under what situation, the creep analysis is mandatory?

[YuJie_PV]

hi, all,

a pressure vessel is designed to ASME BPVC VIII-1 or VIII-2, under what situation shall the creep analysis be mandatory?
At temperatures in the range where creep and stress rupture strength govern the allowable stress? if yes, i am confused why creep analysis is required while allowable stress as given in II-D has already considered creep.

if i am on behalf of the owner, and request the creep analysis to the manufacturer, which paragraph of ASME shall i cite to put forward to them if they defy my request for creep analysis?

Thanks in advance.

 

[Maslov]

You should be concerned for creep at temps around 50% the melting point of the material.

However, as you have pointed out, allowable stress values already account for creep at these temps, and thus there is no code requirement for analysis for Div. 1 vessels. Creep analysis is only useful if you want to extend vessel life or use a higher allowable value (usually by going to Div. 2).

If the manufacturer doesn't want to do creep analysis, then they must refuse to manufacture your vessel. If the owner (or owner rep) deems it mandatory, then it is mandatory.

 

[ShabsRBI]

Creep is time dependent failure mode, which will depend upon high temperature and applied stress. As per API - 571 the recommended temperature above which creep failure becomes a concern are as below
Carbon Steel ( UTS<60 ksi) Temperature limit is 343 Deg C
Carbon Steel ( UTS>60 ksi) Temperature limit is 371 Deg C
If the operating temperature of pressure vessel is above the specified limit then it is advisable to run a creep analysis. If the Operating temperature is below the creep range then creep does not cause a concern.

 

[IdanPV]

Refer to this threads, it might be helpful:

Material in creep range - Boiler and Pressure Vessel engineering

Hello everyone, I am checking a calculation of a pressure vessel, where the operating temperature is 480 C and design temperature is 510 C for SA-387 gr.11 cl.1. In this case In accordance with ASME code the design temperature for this material is in creep range, so in my opinion design...

www.eng-tips.com

Combined Creep and Fatigue Calculation in ASME BPVC - Boiler and Pressure Vessel engineering

Hello, Normally we are working against the PED in Europe but we have came across a problem which PED or EN13445 cant handle so i was trying to find a solution in ASME VIII. But i dont have much knownledge in ASME BPVC. And from what i can find for my problem is the same in ASME and PED. We have...

www.eng-tips.com

 

[TGS4]

I need to ask the OP - what do you actually mean by "creep analysis"? What's the purpose of this request?