[Olivero]

Hey guys!

I am new to this Forum but I figured I might be able to get a good answer.

I was on a site yesterday and the plumber was having a hard time with this stainless steel pipelines, they were apparently leaking steam at certain times but when he showed up, nothing was leaking but at that point, he had already rented a Bobcat 250 Miller welder to try and weld his joints with some stainless sticks, tried running stick on a teflon & goop joint and to no surprise, did not succeed.

So He was talking to one of my co workers trying to sort out what to do and my co worker points at me and goes "he's good at stainless" True, I have a done a LOT of stainless but never done schedule 40 stainless pipe. I think it was some 1 1/2" and 1/2" and 2" joints, totaling 30 or so joints in all.

I have a Dynasty 200 that I think would be up for the challenge, I could not find the gas inlet hookup for the Bobcat 250 to TIG so I figured I can use it as a power source for my Dynasty 200 so I won't blow breakers.

I normally purge when I weld stainless pipe or at least try to but his plan is to make all the joints in the leaking area, socket joints and get them all TIG welded by me and one of his guys. Do I need to purge the line to do this? will be a lot of Argon.

it's a steam line for dry cleaning equipment nothing sanitary or food and it holds about 120 PSI.

Also, any advice would be appreciated, might not be doing it as its a plan B in case it starts leaking but I at least want to be prepared in case.

Thank you!

[Otto Nobedder]

Purge is not generally needed for sch. 40 SS socket welds if you keep your heat under control. This, however, is not the problem you face. Turning screw-pipe joints that are full of dope and tape into weld joints is.

This is not impossible, but I'd approach it with an eye on my wallet and my watch.

I would begin by TIG washing (no filler) a joint, boiling out what will boil out. Wire-wheel it, and repeat. Tungsten closer to the corner each time until the crap cooking out is a minimum. (Let one joint cool while working another.) Then, bridge-weld the joint, meaning don't try to get root penetration in the corner; leave it open and move fast so you don't boil anything else out into your weld. Be prepared to grind and re-weld little spots, especially at your closure weld.

This is clearly not the best way to solve the problem, but it will "fix" the problem and kick it down the road to the next shutdown.

Steve S

[Poland308]

Like Steve said Welding over threaded joints is not long term. They will be prone to cracking from expansion stresses. Just like bottoming out a socket weld joint. Steam for dry cleaning will likely be on and off a lot that means lots of expansion stresses. This is also probably the root cause of the leaking threaded joints.

[Olivero]

Thanks for the reply's.

Yes, welding over a gooped joint is a sad story, no doubt. The plumber will cut it all apart and use new fittings and clean pipe. There won't be any dope or anything when it gets socket welded. We assumed it was due to the expansion and contraction or thermal stress of the piping as well, there was not really another logical reason.

Okay good, so no purge is needed, I will assume I am still expected to get good penetration in the joints, do I run this like I would run sticking pipe? Never done much socket welding, how would you go about it? I did not fully duplicate your bridge welding technique.

[exnailpounder]

Don't bottom out the pipe in your sockets.

[Olivero]

Don't ask how I know.

Okay, now I am just curious.

So keep the pipe centered in the fitting and leave a gap all around, got it.

[exnailpounder]

Don't ask how I know.

Okay, now I am just curious.

So keep the pipe centered in the fitting and leave a gap all around, got it.

No...bottom out your pipe in the socket and then pull it back a 1/16" before you weld it or when the weld cools and contracts, it will pull the pipe into the socket fitting and crack the weld.

[Olivero]

Don't ask how I know.

Okay, now I am just curious.

So keep the pipe centered in the fitting and leave a gap all around, got it.

No...bottom out your pipe in the socket and then pull it back a 1/16" before you weld it or when the weld cools and contracts, it will pull the pipe into the socket fitting and crack the weld.

Lol, got it, thanks

[Coldman]

Leg length of the fillet should be about the same as the wall thickness of the socket for strength. That usually means at least two passes required.


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[Olivero]

Leg length of the fillet should be about the same as the wall thickness of the socket for strength. That usually means at least two passes required.


