Just talked to a local professional aluminum boat builder. He told me they either drain the built in fuel tanks and fill them with water, or remove the fuel tanks before welding on an existing boat. He also said to disconnect the batteries and all hot wired electronic or electrical devices. He also said to drill a small relief hole in any sealed tubing or compartments to relieve air pressure. I knew about the batteries and relief holes, but did not know about the fuel tanks.
Do people really drain and fill boat fuel tanks with water, or remove them from a metal boat before welding on the hull ?
If so, that might explain why it costs so much to have even small welding jobs done.
Also, do these precedures apply to cars?
I have not seen people remove, or drain and fill car gas tanks with water before welding on their car body, frame, exhaust, etc ???
It's a best practice and required by most insurance companies. I have tin boats and I have 50 gals of gas for my lawnmower. After 30 days that's about all that will run on the junk gas we get today.
Highly skilled at turning expensive pieces of metal into useless but recyclable crap..
anthonyfawley
- anthonyfawley
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Joined:Fri Apr 23, 2010 6:58 pm
a good practice thats never used 
I just welded in a patch panel on an old chevy van, around the fuel filler neck opening. I removed the fuel filler neck for access to the back side of the panel, and taped off the opening of the tank to prevent fumes from wafting out, but did not remove the tank (or drain it, etc.) No risk of even sparks landing on it. In other words, used common sense. 
I had welds on cars, bikes, atvs, even welded a tank with some diesel in it.
The thing u should worry about is the car battery, if you forget to ground the car or the clamp doesn't make good contact u will still be able to weld somehow with curent from the car battery and it may explode or damage the accu from the HF (this is a mith I've heard), so I think disconecting the car's batt is a good thing.
The thing u should worry about is the car battery, if you forget to ground the car or the clamp doesn't make good contact u will still be able to weld somehow with curent from the car battery and it may explode or damage the accu from the HF (this is a mith I've heard), so I think disconecting the car's batt is a good thing.
A battery is not much different than a welder. Disconnecting it will help to keep it from being damaged by an over voltage condition but most batteries will handle 15-18v for short periods without problem. When you hook a wedler up to a car and you disconnect the battery you are welding solely in the ground plane so essentially the circuit is broken to electronic equipment. However, HF will induce voltage into electronic equipment and can damage it.
I would hesitate to us a TIG or plasma cutter with HF start on a car with a computer system but MIG or Oxy/Acet are fine. As far as gas in a fuel tank goes, you need the triad (oxygen, fuel, heat) to have fire. Take away any one of those and you are not at risk. Just remember that fuel can come in many forms, and oxygen and heat are impossible to eliminate in the welding process. Ventalation away from the welding area is critical if fuel or fuel vapors are nearby.
I would hesitate to us a TIG or plasma cutter with HF start on a car with a computer system but MIG or Oxy/Acet are fine. As far as gas in a fuel tank goes, you need the triad (oxygen, fuel, heat) to have fire. Take away any one of those and you are not at risk. Just remember that fuel can come in many forms, and oxygen and heat are impossible to eliminate in the welding process. Ventalation away from the welding area is critical if fuel or fuel vapors are nearby.
Highly skilled at turning expensive pieces of metal into useless but recyclable crap..