Very High Temperature Piping Stresses

[RVAmeche]

Does anyone have any experience with very high temperature piping systems, such as 2,200F (1200C) hot? It looks like ASTM B407 and HR-120 alloy may be suitable, but this is pretty far above anything I've done before. ASME B31.3 allowable stress tables seem to only goes up to 1,650F and say that's the maximum temperature for the materials. I've tried digging through Caesar II's material database and don't see B407 so even if I find a spec/alloy I may not have allowable stresses.

Required pressures are very low since it's a pyrolysis process but obviously at these temperatures any material is going to have very little strength left, so I'm curious if I'm missing some other alloy that is better suited for this application. I don't think refractory or ceramic lined is going to be suitable either.

 

[Andrew ONeill]

I did something for a trial in a furnace once ~ 1100 C.

Still used B31.3 / 31.1 principles, but

1) Tracked down material properties at that temp, and used the Su/3, Sy/1.5 criteria to determine an allowable stress
2) Looked at creep data (in my case was short term service (days to weeks for trial, thought it wouldn't matter, trial went for a few weeks, the Equpment stayed installed for about 2 years.)

ended up with stupidly low allowables, but that is what I had to deal with

When the thing was removed after about 2 years sitting in the furnace, had some permanent deflection / creep. Didn't affect function, but tells me I probably wasn't conservative enough / creep matters for durations longer than a few weeks...

From memory I used Inconel 601, might not be the best?!?, but it was available on short notice.

*Also in my case the consequence of failure wasn't a problem, so didn't have to take too much care. However, if the tube side product caused some large consequence when exposed to the furnace, I would have done a lot more work on it.

 

[NovaStark]

Much like Andrew said, at those temperatures your allowables are going be extremely low and are most likely governed by creep rupture properties.

Depending on the application such as a furnace, you might need to look into even more specific alloys, e.g. S+C.