PSV Backpressure Static or Total ?
PSV Backpressure Static or Total ?
(OP)
Hi all
I am trying to settle a slight difference of opinion here. The backpressure on a flowing PSV is made up of the superimposed BP ie:that caused by other valves flowing into the header system, plus the builtup backpressure caused by the valve itself flowing.
If you use Flarenet to model the relief header you can see the STATIC backpressure on the PSV at say 1.2 barg and you can also choose to view the TOTAL pressure which includes the velocity head of the gas and see T say 1.8 barg.
Now the $1M question, which do you put on the PSV datasheet for the vendor the STATIC value or the TOTAL value.
I maintain its the STATIC pressure as it acts in all directions whereas the velocity head contribution is in the direction of flow and hence does not affect the PSV capacity.
Thoughts please?
I am trying to settle a slight difference of opinion here. The backpressure on a flowing PSV is made up of the superimposed BP ie:that caused by other valves flowing into the header system, plus the builtup backpressure caused by the valve itself flowing.
If you use Flarenet to model the relief header you can see the STATIC backpressure on the PSV at say 1.2 barg and you can also choose to view the TOTAL pressure which includes the velocity head of the gas and see T say 1.8 barg.
Now the $1M question, which do you put on the PSV datasheet for the vendor the STATIC value or the TOTAL value.
I maintain its the STATIC pressure as it acts in all directions whereas the velocity head contribution is in the direction of flow and hence does not affect the PSV capacity.
Thoughts please?





RE: PSV Backpressure Static or Total ?
Good luck,
Latexman
RE: PSV Backpressure Static or Total ?
JAC
RE: PSV Backpressure Static or Total ?
RE: PSV Backpressure Static or Total ?
Good luck,
Latexman
RE: PSV Backpressure Static or Total ?
ASME VIII Div 1 1986 (section M-8C) states
"The static pressure developed at the discharge flange of a conventional spring loaded safety valve shall not exceed 10% of set pressure"
RE: PSV Backpressure Static or Total ?
RE: PSV Backpressure Static or Total ?
I can state from first hand experience in more than one organisation, that some Process designers will not always accept that ASME definition - and take it very personnally. Some will only use total because it is also on the printout. Hence my first comment.
RE: PSV Backpressure Static or Total ?