High Temperature Allowable Stresses for Bellows

[flexy]

I am attempting to design a 16" bellows expansion joint for a 2000F application @ 80 psig. At this temperature, it is enormously difficult to select an appropriate bellows material. Even if I am able to do this, at 2000F any material I select would be in the creep range. Should I decide that I DO NOT want to refractory line my EJ, what material would be most suitable (...the media is hot gas exhaust from a aircraft engine)? How could I determine an appropriate allowable stress based on the 2000F temperature? Does the fact that the bellows operates in the plastic range affect how I would select an appropriate allowable stress? Please note that this project is ASME B31.3. I am aware that the code genrerally does not recognize temperatures this high, but, assuming ASME did, how would I approach determining the allowable stress?

 

[StressGuy]

I would definitely seek some expertise from one of the major joint manufacturers, as that sounds like a pretty extreme case. What is the connecting piping to made from?

One thing that you may have to concede to for your application is a planned replacement life cycle for a joint in this type of service.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

All opinions expressed here are my own and not my company's.

 

[bvi]

Frankly, you are well beyond the expertise at this temperature of any of the major bellows manufacturers. EJMA does have some newer rules for creep fatigue design of bellows in an Appendix, but it requires elevated temperature fatigue testing. The pressure membrane plus bending limit should be limited to 1.25S, once you determine what S is a 2000F, which will be next to nothing. Frankly, it is difficult to get a piece of metal to support itself at 2000F, much less contain pressure. Then, you need to deal with column squirm (creep buckling at this temperature), for which there are no documented design rules. The only reasonable solution at these temperatures is to generally internally line the joint such that the bellows metal temperature is much lower. If you cannot do this, you have a research project, not a design project.