PUMPS

OPERATIONS AND MAINTENANCE

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
 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
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.
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.
 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)

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
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

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.
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.
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.

 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
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
• 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.
 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
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
Mechanical seal
Gland Packing
 High-temperature Graphite Braided Packings

General-service Braided Synthetic Packings

High-temperature/Pressure Steam Packing

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.
•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

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.