training session on centrifugal pump
DESCRIPTION
Centrifugal pumpsTRANSCRIPT
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PEP SESSION ON PEP SESSION ON
CONSTRUCTION & MAINTENANCE OF CONSTRUCTION & MAINTENANCE OF
CENTRIFUGAL PUMPSCENTRIFUGAL PUMPS
Khurram Majeed / Najam-us-saqib
Area Engineer / Maintenance Technician
Engro Chemical
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COURSE CONTENTSCOURSE CONTENTS
What is a pump ?What is a pump ?
Types of pumpTypes of pump
Centrifugal pumpsCentrifugal pumps--single & multi stagesingle & multi stage
Parts of centrifugal pumpParts of centrifugal pump
Important terms & definitionsImportant terms & definitions
Pump performance curvesPump performance curves
Pumps troubleshooting & maintenancePumps troubleshooting & maintenance
Preventive Maintenance ChecksPreventive Maintenance Checks
Typical Questions & AnswersTypical Questions & Answers
Pump overhaul procedurePump overhaul procedure
Parts Identification & Practical sessionParts Identification & Practical session
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WHAT IS A PUMP ?WHAT IS A PUMP ?
Pump is used to add energy to the fluid to move it
from one point to another
Pump is used to move the liquid from lower elevation
to higher elevation or from low pressure area to high
pressure area
Pump is used to increase the flow rate of the liquid
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TYPES OF PUMPSTYPES OF PUMPS
1. Positive Displacement Pumps
2. Dynamic Pumps
POSITIVE DISPLACEMENT PUMPS
A pump that first traps liquid and then delivers is called
positive displacement.
DYNAMIC PUMPS
A pump that works on the basis of centrifugal force is
called dynamic pump or centrifugal pump
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PUMP TYPES ORGANOGRAMPUMP TYPES ORGANOGRAM
Positive displacement
Pump
Reciprocating Pumps
Dynamic Pump
PUMP
Rotary Pumps
Screw Pumps
Lobe Pumps
Sliding vane Pumps
Gear Pumps
Diaphragm Pumps
Plunger Pumps
Centrifugal Pumps
Impeller Pumps
Propeller Pumps
Turbine Pumps
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CENTRIFUGAL PUMPCENTRIFUGAL PUMP
A pump that operates by centrifugal force and
develops pressure of the liquid is called
Centrifugal Pump
CLASSIFICATIONCLASSIFICATION
BY PRESSURE
1. Single stage Centrifugal Pump
A pump that is based on one Impeller is called single stage
centrifugal pump. It is used for relatively low pressure applications.
2. Multi stage Centrifugal Pump
A pump that is based on two or more than two Impellers is called
Multi stage centrifugal pump. It is used for high pressure
requirements
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CENTRIFUGAL PUMP CLASSIFICATIONCENTRIFUGAL PUMP CLASSIFICATION
BY FLOW
1. Single Suction Centrifugal Pump
A pump in which its Impeller has only one suction eye at one of its
side is called single suction Centrifugal Pump. Liquid entry from one
side , hence used for relatively low flow applications.
2. Double Suction Centrifugal Pump
A pump in which its impeller has suction eye on both the sides
is called double suction Centrifugal Pump. Liquid entry from
both ends, hence meets high flow requirements.
Thrust due to pressure Imbalance
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CENTRIFUGAL PUMP CLASSIFICATIONCENTRIFUGAL PUMP CLASSIFICATION
BY INSTALLATION
1. PARALLEL ARRANGEMENT
Pumps are installed in parallel to obtain high flow and same
pressures. Eg: P-25201, P-299.
2. SERIES ARRANGEMENT
Pumps are installed in series to obtain high pressure and same
capacity. Eg: Booster Pumps
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CENTRIFUGAL PUMP CLASSIFICATIONCENTRIFUGAL PUMP CLASSIFICATION
BY CASING ARRANGEMENT
1. VERTICAL SPLIT
A pump in which casing split is vertical with respect to ground level
2. HORIZONTAL SPLIT
A pump in which casing split is horizontal with respect to
ground level
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
Casing
Impeller
Impeller
suction eye
Discharge
Nozzle
ShaftI/B
Bearing
O/B
Bearing Sleeve
Gland Packing
Impeller
Lock Nut
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
SHAFT
The basic function of the
sleeve is to protect shaft
from erosion, corrosion and
wear at stuffing boxes,
leakage joints & internal
bearing areas.
