01_Trainning Material_Basic pump theory.pdf

7/30/2019 01_Trainning Material_Basic pump theory.pdf

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DOOSAN HEAVY INDUSTRIEC CO., LTD.

JEBEL ALI POWER AND DESALINATION STATION M


TRAINING OF HORIZONTAL & VERTICAL PUMP OPERATION

AND MAINTENANCE

2010. 04.

HYOSUNG GOODSPRINGS, INC.

HYOSUNG GOODSPRINGS,INC.1 / 68


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JEBEL ALI POWER AND DESALINATION STATION MContents

BASIC & APPLICATION OF PUMP

OPERATION AND MAINTENANCE



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Classification & Types of Pumps

CENTRIFUGAL VOLUTE CENTRIFUGAL PUMP

TURBINE CENTRIFUGAL PUMP

Volute Pump

Multi Pum

TURBO MIXED FLOW

DIFFUSER CENTRIFUGAL PUMP

AXIAL FLOW AXIAL FLOW PUMP

P

U POSITIVERECIPROCATING PISTON, PLUNGER, DIAPHARM

VORTEX

JET PUMP

M

, , ,

WETSCO

VISICOCITY

INERTIA PUMP Diaphragm PumpReciprocating Gear Pump

SPECIAL

BUBBLE PUMP

MAGNETIC PUMP

VACUUM PUMP Screw Pump Vane Pump TUBE PumpLobe Pump



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Pump



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Impeller Type & Configuration

AXIAL FLOWDOUBLE

SUCTIONSINGLE

SEMI-OPEN NON-CLOGGING

WESTCOOPEN



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Impeller Type & Configuration

DOUBLE SUCTIONSINGLE SUCTION

CLOSE TYPE SEMI-OPEN TYPE OPEN TYPE

CENTRIFUGAL SCREWVORTEXNON-CLOGGING



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Type Description Remark

Centrifugal

Mixed flow

Type Description Remark

Foot mounted

Frame mounted

machine- ,

Axial flow

Channel

- Side channel, Peripheral

classification

-

Mounting

Pedestal mounted

Flange mounted

Wall mounted

Tank mounted

Method ofmounting thepump

Stage Two-stageMulti-stage

Centrifugalpumps only

PressureLow-pressure

Hi h- ressureDischargeressure

pe ne moun e

ShaftDirect mounted

Integral

Super-pressure developed

Single/double entry

Axial inlet

Side inlet Suction

Casing

halvesdivision

Split casing (Axial,Radial, Diagonallysplit)

Casing divisionwhere applicable

Top inlet (top suction)

Bottom inlet (Bottomsuction

geometry

Single-volute

Layout or zonta

Vertical

Inclined

Basic layout ofturbo machine

Casingshape

Double-volute

Diffuser

Bowl

Tubular

An le Barrel

Based on shapeof casing Etc.

Wet sump pump

Dry sump pump

Canned motor p/p

Wet motor p/p



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TOP

Definition of Suction & Discharge Nozzle Direction

SIDE

END

SIDE

BOTTOM



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Liquid (High Temp.);

Heat expansion occur at

.

So alignment become

unbalanced.

Without disassembling

piping & a driver, a pump

CENTERLINE

MOUNTING

FOOT

MOUNTING

can e smant e eas y.

This type needs a SPACER

COUPLING.



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Classification by Mounting

CENTERLINEBRACKET

MOUNTING

IN-LINEVERTICALFOOT



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VERTICAL PUMPEND SUCTION PUMP

Classification by Inlet Geometry

FOOT

BRACKET

PULL OUT TYPE MIXED

CLOSE COUPLED IN- LINE

MULTI STAGE PUMP

DOUBLE SUCTION

-


ONTAL VERTICAL


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Overhung Centrifugal Pump(General Service Pump)

CONSTRUCTION CONSTRUCTION

Separate bearing bracket with grease

or self-contained oiling system

Separate bearing bracket with grease

or self-contained oiling system

Anti-friction radial and thrust bearing

Overhung impeller mounting

Anti-friction radial and thrust bearing

Overhung impeller mounting

Case either foot mounted or centerline

mounted

Case either foot mounted or centerline

mounted

Bearing housing provided with cooling

fins or fan for process pump

Bearing housing provided with cooling

fins or fan for process pump

Overhung Radial Split



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Multi-Stage Centrifugal Pump


Radial split casing with nozzles located

in either side or top case

Radial split casing with nozzles located

in either side or top case

Impellers arranged in parallel sets

Stuffing boxes fitted with mechanical seal

Impellers arranged in parallel sets


or packing

Bearing lubrication can be either grease

or packing

Bearing lubrication can be either grease

.

