing shifts, increased vibration, bearing failures, mechanical seal
failures, and cracks in the pump casing.
Types of Misalignment

When checking alignment; there are two types of misalignment that

may be encountered:
• parallel and
• angular.

Parallel misalignment may be horizontal, vertical, or a combination of

both parallel and horizontal.
Parallel vertical misalignment occurs when one of two shafts is higher
than the other.

Angular misalignment occurs when two shafts are at an angle to each

other and are not parallel.
How do you check shaft alignment?

Shaft alignment can be checked in a rudimentary fashion using a

straight edge placed on the pump and drive unit coupling hubs. This
method is sometimes called rough alignment, and may be performed
prior to certain construction activities to confirm that the pumping
unit installation is adequate to continue work.

For most pumps, once installation is complete, much more precise

alignment is necessary. There are two common methods for checking
shaft alignment: dial indicator alignment or laser alignment.

There are three basic methods of alignment.

They are
1) straight edge with a taper gauge, feeler gauge, or caliper;
2) dial indicator; and
3) laser.
Periodic Inspections
TROUBLESHOOTING

No Liquid Delivered:

Pump rotating in wrong direction.

Inlet lift too high; check this with gage at pump inlet.
Clogged inlet line.
Inlet pipe not submerged.
Air leaks in inlet line.
Faulty pressure relief device in system.
Pump worn.
Rapid Wear:
1.Excessive discharge pressure.
2.Pump runs dry.
3.Incompatibility of liquid and pump materials.
4.Pipe strain on pump.
5.Speed too high for abrasives present in liquid.

Excessive Noise:
1.Starved pump.
2.Air leaks in inlet line.
3.Air or gases in liquid.
4.Pump speed too high.
5.Improper mounting; check alignment thoroughly.
Pump Takes Too Much Power:

1.Speed too high.

2.Liquid more viscous than previously anticipated.
3.Operating pressure higher than specified; check this with gage at
pump discharge.
4.Discharge line obstructed.
5.Mechanical defect such as bent shaft.
6.Packing too tight.
7.Pipe strain on pump.
 TROUBLESHOOTİNG

•Rule Number One: “Always do the easy stuff first!”

•Always check the rotation of the pump.

•Make sure relief valve setting is correct.

•Check speed for belt-driven, or vari-drive, cases. Do not take

them for granted.

•Check the integrity of the coupling

•Alignment: How and who? Is piping forced to flanges?

•Trace the system and make sure the valves are open and that
you are pumping from the correct vessel.
•For heavy viscosities, make sure the pump is warmed up prior
to starting.

•Check for high temperature on the bearing housing to detect

excessive thrust conditions. Bearings could tell you a good
story.

•Inspect oil level in the bearing housing.

•Check for signs of discoloration.

•Inspect seals for leakage.

•Only after the above questions are resolved, consider the

removal
What is a Centrifugal Pump

A centrifugal pump is a machine that uses rotation to impart velocity to

a liquid and then converts that velocity into flow.

1. A centrifugal pump is a machine.

2. A centrifugal pump uses rotation to impart velocity to a liquid.
3. A centrifugal pump converts velocity into flow.

Every centrifugal pump includes an impeller. The impeller is the

hydraulic component that rotates to impart velocity to the pumped
liquid.

Every centrifugal pump includes a casing. The casing is the hydraulic

component that captures the velocity imparted by the impeller and
directs the pumped liquid to the pump discharge point.
A centrifugal pump is known to be a “pressure generator,” or a “flow
generator,” which a rotary pump is.

Essentially, a centrifugal pump has a rotating element, or several of

them, which “impel” (impeller) the energy to the fluid.

A collector (volute or a diffusor) guides the fluid to discharge.

At the most fundamental level, a centrifugal pump consists of just

these three components:

1.An impeller that rotates and imparts velocity to a liquid.

2.A casing that captures the velocity generated by the impeller and
transforms that velocity into a stable flow.
3.An assembly of mechanical components that makes it possible for
the impeller to be rotated within the pump casing.
Centrifugal pump performance is primarily controlled by two
variables:

•suction conditions

•total system pressure.