Impeller Gland Packing / Mech
Seal
O/B Bearing I/B Bearing
Coupling
SHAFT SLEEVE
The basic function of a centrifugal Pump shaft is to transmit the
torques encountered in starting and during operation.
It also supports the impeller and other rotating parts.
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
IMPELLER
Impeller is the heart of Centrifugal Pump
It rotates the liquid mass with the peripheral speed of its vane tips.
The whirling movement of Impeller imparts centrifugal force to the
liquid and increases the velocity head.
Impeller does not increase liquid pressure. High velocity head is
converted to pressure head in the volute
Increase in velocity is directly proportional to Impeller diameter &
Pump speed.
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
PARTS OF IMPELLER
Impeller Hub
Central part of Impeller, bored out according to the shaft
diameter.
Suction EyeThe impeller inlet just ahead of the vanes is called the
suction eye.
Impeller shroud
Impeller shroud or enclosing sidewalls totally enclose the
impeller water ways from the suction eye to the periphery.
Impeller VanesVanes are the parts that pick up the liquid and
accelerate it to high velocity. Increase in length of
vanes or Impeller dia will increase the liquid velocity,
hence pump discharge pressure.
Wear rings
Wear rings provide
protection and an
economically
renewable leakage joint
between the impeller
and casing.BALANCING HOLES
These holes are located throughout a single suction impeller for the balancing of
thrust
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPES OF IMPELLER
Semi Open / ClosedOpen Closed
Consisting of Vanes only
No shrouds or sidewalls
Water slippage exists
Relatively less liquid
velocity
Impeller has structural
weakness
Applied in pumps
handling slurries & mud
Shroud on one side only
Water slippage exists but
less than in open type
Greater liquid velocity
than open type
Applied in pumps
handling abrasive liquids
Shroud on both sides
Least water slippage
Greater liquid velocity
than other types
Applied in pumps
handling clear liquids
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
CASING
An enclosed space where the Impeller rotates with the shaft is called
casing. The purpose of the pump casing is to guide the liquid to the impeller,
convert high velocity of liquid from impeller into pressure and lead the
flow away from the impeller to the discharge nozzle
TYPES OF CASING
1. Horizontal Split casing
2. Vertical split casing
3. Volute casing
4. Diffuser casing
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPES OF CASING
VOLUTE CASING DIFFUSER CASING
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
STUFFING BOX
A space provided for Gland Packing or Mechanical seal where
the shaft passes out through the pump casing
Primary function is to prevent leakage along the shaft.
Prevent air leakage into the pump and liquid leakage out of the
pump.
GLAND PACKING
It is a pressure breakdown device
JAM TYPE PACKING AUTOMATIC TYPE PACKING
Adjustable with time
Eg: P-102, P-299, P-201
Not adjustable with time
Eg: P-101
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
GLAND PACKING
A metallic cage about the size of a packing
ring that fits around the shaft sleeve inside
the packing box.
Located between the Packing rings near the
center of the packing box, providing
passage to the liquids for lubrication,
cooling and flushing
LANTERN RING
40 dpm is allowable Packing leakage
This amount of leakage between the packing & shaft is necessary for
lubrication / cooling
Packing ring size: Stuffing Box ID - Shaft OD
2
No of Packing rings: Depth of Stuffing Box
Packing ring size
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
GLAND PACKING
Throat bush is installed at pressure side of the stuffing box to break the
initial pressure.
To break the maximum pressure, clearance between throat bush and shaft
should be kept minimum.
Packing ring ends should be cut at 450 to form a sealing joint for minimum
leakage
Packing rings will be installed with ends at 120o apart
Packing is tightened by moving the gland pusher nut by one flat and wait
for 10 - 15 minutes. If required move another flat.