Pump mounting on foot or bearing

bracket

.

Pump mounting on foot or bearing

bracketetween ear ng a a p t



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Double Suction Horizontal Pump


Impeller is mounted between two external

bearing brackets

Impeller is mounted between two external

bearing brackets

Pump mounting is typically on case center

line

Pump mounting is typically on case center

line


or packing


or packing

or oil lubricated.

Pum mountin is t icall on foot

or oil lubricated.

Pum mountin is t icall on foot

Between Bearing Axial Split



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Volute & Turbine Pump Configuration

Volute pump Turbine pump

NOZZLENOZZLE

CASING CASING

IMPELLER(diffuser)

VOLUTE

CASING VOLUTE

CASING

SUCTIONSUCTION



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Radial thrust magnitude of volute casing

RadalReactio

BEP

Double Volute Casing has been employed to reduce

Flow Rate

radial thrust which is developed from the tip of impeller

There are two reaction forces opposing each other due

to symmetry of double volute casing



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Axial Thrust Balance

Front Area < Back Area

Pressure Drop

After passage

ower

PressureArea

No Balance Device With Balance Holes

The direction of axial thrust will forward towardimpeller suction inlet if no axial balance device

There would cause some trouble on bearing life

The effect of balance holes is to form passage offluid flow and in addition

Development of pressure drop due to friction loss


and strength of shaft


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Balance of Axial Force Features Application

Balance of axial thrust

Achieve pressure drop in chamber whenfluid flows through clearance between wearrings then the fluid flows toward impellersuction through balance holes.

Inappropriate to apply concentration solid

Lower Speed for small &

medium centrifugal volute &

turbine pump

a

He

ma er a n pump ng qu

Disadvantage on increase of leakage loss

Provision of Back Vane Ribs to reduce axialthrust

Mainly applied open type

Ba

The number & diameter of back ribs as wellas clearance between tip of vane and casingaffect axial thrust so that it is necessary toinstall adjustment device of clearance

Pumping Liquid for Slurry & solid

mpe ers

B

V

Disadvantage on increase friction loss

Provide balance disk at the rear of final stage

impeller then achieve pressure drop betweenthose clearance.

Applied high pressure

multistage pumpsDsConnection between Suction Casing andBalance Pipe

No necessary to install thrust bearing

No a lication for forei n material of li uidBa

D



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Balance of axial thrust

a ance o x a orce ea ures pp ca on

No requirement balance device since a double

suction impeller is balanced due to symmetry(Self balance)

Double Suction Volute Pump

cNecessary thrust bearing considering axialthrust in piping system

Easy disassembly and inspection since casingcan be split upper and lower way.

fBa

Symmetry arrangement of impellers Axially Split, Multi-Stage

Pump

Complex casing structure and necessary

casing pattern with same as stage of impellers

Possible on slurry & foreign liquid materialfBa

Disadvantage on increase of friction loss



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Basic Hydraulic Performance

Specific Speed(Ns)

Definition : Specific Speed is the speed in RPM at which an impeller would run if reduced in size to deliver 1

m3/min against a total head of 1m. In order to determine impeller shape and geometry, total head, capacity & RPM

will be used as follows;

43

QNNs

where Ns = Specific Speed

N = perat ng pee RPM

Q = Flow Rate at Best Efficiency Point [ m3/min]

H = Head Per Stage at BEP [m]

* Specific Speed is defined at Best Efficiency Point of pump. The capacity shall be divided by two(2) for double

suction pump. In case of multi-stage pump, total head shall be divided by the number of stages.



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Specific Speed Ranges vs. Efficiency



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WESTCO RADIAL FLOW MIXED FLOW AXIAL FLOW


Ns = 30 ~ 90

Ns = 85 ~ 620

Ns = 390 ~ 1625

Ns=1160 ~ 2325


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WESTCO RADIAL MIXED AXIAL

Specific speed determines

the pump characteristics.

POWER

EFF.

