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SRV discharge piping - minimum wall thickness?

SRV discharge piping - minimum wall thickness?

SRV discharge piping - minimum wall thickness?

(OP)
Is there any guidance in the codes (31.1 in particular) as to the minimum wall thickness for safety relief valve discharge piping, immediately downstream of the valve?

I assume that it will be more than a simple pd/2t calculation, and requires consideration of reaction forces when the valve is operating.

TIA

RE: SRV discharge piping - minimum wall thickness?

kclim..

In ASME B31.1, there is an APPENDIX 2 that addresses the desihn of safety relief valve systems and the pressures generated within the system upon actuation.

For most cases, you will find that Sch 40 piping is acceptable. I have never heard or encountered a system that was any thicker than schedule 40.

In my opinion, I would not use piping that was any less than Sch 40 because of the shock generated during SRV actuation. Having a "stiffer" system that is able to take the internal shock generated is advaiable.

Be sure that the pipe diamter is adequately sized for the service. A good rule of thumb is: Systems reliving steam or flashing fluids, make the tailpipe size two pipe sizes larger than the SRV outlet size by ; for all other services, one pipe size larger..

My opinion only.....

Anybody else have guidelines or websites to offer ?

-MJC

  

RE: SRV discharge piping - minimum wall thickness?

The code appendix that MJCRONIN  refernced is a good place to start. However, the curves in that appendix are only valid for short stacks with few elbows and no outlet restrictions ( ie, fL/D  < 2.0).

If you have a longer pipe with many elbows ( ie, fL/d > 2.0), then you will need to use the compressible flow equations for adiabatic, perfect gas flow ( Fanno flow), to predict the pressure immeidately downstream of teh relif vale ( at the inlet to the exhasut pipe). Outlet restrictions such as silencers or manifold for joining other flows will add more pressure drop and increase the pressure.  

RE: SRV discharge piping - minimum wall thickness?

I agree with davefitz....

kclim: what is the geometry of your discharge piping ?

-MJC

  

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