PWHT Maximum Material Thickness ASME VIII-1 3

[CodeRef]

Am I correct to make the assumption that the intent of UCS-56(d)(1) through (5) term "maximum material thickness"is intended to reference the "governing material thickness" as defined in UW-40(f)(1) through (6)?


FAQ731-376 A question properly stated is a question half solved.

 

[metengr]

Yes, your assumption is valid.

 

[CodeRef]

Thanks Metengr, this question came up to me, and I needed reassurance....perhaps the Code Committee for VIII-1 need to speak in consistent terms.

FAQ731-376 A question properly stated is a question half solved.

 

[metengr]

CodeRef;
Keep in mind that the PWHT requirements and terminology referenced in Subsection C, Part UCS-56 applies only to CS and low alloy materials, whereas, the information in Subsection B Part PW applies to any fusion welded construction, if applicable, and so local PWHT or furnace PWHT may be performed, and different terminology is used.

 

[CodeRef]

Yes, I understand, applicable to Subsection B, Part UW fabrication, however the terminology for PWHT found in some UCS-56 paragraphs are not consistent with the UCS-56 Tables. The tables are using the appropriate term "nominal thickness" whereas the paragraph is using the term "maximum thickness"

Other Subsection C material classes (Paragraphs and Tables) UHT-56, UNF-56, and UHA-32 use the "nominal thickness" term which I believe is appropriate.

FAQ731-376 A question properly stated is a question half solved.

 

[jamesl]

I disagree.

Thickness in UCS-56(d)(1) through (5) is the maximum head and shell plate thickness, which is different from the weld thickness defined in UW-40(f). UCS-56(d) is used to control thermal gradient during heating and cooling. UW-40(f) is for weld depth used to determin if a weld is to be heat treated.

For example, if a 2" thick shell can welded to a 1 1/2" thick shell can. You use 1 1/2" per UW-40(f) to decide PWHT is required; you will use 2" to calculate heating and cooling rate per UCS-56(d).

 

[CodeRef]

I could not find any interpretations other than this one regarding heating and cooling rates....

Interpretation: VIII-1-89-186
Subject: Section VIII, Division 1 (1989 Edition), Nominal Thickness Requirements to Comply with PWHT Procedures
Date Issued: April 3, 1990
File: BC90-305
Question: In using the attachment detail of Fig. UW-13.2 sketch (d) in Section VIII, Division 1, can the weld joint thickness of a shell to tubesheet attachment be considered the maximum metal thickness in determining the rate of heating and cooling for postweld heat treatment?
Reply: No. See UW-40(f)(5)(c).

So then, jamesl, is this interpretation wrong? or did the committee not answer the question?



FAQ731-376 A question properly stated is a question half solved.

 

[metengr]

There is no disagreement. UW-40 provides requirements for PWHT ramping rates based on "thickness" for PWHT. UCS-56 provides specific PWHT requirements based on nominal thickness, which could be maximum thickness, if the rest of the shell is going along for the ride during PWHT.

 

[CodeRef]

Okay, so then, metengr you are saying that USC-56(d)is stating "maximum nominal material thickness" all based upon welded joint governing thicknesses and not necessarily the maximum base material thickness present on the item, correct?

FAQ731-376 A question properly stated is a question half solved.

 

[metengr]

This can be difficult trying to discuss Code requirements/interpretation using a forum like this. I apologize, let me try this again;

Here is what UCS-56 (d) states before going into specific PWHT ramp requirements for controlling thickness of the shell, head, etc

(d) The operation of postweld heat treatment shall be
carried out by one of the procedures given in UW-40 in
accordance with the following requirements:

The requirements in UCS-56 (d) 1-5 pertain to PWHT ramp rates based on what thickness is being exposed to PWHT. The maximum or controlling thickness could be nominal thickness as described in UW-40 or by the thickest portion of the shell undergoing PWHT.

(f ) The term nominal thickness as used in Tables
UCS-56, UCS-56.1, UHA-32, and UHT-56, is the thickness
of the welded joint as defined below. For pressure
vessels or parts of pressure vessels being postweld heat
treated in a furnace charge, it is the greatest weld thickness in any vessel or vessel part which has not previously been postweld heat treated.

 

[jamesl]

CodeRef,

Which edition of the code are you using? The wording in UCS-56(d) is now "the maximum metal thickness of the shell or head plate in inches", not "nominal thickness". If it is nominal thickness, I would agree that it refers to UW-40(f).

 

[CodeRef]

jamesl, lets use the current edition, as it is applicable now. I tried to follow the history of these paragraphs looking for answers and was puzzled from the beginning. The answer to the interpretation I quoted was unexpected to me as I was thinking as you are, "maximum metal thickness".
I think, as metengr has just explained, is that the maximum metal thickness is derived from UW-40(f) which considers the joint configuration as well as base material thickness and should be applied to entire vessel or part of a vessel being post weld heat treated in a furnace charge.
Can it be that significant? probably not, but, I think as you do, the terms should be consistent. Just in this thread alone, there is disagreement, who else needs clarification?

I think the term in UCS-56(d) paragraphs should be "nominal thickness" or at least "maximum nominal thickness" as defined in UW-40(f) for any item in a furnace charge.

FAQ731-376 A question properly stated is a question half solved.

 

[jamesl]

CodeRef,

The code uses "the maximum metal thickness of the shell or head plate", not just "maximum metal thickness". Welds in nozzles thicker than shell or head plates will not be considered here. It is different from UW-40(f).

 

[CodeRef]

jamesl, then I am back to my original question, is the UCS-56(d)(1) through (5) term "maximum metal thickness" intended to reference the "governing nominal thickness" as defined in UW-40(f)(1) through (6)?
metengr says yes..you say no

FAQ731-376 A question properly stated is a question half solved.

 

[CodeRef]

Okay, so, metengr agrees with you per

The maximum or controlling thickness could be nominal thickness as described in UW-40 or by the thickest portion of the shell undergoing PWHT.

Thickest portion meaning maximum metal thickness of the shell or head.

FAQ731-376 A question properly stated is a question half solved.