i want to learn to weld...

[GHarman]

Ryan, How about a picture? If your pieces were not in contact, a thick mill scale coating on one or both, or just a plain bad welding rod, would explain alot. Grounding is tricky on small pieces, unless you have them clamped to a welding table or fixtured. GregH

 

[rbattelle]

Shoot, in my rush to get the job done I forgot about this thread.

I managed to get the thing welded, but I needed a lot of grinding to make the welds look decent (the mark of a bad welder). I think my problem was rod positioning. I repositioned the rod to point more toward the thicker metal, and things worked better.

I'm sorry, I forgot to take a picture and the job is already painted and ready for delivery.

Ryan

 

[DValentine]

I think you figured it out, Ryan. As Greg mentioned, if it did not fit up "tight" it would make it tougher to make the weld. You could always put a little preheat to the thicker piece and that would help you.

Dave

 

[DValentine]

Here are some pix from the last job. Poor quality... cell phone camera.

The power plant.
A repair, being hand beveled. A sponge is stuffed down in the tube and is attached by the wire hanging out of the tube.
A roof tube weld.

 

[DValentine]

A 6g tube test.
A spool piece.
A tube weld. Note I messed up on my side and had to fix. Thus the funny looking root.

 

[GHarman]

Hey Dave!!! Really good pictures. Thanks for posting them. GregH

 

[rbattelle]

Note I messed up on my side and had to fix. Thus the funny looking root.

Professionals mess up too?! Man, that makes me feel a little better!



Ryan

 

[GHarman]

Professionals mess up too?! Man, that makes me feel a little better!



Ryan

Ryan, What Dave isnt telling you is; that alot of that tube is VERY difficult to weld. The alloys used in the high temperature portion of the boiler are high Chrome content and pose huge problems to the very best weldors. They are also, difficult to access and prepare. Not like doing a shopweld on mild steel where everything is handy and can be cleaned and prepped to perfection. GO DAVE!!Oo. GregH

 

[DValentine]

I mess up alot, Ryan. But as Dad said, "a good carpenter can cover up his mistakes. " When we get porosity in a weld you have to get all the messed up metal out of the weld area. Sometimes that can make a large hole say 1/4 inch or bigger, where the original fit up was 3/32 or 1/8th gap. There are some tricks to "sewing up" a large gap. I have learned a few of them. But the x ray doesn't lie, and a big root weld can be seen. See many of these tubes are close together and have to be welded with a partner. The torch will not go in between the tubes. One guy welds toward his partner, while the partner feeds wire on the sides where the tubes almost touch. The guy feeding wire talks to the guy with the torch telling him what is going on in the weld puddle. The guy with the torch can't see the weld, only the back end of the TIG torch. This is where things usually get messed up and they are hard to fix. The torch is not perpendicular to the weld at this point and it is easy to loose gas coverage.

My mess up, above, was all my fault. I dug out the bad metal and fixed it. Then I filled in the hot pass and flushed out the tube. I ground it up a bit blending in my messed up area. Then I finished the weld, capping it out from where my partner had left off, covering up my mistake making the cap even with the number of beads my partner had put in. This is all done off a two board scaffold 180 feet above the bottom of the boiler, with all the tools tied off.

 

[Turbo Tim 1]

Also notice in his pictures the 6G tube test, see how thick that is, that is alot of passes around, alot of patience and alot of perfection to do it right. I know on the bigger pipes in these plants the guys will do TIG roots and then use stick over it and every single pass has to be thoroughly cleaned prior to stating the next pass because like Dave said the x-ray doesn't lie.



You guys are the professionals so correct me if I am wrong, one of the welders on a previous job had to weld a 14-20 inch hi chrome line for main steam that was 1000 psi, the pipe came up next to a concrete pedestal and the wled joint was 6-8 inches off the floor, the pipe was standing verticle and he basically had to stand on his head and weld around this pipe so it is basically like a verticle weld, he told me it took 14 hours to complete that one weld, does that sound right?



You boilermakers are nuts, we had to replace about 90 High pressure evaporator tubes in an HRSG at another job, I think they ended up cutting out about 300 tubes inorder to get to the ones that needed repair, then welding with mirrors, heck I have a hard enough time when I am looking right at it. :{

 

[DValentine]

I am no mirror weldor. But on those main steam lines, yes, 14 hours to make a weld with a wall thickness of 5-8 inches.
That 6 G tube test was with a wall thickness of about 5/8 inch if I recall. You are right, TIG root and hot pass then pour the rod to her to fill it out.
D

 

[opjohnny]

I had a boss that used to tell me "that a person not making any mistakes is probably not doing any work". I am taking a TIG class at Jr College and sometimes I think they should make us stand on are heads to weld every once and a while. It is far easier indoors in a booth on a chair.



