Post Weld Heat Treatment Criteria. 1

[Justinrahamut]

I have to install an expansion joint on the floating head of a vertical heat exchanger. The head thickness is 1" and the reinforcing pad thichness is 1", the thickness of the pipe nipple to be set into the head is 0.562".All material is carbon steel. My question is do i need to stress relieve this joint. There is two major schools of thought on this.

According to ASME Sect 8 there is no need to can some one giude me as to the interpretation of Table UCS-56 and also
UW-40F.

In the instance that I do need to stress relieve then I need to protect the convolutions of the bellows from the heat which is to hold at 1100 Deg F. The bellows is designed for 662 Deg F and there is only about 6" of pipe nipple separating the weld from the bellos material which is Monel 400.

Any Suggestions will be greatly appreciated.

Justin W. Rahamut,
Design Engineer,
Petrotrin,
Trinidad West Indies.

 

[rnd2]

Justinrahamut
Can you describe the welding procedure that is planned?

 

[Cockroach]

I'm not entirely sure of my understanding for your specific application. You are correct in noting no PWHT given wall thicknesses less than 3/4 inches. (Section IX, ASME Boiler and Pressure Vessel Code)

Therefore according to this code, which may not be the governing specification for your jurisdiction, the nipple/head joint need not be PWHT. However, the head/pad joint would need to be given a 1.0 inch thickness.

I would exercise caution and get the regulating authority for your weld inspection and certification to make the call. The head/pad is external to the pressure envelope which is beyond the code, but you would have a case for stress related issues at the support.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[avjJOE]

yoy must get the certifing authority to aprove your procedure. generaly speaking there should be a preheat of 100F and do not exceed 300F in welding should not require a stress relieveing cycle. Ie dime sized spot welds with cooling through completion.