 PUMP MAJOR COMPONENTS:

• Shaft
• Impeller
• Wear Rings
• Stuffing Box
• Diffuser Casing
• Bearings
 Basic Pump Configuration
Discharge

Bearings Gland Casing

Suction

Impeller

25 February 2018 70
A centrifugal pump has two main components:

1. A rotating component comprised of an impeller and shaft

2. A stationary component of casing, casing cover and bearings.
 Centrifugal Pump Impellers
The impeller of a centrifugal pump is rotated rapidly to impart
velocity to a pumped liquid.

Semi-Open Closed

Open Impellers
Impellers

The basic function of the centrifugal pump impeller is to

directly increase the pressure of the liquid being pumped.
Centrifugal Pump Casings

The centrifugal pump casing is the component of the pump that

converts all of the velocity created by the rotating impeller into a
controlled and stable flow and directs it out of the pump through the
discharge point.

The most common type of casing is called a volute and it looks

similar to a snail shell.
MIX FLOW PUMP
Pump Bearings

The final part of the mechanical end is the bearing arrangement.

Generally speaking, centrifugal pumps are equipped with standard
ball-type anti-friction bearings. These are the same bearings used
in everything from electric motors and they are lubricated by
grease or oil.

The pump shaft is supported and held in place by the bearings

which have to be designed to handle all of the loads created by
the rotation of the impeller, and sized to provide a reasonable
service life.

Bearing failures are one of the most common causes of pump

failures.
WEAR RINGS
Wear rings provides an easily and economically renewable leaking
joint between the impeller and the casing clearance becomes too
large the pump efficiency will be lowered causing heat and vibration
problems. With 50 percent decrease in clearance, efficiency is
increased by 2 to 4 percent.
 Wear Ring Clearances:
• Wear ring provides close clearances to minimize leakage
from the discharge to the suction of the impeller.
• As the wear ring wears with use , leakage will gradually
increases , effecting the pump efficiency.
• The gap is destroyed if there is
misalignment or shaft deflection.
• Clearances is taken through the Feeler
Gauge.
• Material : SS or Bronze
Why are wear rings provided in a centrifugal pump?

They protect the rotating impeller from rubbing with the stationary
casing and provides a replaceable wear joint. So, the impeller is
saved from erosion and we do not have to replace it , which would
be very costly to do so, and instead the cheaper wear rings bear the
brunt, get eroded and are replaced periodically.

Another very important function is that they prevent the leakage

losses across the annular path between impeller and wear ring.
Pump Shaft

The impeller is mounted on a shaft. The shaft is usually made of

steel or stainless steel and is sized to support the impeller. Shafts
have to be sized carefully. An undersized shaft can result in
increased pump vibration, shorter bearing life, the potential for
shaft breakage, and an overall reduced pump life. However, an
oversize shaft can increase the cost of the pump unnecessarily.

Shaft Sleeve

In most pumps, the portion of the shaft that is under the sealing
arrangement is covered with a shaft sleeve. The shaft sleeve is a
sleeve of metal, usually bronze or stainless steel, that is designed to
either slide or thread onto the shaft. The shaft sleeve is used to
position the impeller correctly on the shaft, and it also protects the
shaft.
Couplings are mechanical elements that ‘couples’ two drive
elements which enables motion to be transferred from one
element to another. Couplings can also compensate for axial
growth of the shaft .

The drive elements are normally shafts. Shaft couplings

classified into two groups:

1. Rigid
2. Flexible
Pump couplings are used to connect the motor to the pump
D. Keep the pump primed
 Types of Shafts Couplings
• 1. Rigid coupling 2. Flexible coupling

1. Rigid coupling : It is used to connect two shafts

which are perfectly aligned.
• types of rigid coupling are
• a)Sleeve or muff coupling.
• b)Clamp or split-muff or compression coupling,
• c)Flange coupling
• 2.Flexible coupling : It is used to connect two
shafts having both lateral and angular
misalignment.