NPSHre



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Affinity Laws of Pump Velocity triangle diagram will be equal incase of that the geometry of two pumps

has similitude relationship

Velocity triangle diagram will be equal in

case of that the geometry of two pumps

has similitude relationship

3'''

D

D

n

n

Q

Q Flow(Q) varies directly as the ration of

change of speed(N) or impeller diameter(D)

Flow(Q) varies directly as the ration of

change of speed(N) or impeller diameter(D)22

'''

D

D

n

n

H

H

53

Head(H) varies as the square of the ratio of

speeds or impeller diameters

Head(H) varies as the square of the ratio of

speeds or impeller diameters

'p

p

p

p

Dn

n

'HQ

L

Pump brake horse power varies as the

cube of the ratio of speeds and impellerdiameters.

Pump brake horse power varies as the

cube of the ratio of speeds and impellerdiameters.

Where, L : Brake Horse Power

n : RPM in Pump

D : Impeller Diameter

: Pump Efficiencyp



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Performance Characteristic with Change of RPM3

''

n

n

L

L2

''

nH

Cube Curve

Square Curve

Power Total head Operating Condition

Pump Characteristics will be changed in condition of rotation speed change within some

relationship as shown in Figures

Pump Characteristics will be changed in condition of rotation speed change within some

relationship as shown in Figures In general Performance Change will be disregarded within 20% fluctuation of specified speed

Head(H) varies as the square of the ratio of speed or impeller diameters

In general Performance Change will be disregarded within 20% fluctuation of specified speed

Head(H) varies as the square of the ratio of speed or impeller diameters


. .


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Performance Characteristic in Reduced Impeller3

DQ

''

DQ

Trimmed Impeller Diameter Effect of Pump Performance due to Reduced

Impeller Diameter

Trimmin of Im eller Outer Diameter is alternative to adust um characteristics

Machining of Impeller Outer Diameter is recommended for centrifugal type pump.

Angle Adjustment for Axial Propeller Pump


Mixed Flow Pump


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Section 3. Cavitation in Centrifugal PumpsSection 3. Cavitation in Centrifugal Pumps




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Cavitation in Centrifugal Pumps

Formation of Air Air bubbles will be produced in pumping liquid due to a local pressure drop when

Development of Cavitation

Bubbles

Definition

.

A local decrease in pressure is occurred by (1) an increase in velocity (2)

development vortex (3) passing obstruction to the flow called as Cavitation.

Sign of Cavitation This is produced at the entrance of impeller eye.

1. The air bubbles flow with streamline of pumping liquid.

2. When reached at higher pressure, the vapor bubbles will collapse abruptly.

At the same time, vibration and noise shall be observed.

3. Finally the pump will not be operated.

If a pump is operated under cavitation conditions for a long period of time,mpe er me a w e p ng an amage ue o s oc pressure occurre w en

collapse of bubbles. As a result, the suction condition should be considered at thedetermination of pumpollapseollapse off Vaporapor Bubblesubbles

Pressure of Bubbleressure of BubbleCollapse !!!ollapse !!!30000/(by Hallers Experiment)




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Pressure Distribution of Suction Entrance (NPSHre vs NPSHav)

A pressure drop at Impeller

Entrance = NPSH re(head)

Impeller ExitSuction ImpellerVelocity Head = Vs/2g

NPSHreNPSHav

Absolute

NPSHav - NPSHre > 1m

Pressure Head =Pv/

NPSH Margin > 1m


ressure



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Pump Performance and Cavitation

Relationship of pump performance and cavitationsNPSHav

Relationship of pump performance and cavitations

NPSH re

H - Q Curve NPSH av

NPSH NPSHav < NPSHre

Pressure & Flow Drop

HEAD

Efficiency Drop

Efficiency

EFFICIENCY

Stable Operation Unstable

O eration Ran e




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Available Net Positive Suction Head (NPSHav)

Definition : The value of NPSHav shall be determined with the condition of pump suction pipe and system.It has no relationship with pump.t has no relationship with pump.

