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Up Topic Welding Industry / Welding Fundamentals / Distortion in pipe fittings
- - By Plasma-Brain (**) Date 04-11-2008 00:03
Hello all, I'm hoping that I can tap into some of the vast amounts of knowledge on these forums.

I just started a new job and I'm welding "t" fittings (are they also called saddle joints?) on to A53 water pipe. All the pipe I'm working with is in between 1" and 4" dia and anywhere from 2 feet to 21 feet long. I'm having one heck of a time with the fittings distorting once I weld them and throwing it out of level.
The majority of pipe welding experience I've had was with groove welds and I never had to worry about them distorting. I can deal with distortion in a flat plate but pipe fittings are a new animal to me and I'm at a loss as to how to tame it.
So far vie tried different sequences of tacks and sticking to the same pattern when I weld them, but it doesn't seem to make much of a difference.
As for the pattern I'm using, I weld from 6:00 to 3:00, 12:00 to 9:00 then 3:00 to 12:00 and then finish off with the 9:00 to 3:00.
I have no idea if that's the right way to describe it, I'll try and sketch something up in "paint" when I get a few minutes.

Also, are there clamps out there made for welding fittings?
Any help will be greatly appreciated.
Thank you all
-Clif
Parent - By Robert Turney (*) Date 04-13-2008 01:00 Edited 04-13-2008 01:03
Are you stick welding or mig welding?  I make alot of the same welds ( im assuming what i call a fillet weld) and i just put four good tacks and take my time between passes.  Also, how many fittings are you welding per joint of pipe and distance apart.  I hope im right here, so someone let me know.  I guess what he is talking about is like a TD Williamson shortstop or tap fitting?
Parent - - By thewelder (***) Date 04-13-2008 04:32 Edited 04-13-2008 09:08
HI, Plasma-Brain how many passes you do on this pipe? let see here, I allway make 3 passes, root, hot(fillet) and cap, because if you try to do 2 passes, you got the disstortion you mention I know that because it happen to me before, what I do know is this: big tacks, weld from 3 to 6, 9 to 6, 12 to 9 and 12 to 3, let it cool a litto and check the aligment and do the hot pass from 12 to 6 for the opposit side you have the distortion, look the pic's , in this case from 9 o'cloc side, if you have any ? send me a pm and I'll be glad to help you. JAIME. thewelder.
Attachment: pipehelp.jpg (55k)
Parent - - By Plasma-Brain (**) Date 04-13-2008 19:54
Robert, sorry i didnt include all the nessicary info. Im Mig welding, around 18 - 25 volts as near as i can figure... its a tap core machine with high and low and 1 - 6. .035 wire 75/25 gas around 30 cfh. I have no clue about wire feed speed because the adjustment on the machine is by percent and im not sure how to convert that. i have to look up how to figure that out. Yes it is a fillet weld, and there are usually 1 to 4 fittings per pipe, but there can be any number. The fittings are around 1/8th to 3/16s thick. The distance and location of the fittings varies alot between each pipe, some are feet apart on opposite sides and others are as close as 6 inches on the same side of the pipe. 
I have no idea if its a short stop or tap fitting.

TheWelder, i modified your picture a bit to try and show what im workin on, its a little rough but i think it shows what im doing.
The dashes are supposed to be threads, and on the top down view you would see a plasma cut hole in the pipe, but trying to draw that in there wasnt working. Im olny running one pass but its a fillet weld not a groove.
I siwtched what pattern i was welding them in and now there coming out a little better.

Thank you for your replies, i hope this is enough info.
-Clif
Parent - - By welderdude (**) Date 04-13-2008 22:18 Edited 04-13-2008 22:24
is this for sprinkler piping?  if so, then that's sch 10 pipe right?  I think I see what you're getting at.  you can fit and tack up the piece square no problem, but when you're done welding it's not square.  something you can try is restraining the joint.  there are a couple different ways you can do it, but pretty much it just involves holding the pieces solid while it's being welded until it cools down a bit.  you can do that by tacking some angle iron down to the table to hold the pipe down and set the branch on top of the pipe.  then when you weld it the angle iron will hold the pipe down and won't allow it to warp in toward the branch.  or you could make a more permenant jig that looks like 2 jewel clamps out of a piece of angle iron.  or you could tack a piece of angle iron on both sides of the branch down to the pipe to form a 45 or 60 degree angle. 

another way to minimize this distortion is to use the least amount of heat possible and to make the smallest bead possible.  the less heat you put into it, the better. 

also, in the drawing above, if you weld from 12-3 and then 6-9 and then 3-6 and 9-12, that should minimize the distortion too.
Parent - By Tommyjoking (****) Date 04-14-2008 02:09 Edited 04-14-2008 02:11
Hey Clif!!   How are you doing bud?

This is going to draw no matter how you proceed with the welding....welding procedure can lessen it but not eliminate it.  Reason being is your putting all the heat on one side of the pipe....those welds are going to shrink.

