training session on centrifugal pump

54
PEP SESSION ON PEP SESSION ON CONSTRUCTION & MAINTENANCE OF CONSTRUCTION & MAINTENANCE OF CENTRIFUGAL PUMPS CENTRIFUGAL PUMPS Khurram Majeed / Najam-us-saqib Area Engineer / Maintenance Technician Engro Chemical

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Centrifugal pumps

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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

  • 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

    Khurram Majeed / Najam-us-saqib

    1

  • 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

    Khurram Majeed / Najam-us-saqib

    2

  • 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

    Khurram Majeed / Najam-us-saqib

    3

  • 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

    Khurram Majeed / Najam-us-saqib

    4

  • 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

    Khurram Majeed / Najam-us-saqib

    5

  • 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

    Khurram Majeed / Najam-us-saqib

    6

  • 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

    Khurram Majeed / Najam-us-saqib

    7

  • 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

    Khurram Majeed / Najam-us-saqib

    8

  • CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE

    Casing

    Impeller

    Impeller

    suction eye

    Discharge

    Nozzle

    ShaftI/B

    Bearing

    O/B

    Bearing Sleeve

    Gland Packing

    Impeller

    Lock Nut

    Khurram Majeed / Najam-us-saqib

    9

  • 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.

    Khurram Majeed / Najam-us-saqib

    10

  • 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.

    Khurram Majeed / Najam-us-saqib

    11

  • 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

    Khurram Majeed / Najam-us-saqib

    12

  • 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

    Khurram Majeed / Najam-us-saqib

    13

  • 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

    Khurram Majeed / Najam-us-saqib

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  • CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE

    TYPES OF CASING

    VOLUTE CASING DIFFUSER CASING

    Khurram Majeed / Najam-us-saqib

    15

  • 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

    Khurram Majeed / Najam-us-saqib

    16

  • 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

    Khurram Majeed / Najam-us-saqib

    17

  • 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

    Khurram Majeed / Najam-us-saqib

    18

  • 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

    Khurram Majeed / Najam-us-saqib

    19

  • 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

    Khurram Majeed / Najam-us-saqib

    20

  • 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

    Khurram Majeed / Najam-us-saqib

    21

  • 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

    Khurram Majeed / Najam-us-saqib

    22

  • 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

    Khurram Majeed / Najam-us-saqib

    23

  • 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

    Khurram Majeed / Najam-us-saqib

    24

  • 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

    Khurram Majeed / Najam-us-saqib

    25

  • 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

    Khurram Majeed / Najam-us-saqib

    26

  • 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

    Khurram Majeed / Najam-us-saqib

    27

  • 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

    Khurram Majeed / Najam-us-saqib

    28

  • 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

    Khurram Majeed / Najam-us-saqib

    29

  • 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.

    Khurram Majeed / Najam-us-saqib

    30

  • 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.

    Khurram Majeed / Najam-us-saqib

    31

  • 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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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  • CENTRIFUGAL PUMP NOMENCLATURECENTRIFUGAL PUMP NOMENCLATURE

    COUPLINGS

    Flexible couplings have atleast one part that can flex or give

    Flexible Coupling

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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  • Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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

    Khurram Majeed / Najam-us-saqib

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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 ?

    Khurram Majeed / Najam-us-saqib

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