Why is NPSH can not be determined if the suction is flooded (?)
Why is NPSH can not be determined if the suction is flooded (?)
(OP)
Dear everyone,
I want to consult you guys on this. I asked a package vendor (for a chemical injection package) to provide me both Differential Pressure and NPSH for the metering pump. However, the vendor says this is not required because the suction is flooded. See below:
For the differential pressure, vendor says this simply can not be determined because the suction is flooded (sourced tank will be atmospheric). If this is the case, shouldn't the suction pressure be 0 psig? given the discharge pressure - the differential pressure can now be determined. Correct me if I'm wrong.
For NPSH, again this will not be required because as the vendor says the suction is flooded and as long as the sourced tank and pump are mounted on the same level, NPSH is not required. I am puzzled why the vendor can not provide me the value of NPSH. Can you guys enlighten me first?
Regards,
Virata
I want to consult you guys on this. I asked a package vendor (for a chemical injection package) to provide me both Differential Pressure and NPSH for the metering pump. However, the vendor says this is not required because the suction is flooded. See below:
For the differential pressure, vendor says this simply can not be determined because the suction is flooded (sourced tank will be atmospheric). If this is the case, shouldn't the suction pressure be 0 psig? given the discharge pressure - the differential pressure can now be determined. Correct me if I'm wrong.
For NPSH, again this will not be required because as the vendor says the suction is flooded and as long as the sourced tank and pump are mounted on the same level, NPSH is not required. I am puzzled why the vendor can not provide me the value of NPSH. Can you guys enlighten me first?
Regards,
Virata





RE: Why is NPSH can not be determined if the suction is flooded (?)
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.)
RE: Why is NPSH can not be determined if the suction is flooded (?)
Regards,
Virata
RE: Why is NPSH can not be determined if the suction is flooded (?)
Therefore he simply can't be bothered to work out the NPSH because he knows from past experience that it's not an issue.
Metering pumps are usually PD pumps so the differential pressure will be whatever it needs to be to enter your downstream system, up to a maximum as presumably you have stated in the data sheet.
Therefore the differential pressure will vary up to a set maximum when the relief valves lift.
If you're paying for it then the vendor should be a little bit more accommodating.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Why is NPSH can not be determined if the suction is flooded (?)
LittleInch has filled in the other detail.
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.)
RE: Why is NPSH can not be determined if the suction is flooded (?)
RE: Why is NPSH can not be determined if the suction is flooded (?)
It would be like if someone asked, 'How fast are you driving?' and the answer you give is 'I'm on the highway'.
RE: Why is NPSH can not be determined if the suction is flooded (?)
RE: Why is NPSH can not be determined if the suction is flooded (?)
RE: Why is NPSH can not be determined if the suction is flooded (?)
RE: Why is NPSH can not be determined if the suction is flooded (?)
RE: Why is NPSH can not be determined if the suction is flooded (?)
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.)