Med/High Visc - PD pumps PSV's Inlet outlet DP's too high per typ. API forms. - always likely?
Med/High Visc - PD pumps PSV's Inlet outlet DP's too high per typ. API forms. - always likely?
(OP)
I'm revaliding a PHA for a med/high (100-500cp) plant.
We are going through the cases and taking credit for the positive displacement pumps spill back valves for preventing down stream vessel damage in a lock in case.
The problem I encounter is that almost all of them on the high viscosity cases exceed (by a margin) the inlet and outlet DP cases .
Inlet Dp's range from 12%upto 78% , with outlet DP's a similar range of 21 to 78%. Unfortunately the plant is very old (ish) 1980's vintage, I don't believe the fluid conditions have changed so is there a different standard to spill back pumps I'm not aware off.
"back in the day" did vendors/ engineers not calculate this stuff... I doubt it ".. I know different codes apply. but I'd like to get some experienced engineers background.
We are going through the cases and taking credit for the positive displacement pumps spill back valves for preventing down stream vessel damage in a lock in case.
The problem I encounter is that almost all of them on the high viscosity cases exceed (by a margin) the inlet and outlet DP cases .
Inlet Dp's range from 12%upto 78% , with outlet DP's a similar range of 21 to 78%. Unfortunately the plant is very old (ish) 1980's vintage, I don't believe the fluid conditions have changed so is there a different standard to spill back pumps I'm not aware off.
"back in the day" did vendors/ engineers not calculate this stuff... I doubt it ".. I know different codes apply. but I'd like to get some experienced engineers background.





RE: Med/High Visc - PD pumps PSV's Inlet outlet DP's too high per typ. API forms. - always likely?
RE: Med/High Visc - PD pumps PSV's Inlet outlet DP's too high per typ. API forms. - always likely?
You describe this as a "spill back valve" so I don't know exactly what type valve you have. It could be (1) a modern liquid trim PRV, (2) an old style PRV, prior to advent of liquid trim, or (3) a fully modulating liquid service valve like a Fulflo. If the answer is #3 then I don't think you need to be concerned.
When you have a high viscosity fluid, it's often impossible to get the inlet losses to 3% or less. Sensitivity to inlet pressure loss started in the mid 90's with the implementation of OSHA PSM. The irony is that today we recognize that the 3% rule is inadequate for predicting chatter.