ASME B16.5 / B16.47 ratings 1

[gr2vessels]

We have a case where our design pressure is 97.4 barg @ 70 deg C. MOC used is SA 105/ SA 350 LF2. As per ASME B 16.5 edition 2003, this falls under 600# class rating for sizes upto 24". For sizes larger than 24" we have to refer to B16.47 edition 1996, where 600# pressure rating limit is 97.4 barg @ 68 deg C only, so we have to increase the larger flanges rating to 900#. Also, ASME B16.47 states that pressure ratings are the same as B16.5 pressure ratings, but the 1996 edition refers to the 1996 edition of B16.5, not 2003! This conflict has been picked up by the ASME inspector who refused to allow the use of B16.5 - 2003 ratings for B16.47 - 1996.

Any ideas for the way out, in order to keep the logical 600# rating for the vessel?

Cheers,
gr2vessels

 

[metengr]

gr2vessels;
I reviewed my copy of ASME B16.47 -1996 Edition/1998 Addendum, and I could not find the words where

ASME B16.47 states that pressure ratings are the same as B16.5 pressure ratings, but the 1996 edition refers to the 1996 edition of B16.5, not 2003!

that refer back to ASME B16.5 in this document. Where is this located in B16.47? The scope of this standard covers flanges from 26 NPS up to NPS 60.

 

[gr2vessels]

My copy of B16.47 states in the Foreword, para 4, last sentence, that "Pressure-temperature ratings are in accordance with ANSI B16.5". We tried to convince the inspector that the reference to ANSI B 16.5, is actually the latest edition of ASME B 16.5 - 2003, including the revised ratings for Class 600#. Didn't work.
Also, well noted, this standard covers indeed, flanges from 26 NPS upto 60 NPS.

Do we have to drop the P-T to the 1996 level or up-rate to 900# (including the associated cost, then piping, P&ID's...).

Cheers,

gr2vessels

 

[CodeRef]

This is a stretch and may be trivial and use when all else fails. I don't know what else you can do...

In the B16 standards the tabulated pressures are gage pressures and depending on installation site and reference to sea level not all gage pressure are the same in absolute terms.

Make the argument (if it will work) in terms of measuring differential pressure to atmospheric. I don't know if I could reasonably argue this point, but given your situation, it might be worth the discussion if it will benefit your situation.

I know of one interpretation where the question was asked in a way that is opposite of your situation, but in terms of pressure, the reply used the terminology of coincident pressure in lieu of gage pressure.

B31-97-029

Question: For subsea production systems where ASME B31.3 is required, can the internal design gage pressure, P, in paras. 304.1.1 and 304.1.2 be interpreted as coincident internal design gage pressure minus external gage pressure?

Reply: Yes; however, when the coincident external gage pressure is greater than the internal gage pressure, the design shall be in accordance with para. 304.1.3.

Good luck!

 

[JLSeagull]

Process and piping often consider the maximum design temperature - then set the design pressure based upon the more liberal material groups. Frequently the instrumentation is available in Type 316 stainless steel, or relief valve flanges are set by the fire case temperature. Thus we require out-of-spec flanges to interface our components. One solution is to change the system design pressure. This however needs to be done during the first 10% of the design, not the last 10% of construction.

 

[CodeRef]

How about remove the markings, and develop your own pressure and temperature rating (proprietary) for these flanges in accordance with the following Code Interpretations?

Interpretation: I-86-27

Question: For Section I construction, is proof testing permitted for the design of flanges other than those covered by ANSI standards listed in PG-42?

Reply: Yes, or as an alternative, the rules of Section VIII, Division 1, Appendix 2, as permitted by the Preamble, may be used.

Interpretation: I-83-07

Question: May forged steel, integral-type bolting flanges larger than those covered in the referenced standard ANSI B16.5, be designed according to Appendix 2 of Section VIII, Division 1, for applications to Section I?

Reply: Forged steel integral-type bolting flanges larger than those covered in the referenced standard ANSI B16.5 may be designed according to Section VIII, Division 1, Appendix 2, provided the material selection and fabrication comply with the requirements of Section I.



There are three kinds of people in this world; those who can count and those who can't.

 

[gr2vessels]

Thanks gents,

Seems there is some light at the end of the tunnel, good suggestion the reference to Add. 2006, also I still could try the 68 deg C in lieu of 70 deg C. I don't think I could "use" other than standard flanges, the inspector won't buy it. Also, my story might just prompt ASME board to update quickly the B16.47, who knows.

Cheers,

gr2vessels

 

[gr2vessels]

Gents,
I had to bring back this issue, since I received a reply from ASME's Mr. D'Urso (refer below):

Dear Sir,

With regard to your inquiry regarding the difference in ratings between B16.5 and B16.47, please note that they are intended to be identical. Due to a delay in the publication, the latest edition of B16.47 where these ratings have been updated has not yet been issued. The ratings in B16.47 should be the same as the 2003 version of B16.5.

Regards,


Umberto D'Urso
Project Engineering Administrator
ASME
Three Park Avenue
New York, NY 10016
Phone: (212) 591-8535
Fax: (212) 591-8501
E-Mail: dursou@asme.org

Unfortunaltlly, the inspector is stubborn and an e-mail with a name printed on is not going to replace the written code.
Metengr, should I tell the inspector (and the fabricator) they must accept the above e-mail, as formal advice for the incomming revision of B16.47?

 

[deanc]

It would be a mistake to tell anyone "they must accept the email". That will be sure to set a block and a time delay.

Suggest you write a non-conformance per your QC system and submit the email as part of your resolution. Then it could be kicked up the ladder if need be.

 

[DFGD]

Try to use the ASME B&PVC Section VIII Div. 1 Appendix 2 there you can find the rules to design integral non metal to metal contact flanges.

Best Regards,

DFGD

 

[gr2vessels]

Thanks gents,

The inspection agency is LLoyds and they released a project statement (under tremenduous pressure from us) that under no circumstances they will accept ASME board's advice, as a replacement for the current/valid ASME B16.47 - 1996 issue, unless the board will post a formal statement on their web site, similar as advised by Umberto D'Urso in his e-mail (refer above). Since that's not going to happen in a hurry, we gave up and accepted the 900# rating, including the revision of all the related documentation.

Thanks again for the support,

gr2vessels