Pipework MAWS based on ASME B31.3 1

[aadpilma]

Good Day,
Hi all, I'm new in this forum. I calculated pipework thickness (A-106 gr B) with MAWS = 20000 psi (100-500 F) based on B31.3 2004 edition. But our client raised question about MAWS number that we used, since they claimed material that they used was commisioned in 1988 so they used MAWS 15000 psi based on the ASME B31.3 (1980s edition)to calculate required thickness of pipework. The gap of thickness was quite big with two different MAWS. Yes, when we calculated with 15.000 psi resulted thicker req Thickness than 20.000 psi. So, is there any statement on ASME B31.3 stated that we can use MAWS based on the latest edition?. Or, should we use the 15.000 MAWS since the pipework was calculated based on the Code at commisioned date?. I tried to read the current edition of B31.3. But I could not find any clue about it.

Thanks for the answers
Regards
aadpilma

 

[Frank1344]

Hi,

First of all the facility is not new and ASME B31.3 doesn't apply to operational facilities.

Second, you need to use the same codes and standards those were used during the design of this facility and not the latest one.

I can't recall where I read this but I am positive as for a modification of a vessel built in 60's we went a long way to get a copy of ASME code 1965 or so.

For existing facilities take a look at the API-570 for piping and 510 for pressure vessels.

Hope this helps,
Frank

 

[aadpilma]

Hi frank,
Thanks for the asnwer. Ok, since you told me that ASME B31.3 could not be used in existing facilities, how do I determine pipe required/design thickness? Which could be the right codes and standards?

I have read API 571 but I still could not find the way to calculate pipe design thickness except by follow B31.3 rules.

Really appreciate your next respond
aadpilma

 

[ElSid1]

Look at ASME B31G to calculate the life left on the pipe.

 

[Frank1344]

aadpilma,
sorry as I confused you.
What I am trying to say is to use B31.3 with caution for existing facility. The formula for calculating the thickness is still as per B31.3 but the values have to conform to your case. Allowables, allowances,... may not be the same as for the new facility.

 

[aadpilma]

Oh, ok i get it. Thanks frank.
Really appreciate it. If someday you might recall where you read about uding the old codes for the old facilities, really appreciate if you send message or reply again to this thread frank. Meanwhile, I'll try to find it on my own.

Thanks again

 

[StevenHPerry]

I've often used the latest and greatest version of B31 when doing new piping work in an old facility, so long as the owner did not object.

B31 codes have generally grown less conservative and material properties have become more consistent. There is a cost advantage to using the new codes. In aadpilma's case, there could be a 25% reduction in pipe wall thickess. Support steel gets smaller. Loops shrink. Less weld metal and less weld time. Less PWHT.

You're buying new pipe manufactured to the current ASTM specification. There's nothing physically different between A106-B pipe bought today for use on a 1980 design code or a 2010 design code.

- Steve Perry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[aadpilma]

Yes, I got your point StevenHPerry in this case. What if I need the calculation to the old pipe (not for replacement purpose) for defining It's long term corrosion rate?
I am working on an RBI project right now, the diffrent thickness between 15000 psi amd 20000 psi really affecting probability of failure using our RBI software.

Regards
aadpilma