Grandfathered MDMT

[kevlar49]

Is there grandfathering of MDMT (Minimum Design Metal Temperature allowed anywhere in ASME ? if so, could you tell me which para. to read.

thanks

 

[metengr]

kevlar49;
I don't really understand the context of your question. MDMT is a unique value that is selected during the design phase of a pressure retaining item.

 

[kevlar49]

Former Major oil company guidelines allowed grandfathering before ASME rules came out. Is there something in ASME or other codes for grandfathering similar to tanks api 653?

 

[panduru]

OP: What is grandfathering in the context of API 653 Tanks, pl ?

 

[JoeTank]

API-510 may assist you in the evaluation of MDMT for existing vessels.

What are you ntrying to do and why would you even think that existing vessels had to be upgraded to current rules?

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[stanweld]

kevlar49,
Do you intend to rerate an ASME VIII, Div.1 vessel using the 3.5 design safety factor? If so refer to RD-3010 of the NBIC.

 

[kevlar49]

Steve Braune,

thanks for the tip. It is not really an upgrade, but a rule change since previously, we had used an Exxon system of assigning minimum temperatures prior to the introduction of UCS-66.

Stanweld,

Not trying to rerate, but thanks for the info.

Pandru,
regarding api 653, was referring to figure 5-1, step 8. Lowest temperature at which a tank was full.

All, I think that I may have found something in API 579, that suits my needs.

Another question:
In my revision of the minimum temperature during hydrotest, I have been assigning temperatures by the following methodology:

Take the safe temperature (as determined by either ASME IX UCS-66 or FFS) and add 30 F for thk >2" or 10F for thk <=2" (as suggested by api 510). However, some of the hydrotest temperatures per ASME IX UCS-66 are as high as 120F and are greater than 2", so I'd have to assign hydrotest temperatures as high as 150F. I have noticed that hydrotest temperatures need not be greater than 120F, but besides personnell protection, are there other reasons that it would be acceptable to limit hydrotest temperature to 120F vs. the 120+30F assignment?