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.

 

[RVAmeche]

Yeah it's an interesting case and so far I don't see any materials that jump out as long term viable options to me, but we'll be getting a metallurgist report for recommendations and then I assume I'll have to create the material in Caesar to run it. I'm definitely expecting low allowables since it's damn near its melting point regardless if its 308 SS, 800H inconel, or other.

What blows my mind, and I don't believe them, is the client says their pilot line used 316 SS screw augur material in this 2,200F environment with no issues or creep failures or deformation. I just don't buy that.

And we'll have flanged connections that are running at very low pressure but at these temps I still don't know what material would be "approved" since nothing in B16.5 goes that high. Really hoping the metallurgist report provides clear insights.

Thanks!

 

[XL83NL]

We recently did a job with piping at 2100 F, under B31.3, for a plant in the US. In fact, we used B31.3 para 300(c)(3) to go this level. The client required this material since they bear overall responsibility (para 300(b)(1).

Materials were N06025, which per VD-TUV WB 540 has allowable up to I think 1200°C. I think this is one of (if not the) highest you can go with an alloy, as I don't know of any other publication that allows higher than this. Pressure were also very low (near atm.), otherwise it would've been impossible. The allowable stresses at design where around 0.5% of the ambient allowable, to give you an impression. Pipe stress analysis was doable, but difficult. Nozzle loads were the governing design issue in the end. Also, flanges at these temperature are plain stupid. Avoid them at any cost. In the end, I think refractory may have been a better candidate, but Im not sure about that.

Understanding failure modes is key at that temp. Reading the new (2nd edt) of 'Analysis of ASME Boiler, Pressure Vessel, and Nuclear Components in the Creep Range' was also very useful.

PS: in contrary to VIII-1, B31.3 doesn't set hard max temp limits, see 323.2.1.

 

[GD2]

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.

I will be a bit skeptical on the 1200C. What is that process that uses 1200C? Furnace heater tubes goes upto 900C and the high temperature nuclear reactor cores made of graphite materials.
Typically Ni-Fe-Cr alloys can see the max temperature.
If you are talking about Pyrolysis process, users are seen to use the reactor made out of SS to Ni alloys.

 

[EdStainless]

We had a high temp system (2150F) that was very low pressure (<1.5psig) that was done with centrifugally cast piping.
We were basically using the alloy that are used for high temperature furnace rolls
Not to any code as the alloys and method of fabrication are not listed.
It was 'best engineering practice' all the way.

 

[RVAmeche]

The more information we get the more I'm skeptical of the 1200C limit too. I suspect that's a worst case for the heater, but due to the BTUs the heater lists there's no way they're getting up to that temperature. That'll be a fun conversation with the client.

Thanks for the information Ed. If we had to go that route I'd probably try to sub the piping design or something since I know nothing about that stuff and don't want to stamp a bad system.

 

[shvet]

Just stumble upon the ASME's report. Maybe it can help
ASME STP-PT-049 Investigation of Temperature Derating Factors for High-Strength Line Pipe. ISBN: 978-0-7918-3426-8

 

[XL83NL]

Just stumble upon the ASME's report. Maybe it can help
ASME STP-PT-049 Investigation of Temperature Derating Factors for High-Strength Line Pipe. ISBN: 978-0-7918-3426-8

Nah, that wont help, line pipe is for pipeline codes. The report is for X60-X70 grades up to 250 F.