NPSHav=hsv=Ps/NPSHav=hsv=Ps/ -- Pv/Pv/ hshs -- fVsfVs//22gg

where , hsv : NPSH Available (m)

Ps : Suction Surface Pressure k f/ absPv : Liquid Vapor Pressure at operating temperature (kgf/ abs) : Specific Gravity at operation temperature (kgf/m3)

[ -, [ ,fVs/2g : Total Loss Head at suction pipe(m)




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Datum of Available Net Positive Suction Head (NPSHav)

Datum

Datum

Datum in terms of Pump Type and Installation




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Calculation of NPSH available

Suction Lift (Atmospheric Pressure at Suction SurfaceSuction Lift (Atmospheric Pressure at Suction Surface)

lsva hhPPNPSHav

)(

10

, Pa : Atmospheric (1.03 Kgf/cabs)Pv : Vapor Pressure of Liquid (Kgf/cabs)hs : Actual Suction Head(m)hl : Total Suction Loss Head(m)

Flooded SuctionFlooded Suction (Atmospheric Pressure at Suction Surface)

lsva hhPPNPSHav )(10



C i i i C if l P


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Calculation of NPSH available

Closed Tank

10 lsvag

where, Pg : Pressure in closed tanks (Kgf/cgauge)If the liquid in suction closed tank is the same with vapor pressure,

NPSH available becomes

lsav



C it ti i C t if l P


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DOOSAN HEAVY INDUSTRIEC CO., LTD.Cavitation in Centrifugal Pumps

Predetermination of Cavitation Condition

Suction specific speed; Dimensionless rating number which indicates the relativeability of centrifugal pumps to operate under conditions oflow available net positive suction head

nHsvQS 43

21

/

pThe following equation with conversion factor will beapplied except S=1300NPSHre= x NPSHreWhere NPSHre' : Required NPSH at Specificationhere NPSHre : Required NPSH at Specification

NPSHre : Required NPSH at S=1300 : Conversion factor of NPSHre

Conversi

Factor

on


The Prediction of NPSHre according to Q, N Conversion Factor of NPSHre


Ca itation in Centrif gal P mps


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Predetermination of Cavitation Condition

Thoma Coefficienthoma Coefficient

where H : Total Head at Full Impeller Diameter

HNPSHreHHsv //

C

ce

here, H : Total Head at Full Impeller DiameterHsv : NSPH required

The value of cavitation coefficient, , is determined byi t l I f lti t th 1st t

TmaC

experimental. In case of multi-stage pump, the 1st stageimpeller is total head for NPSH calculation.

Ns


Coefficient of Thoma Cavitation




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Stable operation For stable pump operation without cavitation trouble, the suction pressure at

Stable Operation Condition

con on NPSHre x (1 + )]. In general it is safe that the margin shall be no later than 0.3and NPSHre x 0.3 0.5 for minimum requirement.

Stable Operation

Possible Operating Range Left Siderefer to A design condition

Side refer to A design condition

Not AllowableAllowable Operation Range


Relationship between NPSHav and NPSHre




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Specific speed characterize the overall impeller profile shape. Suction specific

speed(Nss) characterized the eye size for give specific speed.(Ns)





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oncep o nc p en cav a on, u e orma on an grow o u o ng




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a Hemis herical bubble attached to wall(b) Bubble moving into pressure gradient

(such as venturi diffuser flow)


DOOSAN HEAVY INDUSTRIEC CO LTD




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Suction Condition will be improved by installation Suction Condition will be improved by installation

Prevention of Cavitation

of Inducer which is located at pump suction. It will

make fluid flow smooth and reduce friction loss.

of Inducer which is located at pump suction. It will

make fluid flow smooth and reduce friction loss.






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Sign of SurgingPressure pulsation in a pressure gage indicator with high magnitude periodically duringpump operation

Prevention of Surging

Cause

Produce period noise and vibration at suction and discharge pipe

Unstable Head Characteristic in Figure 1

The length of discharge pipe is long and the collection of air in the middle of piping in

Control Discharge Valve B where located in the downstream

Operation at below of discharge flow Q

Locate discharge flow valve at the pump dischargeUse bypass pipe to achieve continuous rising head characteristics

Pi in desi n to ac uire no area where are would be athered

Tank

Pump

Valve BValve A


Figure 1 Figure 2




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Section 4. Starting Torque & OperationSection 4. Starting Torque & Operation




Starting torque and operation


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DOOSAN HEAVY INDUSTRIEC CO., LTD.Starting torque and operation

Starting Discharge V/V Closed

pp ca on

Characteristics

-

Starting Torque increases cube of RPM until the normal speed reaches from stopping ofpump

