RE: [PipingDesign] PWHT REQUIREMENT FOR DISSIMILAR THICKNESS WELD

From: <Steve>
Date: Mon Jan 20 2003 - 06:50:00 EST

I am not familiar with the term "pup piece" but it sounds like what we call a "stab in"; one end has the desired connection such as a flange and the other is to be connected at right angles to an existing pipe. I will assume this is the case.
Most codes permit a change in thickness section of 1:5. It you are able to reduce the thickness of the main pipe to 14.3mm (grinder) or whatever your code requires to exclude PWHT then you are in provided the residual wall thickness is sufficient. From experience, I like 5 X wall thickness margin (preferably more) before the taper starts as this seems to reduce root cracking. If the minimum wall thickness exceeds the lower limit PWHT then folow the rules. They are there to protect you.

Cheers

Steve

-----Original Message-----
From: Patil, Pravin [mailto:Pravin.Patil@veco.com] Sent: Monday, January 20, 2003 11:28 PM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] PWHT REQUIREMENT FOR DISSIMILAR THICKNESS WELD

Dear Friends,

  In one of our projects,we want to weld a 24" buttweld valve pup piece with a 24" pipe.The thickness of pup piece is 14.3mm and the thickness of the pipe is 21.45 mm.We want to avoid PWHT to avoid distortion of valve seats. The welding electrode we are using is E 6010 for root welding. Applicable code for piping is B31.3
Can anybody suggest any clause in the code to avoid PWHT. or any other possibility (like by using different electrode) to avoid this. Views are expected on the subject matter.

Regards
Pravin

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