Butt Welded Valves
Butt Welded Valves
(OP)
2 Questions
1) Can NPS 12 class 150 BW swing check or gate valve be welded directly to a BW 90 deg. LR elbow?
2) Can NPS 12 class 150 BW swing check or gate valve be welded to each other?
1) Can NPS 12 class 150 BW swing check or gate valve be welded directly to a BW 90 deg. LR elbow?
2) Can NPS 12 class 150 BW swing check or gate valve be welded to each other?





RE: Butt Welded Valves
Unless I had no room, I woulnd't weld the two valves together, just for the fact that if you had to cut one out and replace it, you would have to replace both.
RE: Butt Welded Valves
RE: Butt Welded Valves
RE: Butt Welded Valves
No room for bad weld repair and vorticies off the elbow may cause excessive movements of the swinging plate. Check would normally go downstream of the blocking valve.
What would you be doing, if you knew that you could not fail?
RE: Butt Welded Valves
But "BigInch's answer "Check would normally go downstream of the blocking valve" needs some clarification.
Normally on a Pump discharge line (in a refinery, chemical plant,etc) that has both a Check valve and a Block Valve the Check Valve is upstream of the Block Valve.
BigInch may be thinking of another application or he misspoke.
RE: Butt Welded Valves
Offtopic, pennpiper is correct...on pump disch. check is upstream of isolation valve.
Thanks.
RE: Butt Welded Valves
RE: Butt Welded Valves
Miketheengineer is also correct. I did not mention the increased possibility of creating heat damage to the valve. We ask for WE valves to be supplied with pups installed on both ends at the valve mfgr's shop to eliminate any possibilities of damaging the valves during field weld-ups.
What would you be doing, if you knew that you could not fail?
RE: Butt Welded Valves
Also I agree with adding venting between the block valve and check, but I've seen where a 1/4" Dia hole was drilled thru the clapper in the check to eliminate the issue of "trapped pressure". FYI - I always wondered wheather seat on a check valve would hold tight enough to cause a problem ...since it wasn't designed for bubble tight shut-off!??
RE: Butt Welded Valves
Thank you!!
I don't know how many times in a P&ID review I have had to argue this point with a client. "But it's an extra valve" or "Can't we just bolt them together?" or "won't the check valve leak enough?".
My response is "do you want to have to explain to the person that gets sprayed with (fill in the blank) that you saved an extra bleed valve this way?"
RE: Butt Welded Valves
I say, "Oh! Are you sure? That's the kind of answer I'd expect from a contractor, or anybody else that's not going to be concerned with operating and maintaining this thing for the next 50 years. Let's call someone from your O&M department to come in here and see what they think of your idea".
Don't clients love to be "penny wise and pound foolish".
What would you be doing, if you knew that you could not fail?