Sent from my electronic thingy using Tapatalk

Okay so run multiple passes on the same bead?

[Poland308]

If it's a socket I like to run the first pass with no filler just fusion. Then I layer in the passes. Depending on diamiter of the socket and pipe Thickness there's no perfect number of passes. Like Coldman said you just need to focous on thickness of the weld. Some may weld it in three passes others in one.

[Poland308]

IMG_0082.JPG (79.4 KiB) Viewed 1555 times

Here's a pick of a socket weld. But this was stick not tig. It was seamless heavy wall carbon on an ammonia project I did. It's actually excessive reinforcement but the blue line is roughly where you would measure the weld thickness.

[Olivero]

Okay so I could fuse the first weld, then run a small bead, then let it cool, do 1 or 2 others, then come back and run another, wider bead enclosing the smaller one and now I have a wider and fatter bead, and then let it cool and then come back until the thickness of the weld bead is the same as the thickness of the pipe?

Really nice weld on that pipe btw.

[Rick_H]

Okay so I could fuse the first weld, then run a small bead, then let it cool, do 1 or 2 others, then come back and run another, wider bead enclosing the smaller one and now I have a wider and fatter bead, and then let it cool and then come back until the thickness of the weld bead is the same as the thickness of the pipe?

Really nice weld on that pipe btw.

Yup, I run a nice fuse on the root, then layer passes like mentioned above, I basically weld out to the edge of the lip on the socket. I do mostly schedule 80...

The 1/16" gap is very important or they will crack

[Olivero]

Okay so let me just make sure I got this right.

I slap my pipe in the fitting, hits the stop. Back it up a 1/16"th of an inch and then fuse the first weld. Then let it cool, (its 304 stainless, I was going to use 308L, 3/32' rod) then I run a bead around it, weaving back and forth from the fitting to the pipe and run my bead. Then I let it cool and come back again, then I just keep repeating that until the bead is as fat as the pipe is thick. I think 2" schd 40 is 1/8" wall and 2.5" schd 40 is 1/4" wall, something like that, so I will just have to pay attention to the pipe thickness.

[Coldman]

The socket fitting will be heavier wall than the pipe. Good socket weld practice is to fill to the thickness of the socket fitting otherwise all else is good.

[Olivero]

Ah, okay cool. Thank you.

Just got word from the plumber, we are not doing it.

Yet... Maybe they will change their mind when the pipeline starts leaking, dripping hot water on people working on the machines and then they have to shut the whole place down for a day or 2 or 1 full night to get it all done.

Man, I wish people would just do it the right way the first time instead of going back and redoing things like this.

I do appreciate the help from you guys, good to know all this stuff, I did some eccentric fittings but they were butt weld fittings, what is easier? butt welding or socket welding? I would think socket welding.

[Coldman]

Here's a video Jody did of socket welding.

https://youtu.be/kX0BCm1F2j4

[exnailpounder]

If people did stuff the right way, what would all of us guys have to do? What I like best about this site is no egos and great welders that bend over backwards to help others. None of us have seen it all but with the combination of experience here, it gets done. Never find a better bunch.

[Olivero]

I guess that's true. But I do prefer not going back and fixing someone else screw-up.

I was actually led onto this site by someone from Miller. I was needing some formal natural gas pipe welding done, since I am not certed I said I don't want to do it and so the guy told me about a local guy, the local guy helped me figure out a better, cheaper way and I did that, worked out great. Then he sent me an email 2 days ago, said he noticed I was still active on Millers forum and I should come check this place out, well now I am addicted to this one too

I do agree, its fast responses and I think your right, its the whole "between me and my brother, we know everything" concept and I like that, really is nice to be able to go somewhere and ask questions that might seem stupid but still get a good answer that doesn't make you feel stupid.

[exnailpounder]

If you ever want to be impressed just ask Steve aka Ottonobedder a question...any question...he's a walking encyclopedia. Glad you're aboard. Lot's of knowledge around here and it's given freely.

[Olivero]

Thanks for the heads up, glad to be a board. Always good to have some experienced folks around.