Centrifugal and PD pumps with discharge valves closed

[Imthiyazh85]

Dear Friends,

Good Morning to all,

Please explain what are all the problems that pump will encounter if the discharge valve is closed in the running condition for both centrifugal and PD pumps.

In case of centrifugal pump, what will be the effect on impeller, pump shaft. seals, pressure inside the casing,NPSH requirement, Power consumption, effects on motor and other issues.

Is it advisable to start the pump with discharge valve closed.

 

[Artisi]

First up you should do some research yourself for questions 1 and 2 - this subject has been beaten to death here in Eng-Tips, and is addressed in just about every book written on pumps. While we endeavour to help posters with problems - these aren't problems as such - it just appears to be laziness on your part.

For the 3rd question, are you referring to centrifugal or PD pumps?

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.)

 

[LittleInch]

This looks suspiciously like a university / school question. If as artisi suggests you do some work, even searching on this site or just looking as vendor websites or other data freely available to understand the basics, then come back with some specifics or a real problem you will get some assitence.

Closing a discharge valve on any pump that is still running will cause problems and can break it so why do you want to do it?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[micalbrch]

This is a place to start:

http://www.pumpfundamentals.com/

It took me less than 5 seconds to find this website.

 

[electricpete]

Some hints:
Why do positive displacement pumps usually have relief valve?
Why do centrifugal pumps usually have mini-flow recirc?

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