sizing PSV outlet around PD pump
sizing PSV outlet around PD pump
(OP)
Hi,
I am trying to calculate PSV that is located at a pd pump discharge, that is routed back to the suction. the psv is sized based on blocked outlet. i understand for the inlet line, i have to meet the 3% set pressure line loss. but i don't know how to calculate the outlet line. do i need to consider a change of temperature also? if so, then overtime if the liquid is increased, the fluid began to flash, then the psv would not be sized based on liquid flow, but it will be sized based on 2 phase flow. is this necessary?
thanks in advance,
bukek
I am trying to calculate PSV that is located at a pd pump discharge, that is routed back to the suction. the psv is sized based on blocked outlet. i understand for the inlet line, i have to meet the 3% set pressure line loss. but i don't know how to calculate the outlet line. do i need to consider a change of temperature also? if so, then overtime if the liquid is increased, the fluid began to flash, then the psv would not be sized based on liquid flow, but it will be sized based on 2 phase flow. is this necessary?
thanks in advance,
bukek





RE: sizing PSV outlet around PD pump
Usually you only size for the liquid flow.
Best Regards
Morten Andersen
RE: sizing PSV outlet around PD pump
As Morten said, I've also only seen single phase flow used for PD pump PSVs. Not to say you can't but it would be unusual situation that would make you need to do so.
RE: sizing PSV outlet around PD pump
Lots of area for discussion here over relief requirements for P.D. Pump versus flammability of fluid, presence of internal relief device vs. need for external r/v, HP of P.D. Pump vs. probability of injury or capital loss, type of P.D. pump, etc.
The more you learn, the less you are certain of.
RE: sizing PSV outlet around PD pump
RE: sizing PSV outlet around PD pump
I dont quite follow. If you sized your PSV correctly you wont se a higher pressure than SP+10%.
Best Regards
Morten
RE: sizing PSV outlet around PD pump
RE: sizing PSV outlet around PD pump
A fault-tree analysis may indicate the best thing would be to stop the pump when the discharge is blocked or to unload suction valves.
RE: sizing PSV outlet around PD pump
the type of pump is a plunger triplex pump. the fluid being pumped is crude.
i never realize that this type of pump requires such a high pressure at the suction too (vendor asked for 3.5 psi - not including acceleration loss). maybe this will be another topic, because i don't have a 100% confident calculating the pd pump suction in regards to including accelaration head to the NPSHA and for calculating the suction pressure.
thanks again!
bukeksiansu
RE: sizing PSV outlet around PD pump
We use Balanced Pressure Safety Valve. Do you know the causes that can fail the bellows?
We are using in the suction and discharge of PD pumps and the discharge valve, releases in the suction.
RE: sizing PSV outlet around PD pump
He is refering to the PSV flange ratings.
The pressure class of the inlet of the PSV should be the same as the pump disharge piping class.
The outlet of the PSV would have a lower piping class, which can be similar to the suction line piping class.
The above explanations does not have any relevance to the sizing of the PSV size, which is a different issue entirely.