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What is basis for establishing pressure ratings of ASME B16.5 standard flanges?
13

What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

(OP)
Hello Gentlemen,

According to the (B16.5) 1-21 interpretation, ratings in B16.5 are a result of theoretical analysis with due consideration for experience in application. It did not mention anything about flange ratings being established by 'proof tests' or 'bursting them and adding factor of safety to the burst pressure'. First, place to look for answer is B16.5 book. Only instance where B16.5 (Ed. 2017) mentions about method used for establishing pressure temperature ratings is In Non-mandatory appendix-B. But it also stops at 'ceiling pressure'. Does not mention how ceiling pressures are determined.

What is exactly the basis for establishing pressure ratings of B16.5 standard flanges?

Thank you in advance for the replies.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

Well that's because flanges don't burst. They just separate and start to leak as you exceed the bolts force holding it closed.

In extremis for say axial force they might fail mechanically, but I would guess that normally the pipe would go first.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

(OP)
LittleInch,
thank you for the reply. It is a notion around and there are couple of sources on internet which mention that B16.5 flanges pressure ratings are established by proof testing or burst testing of flanges. So, if it isn't correct , how are pressure ratings established? Apparently, it does not seem only theoretical stuff. Any ASME code book or publication reference to get a complete answer?

Thank you ones again!

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

Well you could ask subcommittee C (previously no 3) who according to the foreword of B16.9 are responsible for setting the ratings.

https://cstools.asme.org/csconnect/CommitteePages....

on the LHS there is a history button. There is no mention of actual mechanical testing but lots of mention of experience.

1973 seems to be pivotal ( see page 7 of the note)

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

There is nothing currently published. There is a group in B16 that is working on a written criteria. Flanges leak, and don't burst.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

Now, two of you have said flanges leak but don't burst.
However, when you do Appendix 2 flanges, there is a different criteria for strength than for leakage. So why the strength criteria there if the leakage is the only concern?

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

Appendix 2 is for sizing of flanges that are generally understood to be sufficiently robust to resist leakage. But you are correct that there is no leakage criteria. The ASME Code Committee responsible for those flange rules have been working on it since 2000...

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

(OP)
Thank you, gentlemen. For your responses and especially, reference to B16 subcommittee C history.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

(OP)
Thank you for the pivotal reference paper BJI.

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

That paper is a golden nugget worth 10^6 times its weight in LPS. Well done @BJI!

RE: What is basis for establishing pressure ratings of ASME B16.5 standard flanges?

The paper linked to BJI is a great summary of the history of B16 standard flanges. One issue with the standard B16 flanges is the flanges faces are much thicker than those of "compact flanges " as calculated by sect VIII div I ( or div II via finite element analysis). This leads to excessive thermal stresses and fatigue damage for larger high pressure flages in thermal cycling service, espescially if the weld neck is very short which then exposes the weld interface to unacceptable fatigue loads. More than a 50% reduction in flange mass can be had with the compact flanges and also this leads to an improved fatigue life in thermal cycling service.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

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