05-Sundyne Presentation Fs Npsh

8/13/2019 05-Sundyne Presentation Fs Npsh

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NPSH


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NPSH

NET

POSITIVE

SUCTION

HEAD


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DEFINITIONS

NPSH A AVAILABLE (System)

NPSH R REQUIRED (Pump)

IF NPSHA < NPSHR,CAVITATION OCCURS


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ON SITE CASE


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ON SITE CASE


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NPSHR?

NPSHA? P VAP

P LIQUID

HEAD

DISTANCE A B C D E

A : PUMP SUCTIONB : INDUCER INLETC : IMPELLER INLETD : DIFFUSER THROAT INLETE : PUMP DISCHARGE

NPSHA

B

C D E


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HEAD

DISTANCE A C

F

G

F = NPSHAG = NPSHR

P VAP

GAS BUBBLES APPEAR & ... IMPLODE

NPSHA < NPSHR

P LIQUID


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HEAD

DISTANCE A B C D E

INDUCER EFFECT A : PUMP SUCTION

B : INDUCER INLETC : IMPELLER INLETD : DIFFUSER THROAT INLETE : PUMP DISCHARGE

INDUCER EFFECT

P LIQUID

P VAP


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HEAD

DISTANCE A C

GF

F = NPSHAG = NPSHR

B

NPSHA > NPSHR

P LIQUID

P VAP


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NPSHA CALCULATION

STATICHEAD

SURFACEPRESSURE

HEADFRICTIONLOSSES VAPORPRESSURENPSHA = + - -


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NPSHA OPEN TANK

STATICHEAD

SURFACEPRESSURE

HEADFRICTION

LOSSES VAPOR

PRESSURENPSHA = + - -

0 BARGOPEN TANK

WATER

Line losses:

0,8 m

TEMPERATURE = 80 C PRESSURE AT TOP = 0 barg or 1 Bara VAPOR PRESSURE AT 80

C = 0,47 Bara SPECIFIC GRAVITY = 0.97 @ 80

CH = 2,5m


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NPSHA OPEN TANK

STATICHEAD

SURFACEPRESSURE

HEADFRICTION

LOSSES VAPOR

PRESSURENPSHA = + - -

2,50 m

TEMPERATURE = 80

C PRESSURE AT TOP = 0 barg or 1 Bara VAPOR PRESSURE AT 80


C

0 BARGOPEN TANK

WATER

Line losses:

0,8 m

H = 2,5m


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NPSHA OPEN TANK

SURFACEPRESSURE

HEADFRICTIONLOSSES VAPORPRESSURENPSHA = + - -

1Bara x 10.20.97

2,5m

TEMPERATURE = 80


C = 0,47 Bara MASS DENSITY = 970 kg/m 3 @ 80

C

0 BARGOPEN TANK

WATER

Line losses:

0,8 m

H = 2,5m


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NPSHA OPEN TANK

FRICTIONLOSSES VAPORPRESSURENPSHA = + - -

0,8m

10,5m

TEMPERATURE = 80



C

0 BARGOPEN TANK

WATER

Line losses:

0,8 m

2,5m

H = 2,5m


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NPSHA OPEN TANK

VAPORPRESSURENPSHA = + - -

0.47Bara x 10.2

0.97

0,8m

TEMPERATURE = 80



C

0 BARGOPEN TANK

WATER

Line losses:

