Sizing the vents off the pressure regulator

[PEDARRIN2]

I am trying to size the vent off of a pressure regulator from a medical oxygen manifold. Pressure is ~350 psig. The vent is about 150 feet in length to get to the exterior of the building.

The manifold manufacturer recommends 1/2" pipe for the first 50 feet and 3/4" for the remaining. That just seems too small.

I have also seen a rule of thumb that say you increase your pipe one size for every twenty feet. That would put me at 2.5" by the time I get outside. That seems excessive, but I do not have any justification against it.

If anybody has any suggestions, I would appreciate it.

Thanks

 

[Latexman]

A pressure regulator has a high pressure inlet and a low pressure outlet. Most have a vent connection that puts atmospheric pressure on the non-process side of the diaphragm.

Are you piping the vent connection outside in the event of diaphragm failure?

Good luck,
Latexman

 

[PEDARRIN2]

Yes I am.

Typically the rooms with the manifolds are very close to an outside wall or to the roof.

This project is a remodel and the room is in the basement. The only route to the outside is in a storage room and through three floors to the roof.

 

[Latexman]

On the regulators I am familiar with, if they have a diaphragm failure, the high pressure gas flows through the regulator orifice to the outlet side, a tube that connects the outlet side of the regulator to the underside of the diaphragm (assumes no leakage through the valve stem and it's bushing, the hole in the diaphragm, the vent connection, and finally through the piping you are going to install. If we assume the hole in the diaphragm is large, i.e. offers little resistance, you have 4 resistances in series:

350 psig ---> regulator orifice ---> equalizer tube ---> vent connection ---> vent piping ---> 0 psig

Now you just need the details from the regulator and a good compressible flow reference, or textbook, and work it out. By hand, it's a two martini problem, but with the right software, it's a 5 minute job.



Good luck,
Latexman