John

 

[nickleinonen]

I am no mirror welder.

i've done that before. . modifying air piping on locomotives to add an air dryer. the one joint is a bad one and you can either weld it blind or use a mirror and try and remember to pull towards you on the stick and that left is now right. .

last welding i did was on a locomotive fuel tank. that was an interesting first for me having never welded on a fuel tank before. . there was a 6" crack in a weld seam that had been previously been fixed. my 6" crack after grinding and gouging ended up being a weld that is about 20" long. now i am no expert welder so i am sure glad it was basicaly a flat weld. good root pass with 7018 which i gouged out to make sure i had no slag in it. then weaved a cap over it, gouged that out smooth and weaved another cap over that and called it good. with that fuel tank there is no real way to pressure test it for leaks so full of fuel it got [18,000 liters] and no leak. don't really want to get management into the habit of using me as a welder for fuel tanks. but i was very happy with my welding that day. that is the first time i have had the flux off 7018 curl up and fall off on its own like 7014 does.

 

[rbattelle]

Speaking of fuel tanks and welding, is it possible to weld a pipe carrying pressurized water (or any other liquid) without shutting off the flow? In other words, is it possible to weld a cracked pipe closed while water is gushing out of it?

Ryan

 

[nickleinonen]

maybe... if you can manage to stop the flow by peening the crack over then run a bead over it.

 

[GHarman]

I have done this on Natural Gas Pipelines. No worries, No Oxygen in the pipe. It doesn't burn until you strike the arc, then you better watch yer beard:-laf. However, if the flow of WATER is not causing YOU to be part of the arc? I would drain the pipe if the leak is large. I do know that building a bypass and using Meuller tapping and stopping equipment would allow for a replacement section to be installed and still allow water service. Welding a leak on top of a pipe carring water, with the water shut off would be doable. If the leak were on the side or bottom, I would be concerned with getting wet and grounded. I'll bet somebody has done it. They need to speak up. GregH

 

[Coalsmoke]

Speaking of fuel tanks and welding, is it possible to weld a pipe carrying pressurized water (or any other liquid) without shutting off the flow? In other words, is it possible to weld a cracked pipe closed while water is gushing out of it?



Ryan

Not really, not if you want it to be of good structural integrity at least. You will find porosity will be a big problem if you try it.

 

[GHarman]

Coalsmoke, Good to hear from you!!!! Using ER-6010 or ER-7010G HYP would do the trick. Yes there would be structural issues if there was water present at the hole or crack being fixed. If the leak could be controlled temporarily till the crew could come back and do the bypass/replacement maintainence. IMHO only, water is not my area of expertise. GregH

 

[Coalsmoke]

Thanks Greg. Water is not my specialty either, but I know when welding in pilings if there is water running down the inside of them from heavy rain, the root will be a PITA to put in without porosity. I have had to do a 3000psi hyd. oil line where there was always a trickle of oil and I couldn't get it porosity free, but it was not structural, just had to minimize the leak for a couple of weeks until it could get fixed proper.

 

[Bob Cochran]

You guys are good; hope someday as a hobby welder can even be 1/10 as good on my best day. I got a question though I have had a Lincoln AC225 for some time. Not good or bad with it just get by mostly. I need more practice. Awhile back the wife has one of the garden windmills. With the high winds up here the blades flung off!! I welded it back together using the stick welder was a trick to weld back on the 22 gauge(new blades I made) that are perpendicular to the 12 gauge 3/4 wide base ring without blowing out the 22 gauge. I got it done but was ugly!!!!

Well it came apart again. Since then I have bought a Lincoln 180 MIG and plan on using it this time. I have just started practicing with it and wondering how to approach welding the 22 gauge blades perpendicular to the 12 gauge base ring. I have read you should set the wire feed and temp for the 12 gauge not 22 gauge is this true? You should focus the arc on the 12 gauge get your puddle and sort for push the puddle up the 22 gauge true?. I plan on using Lincoln SuperArc L-56 . 025 wire with 75% Argon and 25% CO2. This sound right? I have some of those I think carbon or ceramic magnetic blocks(not sure where I got them) and place that behind the 22 gauge blade to help keep from blowing it out does this sound right also? The outside ring is 1/8 rod running through holes the blades toward the outer edge. I used one rod last time this time will run 2 rods. That is what broke this last time cause it to come apart.

Oh last question and kind of just probably a personal preference thing. When you set the shielding gas flow some say set for 15, others 30 and even as high as 45!!! So what is right to start at 15 and increase if needed to get the proper shielding?

I have not finished reading all the post here yet. So if this question has been answered I apologize.