Pressure vessels settlement criteria

[Argoil]

Dear Experts

I am a materials engineer currently working as a tank inspector in a refinery. Right now i'm working with the settlement analysis of pressure vessels, but having trouble in finding a good acceptance and rejection criteria about it. I am working with ASME VIII and API 510 but they don't seem to have any. I would like to know if anybody has a reference where I could study the settlement evaluation of tanks and pressure vessels.

Thank you

 

[r13]

I don't think there is one fit all criterion, instead you need to evaluate your equipment's tolerance on settlement and rotation, so not to impair its operation. Also, this thread may help. Link

 

[HTURKAK]

..... i'm working with the settlement analysis of pressure vessels, but having trouble in finding a good acceptance and rejection criteria about it. I am working with ASME VIII and API 510 but they don't seem to have any...

Dear Argoil (Petroleum),

Yes...you are right ..Both API and ASME codes are silent in this regard.
I think , a reasonable amount of uniform settlement should be acceptable. In order to investigate the reasonable settlement amount, during design studies, settlement analysis should be performed and the predicted total settlement should not overstress the nozzles and connected piping, and differential settlement should comply the dimensional requiremnts , (pls look verticality requirements for floating roof tanks etc) and should not cause ovalisation of the tank and should not be detrimental for the Shell and bottom plates. The safety and integrity of the storage tank and pressure vessel shall be provided to all costs .In this regard, the options on the table are , changing the type of foundation (piled found...), soil improvement, provisions for connected piping (changing the pipe support locations, pipe route etc...

Regarding storage tanks, yo may look to Appendix B of API 653 (EVALUATION OF TANK BOTTOM SETTLEMENT) in order to determine the acceptable level of out of plane settlement.

Finally, in my opinion, 50 mm uniform settlement should be acceptable if is not detrimental to piping and vessel.

 

[MMM]

Yes the value of the settlement is not define. as it is not acceptable but the API mention to do settlement measurement every 5 years ans some aspect 7 years, the problem is causing oval of the circularity of the tank and it will be harmful for the floating roof tank but in case of fixed roof it will be some irregularity which will be check by fitness for service API 579. So if you have a normal soil condition you design as the principal of the bearing capacity.it is presented in onshore calculation book.
you can make back analysis but it is complicated and no gain from it.