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Thanks Pierre, That's a good article. He doesn't specifically clarify whether or or not it is a pump index that doesn't change with speed....or if it can be calculated at any given speed (with BEP flow and BEP NPSHR) My two reference points are Mr Budris, who was the product development...

You are correct. I did grab the wrong quote from API-610. But right below it says the same thing for Suction Specific Speed. "....at a given rotative speed..."

So I took a closer look. Using the BEP flow, and the BEP NPSHR for each speed. Nss does come out to a different value for each speed?

Ah...I see what you are saying. I did take a particular Goulds 3196 and tried two different speed. I get close to the same Nss. See below. In the ball park anyway, I probably wasn't picking the exact spot on their software. Now I understand what Alan Budris thought the term "Suction Energy"...

Yes. I know all that. Thanks. My point is that there is no such thing as a BEP speed. Maybe I misunderstood your 1st post, but it sounds like you were indicating there there was a BEP speed. What I am trying to ask is.....like API-610 indicates. Can you use "a given operating...

Not quite following you. For every operating speed, there is a different Q (BEP), and a different NPSH3 (BEP). Below is a sample Goulds 3196. The BEP flow moves is direct proportion with pump speed. API 610 does indicate "at a given rotative speed". Therefore, I believe it is appropriate...

Hi, I had been under the assumption that the calculation of Suction Specific Speed used the actual operating speed, not the maximum design speed. Last week, I noticed that the Goulds E-Prism program shows the same Nss regardless of speed. i.e... they show the same Nss for 3600 rpm, 1800 rpm...

Hi Several studies and authors have noted that peak impeller damage can happen around 1.5 to 2 X the NPSHR(3%) line. Mr Budris even managed to get that language into the 1998 version of ANSI 9.6.1. Peak erosion, peak noise, peak pulsations, all happen in this area. Once air starts coming...