crazy welder issue...sort of

moonlight machine · Dec 16, 2008

My Air Products vis arc thfc 300 rj welder is equiped with the usual Tig torch but also has stick welding cables. They hang under the welding table with my air compressor in front of them also under the bench. So about 1/2 hour ago I'm tig welding and all the sudden there is a pop, sparks, and a loud hissing sound of an air leak...wtf?? So I pull the compressor out and it has a hole burned through the tank! The stick weld cable had a bad spot in the insulation and was against the compressor tank. When I was welding with the tig torch the stick leed had power to it also and was arcing to the tank through the bad spot in the insulation. But how did it ground? It has to be through the power cord as the compressor was not hitting the bench. The hole is only about .020 dia cone shaped out to about .090 Dia. Do I weld it up? the rest of the tank is welded together so a little weld should be ok, what do you think?

5thwheel · Dec 16, 2008

I had a little half horse compressor that rusted out in one spot. I put a metal screw in the hole and it lasted for several years but it finally gave away one day while I was using it. It was amazing how loud a pop it made when the rust spot broke through under full pressure. Sounded like a 22 pistol firing. I did not think it was worth re tanking. A friend took it and welded up the hole. He has been using it for over six years now. I guess it is OK to do it but being rusted I would figure it would eventually rust through some where else by now.

I don't know how safe welding it would be but since the hole is arked through instead of rusted through It would probably hold up. I have no idea if the heat from welding would soften the metal of the tank. :scratchchin:

moonlight machine · Dec 16, 2008

I cleaned it up and welded it up with the tig... seems ok. I disconected the stick weld leed, I can't remember the last time I used it anyway and it only takes a minute to connect it if I do need it. It was pretty loud when it poped, sure got my attention......

lazarus · Dec 16, 2008

If your compressor and welder are plugged into the same power source, the ground went thru the cords and made the loop. Wierder things happen like pulling the plug wires off your Harley, leaving them on the head, turn it over to adjust the valves and it starts. Ain't figured that one out yet!

Carl Darnell · Dec 16, 2008

Personally, I would never have anything under the welding table for just the reason you experienced. All kinds of grit and slag, etc. fall under the table and having stuff under it would make it hard to clean up.

On the other hand, my welding table is on wheels and I move it for some jobs.

As to welding the tank, you did fine welding it up.

moonlight machine · Dec 16, 2008

Carl, I don't like it under the table eather, but if you could see this shop you would know why it's there! I was thinking about putting it in the atic.
Its not heated. What about condensation? PITA to drain. real hot in the summer, If the motor was to burn out or other possible electrical or fire problem I would not know till it was too late....what do you think?

HuFlungDung · Dec 16, 2008

My opinion is that the transformer in the welder should be isolating the cable circuit from the mains.

I once had an old stick welder that pulled a similar stunt: I laid my angle grinder on top of the welder (IIRC) and all of a sudden, the cord on the grinder started to smoke. I couldn't figure out what the hell

I took the cover off the welder, and there was a fairly beefy conductor inside there, that had leaned over and was touching the chassis. It was a paper insulation wrapped conductor, but I guess vibration must have worn through the wrapper over the years. I simply moved the conductor clear of the chassis and wrapped it with a bit of electrician's tape. This seemed to fix the problem.

Mud · Dec 16, 2008

Were you using high frequency at the time? HF will arc to things that are not grounded.

I put a water tank repair screw in the bottom of a compressor tank to fix a leak 20 years ago, it's still there and doing fine.

Carl Darnell · Dec 16, 2008

Can you put an open ended cover over it? I wouldn't put it in the attic either.

moonlight machine · Dec 16, 2008

I was welding steel....HF was on start only... it happened while HF was on...

Frederick Harvie · Dec 16, 2008

Unless you are certified to weld pressure vessels I would replace the tank. Air tank failures can be spectatular and deadly.

Dave D · Dec 17, 2008

Weld it or screw it provided the tank is not rusting out and is worth the effort. You'll find out soon enough if it is badly rusted and you try to weld it. You could weld a female pipe fitting around the hole and use it or at least make it look like it was intentional (drill it out after the weld).

The one concern I would have is to make sure someone else had previously decided to wash the tank out with gasoline or something else exciting. A screw might be the simplest/safest. Dave

macona · Dec 17, 2008

The output from a welder is completely isolated from mains. If there is weld current to ground than you need to start looking because something is wrong.

I would toss the tank. Not worth it...

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crazy welder issue...sort of

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