High Temperature PSA
High Temperature PSA
(OP)
I am working on a project that involves a short section of piping that is at 1,800°F and 5 psig design conditions. I have been requested to provide the stress analysis. They want the design to B31.3, even though it is not considered pressure pipe. The conundrum is what allowable stresses to use as B31.3 only goes to 1,500°F and the stress is only 1,100 psi. The material they plan to use is A316-Type 321H. I have a similar question for the flanges (B16.5 allows 1,500°F @ 40 psi).
I know that B31.3 considers high pressure design but what is your experience with high temperature piping? Any suggestions as to how to approach this from a pipe stresser point of view?
Thank you in advance!
I know that B31.3 considers high pressure design but what is your experience with high temperature piping? Any suggestions as to how to approach this from a pipe stresser point of view?
Thank you in advance!





RE: High Temperature PSA
I'm not sure that such a job could be performed using only typical pipe stress analysis tools.
What is desired life? What are the operating conditions? The operating conditions are more important in this scenario than the design conditions.
RE: High Temperature PSA
RE: High Temperature PSA
You can have a look at it, maybe there are some general guidelines in there, but I dont think it's design code for your application.
I guess youll need due consideration of basic mechanics, added w/ creep, and sound engineering practice on this one.
RE: High Temperature PSA
RE: High Temperature PSA
I have just been informed that the max pressure (rupture disk burst pressure) is 30" w.c., so pressure will not be an issue, which works in our favor.
The operating conditions are close to the design: Max 1700°F and normal 1600°F. I can use B31.3 up to 1500 °F but the material needs to be heat treated to a min. of 2000°F as indicated in the note in Appendix A to use these allowables. Their spec calls for heat treatment to 1625°F, once again against us. The normal ope temp is also 100°F above the max B31.3 limit.
I understand fully that this will not be designed to B31.3, but I am using it as a safety guide to have some peace of mind that this will be a safe system. If I don't get a good handle on this, they will need to retain an engineer that does have experience with this.
If the design was requested per B31.3 we are looking at a 20 year life span, if I am correct.
Are there any calculations or standards that account for creep, to de-rate allowable stresses and what to do about the extra 100°F (fm 1500 to 1600) of heat w.r.t. selecting allowable stresses.
RE: High Temperature PSA
RE: High Temperature PSA
I have been involved in extremely high-temperature designs (2000°F +) with exotic materials, but even then we were using a design-by-analysis approach with self-derived allowable stresses, which limited to life to much much less than 100,000hrs. Based on what you have written, I would tend to think that the piping that you describe will need a similar approach.
Or, you can line the pipe with refractory.
RE: High Temperature PSA
RE: High Temperature PSA
How would the refractory improve the situation TGS4?
The piping is NPS-4 Sch 40 by the way and is actually exhaust piping from an activator through a HEPA filter and to atmosphere.
If it is a time relates issue, then perhaps they have to replace the piping every 5 years. Not the greatest design but it is their design.
RE: High Temperature PSA
RE: High Temperature PSA
And would 310 be a better option against oxidation?
RE: High Temperature PSA
http://www.specialmetals.com/documents/Inconel%20a...
RE: High Temperature PSA
Considering that you are only discussing exhaust piping, then I would definitely recommend refractory lining of the pipe - just as XL83NL suggests. That would greatly reduce the design metal temperature back into the B31.3 temperature range.
RE: High Temperature PSA
The new scope for them is their client requesting a PSA report which is how I got involved.
I recommended to model the piping to the highest temperature below which creep will not be an issue. I understand that this is approx. half the melting point (to be confirmed), although I read another report that indicates that this is approx. 1050° for SS. This is as far as I am prepared to stick my neck out and if it is contended with their client, we can recommend to change materials to Incoloy.
Any other comments please let me know and thanks again for the knowledge.
RE: High Temperature PSA
The (approximate) onset of creep can be found in ASME II-D. From the top of my head, itll be around 600 C for 321H.
1050 deg C is where SS is typically annealed.
Anwar, as TGS4 posted stick to linde pipe. B31.3 has a special section for this, so the code 'will suit you well'. For the shell, you can then switch to e.g. standard A106B CS Pipe, which is way chapter than 800H/HT.
Good luck.
RE: High Temperature PSA