Packing SATURANT is a lubricant which lubricates the packing during
running
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
MECHANICAL SEAL
An average of 10% to 35% of the allotted pump-engineering time is generally
spent on the mechanical seal system
Prevents major fires, release of toxic materials having safety hazards and
reduces unit down time
FUNDAMENTAL SEALING PRINCIPLE
Fluid is to be sealed in a
container through which a
rotating shaft extends
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
FUNDAMENTAL SEALING PRINCIPLE
The shaft shoulder is replaced by a separate
piece and another adjacent member is
inserted into the housing wall. These two
members, the primary seal and mating ring,
are the heart of the mechanical seal
Other leakage paths are sealed
with secondary seals such as
O-rings, wedge or bellows
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
FUNDAMENTAL SEALING PRINCIPLE
The shaft shoulder is replaced by a separate
piece and another adjacent member is
inserted into the housing wall. These two
members, the primary seal and mating ring,
are the heart of the mechanical seal
Other leakage paths are sealed
with secondary seals such as
O-rings, wedge or bellows
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
FUNDAMENTAL SEALING PRINCIPLE
The spring is placed under tension by a retainer
which provides positive drive for the seal. This
completes the seal assembly.
The precision lapped faces are automatically
kept in constant by the insertion of a spring. A
single or multi springs can be used
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPE CLASSIFICATION
In pusher seals, as face wears, the secondary sealing members slide along the shaft to
maintain a seal. These secondary sealing members are commonly dynamic elastomers
e.g. O-rings. In Non-Pusher or bellow type seal, the secondary element does not slide
along the shaft therefore it is far less susceptible for hang-up. I.e. excessive opening of the
seal faces. These seals utilize both elastomer and metal bellows.
Pusher or Non-Pusher Seals
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPE CLASSIFICATION
Mechanical seals are described as inside if the hydraulic pressure being contained acts in
closing direction. With an outside seal hydraulic pressure acts inn an opening direction.
The internal seal is a more stable type; The external seal tends to lose face contact with a
sudden surge and quite often it is impossible for it to reestablish face contact
Inside or Outside Seals
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPE CLASSIFICATION
Hydraulic balance refers to the relationship between the pressure of the fluid being sealed
and the contact pressure between the seal faces., In the case of an unbalanced seal,
hydraulic pressure is unrelieved by the face geometry so that the face contact pressure is
equal or greater than the fluid pressure. With a balanced seal the design proportions the
radially disposed areas so that the effective contact pressure is always less than the fluid
pressure
Balanced or Unbalanced Seals
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
TYPE CLASSIFICATION
Single seal has one set of sealing faces and are commonly used as sealing device. Double
seals have two sets of sealing faces are normally recommended for safety and
environmental reasons. The buffer fluid is contained externally in an external auxiliary
seal flushing reservoir. Double Mech seals have following classification.
Tandem Seals
These are mounted one seal facing
inboard towards the pumped liquid,
and the other facing outboard
towards atmosphere. The buffer
fluid is maintained at a pressure
greater than the service fluid
pressure
These are used for fluids having
environmental and safety hazards.
The outboard seal has a separate
low pressure buffer liquid into the
space between it and inboard seal.
Back-to-Back
Single or Double Seals
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
BEARINGS
The bearings in a centrifugal pump must
In friction bearings there is little
friction between rotary & stationary
parts because of more contact area
between shaft and bearing
TYPES OF BEARINGS
Friction Bearings Anti-friction Bearings
Allow the shaft to rotate with practically negligible friction
Hold the rotating element in its proper position relative to the stationary
parts of the pump, both radially and axially, so that the rubbing cannot
occur
Be able to absorb forces that are transmitted to them from the impeller
Give trouble free service for long periods of time
To prevent or oppose rubbing, rolling
contact or friction between rotary &
stationary parts anti friction bearings are
used. They have little contact between
balls and races.
Journal Bearings (Radial & Thrust)
Ball Bearings Roller Bearings
Deep Groove Ball Bearings
Angular Contact Ball Bearings
Self Align Ball Bearings
Thrust Ball Bearings
Cylindrical Roller Bearings
Spherical Roller Bearings
Taper Roller Bearings
Needle Roller Bearings
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATUREBALL BEARINGS
Deep Groove Ball Bearings Angular Contact Ball Bearings
This type of Bearings has a
deep groove in its outer &
inner race
Carries radial & axial loads.
Operating at high speed.
Support heavy load.
Very limiting capability of
accommodating
misalignment.
Maintains free rolling
contact between balls &
races.
Single row for medium load
and double row for high
load.
Generally used in motors,
pumps & Gear boxes.
This type of Bearings has a collar on one
side of outer race to support the rolling
elements in one direction.
The contact of balls and races is on
angel.