0,8 m

10,5m2,5m

H = 2,5m


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STATICHEAD

SURFACEPRESSURE

HEADFRICTIONLOSSES VAPORPRESSURE

NPSHA CLOSED TANK

NPSHA = + - -

TEMPERATURE = 38 C PRESSURE AT TOP = 2,5 barg or 3,5 bara VAPOR PRESSURE AT 38

C = 3,6 bara SPECIFIC GRAVITY = 0.56 @ 38

C

N-Butane

Gas 2,5 barg

Line losses:0,8m

2,5m

H = 2,5m


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SURFACEPRESSURE

HEADFRICTIONLOSSES VAPORPRESSURE

NPSHA CLOSED TANK

NPSHA = + - -2,5m

3.7 Bara x 10.2

0.56 TEMPERATURE = 38 C PRESSURE AT TOP = 2,7 barg or 3,7 bara VAPOR PRESSURE AT 38


C

N-Butane

Gas 2,7 barg

Line losses:0,8m

H = 2,5m


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FRICTIONLOSSES

VAPORPRESSURE

NPSHA CLOSED TANK

NPSHA = + - -67,4m

0,8m



C

N-Butane

Gas 2,5 barg

H = 2,5m

Line losses:0,8m

2,5m


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VAPORPRESSURE

NPSHA CLOSED TANK

NPSHA = + - -0,8m

3.6 Bara x 10.2

0.56

67,4m2,5m



C

N-Butane

Gas 2,5 barg

H = 2,5m

Line losses:0,8m


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65,5m

NPSHA CLOSED TANK

NPSHA = + - -

NPSHA = 3,6m

0,8m67,4m2,5m



C

N-Butane

Gas 2,5 barg

H = 2,5m

Line losses:0,8m


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HOW TO INCREASE NPSHA

INCREASE SUCTION VESSEL PRESSURE

DECREASE VAPOR PRESSURE

( DECREASE SUCTION TEMPERATURE)

DECREASE LINE LOSSES

INCREASE STATIC HEAD


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NPSH TESTING

SET FLOW RATE, DETERMINE DIFFERENTIAL PRESSURE

REDUCE SUCTION PRESSURE (APPLY VACUUM)

WHEN DIFFERENTIAL PRESSURE DROPS BY 3% UNIT ISCAVITATING

NPSHA FOR THIS OPERATING CONDITION IS EQUAL TONPSHR

NPSHA = NPSHR


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INDUCER PERFORMANCE

"GENTLE" BREAKDOWN

3% PUMP SUPPRESSION 1% SUPPRESSION

"SHARP" BREAKDOWN

100%

97%

ADEQUATE NPSH

A P U M P O

R I N D U C E R

H E A D R I S E

NPSH


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THE INDUCER FAMILY


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THE INDUCER FAMILY


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WHAT DOES THIS HAVE TO DO WITH PUMPMAINTENANCE?

INDUCER OR IMPELLER CAN FAIL MECHANICALLY

RESULTING HSSA UNBALANCE CAN LEAD TO BEARING FAILURE

IDENTIFICATION OF CAUSE REDUCES MAINTENANCE


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CAVITATION EFFECT ON AN IMPELLER INCASE OF INSUFFICIENT NPSH MARGIN


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CAVITATION EFFECT ON INDUCER


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FLUID TEMPERATURE RISE

TEMPERATURE RISE FROM SUCTION TO DISCHARGE - RESULTOF INEFFICIENCY

TYPICALLY OF LITTLE OR NO CONCERN

OF CONCERN IN CLOSED LOOP SYSTEM WITHOUT COOLING

OR WHEN NPSH IS MARGINAL


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HEAD

DISTANCE A B C D E

A : PUMP SUCTIONB : INDUCER INLET

C : IMPELLER INLETD : DIFFUSER THROAT INLETE : PUMP DISCHARGE

INDUCER EFFECT

TEMPERATURE RISE INFLUENCE

P LIQUID

P VAP


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FLUID TEMPERATURE RISE RESOLUTION

INCREASE BYPASS TO SUCTION VESSEL

VENT PORT #6 TO SUCTION VESSEL

INCREASED EFFICIENCY LEADS TO DECREASED INTERNAL

RECIRCULATION (OPERATE NEAR BEP)


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TO REMEMBER

What is NPSH?

How to calculate it?

What is the effect of an inducer?

What is cavitation?

05-Sundyne Presentation Fs Npsh

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