• Types of flexible coupling are

• a)Bushed pin type coupling,

• b)Universal coupling, and
• c)Oldham coupling
Marine type flange coupling
Bushed-pin Flexible Coupling
•Hirth joints are a type of rigid coupling that transmits power by using
two shafts that have interlocking teeth.
•Hirth joints are commonly found on high speed high torque industrial
machinery that benefits from the hirth joints self centering
capabilities. Common applications include gas turbines, turboprops,
steam generators.
•Flanged couplings are a type of rigid coupling that utilizes flanges
and bolts to couple to shafts together.
•Common applications of flanged couplings is joining two pipes
together in order to transmit water pressure, it can also be used to
extend a rotating shaft.
ALL CENTRIFUGAL PUMPS ARE NOT SELF
PRIMING.
Low water level in the wet well can cause cavitation.
Maintenance Of Pumps
 Shaft Run Out
• Runout checks are made to determine out of roundness
conditions (eccentricity) in a shaft. Whether shaft is
concentric or not ?
• Runout occurs due to:
a) Machining Process
b) Dents from handling.
c) Rust patches.
d) Rotor bow / sag due to thermal effects, gravity, or other
influences/loads.
e) Defective or worn bearings in the machine or lathe supports
 Cont’d
• Moderate to excessive run out will create
moderate to excessive vibration within a pump
(may cause rubbing).
• Firstly shaft itself is checked and then
along with its attached components
(wear ring , impeller etc.)
• Dial Indicator is attached on axially
given points. Variation in readings
indicates:
 Balancing Check
• Balancing of a rotor is carried out to eliminate the
vibration.

• Balancing correction weights may eliminate the

dynamic forces but they will not resolve the
eccentricity issue.

• Correction weights may added or material may

remove for the balancing.
Cont’d
Dial Indicator
Feeler Gauge.
 BEARING

• Providing Support to a shaft for smooth Running.

• Lubrication prevents metal-metal contact.
• Thrust Bearings are used to
compensate/bear axial load.

Bearing inspection is very important during

Pump maintenance.
Causes of Bearing Failure:
Flaking , Spalling , Rust & Corrosion, wear ,
Babbit metal remove , loss of lubrication etc.
RULMAN ISITMA CİHAZI

ÇEKTİRME
 Inspection During Maintenance:

• Pump Impeller.
• Mechanical Seal.
• Gland Packing.
• Shaft Sleeve.
• Relieve Valve.
• Pump Element.
Sealing Arrangement
The location where the shaft passes through the casing is called
the stuffing box. A sealing arrangement must be used to seal the
gap between the shaft and the wall of the stuffing box.

Either packing or a mechanical seal may be used to seal this area.

To prevent overheating and scoring of the shaft after
repacking the stuffing box, tighten the packing in small
increments while the pump is operating.

When renewing spiral packing in a centrifugal pump stuffing

box, after the packing is firmly seated, the packing gland nuts
should be loosen and then retightened with the pump running
under normal conditions.
 Mechanical Seal

 Seal may fail due to lack of

lubrication. Due to which
temperature rises at the
sealing faces that will
damage the elastomer part
of the mechanical seal.
 Pump Vibration. Vibration
imparts forces on each part
of the seal components.
Vibrations may be due to
worn bearings.
Mechanical seal
Gland Packing
 High-temperature Graphite Braided Packings

General-service Braided Synthetic Packings

High-temperature/Pressure Steam Packing

OPERATION OF CENTRIFUGAL PUMPS
Startup Procedures.

Centrifugal pumps should always be started with the discharge valve

closed. As soon as the pump is activated, the valve should be slowly
opened to its full-open position.

The only exception to this rule is when there is positive backpressure

on the pump at startup.

Without adequate backpressure, the pump will absorb a substantial

torsional load during the initial startup sequence. The normal tendency
is to overspeed because there is no resistance on the impeller.
Bypass Operation.

Many pump applications include a bypass loop intended to prevent

deadheading (i.e., pumping against a closed discharge).

