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1/4" thick repad to reinforce branch connection

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csquaredng

Mechanical
Dec 1, 2021
4
CA
Hi guys,

I have typically designed with a minimum repad thickness of 1/2" on welded branch connections. This time around, I am dealing with a 4" branch on a 36" run pipe. The problem is with a 1/2" repad, I have a weld proximity issue where the repad weld toe is only 1 mm away from the adjacent small fitting weld. While using 1/4" repad provides enough reinforcement as per B31.4 calculation, it also contradicts the common practice where repad thickness equals the header thickness. I read on another thread that repad thickness is 0.75 x header thickness at minimum and 1.5 x header thickness max. Any of the experts here can provide some explanations on the minimum repad thickness limit?

Much appreciated!

 
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I don't see that the Code specifies a minimum thickness (assuming B31.4 is your design code). I would be concerned about getting a poor, hard weld if that 1/4" fillet gets made in a single pass. The thinner repad only gives you an additional 1/4" of clearance from the other weld, which is still closer than may companies allow.

Why not use a weldolet in this application? Smaller footprint, fewer welds, and integrally reinforced.
 
akpipelineengr,

B31.4 do not specify that but thank you for sharing the possible hard weld problem. I'm not yet well-versed in welding. As for the weld proximity, the client spec has a provision for small fitting that allows minimum weld spacing; I simply want to maximize this spacing as much as I can.
 
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