pump selection 1

[amine1340]

hello everyone ,
currently i'm working on a project where i have to select between two pumps which got me a little confused :RATED FLOW IS 129 M3/H ,NPSH A = 4.5 m.
1st pump :
it has a high NSS 13600 .
NPSH R at end of curve is = 2.8 m.
rated flow is 97% to BEP FLOW( 130 m3/h) .
Minimal stable flow : 55 M3/H AROUND 40% OF BEP .
2nd pump:
it has NSS 10980.
NPSH r at end curve is 5 m so vendor propsed to limit flow at end curve to 110% BEP in order to have NPSH R of 4.4 m ( which is a deviation from API that states that end curve should be 120% BEP)
rated flow is 79% to BEP flow .
- 1 st pump :in out project specification NSS is limited to 11000 , since going higher would limit the operating range.
- 2nd pump end curve is limited to 110% BEP, and rated flow is 70% of BEF which a bit far .
i hope that my explanation of the problem was clear
thank you in advance for your precious insight

 

[mk3223]

IMO, the 2nd pump is the better choice if there are only two options as described, for the potential saving in maintenance costs and better reliability.
Or, you may contact other Company approved vendors for additional proposals.

 

[Artisi]

I would agree that pump 2 is probably the best choice, and bear in mind API is a guideline and not an absolute rule.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)