NPSHR testing 1

[iceland1]

Hi, Can anyone advise if there is a general requirement to individually test the NPSHr for each pump of a batch of pumps when undertaking the head / capacity testing?

Is it acceptable to base the NPSH values on calculated values and evidence from previous similar pumps that were tested?

any advice welcome, thanks.

 

[Artisi]

A lot will depend on why you are testing- if it is to check that a standard production pump reaches its published curve and NPSHr is not a critical factor in its operation - probably no need to run a full NPSHr test - NPSHr at the duty point is probably sufficient.

 

[vpl]

I would think you'ld want to test at least one pump in the batch, to make sure your NPSHr is meeting your calculations. Then for the rest of the pumps you might be able to test only at one point or rely on the calculations, if you feel really confident that your manufacturing conditions haven't changed. Worst case is having your customer run an NPSH test and finding you don't meet your spec. Then you're into warranty issues.

Patricia Lougheed

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[rmw]

Many years ago I worked for a firm that made evaporators hence they had 3 different saturated fluid flow loops. They tested all pumps and found that often the curves published by the pump manufacturers were "optimistic" to say the least.

After some testing they learned which manufacturers could be trusted and which ones 'pushed the envelope'.

rmw

 

[MrsMason]

NPSH testing is only required when the NPSHA/NPSHR margin based on calculations is 3 ft. or less. In this case usually only one of a like batch of pumps needs to be tested, assuming the others have the same impeller dia. as the one being tested.