Re-rating PV... which allow. Stress??? 1

[Heyner]

Hi Everyone!

I'm re-rating a vessel constructed by 1985 and I want to know if the allowable stresses per A515-70 and A516-70 are to be considered as shown on today's section II-D or as shown on that year one... there is a substantial difference there.(20ksi or 17.5ksi?)

One more question, about the same: what's the criteria for increasing the allowable stress in a newer code edition??

Any additional tip for this labour will be appreciatte!!!

Thanks a lot!!!!!!

 

[dig1]

Hi Heyner,

Look in NBIC RC-3022 and RC-3024, and RD-3000.

It is permitted to use the higher allowable provided these requirements are met and your local jurisdiction concurs.

Good Luck.

 

[jte]

Heyner-

As dig1 pointed out, the local jurisdiction must concur. In California, the State pressure vessel folks "...will not entertain..." any proposals to rerate a vessel using a different design factor than it was originally built to.

The reasoning behind the change in design factor is essentially that design and analysis, material production, fabrication, and inspection have become better over the years. Basically the same as the reasoning when the factor changed from 5 to 4. Also, the ASME needs to stay competetive on an international basis, and the design factor of 4 was not competetive. The new Division 2 (expect to see it in '04 or '05) will use a design factor of 2.4 to be competetive with the European codes. There are lots of technical papers published by the ASME Pressure Vessels and Piping conference

http://members.asme.org/catalog/CategoryView.cfm?Category=CP&SubCategory=PVP

which provide more detailed explainations for the Div. 1 change and the upcoming Div. 2 change. For what its worth, Div. 2 will be entirely re-written, not just have its allowable stresses and a few related things changed.

jt

 

[Heyner]

Hi, it's me again!

Now I know I have to use the 1985 Allowable stress in this case. Can somebody help me with this data?

Material: A515-70 & A516-70
Design Temp. 150°F
Allow. Stress as per Section II-D ASME BPV code for year 1985 (I suppose it is 1983 ed.)

Or.. Where can I find it???

Thanks a lot!!!!

Heyner.

 

[LSThill]

I hope I did hit the right Data Base

A516-70 = 17500@150F
A515-70 = 17500@150F

Leonard@thill.biz

http://www.thill.biz

 

[Heyner]

What do you mean, lsThill?

You are not sure about that numbers? Where did you take them from?

 

[jte]

Heyner-

The SA515 and SA516 grade 70 materials have an allowable tensile stress of 17.5 ksi (that's 70/4) up to 650°F when you are using a version of Div. 1 which uses a design factor of 4 against UTS (or 2/3 yield, but that doesn't govern your situation). So unless you have a seriously old vessel (you don't), or a post 1999 vessel (you don't), the allowable tensile stress at 150°F is 17,500 psi.

I might have a 1982 edition of the Code at home; if you really need a copy of the allowable stresses from that era, let me know your email and I'll look for it and scan it and email it to you.

jt

 

[Heyner]

Hi Jte!

Thanks a lot for your explanation... YES, I'll really appreciatte if you can send the page showing allowable stress from that era. My e-mail address:

heyner_garcia@hotmail.com

Thanks in advance...

 

[MJCronin]

To all,

After reading through all of this.... Heyner asking basic questions involving fudamental underatnding of ASME Setion VIII rules regulations and methods of doing business

Does anyone really want to stand around pressure vessels (I must assume that they are used)that Heyner has rerated ?

Heyner, do you have an MBA as your boss ?

MJC

 

[Heyner]

MJCronin:

Hi. Please don't be cruel. For real, this is the first time I am attemping to understand this topic (rerating), so don't worry, nobody is in danger yet!

What's an MBA??

Regarding my boss, he says ASME has a round bussiness in changing continuosly the ASME BPV Code, he says:

"Suppose I have a plate from years ago, well stored, in good conditions. You are telling me I have to use the Allowable stresses shown on an old edition of code because that´s the edition to be applied to my plates? I don't think so. Quality of material have not been improved since materials standards have not changed..."

It's a hard discussion I can't fight...

What do you (all) think?

 

[jte]

Heyner-

The stress pages are on the way (if anyone else wants copies, I'll ask Heyner to forward them to you!). If you had SA516-70 plates stored around with the MTR's, you could use them now to build a vessel to the new Div. 1 allowables. What's missing from your boss's "understanding" is that the remaining issues - design, fabrication, and inspection have gotten better over the years. This is probably the same boss who would tell you to get out of his office if you were to try to discuss issues regarding fatigue. "There's no such thing as tired steel!"

As far as his "understanding" of the code continuously changing, ask him why the other laws governing his life are continuously changing - from tax law to criminal law to traffic laws...

jt

 

[QAScott]

jte,

I was reading your reply above. You stated "In California,the State pressure vessel folks ...will not entertain... any proposals to rerate a vessel using a different design factor than it was originally built to." Do you know why this it true? I'm from Ohio, and it is permissible to rerate using a later ED and Add of the original code of construction which permits higher allowable stress values for the material than was used in the original construction. I must be in compliance with NBIC interpretion 98-14 and note this interpretion on the Form R-2. I have been told that California dose not permit the use of NBIC interpretions, is this why it is not permissible?

Thank You,

QAScott

 

[jte]

QAScott-

I deal with the California DIR-DOSH Pressure Vessel Unit (PVU) often enough to be on a first name basis with them. Having said that, I will not presume to fully understand their intentions. California is kind of a wierd state (I realize this is a shock to many of you!). State law mandates the use of NBIC '92:

http://www.dir.ca.gov/Title8/6857.html

part (d)(1). Later editions may be used on a case-by-case basis with the prior negotiated approval of the PVU. For what its worth, the PVU folks would like to use the latest edition of the NBIC, but they cannot change the law, and industry hasn't made a big stink about it. NBIC interpretations are used to support positions by both industry and the PVU.

If you have any specific questions or situations you would like to discuss, I'd suggest you contact the Oakland office:

http://www.dir.ca.gov/DOSH/pressure.html

jt