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Welding Pipe with smooth seams on the inside ?

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Re: Welding Pipe with smooth seams on the inside ?

Postby Hilltop » Wed Dec 06, 2017 1:16 pm

Old thread but Pinto I thought I would add something here, I'm a combo pipewelder, never, ever put duct tape on stainless pipe, it contaminates it. If it is placed near the weld joint the next weld will cause the welder to cuss, to tape off large pipes, we use the cap that comes with the pipe, a board cut to size or special purge paper and tape.

Multiple welds close together on stainless should be done with the special purge tape as it doesn't contain the sticky resudue that will contaminate the weld, if no other tape is nearby turn the duct tape backwards so the non sticky side is not touching the pipe.

On stainless we use the key hole technique with a 3/32 gap. Open a little hole dob the wire, move up a tad open the hole dob the wire repeat. If you can't set your bare hand 6 inches from the weld zone your getting the pipe too hot. Don't rush stainless.

I've actually seen folks fired in power and Nuke plants for putting duct tape on stainless pipe. It's very important with Stainless to use the same number alloy as on the pipe, once on a job we used 316 to weld 304 stainless pipe, the acid eat the welds slam out. The proper metal was 308 stainless and this lesson cost us money.

Always use tigar paws " 4 inch sandpaper disks for a grinder" and flapper wheels for an end grinder on the inside. Never use grinding rocks.
"Virtute et armis" By valor and arms

Let's keep our country free as God has given us.

"Give me Liberty or Give me Death."
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Re: Welding Pipe with smooth seams on the inside ?

Postby Hilltop » Wed Dec 06, 2017 1:27 pm

On schedule ten pipe 3 inch and smaller I may use a slightly smaller gap say 1/16 as on a still you don't want excessive root penetration. The alcohol will puddle behind a large root. At the Coca Cola plant we weld polished stainless sch 5 this way. The root is actually the filler too, your basically fusing the pipe add filler as needed, completely cool then cap.

If the root is black from excessive heat input, often i will let it completely cool, refill the purge and walk right back through my root.

Never touch anything to stainless that has touched carbon. Never throw grinding dust on stainless.
"Virtute et armis" By valor and arms

Let's keep our country free as God has given us.

"Give me Liberty or Give me Death."
User avatar
Hilltop
 
Posts: 45
Joined: Thu Aug 17, 2017 11:16 pm
Location: Dixie
Equipment type: Small pot stiller

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