Suitable for angular load, compensate
for alignment, high load carrying
capacity, high running accuracy &
suitable for combined loads (radial &
axial)
Single row (Back to Back, Face to Face,
Tandem arrangement) & Double Row
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATUREBALL BEARINGS
Self Align Ball Bearings Thrust Ball Bearings
The outer race of this
bearing is an arc, so it can
tilt over the balls an any
angle and adjust itself
according to the
misalignment of shaft.
Has two rows of balls in
separate grooves in inner
race but has only a single
spherical cage
Adjusts itself quickly to a
force from any direction
Suitable for any
misalignment, permits
angular misalignment of
shaft upto 3 degree
Takes, axial, radial &
angular load
Capable for medium loads /
speeds
These bearings have no outer or inner
race.
Rolling elements rotates between two
discs called washers.
Capable for Heavy thrust loads, high
running accuracy & high load carrying
capacity
Single and double direction bearings for
accommodating thrust in one or both
directions
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATUREROLLER BEARINGS
Cylindrical Roller Bearing Spherical Roller Bearings
The rolling elements are true cylinders.
Capable of carrying high radial load & high
speed
Assembly is separable hence easy to mount
& dismount.
The rollers have line contact with inner
race and point contact with outer race.
Contains two rows of rollers with a
common outer raceway.
Bearing is capable to accommodate
heavy radial and axial loads.
Run at low temperatures, have long life,
accommodate angular misalignment and
available in taper bore with adapter
sleeve.
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATUREROLLER BEARINGS
Taper Roller Bearing Needle Roller Bearings
Its inner & outer race are tapered with
tapered rollers in between. Cone & cup
arrangement.
Capable of carrying high load and
compensate misalignment due to tapered
parts.
Single, double or multi row bearings
The bearings with 5 mm or less than
5mm of rollers with extra long rollers are
called needle roller bearings.
Capable of carrying high load
Can be used with or without inner race.
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
JOURNAL BEARINGS
A Sleeve or Journal bearing provides radial support and positioning of the shaft while permitting it
to rotate
Tilting Pad Thrust Bearing /
Kingsbury Thrust Bearing
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
COUPLINGS
The device which which joins two separate shafts together is called a coupling
It is a common method of transferring force or torque from one machine to another
Rigid Coupling Flexible Coupling
A coupling that permits neither radial nor
axial relative motion between the driving
and driven shaft is called Rigid Coupling
A Flexible coupling is a device that
connects two shafts while allowing for the
minor misalignment (angular, parallel or a
combination)
A flexible coupling must also permit some
lateral float of the shafts so that the two
shaft ends may move closer or farther apart
under the influence of thermal expansion
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CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE
COUPLINGS
Flexible couplings have atleast one part that can flex or give
Flexible Coupling
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IMPORTANT TERMS & DEFINITIONSIMPORTANT TERMS & DEFINITIONS
PRESSURE:
Pressure is the force acting on a unit of
area
HEAD:
Head is the height of liquid
Head = Pressure
Sp. Gravity x 0.433
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IMPORTANT TERMS & DEFINITIONSIMPORTANT TERMS & DEFINITIONS
NPSH:
Net Positive Suction Head is the absolute suction head minus the vapour pressure head
NPSH Available:
Absolute pressure at the pump suction, changed into head minus the vapour pressure of the
liquid being pumped, changed to head.
NPSH Required:
Minimum head needed at the suction to get the liquid into the impeller without vaporizing
NPSHa must always be greater than NPSHr
NPSH = Absolute pressure at Pump suction - Vapor pressure at pump temperature
Specific Gravity x 0.433
CAVITATION:
Continuos formation & collapse of Vapor bubbles in the casing of pump is called Cavitation
Cavitation could be due to ingression of air inside the casing or due to vaporization of pumping
liquid
CAUSES OF CAVITATION:
Air Ingression, Insufficient suction, Closing of Discharge valves for longer time, Choking of
suction strainer, Discharge Head is more, Suction lift is more, Low efficiency of intercoolers,
Impeller clogging, Wear ring clearances etc
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IMPORTANT TERMS & DEFINITIONSIMPORTANT TERMS & DEFINITIONS
PRIMING:
The filling up of pump casing with liquid before start up is called priming
Liquid is brought into the pump by venting the casing
Care must be taken to make sure that the suction line to the pump remains full of liquid
SHUT OFF PRESSURE:
A plate installed at pump suction to break liquid whirls, hence provide continuos flow to
impeller
Vortexing can be very damaging as it reduces the NPSHa
VORTEX BREAKER:
The maximum pressure produced by a pump is called shut off pressure.
