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Centrifugal Pumps & Npsh

process pump hydraulics sizing chemical refining design vessel safety hazard

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#1 Batta

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Posted 03 December 2019 - 02:34 PM

Considering the scenario where a vessel's bottom is connected to a centrifugal pump, what may go wrong in terms of Normal operation/Safety from point of view if during detailed designing one increases the elevation of a vessel (compared to FEED) to match the NPSH available?

 



#2 latexman

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Posted 03 December 2019 - 03:42 PM

Raising the suction vessel is an old trick that is tried and true.  It improves operation/safety.  It is usually capital intensive as a modification to an existing facility.  You only get one shot at doing it fairly inexpensively, during design.



#3 Sharma Varun

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Posted 03 December 2019 - 10:51 PM

Its a common practice to increase the vessel elevations from FEED stage during detailed engineering. It will enhance the operability of pump. It's good from both pump operations & safety point of view.



#4 Bobby Strain

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Posted 03 December 2019 - 11:33 PM

There are likely many more errors from the FEED. Sounds like a case of poor engineering. Maybe it was the lowest bidder who executed the work.

 

Bobby



#5 fallah

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Posted 06 December 2019 - 06:20 AM

Considering the scenario where a vessel's bottom is connected to a centrifugal pump, what may go wrong in terms of Normal operation/Safety from point of view if during detailed designing one increases the elevation of a vessel (compared to FEED) to match the NPSH available?

 

 

Hi Shiva,

 

Following things may go wrong:

 

-Operating temperature or vapor pressure had been taken lower

-Operating pressure had been taken higher

 

Hence one has to increase the vessel elevation for static head increment to compensate for head shortage due to one of, or both, above mentioned mistake...



#6 breizh

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Posted 06 December 2019 - 08:14 AM

Hi,

To add to fallah's list , the level in the tank which may vary and go lower than initially thought .

Risk of Cavitation (NPSH)  is a key parameter to be checked to decide the location of the equipment (pump, tank)   

3 D model should help .

my view

Breizh


Edited by breizh, 06 December 2019 - 08:14 AM.


#7 Chemitofreak

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Posted 13 December 2019 - 01:39 AM

Considering the scenario where a vessel's bottom is connected to a centrifugal pump, what may go wrong in terms of Normal operation/Safety from point of view if during detailed designing one increases the elevation of a vessel (compared to FEED) to match the NPSH available?

 

 

Hi,

 

NPSH of a centrifugal pump depends on the following factors:

 

1) Suction vessel elevation

 

2) Condition of liquid i.e. Saturated or Subcooled

 

3) Suction vessel pressure

 

4) Line loss in the suction piping

 

Elevation of the suction vessel will not have any impact in terms of operation of the pump, it will lead to high civil structure cost.

 

Regards 






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