Valves fabricated by welding

[zhlin]

Need helps for the valves fabricated by welding.

A valve uses a tee as body with flanges welded on and is designed by using B16.34 as a guide, but not exactly followed.

Per ASME B16.34, welds of this type of valves should be NDT examed. I understand that the formula used for calculating wall thickness does not contain any welding effection - joint efficiency.

But due to B16.34 is a just reference, no NDT is required and performed to the welds between body and flanges.

What I am trying to figure out is how we could do to consider welding effection by design calculation as pressure vessels' to ensure pressure safety without any NDT to welds.

Appreciate any comments

 

[metengr]

Why don't you RT (x-ray) the welds? If you conduct 100 %RT, you don't need a knock down factor for welds. Also, you should hydrotest this valve after all is said and done.

 

[zhlin]

The manufacturer chooses no RT or NDT. I am trying to think whether there is any way to do as pressure vessel's design.

Yes, hydrotest for both body and assembled valve is performed.

Thanks.

 

[DVWE]

You can follow the code recommended weld joints, there are a lot to choose from in part UW of ASME Section VIII, but you can't claim the weld joint efficiency unless the required NDE is performed. I don't think there is any way around that.