ASME Sec VIII Div 1 to API 620 1

[curlyjackme]

If an ASME vessel is going to be re-rated as an API 620 tank, can the ASME calculations be used to verify the thickness and stability of the tank? Or does a new set of API 620 calculations for the tank need to be performed? Any opions and why.


Just for information a client has two ASME vessels that were fabricated for a project and it was shut down, now they need tanks for a new project and want to utilize these vessels instead of having new tanks fabricated.

 

[JohnGP]

I'm struggling to see why the ASME vessel needs to be rerated to API 620. Normally design to an ASME vessel code would be over the top for a storage tank, but if already designed per ASME then stay with it.

There is nowhere in the ASME codes that I have dealt with that says you can't operate an ASME vessel at a lower operating pressure than it was designed for.

Of course if the tank design pressure exceeds the vessels MAWP, then you would obviously need to perform a new set of calculations.

That's my opinion anyway.
Cheers,
John

 

[curlyjackme]

The client wants a API 620 tank instead of the ASME vessel due to in house inspection requirements. The new design will be atmospheric. Also the vessel/tank has 2:1 heads therefore API 620 and not 650.

 

[JStephen]

I would assume new calculations were required, as the same methodology is not used in both standards. For example, in times past, I found the API-620 design to be overly conservative as applied to the knuckle region- heads that would meet ASME wouldn't meet API-620 design- so don't just assume that the re-rate is feasible until you try.

ASME clearly states that tanks with pressure less than 15 psi are exempt, but may still be stamped with the ASME symbol if built in conformance to the code.

 

[curlyjackme]

Thanks. That is what I was concerned about.