Most bypass loops consist of a metered orifice inserted in the bypass

piping to permit a minimal flow of liquid. In many cases, the flow
permitted by these metered orifices is not sufficient to dissipate the
heat generated by the pump or to permit stable pump operation.

If a bypass loop is used, it must provide sufficient flow to assure

reliable pump operation. The bypass should provide sufficient
volume to permit the pump to operate within its designed operating
envelope.
This envelope is bound by the efficiency curves that are included on
the pump’s hydraulic curve, which provides the minimum flow
required to meet this requirement.
Stable Operating Conditions.

Centrifugal pumps cannot absorb constant, rapid changes in operating

environment.
For example, frequent cycling between full-flow and no-flow assures
premature failure of any centrifugal pump.

The radical surge of backpressure generated by rapidly closing a

discharge valve, referred to as hydraulic hammer, and generates an
instantaneous shock load that can literally tear the pump from its piping
and foundation.

In applications where frequent changes in flow demand are required,

the pump system must be protected from such transients. Two methods
can be used to protect the system.
A) Slow Down the Transient.

Instead of instant valve closing, throttle the system over a longer time
interval. This will reduce the potential for hydraulic hammer and prolong
pump life.

B) Install Proportioning Valves.

For applications where frequent radical flow swings are necessary, the
best protection is to install a pair of proportioning valves that have
inverse logic. The primary valve controls flow to the process.
The second controls flow to a full-flow bypass.
Common problems in pumps and their symptoms is extremely
important for maritime professionals who want shipping operations
to be smooth and safe in the engine room.

Mentioned below are 10 practical tips which would help engineers to

understand pumps on board ships and troubleshoot problems related
to them.
1. Temperature – While taking engine room rounds, check the motor
temperature (by thermal gun or by feeling the motor by hand). Any
abnormality or increase in temperature indicates problem in the
pump- motor assembly.
2. Current – Monitor the pump motor amperage regularly. Any
variation or abnormal change in the current indicates some kind of
problem in the pumps.
3. Vibration – Continuous monitoring of pump vibrations is also
very important. Any sudden or gradual increase in the vibrations
indicates one or all of these – loose foundation, loose coupling,
misalignment, shaft-bearing wear out etc.
4. Sound – Regular monitoring of the pump’s sound helps seafarers to
recognize the normal working sound of the pump and also helps
to understand a problem from any change in the usual sound.
5. Pressure – The main function of the pumps is to supply/transfer
liquids or semi-liquids with pressure. Ensure that the rated pressure is
maintained at all times. If the pressure reduces, check the pump and
operations of associated parts (filters, valves etc.).
6. Running Hours: Every mechanical part comes with limited running
hours. Once the running hour of the pump part is over, it need to be
renewed. Keep a proper note of the running hours of pump parts and
change them whenever required without fail.
7. Planned Maintenance: The Planned Maintenance System (PMS) of
the pump is to be followed and overhauling of the pumps is to be
carried out at regular intervals of time as stated.
8. Gland Packing and Seals: Ensure that the gland packing and
mechanical seals of the pumps are in proper condition. Any leakage in
them is to be attended immediately for ensuring proper operations.
9. Motor/ Prime Mover Condition: A pump is driven by either an
electric motor or a prime mover engine. Ensure that the prime mover
engine is in proper working condition or the motor winding and its
insulation etc. are in good condition at all times.
10. Correct Operating Procedure: There are several different types of
pumps in the ship’s engine room which require specific operating
approach. Ensure you know the correct operating sequence for
different types of pumps.
 What's the difference between a centrifugal and positive displacement pump?

•Centrifugal pump are high capacity and relatively low head pump where as positive
displacement pumps are low capacity high head pumps.

•The centrifugal pumps work on the centrifugal action of rotating impeller to push the fluid.
Positive displacement pumps draw fluid into a compartment at the inlet and move it to the
outlet for discharge. It works on the rotary, reciprocating or diaphragm principle to move fluid.

•The main difference between the centrifugal pumps and positive displacement pump is that
positive displacement pumps moves fluid at the same speed regardless of the pressure on the
inlet end and centrifugal pumps will not.
•The positive displacement pump is use when we need high pressure whereas the centifugal
pump is used when we need a high flow rate .
 If a centrifugal pump is delivering less quantity than the design capacity, what are the
possible reasons?

