Safety Relief Valve on Flash Tank

[Jaroy]

I have a flash tank with a safety relief valve and was asked by my boss if we could move the relief valve to the roof. By code, is this allowed? Is there a minimum distance that the relief valve has to be from the flash?

thanks for the help.

 

[MikeClay]

It is allowed by code. In general, the inlet pressure drop should be less than 3% of the PSV set pressure. See API RP 520 Part 2.

Moving the PSV to the roof may force a larger diameter inlet pipe, assuming the vessel nozzle is large enough. If the pressure drop is still too high, then a remote sense pilot relief valve could be used. Just make sure to adjust the PSV inlet pressure for the inlet line loss.

There is no minimum distance. It is not uncommon to bolt the PSV directly to the vessel.

--Mike--

 

[DaChief]

In PEI the code says to locate the safety valve as close as possible to the vessel that it protects.