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[MW:28064] Re: PWHT

By Materials & Welding

To compute the control thickness we have to take the lesser of:

1-thickness of the weld

2-thickness of the base material joined

So for branch welds the thickness of the running pipe always commands (thickness of the base materials joined).

 

For better understanding I quote the reference code section of ASME B 31.3 edition 2014:

 

QUOTE

 

  



On Wed, Jul 11, 2018 at 3:54 PM, Peter Soloman <petervsoloman@gmail.com> wrote:
Dear Team,

MTO, not the control thickness for PWHT.  For piping classes like D1, D12 and E1H, this will become critical as the PWHT requirement is above 20mm.  (For other piping classes it is above 38mm(CS material))

 

CASE I  :For long weld neck flanges, the thickness is 15.85mm, when considering the throat thickness  the control thickness will be more than 20mm and so requires PWHT.

 

CASE II:  As the pipe to pipe branches are all having RF PADs, again the control thickness for D1, D12 and E1H piping classes will become critical. Control thickness is the thickness of Header + thickness of RF pad and the fillet weld above as per below sketch.  So I think any header thickness above 8mm surely must have PWHT.

For other piping classes we have to check as the PWHT requirement is above 38mm only.

 

CASE III:  The Olet welds in these three classes also to be checked individually (B 31.3 2014 revision illustrates with pictures for Olets as well.)

 

 

In the older revisions of B 31.3, there was a clause " Heat treatment is required when the thickness through the weld in any plane through the branch is greater than twice the minimum material thickness requiring heat treatment".  This clause is removed in 2014 revision which we are following.  Please correct me if I am wrong.  If I am right, as the control thickness is not marked in Easy piping these joints may  not be getting PWHTed.  Need immediate action.

 



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