Starting Torque of motor increases square of RPM approximately. Shut-off Torque(T2)reach Point C as shown on Fig. 1 Toque Characteristics

- T1 : Torque to overcome the static mechanical friction and rotor inertia moment

~ ,

- T2 : RPM 100% ( B C : Water Horse Torque)- T3 : Discharge Flow Rate 100% ( C D : Brake Horse Torque)

Sequence of

Starting Torque

Torque,

%

arac er s c

A B C DFlow Rate, %


A B C DFig. 1 Torque Characteristics at Discharge Valve Closed

,





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Starting Discharge V/V Opened

Application

Characterstics

Application of General Centrifugal Pump (BHP at Shut-Off < 1)

Starting pumping from partial speed, n (variable point D).When reached 100% of RPM, Starting Torque becomes Rating Torque T3 since ratingflow begins as shown on Fig 2.

Starting Torque is higher than starting when discharge valve closed

Torque,

Power

Starting Torque

Characteristic

Torque,

%

System Resistance Curve

A B D ERPM,%

Flow Rate, %


Fig. 2 Torque Characteristics at Discharge Valve Opened





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Starting Discharge V/V Opened

Application

Characteristics

Axial-Flow Pump

Rating Toruqe, T3, for axial flow pump is lower than T2, which is brake-horsepower atshut-off Standard motor cannot obtain such T2 pull-in torque as shown on Fig 3hut off. Standard motor cannot obtain such T2 pull in torque as shown on Fig 3.

Sequence of Torque Torque,

Torque

(Power)

A B D ERPM,% Flow Rate, %

System Resistance Curve


Fig 3. Starting-Torque Characteristics for Axial-Flow Pump




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Section 5. Pump Operating PointSection 5. Pump Operating Point




PUMP OPERATING POINT


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,

Actual Head

Constant

Operating Point : An intersection, A of H-Q curve and system curve

If the system curve is changed to R then the operating point is B

Actual Head ; Constant






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Actual Head

Chan eable

Operating Point : The range of an intersection of H-Q curve and R, R

Actual Head Change

Actual Head ; Changeable

Dis. Rate Change






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Valve Control Operating Point : An intersection of H-Q curve and each system curveBy controlling the open and close of the discharge valve the system

, .

Valve LossPipe Loss

Valve Control






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Velocity

Control

Operating Point : A1 B2 B3An intersection of the new H-Q curve (n1, n2, n3) and a system

curve

Velocity Control






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ParallelParallel andand SeriesSeries OperationOperation

According to the shape of a system curve, parallel or series operation is determined.

In case of an intersection, a, which has both arallel and series characteristic, the choice is limited.

A system curve, R1 is lower than R2 Parallel operation is profitable.A system curve, R3 is higher than R2 Series operation is profitable.In case of the actual head and a system curve is changed widely, combine 2 pumps in series or parallel.


Characteristic of Parallel and Series Operation of the same pumps




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Section 6. Temperature Rise & Over-Heating in PumpsSection 6. Temperature Rise & Over-Heating in Pumps




Temperature rise & Overheating in pump


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Temperature Rise The temperature of operating liquid rises since the power of motor will be converted toheat when either zero-capacity or less than minimum flow of pump operation.

Temperature Rise & Preventive

Decrease the ratio of temperature rise sharply till some discharge flow rate

Increase with total head characteristics

Temperature rise will be higher If RPM increase at the same discharge head.

Effects of

OverHeating

Occur thermal distortion.

Produce Cavitation Problem due to development of vapor

Seizure between Rotating Element.

Possible to occur vapor explosion

**

Install Relief V/V continuous

operated

Use check valve with automatic

Temperatur

ev ce va ve

Operate Relief Valve sensing flow

rate Temperature Rise

eRise

TeE

f


Fig. 1 Water Temperature Rise Curve Fig. 2 Typical Temperature Rise Curve

,Pump Efficiency

ead

p.rise

ficiency



Temperature rise & Overheating in pump


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CASE OF PUMP CASE EXPLOSION DUE CASE OF PUMP CASE EXPLOSION DUE

TO SHUT-OFF OPERATION

1 hour o eration durin dischar e v/v closed

TO SHUT-OFF OPERATION

1 hour o eration durin dischar e v/v closed

Shut off pressure ; 10.3kgf/cm2

Vapor pressure : 15.7kgf/cm2

Shut off pressure ; 10.3kgf/cm2

Vapor pressure : 15.7kgf/cm2

.

