PRV Sizing for Use during Hydrotest of Piping Systems
PRV Sizing for Use during Hydrotest of Piping Systems
(OP)
I work as a client rep. and in one of the clients specs there is a requirement for sizing the PRV used during hydro testing any piping system per API 520.
I did some research on sizing the PRV and found that the relief capacity depends on the flow rate. We mainly use water for pressure testing, so I assume that there will be no much flow coming from the hydro test pump after reaching the required test pressure and before over-pressurization, specially for small piping systems.
Can you advise how can we size PRV for a hydrotest? and what would be the worst over-pressurization scenario?
Thanks.
I did some research on sizing the PRV and found that the relief capacity depends on the flow rate. We mainly use water for pressure testing, so I assume that there will be no much flow coming from the hydro test pump after reaching the required test pressure and before over-pressurization, specially for small piping systems.
Can you advise how can we size PRV for a hydrotest? and what would be the worst over-pressurization scenario?
Thanks.
Regards,
Mohammed





RE: PRV Sizing for Use during Hydrotest of Piping Systems
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: PRV Sizing for Use during Hydrotest of Piping Systems
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: PRV Sizing for Use during Hydrotest of Piping Systems
RE: PRV Sizing for Use during Hydrotest of Piping Systems
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: PRV Sizing for Use during Hydrotest of Piping Systems
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: PRV Sizing for Use during Hydrotest of Piping Systems
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: PRV Sizing for Use during Hydrotest of Piping Systems
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: PRV Sizing for Use during Hydrotest of Piping Systems
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: PRV Sizing for Use during Hydrotest of Piping Systems
We had some cases where the PRV did not function after exceeding the set pressure, but I believe this has nothing to do with the sizing. These are probably malfunctioned PRVs.
Regards,
Mohammed
RE: PRV Sizing for Use during Hydrotest of Piping Systems
Spring relief valves are very reliable systems, but need to be set correctly and installed correctly ( top of pipe, no dirt etc). If they really did malfunction I would start to get very worried indeed. PRVs are relied on the world over to open when required to a very high level of reliability.
I strongly suspect / hope you mean incorrectly set. What the valve says on its name plate is only as good as the day it left the factory. Once people start messing around with them and re-setting pressures, changing springs etc, the name plate should be amended or ripped off but no one does in practice.
Insist on up to date calibration certs for the valves or get them bench tested before use if the paper work is poor or non existant.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: PRV Sizing for Use during Hydrotest of Piping Systems
RE: PRV Sizing for Use during Hydrotest of Piping Systems
So the sizing wouldn't be any different than a normal blocked outlet case. The main driver here is making sure the desired set pressure is correct.
The pressure spikes cause the PSV to lift with every stroke. They tend to hold just fine after we have reached our desired test pressure. However, they will likely be repaired more frequently due to this.