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How much is the different margin of NPSH should be?

How much is the different margin of NPSH should be?

How much is the different margin of NPSH should be?

(OP)
Is there any rule of thumb or standard that specified how much NPSHa - NPSHr should be? Thanks

RE: How much is the different margin of NPSH should be?

RE: How much is the different margin of NPSH should be?

I've seen companies use ratios and margins.  They also make a distinction on the type of application, like process, utility, cooling water.  Using a maximum flow design case, a 3 ft margin and NPSHa/NPSHr = 1.1 is common for process and utilities.  On cooling water, I've seen a more conservative ratio of NPSHa/NPSHr = 1.2.

Good luck,
Latexman

RE: How much is the different margin of NPSH should be?

We use a margin of 3 feet or 15% on hydrocarbon services and 5 feet or 15% on water services.  We are considering increasing the margin requirements.

Johnny Pellin

RE: How much is the different margin of NPSH should be?

chong....

As stated by 25362, the best and most authoritative source of information on NPSHA margin is Hydraulic Institute Standard 9.6.1

You should note that the suggested margin is based on the expected pump and system operating conditions. A cooling tower pump has a higer margin than a chemical plant process transfer pump.

   

RE: How much is the different margin of NPSH should be?

NPSHa > NPSHr

Let your acquaintances be many, but your advisors one in a thousand'  ...  Book of Ecclesiasticus

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