Expansion Joint Allowable Design Stress - High Temp

[nickelkid]

bellows material B409 AlloyH (NO8810)
design temp specified 1200F

a exp.joint manufacture has come back with a design temp of 1000F, allowable stress 14,400 psi, elastic modulus 24.2E6 psi.

using MatPro (paulin.com) I was able to obtain a yield stress of 7,400 psi @ 1200F, elastic modulus 23.2E6 psi.

Not being a metalurgist of expansion joint professional I am curious if specifying the design stresses calculated with MatPro would be unrealistic.

Does any one have experiences with this type of material application???

Thanks

 

[metengr]

robinchandy;
Go to the web site below and download the Technical Publication on Alloy 800H/800HT. This is a comprehensive technical paper and provides actual material property data on elastic modulus and low cycle fatigue strength among other important items.

I would contact several more expansion joint suppliers nad have them provide you with an expansion joint material recommendation and design to evaluate. Having the above paper, you can verify material property inputs, and ask good questions.

http://www.specialmetals.com/products/incoloyalloy800h&ht.htm

 

[metengr]

One other note to add... ASME SB 409 UNS 08810 solution treated condition has the following allowable stress values per ASME B&PV Code, Section II, Part D Table 1B

@ 1000 deg F 14 Ksi
@ 1200 deg F 7.4 Ksi

The above stresses are allowable stresses as determined by the requirements in ASME B&PV Code, Section II. At 1000 deg F, this material behaves time independent, meaning designing at or below this stress value will avoid failure from tensile overload, yield, creep deformation or stress rupture in service.

At 1200 deg F, time dependent properties come into play. In this case, the allowable stress is controlled by creep deformation (permanent deformation after so many hours in service). So, you need to remain at or below 7.4 Ksi in your design to assure remaining below 1% permanent deformation in 100,000 hours.

 

[nickelkid]

Thanks metengr. FYI, we are going to design for 1200F, limit maximum operating temperature to 1185F, normal operating will be 1050F.

The specialitymetal document was most helpfull.