Welding.

[W5FL]

Welding is simply the process of heating the metal with an electric current. The arc has a negative resistance and will sustain an arc. Arc welding is DANGEROUS if it causes sparks in flammable vapors or causes large currents to go through close tolerance parts as they will also arc and pit the bearings or other precision surfaces.

The problem can be minimized by clamping the ground as close tot the surface to be welded as practical to ensure that the flow of current from the rod to ground is localized to the maximum extent. Removing the battery leads simply removes one more path for current to flow, but does little to protect anything that I can think of on a tractor. As long as you use common sense, you should have no problems. Removing the part from the tractor is always the safest way.

 

[gordon]

I'll remember that one, like you said a quite simple cure.
Thanks for the info Tom
Gordon

 

[dullpain]

Thomas
Checked all my books last night. No mention of any type of rod designated as MR xxx. As some books are a little dated, I called my welding supply house this AM and they had never heard of any such bug.

 

[Anonymous Poster]

Welding current flows between the ground clamp and the welding rod or wire (if MIG). Most of the current flows via the path of least resistance (typically most direct path composed of conductive materials with least discontinuities) B U T some current may flow where you don't want it (bearings and such) POTENTIALLY (intended pun) causing great grief. When in doubt, isolate. Attach ground clamp as close as practicable to site to be welded and away from bearings etc. A N D R E M E M B E R All it takes to ruin your day is one welding spark out of the millions you will make landing near or passing by the battery caps. Batteries give out hydrogen (extremely explosive) and just a small amount can explode with enough force to scatter the battery's internal parts A N D the sulphuric acid over a considerable area. I once blew the caps off of a battery about 20 feet from where I was welding. Not likely, but possible. Luckily there wasn't much hydrogen in the battery just then and it only blew a couple of the caps into the 20 ft ceiling but did not rupture or otherwise harm the battery or any of the surprised crew.

 

[W5FL]

Batteries only give Hydrogen gas out when they are being charged. See the little bubbeles come to the top of the liquid...

 

[Tobias Dunlap]

I've seen one case in my career with bearings being damaged. No it wasn't me. The welder was installing jackbolts on a large electric motor base and for some reason the fool clamped his ground to the motor's drive coupling and the current passed through the bearings on its way to the arc. They didn't realize anything had happened until they began the primary alignment and the shaft wouldn't turn at all. Upon disassembly of the bearing case, the shaft and surface of the bearing were bonded in some places and heavily pitted all over.

A good rule of thumb to follow is anytime you weld on machinery is to keep your ground clamp no further than four feet from your arc, and to try to prevent the current from travelling through sensitive areas.

Another hint that an old welder once told me is to wrap a chain around the rear axle and let it drop to the ground. Gives the current a direct path to earth.

Unhooking the battery is always a good idea. Be very cautious around them because they will continue to vent hydrogen for quite a while after a charge cycle and/or running the machine. A small spark in the wrong place in the right conditions will cause a **** of a bang and that acid burns like **** when it gets on you.

Hope this helped.

Toby

 

[Tobias Dunlap]

wow, I just realized this thread is 12 years old. I was only 14 when this was started. I feel old now.:ashamed::confused2:

 

[rcowan]

Wow. It's funny how things keep popping up.
Kinda like Capri pants. Next thing you know the mullet hair cut will be back.:thumbsup:

The information is still valid. Disconnect the battery and keep the ground clamp close.


RC

wow, I just realized this thread is 12 years old. I was only 14 when this was started. I feel old now.:ashamed::confused2:

 

[kentuckydiesel]

Disconnect the battery if you choose, but I don't do it, even on vehicles with ECMs...never had any issues...and I do ALOT of welding. In fact, I've been welding on some of our press brakes lately which have around $10,000 in computer controls per machine. No issues there either.

As far as bearings go, that is a non-issue so long as you don't ground to something that will force the current through the bearings. Examples would be grounding to the engine block to weld on the crank pulley, grounding to the wheel to weld the axle housing, etc.

-Phillip

 

[Jesse masterson]

Wow it is 12 years old , I wonder if all the people that posted are still alive . A little creepy.