The pump is operated at shut off pressure during start-up to avoid overloading / adequate liquid
delivery to the required point.
PUMP CAPACITY:
Amount of liquid that a pump moves in a given length of time is called Pump capacity.
Expressed in GPM, Barrel / day etc
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When the total Head decreases, the
pump capacity increases, except at
very low capacity.
As the pumping rate increases, the
NPSH required increases
For every pump there is a capacity
where the pump operation is most
efficient and therefore most
economical
As the flow rate increases, the
horsepower required increases
The capacity and head characteristics
of a pump do not change when the
specific gravity of the material being
pumped changes, but the horsepower
required does change
Increase in Impeller dia will increase
NPSHr, Pump capacity & Discharge
Head.
Pump speed will also increase
capacity & Discharge Head
PERFORMANCE CURVES
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP DOES NOT DELIVER LIQUID
Probable Causes
Pump not primed / pump or suction line not filled with liquid
Suction lift too high
Insufficient margin in-between suction pressure and vapor pressure
Air pocket in suction line
Inlet of suction pipe insufficiently submerged
Speed too low
Wrong direction of rotation
Total head of system higher than Pump design Head
Parallel operation of pumps unsuitable for such operation
Foreign matter in impeller
Choking of Foot valves / suction strainer
Loose impeller / Lock nut
Broken shaft
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
INSUFFICIENT CAPACITY DELIVERED
Probable Causes
Pump or suction pipe not completely filled with liquid
Suction Lift too high
Insufficient margin between suction pressure and vapor pressure
Excessive amount of air or gas in liquid
Air pocket in suction line
Air leak into pump their stuffing boxes
Foot valves too small
Foot valves partially clogged
Inlet of suction pipe is not sufficiently submerged in liquid
Speed too Low
Total Head of system higher than Pump design head
Viscosity of liquid differs from that for which designed
Foreign matter in Impeller
Parallel operation of Pumps unsuitable for such operation
Wear rings worn
Impeller damaged
Casing gasket defective
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
INSUFFICIENT PRESSURE DEVELOPED
Probable Causes
Excessive amount of air or gas in the liquid
Speed Too Low
Wrong direction of rotation
Total head of system more than pump design head
Viscosity of liquid differs from that for which designed
Parallel operation of pumps unsuitable for such operation
Wear rings worn
Impeller damaged
Casing gasket defective
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP LOSES PRIME AFTER STARTING
Probable Causes
Pump or suction pipe not completely filled with liquid
Suction lift too high
Excessive amount of air or gas in the liquid
Air pocket in suction line
Air leakage into suction line
Air leakage into pump thru stuffing box
Inlet of suction pipe insufficiently submerged
Water seal pipe plugged
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP REQUIRES EXCESSIVE POWER
Probable Causes
Speed too high
Wrong direction of rotation
Total head of system higher than pump design head
Total head of system lower than pump design head
Specific gravity of liquid different from that for which designed
Viscosity of liquid different than design
Foreign matter in Impeller
Misalignment
Shaft Bent
Wear rings worn
Rotating part rubbing on stationary part
Packing improperly installed
Incorrect type of packing
Gland too tight, resulting in no flow of liquid to lubricate packing
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
STUFFING BOX LEAKS EXCESSIVELY
Probable Causes
Misalignment
Shaft bent
Shaft or shaft sleeve worn or scored at the packing
Packing improperly installed
Shaft running off-center due to worn bearings or misalignment
Rotor out of balance resulting in high vibration
Failure to provide cooling liquid to water cooled stuffing boxes
Excessive Packing clearances at bottom of stuffing box between shaft and casing,
causing packing to be forced into the pump
Dirt in sealing liquid, leading to score the shaft or sleeve
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PACKING HAS SHORT LIFE
Probable Causes
Water seal pipe plugged
Misalignment
Shaft bent
Bearings worn
Shaft or shaft sleeve worn out
Packing improperly installed
Incorrect type of Packing
Rotor out of balance
Gland too tight, resulting in no flow of liquid to lubricate packing
Failure to provide cooling liquid to water-cooled stuffing boxes
Excessive clearance at bottom of stuffing box between shaft and casing, causing
packing to be forced into the pump