T = 184

.

T = 184





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Section 7. Case Study: Pump TroubleSection 7. Case Study: Pump Trouble




Case Study: Pump Trouble


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Customer : N Steel Company (Japan), MODEL : VMF350-390 , Service : Pressure Filter Feed Pump

Effect

Crack occurredrack occurred

Shaft was cutecause of cavitation, the holes aremade on the surface of a suction bellCrack occurred

made on the surface of a suction bell.

Crack occurredVibration occurred

Suction bellDestruction


CASING =GC250, 2000.11.22.





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Changed water inflow(150mm, 7 holes)UMP3 PUMP2 PUMP1Cause

A suction bell was cutby induced bubbles

Unstable water flowVibration occurred.The originalwater inflowater inflow(CLOSED)

Crack was occurred.

BAFFLERotating parts were stuckThen the shaft was cut.

Bubble WALL

BAFFLE


Bubble WALL





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Customer : P Steel Company , MODEL : HDR 300-400B , Service : Water Treatment Facility

EffectBecause the flowrate was small, theimpeller wasdamaged.

A i lln impellerMaterial: GC200


: GC200





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Cause1. The suction strainer was closed. ( Among 4pumps, 2 were closed and the other were not.)

. - .

It became the cause of cavitation.

3. Because a suction bell mouth is horizontal, the probability of inducing air is increased.

SolutionWRONG RECOMMENDED1. BY-PASS pipeline should be. BY PASS pipeline should be

location which is far from pumpsuction.

2 Th d f i li t b. The end of pipelines must beunder the water and install a baffleto eliminate the flow of the bubbles

PUMP SUCTIONBAFFLEnto the pump suction.






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Customer : L Oil Company, MODEL: 150x80 UCW 40 , Service : DESALTED WATER PUMP

Effect

Impossible to rotateA ball was damaged.

Impossible to rotateA shaft was damaged.

1995 07 21HYOSUNG GOODSPRINGS,INC.61 / 68

1995.07.21.





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Customer : S Oil Company, MODEL : 250x200 KS-40, Service : HVGO pumpCause When performing the weld at site, the electricity was induced inside a pump.So spark was occurred in a gap of the bearing.o spark was occurred in a gap of the bearing.

WELD MeltedMetalCompression

(0.5~1mm)

High temp.Expansionpark

T t ARC WELD POINT WELDSpark was made SPARK caused the weld.

Flaking wasoccurred

Balls and the shaftwere damaged.

Compression wasoccurred by high temp.

Test POINT WELD It was impossibleto rotate.

A bearing was damaged and


A bearing was damaged andbecame useless.





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Customer : L Oil Company, MODEL : 50x40UCWM-25, Service : RECYCLE LIQUID PUMP

Effect The oil color was changed.Cause The oil level was lowered but the oil wasnt supplied from an oiler. (04.01.20)

OIL LEVEL CurrentOil LevelGaugeTRICOOil LevelGaugeg

OIL LEVEL POSITION Half of a brain bottlewas empty but the oilwasnt supplied.In case of a current oil level gauge, if itis stood, then the oil cant be supplied.However if a TRICO oil level gauge is used,then the problem can be solved


then the problem can be solved.





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1. Attach an oil levelgauge to arotating partotating part.2. Install an auto-airvent.3 Avoid the effect of. Avoid the effect ofwind.






65/68

Customer : H Chemical Corp., MODEL :50x40 IFWM 1613, Service : Waste Solvent Transfer PumpEffect

2003.03.03. Material : SSC14, Liquid : HEXANE

CauseDuring implementing test working,


Highly corrosive and unstable was induced.





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Customer : P Steel Company, MODEL : HDR200-500 , Service : Cooling Water Pump

Effect Cause

By mixing of corrosive liquid and water,the impeller was corroded during pump operation.- PH 2.2~PH2.6- Corrosion is concentrated on the end of impeller vanes.- The corrosion caused by cavitation starts from an entrance

f thf the vanes.- Elbow, shaft, key and etc. were also corroded.

Material: GC200 2003 03 12HYOSUNG GOODSPRINGS,INC.66 / 68

Material: GC200, 2003.03.12




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01_Trainning Material_Basic pump theory.pdf

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