Manhole ASME VIII Div. 1 - PWHT - requirement 1

[DesignerKPB]

We are installing a new manhole in an old vessel made with ASTM A516 Gr.60 material. The detail of the weld is according to ASME III Div.1 figure UW 16(e) and it is necessary to add a separate reinforcement, this plate will be welded to the manhole and also to the vessel shell with a full penetration groove weld. The thickness are: t = 1 ¼”, tn = 1”, tc = 1/8” and te = 1”. According to UCS 56 is necessary to perform PWHT if the thickness is equal or greater then 1 ½”.
When checking if it will necessary to perform a PWHT a doubt has raised up, which thickness should be considered as nominal?
We understood that is the greater among t, tn, tc and te; but another guy thinks that it should be t + te. If we are right according to the paragraph UW 40 (f) (5) (d) it won’t be necessary the PWHT.
Otherwise the sum t + te is equal to 2 ¼”, and it will be necessary to perform the PWHT.
We also understand that the PWHT is only for stress relieving and not for eliminating hydrogen embrittlement.
Could anybody analyze and give us a hint?

Thanks beforehand.

 

[Estassoc]

If the maximum weld thickness is analyze as shown below,
then IMO the connection is exempted from PWHT based on
UW-40(f)(5)(a), keywords "2 adjacent butt-welded parts":

1. Weld size, nozzle (tn) to shell (t) 1-1/4 in.
2. Weld size, repad (te) to shell (t) 1 in.

Maximum weld size (based on 2 parts) 1-1/4 in.

The weld size (t + te) involves 3 butt-welded parts
and is contrary to the *keywords* cited above.

IMO, the weld between the nozzle and the shell is
considered as an integral part of the shell when
determining the weld thickness of the repad to the
shell. See UCS-66 and Fig. UCS-66.3 for a similar
analogy in determining MDMT for welded assembly.

Just curious, why not make the nozzle thicker instead
of providing a reinforcing pad (maybe use a forging).

Leo

 

[prex]

UW-40(f)(5)(a) has nothing to do with nozzle welds.
Instead your analysis, DesignerKPB, is correct: UW-40(f)(5)(d) decides on your issue, only the thicker of shell OR repad counts for PWHT (by the way this is quite common practice).
What I don't understand in your post is the reference to the figure and how you can connect the repad to the shell with a full penetration weld. prex
motori@xcalcsREMOVE.com

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Online tools for structural design

 

Determination of nominal thickness as per UG-40(f)(5)(d)for the purpose of UCS-56 is correct. Hence in this case it is 1 1/4". PWHT is not mandatory as per UCS-56, but following points are to be considered before arriving at final conclusion.
1. As you mentioned that the vessel is already in use, if the orginal equipment was subjected to PWHT, then PWHT becomes mandatory for this new weld joint also.
2. UCS-68 shall also be checked for MDMT.

Best regards,
M.Rajeswara rao

 

[Amsterdam]

Start looking in the NBIC for repairs and alterations.
RC-1103 - Alternative PWHT methods, then go over to Part RD

GL