Dirt in sealing liquid
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP VIBRATES OR IS NOISY
Probable Causes
Pump or suction pipe not completely filled with liquid
Suction lift too high
Insufficient margin between suction pressure and vapor pressure
Foot valve too small
Foot valve partially clogged
Inlet of suction pipe insufficiently submerged
Operation at very low capacity
Foreign matter in Impeller
Misalignment
Foundation not rigid
Shaft bent
Rotating part rubbing on stationary part
Bearing worn
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP VIBRATES OR IS NOISY
Probable Causes
Impeller damaged
Rotor out of balance
Excessive thrust caused by a mechanical failure inside the pump
Excessive amount of grease or oil in the housing of an anti-friction bearing or lack of
cooling, causing excessive bearing temperature
Lack of lubrication
Improper installation of anti friction bearings (Damage during assembly)
Dirt getting into bearings
Rusting of bearing due to water getting into housing
Excessive cooling of water cooled bearing resulting in condensation in the bearing
housing of moisture from the atmosphere
Khurram Majeed / Najam-us-saqib
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
BEARINGS HAVE SHORT LIFE
Probable Causes
Misalignment
Shaft bent
Rotating part rubbing stationary part
Bearings worn
Shaft running off center
Rotor out of balance
Excessive thrust caused by a mechanical failure inside the pump
Excessive amount of grease or oil in the housing of an anti-friction bearing or lack of
cooling, causing excessive bearing temperature
Lack of lubrication
Improper installation of anti friction bearings (Damage during assembly)
Dirt getting into bearings
Rusting of bearing due to water getting into housing
Excessive cooling of water cooled bearing resulting in condensation in the bearing
housing of moisture from the atmosphere
Khurram Majeed / Najam-us-saqib
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CENTRIFUGAL PUMPS TROUBLESHOOTINGCENTRIFUGAL PUMPS TROUBLESHOOTING
PUMP OVERHEATS AND SEIZES
Probable Causes
Pump not primed
Insufficient margin between suction pressure and vapor pressure
Operation at very low capacity
Parallel operation of pumps unsuitable for such operation
Misalignment
Rotating part rubbing stationary part
Bearings worn
Shaft running off center
Rotor out of Balance
Excessive thrust caused by mechanical failure inside the pump
Khurram Majeed / Najam-us-saqib
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PREVENTIVE MAINTENANCE CHECKSPREVENTIVE MAINTENANCE CHECKS
Define Frequency & Check the following
Pump vibration (Horizontal, Vertical & Axial)
Pump Inboard & Outboard Bearing Temperatures
Gland Packing / Mechanical Seal Leakage (DPM)
Foundation Condition
Mechanical Looseness
Oil Level / Condition / Leakage
Abnormal Sound
V-Belts / Pulley condition
Cleanliness
Khurram Majeed / Najam-us-saqib
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TYPICAL QUESTIONS & ANSWERSTYPICAL QUESTIONS & ANSWERS
1. What is the difference between Positive Displacement Pump and
Centrifugal Pump ?
2. What is the difference between Impeller, Propeller & Turbine Pump?
3. Will all the impellers installed in a multi stage pump produce similar flow /
pressure or not ?
4. A pump having 12 Dia Impeller operates at 250 psig. What can we do to
increase the pressure of this pump ?
5. What is the difference between single suction and double suction
centrifugal pump?
6. If four pumps are operating in parallel and producing 400 gpm & 100 psig
each. What will be the operating conditions in the common discharge header
?
7. What is the difference between Pusher and Non-pusher Mechanical Seal ?
8. What is the difference between Inside and outside seal ?
9. What is the difference between Balanced and Unbalanced Mechanical seal
?
10. What could be the effects of excessive Lubrication ?Khurram Majeed / Najam-us-saqib
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TYPICAL QUESTIONS & ANSWERSTYPICAL QUESTIONS & ANSWERS
11. What are the advantages and disadvantages of Vertical pumps ?
12. What are the causes of Pump having loss of flow or no flow problem ?
13. What could be the possible causes of high vibrations in pump ?
14. What is the difference between application of Ball Bearing and Roller
Bearing ?
15. What could be the possible causes of Bearing failures ?
16. What is the difference between application of Grease and oil ?
17. What is Brinelling and False Brinelling ?
18. What are the methods of Bearing mounting ?
19. What are the methods of Pump alignment and what could be the effects of
Misalignment ?
20. What is Soft Foot ?
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