ASME Section VIII, Pre 1970

[mgortel]

I have a pressure vessel built in 1970 and need to determine if it is ok at a MDMT of -20F.

I have the U-1A Form...but it does not indicate a MDMT.

The U-1A form also does not indicate that impact testing was performed.

The material is as follows:
Heads SA-455-B, 0.525 inches thick
Shell SA-515-70, 0.9375 inches thick

Per current ASME Section VIII neither material can be exempted from impact testing at these thicknesses per UG-20f or UCS-66.

HOWEVER, I realize that since the vessel was built in 1970, the original code version it was built to applies.

I believe there was no detail sections tocover impact testing back then...I think it was just a simple -20F min temp and thickness less than 4" and you were ok to operate as low as -20F......but, I was hoping someone would have a copy of the 1968 (I believe that was the most recent before 1970) version of the code and could confirm that impact testing would not have been required for the heads or shell. Even better....a copy of the code sections that confirm this would be really great!

I cannot find where to buy an old code online.....so I am kinda stuck here....thanks for your help guys!

Mike

 

[metengr]

My suggestion is to use ASME FFS-1, (API 579). Look at risk of brittle fracture. I would have serious concerns with SA 515 Grade 70, especially since this material could have been supplied as coarse grained for elevated temperature service.

 

[mgortel]

Thank you for the response.....kind of confirms my fears as well.

Here is maybe a crazy thought...I have never heard of this being done...but....

Do you know if it is possible...or allowable....to cut out a section of the shell and have it impact tested? Then repair the vessel per API-579? I do NOT think this would be practical for the heads though....or would it?

Thanks!
Mike

 

[stanweld]

In 1970 the lowest opeating or design temp was -20F and there would have been no requirement for impact testing. Remember that the design safety factor was 4.0 for temp up to 650F back then rather than the 3.5 today.

Are you considering rerating? If so you may not be able to unless you choose a MDMT such that no impact testing is required. Do you really intend to fully pressurize at -20F and, if you are, think again!

 

[mgortel]

NOPE....not gonna do it....not based on what I came up with based on current ASME Section VIII, Div.1....coupled with your responses.....thank you guys!

 

[jtseng123]

mgortel,
Full pressurized at low ambient temperature is possible during shut down. You shall check with your process engineer.