This is just a suggestion but it works on most things that get welded on one side and draw into a bow.   As said above if you can restrain the pipe before welding.   What I am suggesting here is to restrain or bow the pipe in the opposite direction that it draws.  Start out with roughly the amount of bow (opposite direction of after weld bow) that the pipe exhibits after welding.  Tack up and weld out the tee....see where it ends up after cooling down completely.....then add more or less (preweld-bow) to suit.   You can do this with weights but it will work best if you have a solid restraint such as clamps, sawhorses/piperolls or something to solidly fix the pre-bow with.   Somebody will probably post a simple method of achieving this but thats my two-cents.  Good luck.

Tommy
Parent - By medicinehawk01 (**) Date 04-14-2008 08:28
I agree with restraining the pipe (header), I have heard it called using a "strong back". You can do it before or after the saddles are tacked up. If I have 2" X 1/2" f.b., tack one edge to one end of the header and shim (behind the hole on the header) where the weld(s) will be made and tack up the other edge of the header pipe. After some trial & error you'll be able to determine how much shim to use, start with 3/4" (shim) and really it will depend on how many branches you have coming off said header. You'll need to have enough shim to make the pipe curl opposite the branches and leave it on until it is cool enough to tough with a thin welding glove on. It has worked for me especially on stainless steel pipe where distortion is the norm.

Hawk
Parent - - By johnnyh (***) Date 04-14-2008 18:06
Maybe I am wrong but I am not sure if this is considered a fillet weld.  If it is is a saddle-in, wouldnt this still be considered a butt-weld?  Maybe I am just completely misinterpreting the sketches.
Parent - - By patg (**) Date 04-14-2008 22:55
i would also try a strong back
Parent - - By Plasma-Brain (**) Date 04-15-2008 02:42
Ok, im trying to respond to several posts in one here... so bear with me.

Welderdude, yes you are correct this is sprinkler piping. Most of it is sch 10 but ive run into a bunch of sch 40 allredy. Ive set it as low as i can get away with and still have it solid when im done, and the first patter i tried was the one you described. the fittings still seemed to pull out of square and when i switched to the pattern in the sketch they seemed to get better. I notice them tweak out more with smaller fittings, around 1 to 1 1/2, over the larger ones im welding which are around 2 to 2 1/2. Any clues as to why thats happening would be grand...
also, im gonna sound dumb.... but whats a jewel clamp? is that like a bessie clamp?

Tommy! Good to hear from you, hope everytings well on your end. Ive been swamped between school and work...
You have some sound advice there, but i really hope that the whole pipe isnt bending from the tiny 1 1/2 inch outlet i welded on one end. That would open up a whole new can of worms. Ive used that trick of pre-bending parts before, it defently works and it has totally saved my arse many a time... i was just hoping that i wouldent need it and before you and others mentioned it, the thought hadent crossed my mind. Bending a 3/16 post over a 4/4 with a few bessie clamps was tricky enough, i really want to avoid having to figure out how to do that to a 21 foot peice of pipe...

Medicinehawk, patg, if i can figure out how to get the 2 tabels i have available to me to work on together and level and such, ill try and get a strong back setup... im olny using a singe chain clamp on a relitivly small tabel at the moment to hold the pipe from rolling and throwing off my level when im working on it. not the best of setups but im new, im still claiming my territory so to speak ;)

johnnyh, i havent the slightest clue if its a butt or a fillet. i look at it and see 2 peices of steel coming together at a 90 (around the fishmouth anyways...) and that seems like a fillet to me. but im also not up to speed on all of the pipe welding lingo. I didnt draw it too well in the sketch.. i think i might borrow dads digital camera and see if i can get some pictures of what im workin with for all to see.

Ok, im too tired to spell/grammer check this post... and i really need to shower...
Thank you all for your replies and experience :)
Goodnight
-Clif
Parent - - By 803056 (*****) Date 04-17-2008 01:51 Edited 04-17-2008 02:04
These are branch connections (ASME lingo) and the welds are usually complete joint penetration groove welds unless the fittings are relatively small diameter. If the fittings are beveled, CJP is the typical requirement and they require a reinforcing fillet over the CJP groove weld. The size of the fillet is dependent on the specific code requirements. Please note that the operating pressure is not a variable, i.e., weld size is independent of the pressure rating.

As for the joint type, they are simply called branch connections. Small diameter branch fittings can be half couplings that are either fillet welded to the run pipe or they can be beveled and welds just like any other bevel groove detail. Large diameter branches or branch connections,  larger than 1/4 the diameter of the run pipe (header to some), typically require an integrally reinforced branch fitting (a "weld-o-let" to some).  A typical welded branch of the "Weld-O-Let" variety looks more like the sketch to the left. The sketch to the right is sometimes referred to as a "stab in" (an other case of slang). Please bear in mind that the size of the reinforcing fillet weld in the sketches may not be the same size as those required for your project.

