Steam Relief Valve Discharge Pipe Sizing 2

[BronYrAur]

Anyone know where I can find a written reference from a creditable organization recommending steam relief valve discharge pipe sizing? I have a situation where a relief valve sized for 2,730 Lbs/hr at 25 psig lifted. The valve has a 2" inlet and 2-1/2" outlet. The valve discharges through a 2-1/2" pipe into a drip pan elbow. The drip pan elbow literature calls for a 3-1/2" or 4" discharge line.

Here's my problem, the installer put a 4x2 concentric reducer on top of the drip pan elbow and tied the relief line in to a 2" header. As I mentioned, the relief valve lifted and as you can imagine, I have a big mess of wet/melted insulation from steam blowing out the drip pan elbow atmospheric break.

So I know full well that a 4" line is required, but where can I find it in writing. I need some design specs in my arsenal to demonstrate that reducing to 2" was the cause of the problem.

 

[davefitz]

Try asme B31.1 appendix II, which is based on the Bechtel- Liao method.

Based on that method, or by observation of teh relationship of choked flow discharge pressure vs mass flux ( P vs W/A), the 2" header shold not have ben used and a 4" or larger header and discharged shoulr have been used. If teh discharge pipe is long enough or has a lot of bends, it might need to be increased to 6" .

 

[GenB]

2700 lbs is not a whle lot of steam, the problem of drip pans is the open design which i do not agree with.
2in should be plenty for a short run discharge if the pan was threaded or flange/bolted to the discharge pan.

But if the pan has a 4in and was reduced is not acceptable