The reasons are;

•CHECK THE PRIME MOVER FIRST

•Cavitation ,
•leakage and recirculation losses,
•valve failures,
•leakages in line,
•water line routing ,
•No of bends ,
•Foot valve failure or jam,
•Gland leakages
Why is there no relief valve on centrifugal pump?
Basically pumps are 2 types:
Positive displacement pumps and centrifugal types.

Relief valve at the discharge of the pump is required to protect the pump and discharge pipe
and its components due to overpressure caused by the pump.

Relief valve is always required for the positive displacement pump as it can theoratically
generate infinite pressure when its discharge valve is closed and pump is in operation.

But centrifugal pumps, relief valve may not require.

A positive displacement pump should not be run with the discharge valve closed. A centrifugal
pump that is pumping against a closed valve will just build up to some maximum pressure for
that pump, but a positive displacement pump will continue to discharge fluid into the fixed
volume ahead of the closed valve until the line busts or the pump is damaged.
 What happens when we close the valve in a discharge line while the pump is still working?

If it is centrifugal type, the outlet will go back again the pump case and turn again inside it and
there will be heat.

If it is positive displacement type, there will be high pressure and no going back to case due to
seals and low space. Finally, there will be damage and breaking in weakest part in circuit.

What happens when a centrifugal pump runs dry (without any liquid)?

it is not desirable and it may lead to bearing and mechanical seal failure.

With no liquid around the mechanical seals liquid film between the seal faces will disappear
and the temperature will rise dramatically. The heat thus produced may damage the
elastomeric parts or seal faces itself.

Whenever pump is run dry i.e. without water, air is the working fluid which does not act as a
coolant. So the pump will be overheated and damage the bearings, shaft and impeller.
Basically it will seize the pump.
 Is positive displacement pump more efficient then centrifugal pump?

Yes..

There is no back flow of water in the positive displacement pumps. All the fluid enters the
suction will come out thro the delivery.

In case of centrifugal pumps, there is back flow of water. Not all the fluid enters the suction
comes out thro delivery. Some will recirculated in the space between impeller and casing.

Which pump is more efficient, centrifugal pump or reciprocating pump?

•Centrifugal pumps are less efficient compared to reciprocating pumps.

•Reciprocating pumps are more efficient compared to centrifugal pumps.

Fluid Discharge

•Centrifugal pump discharges fluid continuously.

•Reciprocating pump discharges fluid in pulses.
•If the purpose is high flow rates to distances and alot of places like
cooling pump in engines where high pressure is not required, then
the centrifugal pump will be good.

•If you want high pressure or high capability of overcoming the

resistance like water elevating pump and fuel pump in engines, then
the displacement pump will be good.

•The centrifugal has more flow rates than positive pumps.

•The positive pump has more pressures at output than centrifugal

pump.
ALWAYS REMEMBER
•Rule Number One: “Always do the easy stuff first!”
•Always check the rotation of the pump.
•Make sure relief valve setting is correct.
•Check speed for belt-driven, or vari-drive, cases. Do not take them for
granted.
•Check the integrity of the coupling.
•Alignment: How and who? Is piping forced to flanges?
•Trace the system and make sure the valves are open and that you are
pumping from the correct vessel.
•For heavy viscosities, make sure the pump is warmed up prior to starting.
•Check for high temperature on the bearing housing to detect excessive
thrust conditions. Bearings could tell you a good story.
•Inspect oil level in the bearing housing.
•Check for signs of discoloration.
•Inspect seals for leakage.
•Discuss changes in operating condition: New product introduction or
adjustment? Compare stories.
•Discuss changes in line-up or changes in operating performance.
•Only after the above questions are resolved, consider the removal of the
pump from service.
 A centrifugal pump not taking suction, what action you are going to
take?
•Check valves open
•Suction live have crack/leakage
•Air Ingress to check, primer to check
•Suction line jointing to check
•Check suction filter clogged
•Should the above not complying check the wear ring clearance
excessive
•may be the impeller securing arrangement detached.

