Welding of 12" schedule 10 304L SS pipe - mucho problems 3

[KernOily]

Guys my contractor is having a very tough time with buttwelding 12" schedule 10 SS 304L pipe. Every time they cut it, it distorts and goes out of round, requiring a lot of banging and clanging and pushing and pulling to get a circular cross-section so it can then be buttwelded. They are using a plasma cutter. The weld process is stick, all outdoor (no shop fab), and many of the welds are position welds.

Due to all this extra work, it has run up the labor cost, so they have now eaten up all my savings that I claimed from material savings of going with sch 10S instead of standard weight pipe.

So now I have to install another thousand feet or so of the same pipe. The contractor is pushing hard for me to buy heavier-wall pipe, e.g. sch20S or std. So my material cost is potentially going through the roof and hence along with it my project economics.

Questions:

1) Is this problem due to the skill level of the contractor?
2) Is there a way to cut and weld sch 10S big-inch pipe without distorting the cross-section, especially in a non-shop environment?

Thanks guys ! ! !


Thanks!
Pete

 

[MintJulep]

Preheat?

 

[metengr]

Yes, for a 12" Sch 10 (0.180" wall) switch to abrasive cutting in lieu of plasma cutting. This should reduce the amount of distortion and provide for better fit-up in the field. Once the end of the pipe section is prepped, tack into position and weld out the root. I would

Keep in mind that your welders need to use caution in handling this material and to maintain cleanliness. Keep the abrasive wheels segregated for stainless only - do not use on any other material.

 

[boo1]

Consider cutting with a band saw.
Cean the join before welding, clean tools too
Stitch welding the root to reduce distortion

 

[StoneCold]

74Elsinore
Cutting with an abrasive saw or cutoff wheel on a 6" grinder is the way to go.
Funny how some projects turn out. Sometimes the harder you try to save money the less it works out. I recently had a project that I switched from butt weld fittings to socket welded fittings because I thought I would save a ton of time in the fabrication process. I knew I was in trouble when my "experienced contrator" was tig welding the root pass of the socket weld fittings. Needless to say there was no savings and the piping turned out ugly. Amazing that you can really save money by just going Sch 40 butt weld. Contractor skill and experience play a huge part in the cost of a project and if you have not used the contractor for that exact type of project then it is a guess on how it will turn out.

Goodluck.
StoneCold

 

[KernOily]

Thanks guys. After abrasive cutting or bandsaw cutting, how do they make the bevel?

Thanks!
Pete

 

[unclesyd]

There should be not a problem cutting and welding 12" Sch 10 SS pipe. I would be looking to get your contractor some expert help.

My procedure for a standard butt weld joint is to mark the pipe with a “wrap around” and cut with an abrasive blade in a Skill saw. On Sch 10 I will normally prepare the edge with a high amp 4" angle grinder with a flat wheel made for side grinding. Myself and everyone I know uses a feather edge prep and TIG welds with a “walking the cup” torch movement. I use a minimum of 4 tacks, sometimes more depending on the fit and feather all tacks. The tacker has to certified and capable of putting in a good tack. I like to tack myself if possible. If possible I’ll use a gas purge. If a good gas purge isn’t possible I’ll use a 1" wide band of welding paste/flux on the inside of both pieces of pipe or fitting.

Cutting with a skill saw takes a few minutes to get use to. Walking the cup is just one of several techniques used to manipulate a TIG torch. Make sure your procedure allows the end prep you choose to use. Make sure the welder and fitter are on the same page.

One trick that I like to do is have a flat sheet of all that will cover the end of the pipe to check the cut and then the prep.
Get your consumables from a reputable welding supply center.

http://www.pipefitter.com/

http://www.solarflux.com/Pages/Menu.html

 

[KernOily]

Unclesyd thanks for the great help. Is this something that can be done in the fiels, and can it be done in a position weld, for example, up in an elevated pipe rack? Thanks!

Thanks!
Pete

 

[unclesyd]

Yes, this is a standard SS field welding process and is in use as I write this.

There are a lot of tools and jigs that will aid an experienced fitting. If the fits isn't right the welder is out in the cold. We operate that the Welder has the right of first refusal on a fit up/set up.

Like any type of welding experience helps. Do your people have any experience in welding and fitting SS?

Here is a jig that would be a great help in aligning and rounding your pipe. This forces you to get the end prep right. You should be able to rent this tool locally.

http://www.walhonde.com/pipe.html

 

[arto]

make sure they passivate it after cutting with a band saw or "dirty" wheel, hammer marks, etc.

http://www.stellarsolutions.net/2310data.htm

http://www.derustit.com/product-ss3.htm

good info on stainless [i.e., they're supposed to know this]

http://www.nickelinstitute.org/mult...re_pdfs/11000_reference_book_series/11007.pdf

 

[KernOily]

Thanks unclesyd. Good stuff.

My contractor is pretty good at std wt/sch 40 SS but he got into trouble with this sch10S. I am in sort of a peculiar position as far as the relationship with the contractor goes, i.e., I got no stroke.

I put together a memo based on your info here. I will run it up the flagpole and see if anybody salutes it. THanks ! ! !

Thanks!
Pete

 

[EdStainless]

I have seen a lot of light wall 6", 8" and 10" installed. It was all cut with a track fixture and a hand saw or grinder. The ends were faced with little or no bevel. (depending on hte use of filler)
The welding can be done with a semi-automatic track weld system. Just a large version of automatic orbital.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[KernOily]

EdStainless said:

"The ends were faced with little or no bevel. (depending on the use of filler)"

Correct me if I'm wrong, but this means that if there is no bevel, then the pipe joint is a butt joint (not a groove joint) and the weld joint is a cap-only type weld because there is no groove. How did you ensure penetration to the bottom of the joint? Was this in pressure pipe built to code, e.g. B31.3? How did the joints pass RT if you didn't have full penetration?

"The welding can be done with a semi-automatic track weld system."
Is this something that can be done in the field?


Thanks!
Pete

 

[Heckler]

Pete,

The better the prep the better the weld. Here is a site for a company that makes pipe prep equipment

http://www.tritool.com/

You will need one of there 600 series clam shells. The have form tooling to achieve just about any weld prep. I use to work for this company and the equipment is extremely durable.

 

[nycpipewelder]

First off do you know your procedure? Do you need a root pass? What about purge gas's? Argon or argon mix helium? You haven't listed any of this! First you can get a actual torch hanlde for your plasma cutter that adapts to a pipe beveler ESAB makes this! I would not go with a 37 1/2 degree bevel I would go a little more and you can do this with a grinder also make sure you use flapper wheels to get a smooth surface on the bevel! Make sure YOU CLEAN ALL CONTAMINATES OFF THE AREA TO BE WELDED AND YOUR GTAW WIRE WITH ACETONE !!! For 12" pipe you need more than four tacks also get some stainless steel strips to tack on the pipe after you tack it so it won't shrink! Now what clown told you to weld sch. 10 with a smaw process? GTAW is absolutly the way to go and go cold on a low amperage! Your contractor should know all the following: Tugsten size, Tig wire, purge flows, torch gas flow , polarity, machine amperage and if he doesn't man you got problems!!! Your boy doesn't have a clue!

 

[sjrfc2]

I'd second the TriTool gear recommended by Heckler. The stuff saves huge amounts on labor in fitup.