2 replies to this topic

[joseph sanchez]

Customer is supplying 250psi natural gas to our peco filter. I have a 1st cut regulator upstream of the peco set at 100 psi. Down stream of the peco, 100 psi supply pressure is supply NG to (4ea.) NG engines. A 2nd cut regulator at each engine is set at 100psi in and 5psi out to engine. Each consume 61cfm. The peco MAWP is 285psi.  I would like to size the PRV on the Peco to 130psi vs. mawp of the peco and not starve the engine of NG fuel when the engine or engines are operating. What discharged flow rate should be considered for the PRV? 

[Saml]

I assume that PECO is a trademark for a cartridge filter, with a housing built to ASME and that you do't have other element in your system rated for lower pressure. That is, the second regulator and all the piping is rated for at least 285 psig.

 

You can set your PRV at 130 psig (well below the MAWP). 

Per ASME

UG-134: set presssure shall not exceed MAWP (that is, you can set it lower)

UG-125: should prevent pressure from rising above 10% of MAWP

 

In theory, you could calculate the flow rate at 110% of MAWP (313 psig) for the governing case , and set the valve at 130 psig (45%).

 

However, this is not usual. I doubt that a valve vendor would take this spec where the accumulation over set point is 140%.  Probably they'll recommend having the full flow at 10% accumulation over the set point of the valve. So please discuss with a PSV supplier since they are responsible for certifying that the valve meets the required capacity. 

 

¿Now, what would be the use of this set point at  lower pressure? ¿Why not set it at MAWP? ¿Why do you think you'll starve the engines if you set the pressure higher?

Edited by Saml, 26 May 2017 - 01:23 PM.

[fallah]

joseph,

 

A simple sketch would be more helpful to provide a reasonable response than your description...