As for the distortion; you can pre-spring the pipe as already mentioned or contrary to some suggestions, use as few passes as possible to fill the groove to reduce the "thermal history", that is reduce the number of thermal cycles where the base metal or previous weld experiences thermal excursions above the lower transformation temperature (about 1330 degrees F). The last suggestion is to weld an "X" on the run pipe (header) opposite the branch fitting that is equal to the diameter of the branch fitting. The idea being that the "X" will cause sufficient residual stress to counter the residual stress caused by welding the branch fitting. Multiple passes over the "X" will increase the forces developed and will minimize the deflection caused by welding the branch fitting.

Best regards - Al
Attachment: BranchFitting15-Oct-07.dwg (35k)
Attachment: BranchFitting15-Oct-07.wmf (44k)
Attachment: 6923BranchFitting15-Oct-07.dwg (35k)
Parent - - By Plasma-Brain (**) Date 04-18-2008 21:12
Al, I can only look at one of the sketches you posted because I don't have a CAD program to open the other 2.  :( If you can get the other 2 in the .wmf format then I can see what you're cooking. :)
Thank you for providing the correct terms for what I'm working with. The "weld-o-let" is what I'm using at work, and there all about 1/8 to 3/16th thick and pre-beveled. I'm not sure they would let me weld an X on the header, but if I keep having problems i'll ask them.

Welderdude, were almost on the same page. The pipe I'm working with is larger than hand rails, anywhere from 2 to 4 inch OD sch. 10 to sch 40. But other than that you're right on the money. Water tight and square to the pipe is what I'm after. Water tight is easy; getting it square after I'm done zapping it is proving to be the hardest part of the job. Any idea where I can find a jewel clamp, somehow I get the feeling that "home defect" doesn't have it...

I've been practicing it more and I found a new patter that is working pretty dang good. I start at 6 and go to 3 then 6 to 9 then 12 to 9 and then 12 to 3. I've been leaving the level on the piece of threaded pipe I use to adjust it while tacking the fitting in place and I can watch the heat from the welds pull the bubble around.

Thank you all for your knowledge and time :)
-Clif

Parent - By 803056 (*****) Date 04-18-2008 21:19
Both sketches are the same, different formats.

The "X" can be done with  GTAW torch. The intent is to "spot" heat the back side of the run pipe. The greater the delta T, the better the draw. You can use an oxy-acetylene torch, but the heat is too dispersed to get the benefit you would get with a GTAW torch.

Point of information: the bevel and root face of the "Weld-O-Let" are to be "dressed" to properly fit the run pipe. Some welder are under the impression they are ready to use as purchased. That isn't the case. They have to be hand fitted to provide the proper root opening and bevel.

Best regards - Al
Parent - - By welderdude (**) Date 04-17-2008 20:46
a jewel clamp is like the chain clamp you're using now, but it has 2 chains on it for clamping 2 pieces of pipe to keep them aligned until you tack weld them.

I know exactly what you mean when you say sprinkler pipe.  pretty much it's like welding a handrail.  and you work in a production shop, so all they want is threaded and victaulic fittings welded on so they'll hold 120 psi and they're square to the pipe and they want it done fast.  your best bet might be to pre-bend the pipe.  find out how much you have to bend it and make yourself a spacer to put under the fitting you're about to weld on.  then clamp the pipe down on both sides of the fitting.  that might be the fastest and easiest way to handle it.
Parent - - By Superflux (****) Date 04-19-2008 09:56
Plasma-brain, a pair of vise grip 11R clamps with a 2" piece of angle iron welded to them and a small length of channel iron makes for a cheap jewel clamp.
Parent - By PipeIt (**) Date 04-25-2008 19:19
Something else that works slick is take the stainless portion of a no hub band used for connecting cast iron plumbing pipe and you can use it to fit the joint, you can also cut a window in for holding internal purge. It works good on diary tube and schedule 10 stainless.
Parent - - By LongArc (**) Date 05-08-2008 03:34
Try intermitin welds 1 inch long 2inch space, It will look grappy if your doing one pass. The spaces should reduce distortion.
Parent - By Stringer (***) Date 05-12-2008 00:46
I weld a lot of stainless 2, 3, and 4 inch sch. 10 and 40. Oddly, sometimes the sch. 40 fittings are really sch. 80, but lathed down on the openings. Anyway, the 90 elbows are only 90 fifty percent of the time and the tees are always off. Always.
Pulling back and forth across square is a function of the heat of course, but clamping and air quenching can fix most of that. What really boggles the mind is when multiple fitting welds rotate! This is harder to fix so it's best to prevent. I treat the tacks the same way I tighten lug nuts on a car. Sometimes if I have a series of fittings I'll increase the number of tacks, bouncing around to keep the heat evened out. I usually do eight tacks on a three inch diameter if I'm trying to prevent rotation distortion. Once you've got it rotated wrong, all you can do is re-grind all the bevels and I hate the results.
Mathey Dearman makes nice clamps. Most are too big, but not all.
Up Topic Welding Industry / Welding Fundamentals / Distortion in pipe fittings

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