Welding Sq Four Petrol Tank

[keith wainwright]

Hello all some advice please? I need to do some welding on my petrol tank without putting myself into
orbit. First I am going to flush the tank several times with hot water with washing up liquid added. Use a steam cleaner on it for about 30 minutes. Then block the two tap holes and fill the tank with some Carbon Dioxide (I use it for my beer making) I thought of using the exhaust fumes from my car but its a diesel? Does this method sound safe. Any further ideas would be much appreciated.

Keith

[nevhunter]

If you can get a bit of dry ice and put it in there, that should do the trick. Keep it away from the hot part. You can also get small CO2 cylinders for putting the "fizz" in drinks. Nev.

[adrie.degraaff]

I wash them with petroleum, (wich takes the petrol fumes), leave some in and weld, it is giving a few lite pufs during welding so stay clear of the cap hole.
I Never use water.

[brenton.roy]

Hi Keith,
whatever you do, you'll be uneasy. The goal is only to reduce the combustion area without making it impossible to weld, due to too much heat transfer. I use soapy water and still have all my body parts (whether they all still work properly is another iussue...). I give tanks a good wash first, as you suggest.

Adrie's comment is interesting - in Australia, petroleum is petrol...
Brenton

[nevhunter]

There's always an element of danger. With rusty tanks the rust holds a lot of fuel to vapourise, when you heat it. Having an inert gas Nitrogen or CO2 should displace the oxygen so it will not burn. I've almost filled the tank with water after just emptying the fuel which was alcohol and the tank was aluminium, and clean. But be careful. A lot of people won't do them. They can blow up years sfter the fuel was emptied from them..Nev

[simon.holyfield]

In my world, Petroleum is otherwise known as crude oil.

Still pretty undesirable to have in a confined space with a lot of heat.

What did you mean Adrie?

[john.whiting]

Theoretically,Adrie is correct.When the concentration of vapor to air is greater than a certain limit,it is no longer explosive. A flooded engine wont start,because the rich mixture wont burn. With the heat from welding the vapor level will only increase,so you should be perfectly safe. Dont try this at home.Regards John.

[keith wainwright]

Hello Lads

Thanks for all the useful information. I will admit to what I done? one of the tank bolts was just a shade two long and overtightened and pushed into the bottom of the tank. Its going to be a real pain in the arse job because. I will have to very carefully cut the fixing lug of the tank to expose the indented area to be repaired. I think I will silver solder to keep the heat down to a minimum. I am going to drill wiring hole's in the head's of all four fixing bolts. SO WARNING do not over-tighten those four bolts. Nip them and wire up. Just one small note if you do not hear from me again,you will no what's happened? I think filling the tank with Co2 will protect me. I have got plenty of that, I use it for brewing my beer. Giving it some thought its going be a good idea to have a couple of glasses of my beer before I start, calm my nerves down?

Thanks again for all your help Keith

[nevhunter]

If you do a good job of cleaning and tinning you can use 50/50 tinmans solder there . It's not a load repair. It's a common fault with those tanks. I have used studs with a short thread on the upper end to avoid the tank being holed. Nuts with lockwire complete the picture. Nev

[brenton.roy]

Hi Keith,
Nev makes a good point. As much fun as it is risking limbs, high lead solder will do a good and safe job. The trick is to get everything really clean and tinned properly.
Brenton