Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
(OP)
Dear Experts,
Kindy please advise the inlet pressure loss criteria for high viscous service?
We have viscous fluid viscosity around 15 Pa.s.
As we are aware that API states the inlet line pressure loss shall be less than 3% of set pressure.
Thanks and best regards,
Joko
Kindy please advise the inlet pressure loss criteria for high viscous service?
We have viscous fluid viscosity around 15 Pa.s.
As we are aware that API states the inlet line pressure loss shall be less than 3% of set pressure.
Thanks and best regards,
Joko





RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
Do you have any reference? Then I can follow as basis of our calculation. thanks
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
PSV Set pressure 3.5 barg
Criteria of pressure loss for inlet line of PSV is 3% = 0.105 bar
We have inlet line length 1 meter and 1 gate valve.
Viscosity 15000 cP.
Flow 128250 kg/h
Density 726 kg/m3
The resulf of pressure drop as follows :
size 10" = pressure loss is 0.205 bar,
size 12" = pressure loss is 0.170 bar,
it means higher than criteria.
So that's why Iam asking is there any other standard? or for high viscous service is excluded from API/ASME criteria?
Please advise,
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
(BAR)"
10" 12" 14" 16"
0.161 0.17 0.184 0.21
Eventhough we increase the line size, still we can't meet criteria 3% of 3.5 barg = 0.105 barg
How is it?
thanks
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
Maybe there are others reading this discussion who can help with these fitting equivalent lengths for the gate valve and reducers at these low values for Nre.
Also check that you've accounted for exit loss for the RV nozzle on the protected equipment.
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
Since the exit loss is not included in my approx calcs, it does look like you need more than 14inch.
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
Also the 3% rule is part on the non-mandatory Appendix M of ASME. You could perform an engineering analysis outlind in API to see if the valve will chatter or not, and whether the pressure accumulation is acceptable.
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
With the information so far, I would be looking at a spring operated PSV with a top mounted actuator with lift assist. Depending where the installation is located, this set up should be allowed by ASME VIII since the opening is not restricted. The controller to the actuator may also be a triple type as per ISO/PED EU rules (1 working, 2 redundant.
You also need to consider the viscosity correction Kv factor to be applied to the PSV sizing by factoring the Reynolds number per API 520 against initial sizing (as well as the inlet pressure loss). Maybe also consider a heated inlet design by lagging, jacketing or other. These factors of course affect the rated flow.
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
The controller/sensor for the actuator would need a chemical barrier.
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
RE: Safety Valve Inlet Pipe Pressure Loss Criteria For High Viscous Service
One thing I didn't notice anyone else commenting on. If the gate valve is on a line you are designating as your 'relief path' you should only have a full bore valve.
API 520 part 2 includes provisions on engineering a larger inlet pressure drop. You might want to proceed down this path. I would point out that you should ensure you carefully document your thought process for this project. So that if other folks in your plant who don't readily understand the process will at least understand that you do.
The pilot operated valve would be my second choice if you cannot engineer out the inlet pressure drop. Of course you will have some challenges with the sensing line. You might need to trace it, or something to ensure you don't plug it up.