ASME Code Case 2148 - Nozzles 1

[reesh]

I'm currently dealing with a Sect VIII Div. 1 vessel that has 2" and 1.5" nozzles which fall under this Code Case. They are made from SA-479 316L and their wall thicknesses are less than their NPS Sch 40 counterparts (they are close to the Sch 5 thicknesses). The nozzles were not manufactured using the "ring method" that the Code Case suggests.

I was hoping to perform a stress analysis on the nozzles to justify them, but I need a paragraph from Div. 1 that allows me to do so. I seem to remember that there is a clause which allows methods that are "as safe as intended by the Code", but I could be remembering this from Sect. III.

Can anyone help? Or if this doesn't seem like the right way to justify them, could you suggest a different route?

Thanks!

 

[TGS4]

U-2(g) perhaps?

 

[reesh]

Thanks! I think that may be it.

I've been looking for over an hour for that. 1000 yard stare I guess.

 

[JoeTank]

The Code also states that "engineering judgements" may not be used as a basis for not following the code rules. I don't know your situation, but you cannot engineer your way out of a Code violation either.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[deanc]

If I am reading this right-you bored bar stock for a nozzle?

If so you are entirely outside the Code Case and there is no way this is acceptable.

Reread the Code Case and UG-14,UG-45.

 

[CodeRef]

ASME VIII Div 1 does not allow nozzles made from bar stock greater than NPS 4, or if nozzle nominal wall thickness is less than that for standard wall pipe, or the design hoop tension stress is greater than 50% of the allowable stress value, if any of the cases above are not met, the material shall be formed into a ring.

As Steve above stated, if rules exist in the Code for a certain design, the rule cannot be superceded by U-2(g).

Just as you cannot run a proof test to prove a design when rules are provided in the Code for that design.

At a minimum, your nozzle thickness shall not be less than standard wall pipe of the same diameter.

 

[reesh]

U-1(a)(3) says that you can't use engineering judgement to supercede mandatory requirements or specific prohibitions of the Code.

Is a Code Case considered a mandatory requirement, or is it advice from the Committee on recommended practice, but not necessarily madatory?

Just curious. For the record, we're not the manufacturer, we're performing an analysis on a vessel that was already built by a client of ours, so that it can be registered for a CRN in Ontario. We weren't the designer.

 

[CodeRef]

The Foreword of the Code addresses the use of Code Cases, stating: "Manufacturer's and users of components are cautioned against making use of revisions and Cases that are less restrictive than former requirements, without having the assurance that they have been accepted by the proper authorities in the jurisdiction where the component is to be installed." Not all jurisdictions/provinces automatically accept Code Cases. Some jurrisdictions/provinces are opposed to certain Code Cases. The jurisdiction/province of installation will need to be contacted to answer your question.
As a side note: The 05 Addenda to VIII Div 1 is perhaps going to put this issue to rest by adding a new paragraph UG-14(b) explicitly prohibiting the use of rod and bar for certain applications, while allowing its use for small diameter hollow parts consistent with the ASTM/ASME material specifications for forgings and fittings.
Contact an AIA for more information.

 

[deanc]

You will have fun in Canada and they may not accept this design. Suggest you hire a French speaking,Canadian PE to help you. Really! There are several very capable people who do this. It is money well spent.

 

[reesh]

Actually, that's exactly what I am (except the Frech part) and the service I am providing.

The TSSA has pulled this Code Case out, which they haven't before, and are refusing to register the design. I've never had this problem before.

I'm just trying to get some ammunition to go back to them with, though it looks like there isn't much.