We are discussing the reliability of the tube to tube sheet joint given in UW-20.1. Especially with type “c” our concern is that the root weld could not weld properly.
Our company standard calls therefore for a j grove with an af value of 3mm. Of cause then af = ag is not true.
Therefore my questions:
1. What are your experiences with type c?
2. If we are diverting form UW-20 do we get a problem with the AI for the U stamp?

Thorium,

if you are specifying type c, your af must be equal to ag, otherwise you got type d.

Acording to my experience as Inspector, the optimum would be tubes expanded and seal welded. For best results, two pass welding.

However, many factors are influencing the solutions, what does your design calculation say, will the weld be load carrying, do you have U-tubes, lethal service, Unfired Boiler, or direct firing?

Why do you have a problem with type c?

I suggest to consult an experienced designer of HX. The AI will accept any design that meets the Code requirements.

DK