ASME 16.5 question?

[AJerry]

We are looking for a replacement PSV and an Engineering Firm that we used has given me a spec. and the flanges are rated as per B16.5 -81, I can not find -81 in ASME B16.5, can someone point me in the right direction?
Thanks

 

[jte]

AJerry-

You'll find the -81 on the cover and title page of the 1981 edition of B16.5 Your firm is apparently not willing to buy a copy of that standard which is less than 25 years old. Kinda makes you wonder about their commitment to staying current. The next question, naturally, is "So is it different?" Yes, it is. Not all ratings have changed, but many have. I would "encourage" them to spring the dollars loose to buy a new edition (I'll bet they can get a '96 edition cheap on Ebay!). It'll be passed on to you in the quote, but at least they'll have a recent edition. Until the 2007 edition gets released...

jt

 

[JLSeagull]

My copy says ASME B16.5-2003 (Revision of ASME B16.5-1996).

 

[NozzleTwister]

AJerry,

jte is correct in that they are referring to the 1981 edition of B16.5.

I don't agree with his assesment that it because they are too cheap to buy a current edition.

I would guess that since this is a replacement valve, the 1981 edition is the code of record for the original installation and they want to maintain the same pressure ratings they now have.

Many ratings have changed over the years, especially with alloy and stainless materials in the higher temperature range, but like jte said, a lot have not.

My understanding is that the specification is asking the PSV manufacturer to certify the valve to no less than the ratings of B16.5-81 for your material and flange class.

NozzleTwister
Houston, Texas

 

[JLSeagull]

When we design a plant we use the version of various codes and standards that apply at the time of the contract execution. On a large project several codes and standards will be updated between starting the design and starting the plant. If I start a plant today the National Electrical Code applied is NFPA 70 2005. The inspector cannot whip out the 2008 version to see if my design qualifies.

This applies to product designs too. The FAA publishes design regulations for aircraft. If the Cessna 172 or other aircraft was certified by an earlier set of regulations they do not have to redesign the aircraft when the criteria changes.

If the valve casting pattern for a model was made in 1975 then the ASME codes of 1975 would have applied. The manufacturers may not modify that model for many years. If my specification states the design pressure and temperature and includes a flange class based upon ASME B16.5 I would expect the seller to furnish a valve compliant with the current version.

I have done plant modification work and found adjacent Class 150 valves in applications that now require Class 300. Any new flange is Class 300 but existing equipment not affected by the modification remains unchanged. The owner is typically advised in such situations. If appropriate the scope could be expanded to bring everything into compliance with the new code requirements. However it is rare to expand the scope of work because of insignificant code changes.

 

[AJerry]

Thanks, we do have an ASME B16.5 2003, but the firm that built this in 1996 stated the 1981 edition I guess.

 

[NozzleTwister]

AJerry,

From what you have just said, it appears that the spec. sheet used by your engineering contractor was incorrect and/or obsolete. I see this all the time. Someone will use a spec sheet from a previous project and never review it for correctness or update it to make it current.

Unless there was an addendum, and I can't remember ever seeing an addendum to B16.5, the recent issue dates (from the B16.5 Forward) are:

ANSI B16.5-1977
ANSI B16.5-1984
ASME / ANSI B15.5-1988
ASME B16.5-1996
ASME B16.5-2003


NozzleTwister
Houston, Texas