Why positive displacement pumps require relief valves?

With the pumping action, pumping rate is same but if the delivery is
obstructed the pressure will be built up gradually, which will damage
line, casing etc. To protect from above relief valves are required to be
fitted.
What is the correct method of starting and stopping as centrifugal
pump?

The correct way to start and stop a centrifugal pump is with the
discharge valve from the pump closed, i.e. less load on the motor
when starting and stopping

What does a positive displacement pump require that a centrifugal

pump does not?

A relief valve
Give possible reasons why the engine room bilge pump may not be able
to empty bilges?

•The strum box from the bilge may be fouled. Bilge pump suction filter may be
blocked
•A valve may be left open from an empty bilge
•There could be a hole in the system on the suction side of the pump
•Depending on type of bilge pump, the pump suction or discharge valves may
need overhauling

What would happen to the amperes of a centrifugal pump if it were with

the discharge valve shut?

The amps would drop as there would be no load on the pump

How many pumps are there in the engine room that you can pump bilges
with?
A bilge pump which is normally positive displacement. The others may vary
from ship to ship but can be the ballast pump, genaral service pump and main
Sea Water pump. These pumps are only used for pumping bilges in the event
of emergency and have an emergency bilge suction/injection valve connected
to them.

What types of pumps are used for pumping bilges in an emergency?

High capacity centrifugal pumps (mostly main cooling s.w.pump)

Why is gear pump used for pumping oil, while a centrifugal pump is used
for pumping water?
A gear pump is used for pumping oil as it has a high suction lift, is self priming,
able to produce the discharge pressure required by the system and can handle
large amounts of vapor or entrained gases. If is also able to pump high viscous
fluids

A centrifugal pump is used for pumping water, as it is unable to pump high

viscous fluids such as oil; the centrifugal pump is not self priming
What are the uses of centrifugal pumps, positive displacement pumps
and gear pumps on board a ship?

a.Centrifugal pumps :

• SW Cooling Pumps
•MEJCW Pumps
•Boiler Feed Pumps (multistage pumps)
• FWG Ejector Pump
•FWG Fresh Water pump

b.Positive displacement pumps:

•Bilge pumps
•Steering gear pumps
•Cargo pumps
•Gear pumps f.o.booster pumps, f.o.transfer pumps
• LO Pumps

What would happen if the M.E L.O pressure dropped too low on a pump?
If the M.E.L.O pressure were to drop too low on the L.O pump, the stand by L.O
pump would cut in.
What pumps in the Engine Room would supply the Fire Main?

As well as the Main Fire Pump, several pumps are arranged to supply
the Fire Main, their number and capacity set by legislation.

These pumps are normally: ballast pumps, general service pumps

Pump couplings are used to:
A. Ensure pump is properly connected to discharge piping
B. Connect the motor to the pump
C. Provide cooling water for the stuffing box
D. Keep the pump primed

Check valves are used to:

A. Control leakage from the stuffing box
B. Ensure pump is isolated from the system for maintenance
C. Prevent water from flowing in reverse
D. Fill water storage tanks

Packing should be adjusted when:

A. Excessive leakage from the discharge pipe is noticed
B. Excessive leakage from the stuffing box is noticed
C. Pump prime is lost
D. The pump is shut down
What is the purpose of pump mechanical seals?
A. Keep leakage off slippery floors
B. Prevent leakage between the pump casing and shaft
C. Provide an effective backflow prevention device
D. Seal water to maintain pump prime

Which type of pump is frequently used to pump water from wells?

A. Progressive cavity pumps
B. Submersible turbine pumps
C. Reciprocating pumps
D. Circulating pumps
What is the definition of pump?

•A pump is a device used to lift a liquid or gas from a low level to a

high level, to transport a liquid or gas from one place to another.

How Pumps are classified?

•Positive Displacement pumps Ex reciprocating pump, gear pump,etc..

•Dynamic pressure pumps. Ex centrifugal pump.