Drooping head pump head curve
Drooping head pump head curve
(OP)
We have testd three high head multi-stage pump in LNG / LPG and obseved that all three pumps (Sp. speed 800, 1000, & 1250) have drooping head curve. Is there any solution or method to change this performance to continously rising curve to shutoff head by reworking on existing impller or diffuser. All pumps have integral vaned diffuser and return vane.





RE: Drooping head pump head curve
It reviews the subject and presents some explanations in its chapter on Performance Factors (Item: Recirculation at the impeller outlet).
RE: Drooping head pump head curve
RE: Drooping head pump head curve
a)Whether for large Circulating water pumps (like in power plant application) variable angle impellers are used with single speed drive so that the pump may be operated for different flow/head due to variation in plant load(output)?
b)If yes, name of such installations?
b)If Yes, manufactureres of such pumps in the industry?
c)Will there be any complication in operation of such pumps?
d)Is it not better to design pumps variable speed drives instead of variable anagle impeller from cost and ease of operation?
RE: Drooping head pump head curve
Apply a 15 degree or greater bias on the b2 diameter, i.e. trim the impeller so that the front shroud diameter in greater than the rear shroud diameter (equivalent to 15 degrees as viewed from the side. Take into account the average diameter for head.
Impellers with discharge vane angles of 25 degrees or more droop. Also, too many vanes can promote droop.
Scallop the shrouds, but lose 3 to 5 pts of efficiency.
Some things that did NOT help:
add nose cone to impeller
small bias on impeller (4 degree)
increase cutwater
trim only the vanes
RE: Drooping head pump head curve