Are socket welded connections acceptable for raw water?

[Design-fab]

Hi folks, the situation is 2-1/2" 316 schedule 10 pipe connecting to "commodity" type CF8M 3 piece ball valves. The proposal is to GTAW with back purge. A couple of general questions if anyone has experience with this:

1. Is pickling required?

2. If yes I'm not sure that the pickling solution would properly wet out the back of the weld given the geometry of the sockets?

Any insight on this would be greatly appreciated.

Regards, John.

Edit: We would consider using a CF3M valve and 316L pipe if that solved the problem.

 

[bimr]

Have you considered FRP instead of stainless steel?

 

[Design-fab]

Hi bimr, no we did not. Good suggestion but we're pretty much set on metal for this section of the piping.

Littleinch yeah I know SS sounds a bit rediculous for the application but it's only a small section that needs to be metal. So my line of thought is that if we use sch 10 SS then the total cost of the pipe itself isn't significant. The money is in the valves and fittings of course.

Gal has leaching issues like copper because of the PH unfortunately.

After much deliberation we will proceed with the butt weld option. Hopefully we can keep the HAZ to AWS D18.2 #3 or less with careful shielding, if not we will pickle.

Anyhow I have thank everyone for their input on this thread. It has been most valuable. I certainly appreciate you sharing your hard earned experience and knowledge.