welding fuel tanks

[scorched]

Need to remove a section of the petrol fuel tank.

Ive takin it out and drained it but is there any advice for cutting and welding the thing.

Should i just take it to a professional?
If so who would be able to do it?

cheers

[bigpat]

Ask yourself if you trust your own welding first of all.

Being thin, use LOTS of tacks, before fully welding it to reduce any warping. Use wet rags to cool the surrounding area as you go.

The tip is to put as little heat as you can into it. MIG welding is cool, but I reckon TIG would be mint in terms of strength, and ability to weld the thin sections. Other than that, theres not much science to it

[scorched]

i was wondering about the whole fume kinda thing and it blowing up as i cut into it with a saw???

[MY45]

I think you should leave this one to a pro, i have asled my old man the same question and he said that the tank needs a pro wash to remove fumes ect. There have been many accidents on farms and places where people try to weld fuel tanks

I wouldnt, and thats coming from the king hillbilly

[fisho64]

There are ways to do it, flush it out with water a few times then fill it with exhaust gas (from a petrol car) nitrogen or another inert gas, or better still with the area you want to cut at the highest point and fill it with water. But, at your own risk!!

[BundyRumandCoke]

I had a crack in a Suzuki tank welded once. It was migged. It was drained, then repeatedly flushed for about an hour, then connected via a radiator hose from filler pipe to exhaust of a diesel vehicle, which was left running while the welding took place. It worked out successfully. It was done by Driveline Services, or a similar named business in Cairns.

[V8Patrol]

This is NOT a job for the home handy man

Having said that, there a a few ways of doing the job that will minimise the posibility of an explosion ........ that means that there still remains a small element of RISK so be ulta carefull.

Inert gases will greatly diminsh the posibility of an opps, the gases listed as posted by other members will work to a degree but please add to that list ARGON....... or argoshield from ya mig bottle
You will need to set it up in such a fashion so that there is a constant flow of gas into the tank during the cutting and welding stages.

Water flushes will assist with removal of liquid fuel that remains after emptying. There are chemical additives that will greatly assist with the breaking down of any remaining fuel droplets aswell ....... the concrete cleaner which is used to remove oil stains from concrete driveways ( as seen on TV commercials ) is quite good at breaking down much of the fuel droplets which will remain

Cutting the tanks is most dangerous stage as it is the first time both heat and sparks can actually enter the container........ angle grinders therefore are best left in the cupboard and an alternative cutting device should be found.
Nibblers or air chisels are a far safer alternative cutting device as the likelyhood of an ignition spark is much lower compared to a grinder.
Hint: ya local panel beater should have a panel cutter ( like a nibbler ) and these are awsome for fuel tanks.

Although welding stage is usually done at the end of the process there is STILL a chance of an explosion, heat from the actual weld often condences fuel vapour that exists withinin the actual metal........
Metal is porous to a certain extent and although it doesnt leak petrol the petrol does "soak" into the metal..... endless flushing and inert gas introduction can NOT prevent the fuel from reforming either into a vapour or droplets after it has been heated from the welding process. Usually its at the welding stage that an explosion occours because ppl dont allow for the fuel that has soaked into the metal.... so be well warned

Welding ...... as stated Tig is a far safer option over Mig but it still is a very high risk option, SOLDERING for example would be a much safer option for a tank with a hole either by filling a small hole with solder or the addition of a patch over a larger area.
I have fixed plenty of tanks using solder, even great open gashes are an easy fix using this method....... I did a tank not so long back that had been ripped open from the front edge to the back by a lump of steel ( it was a broken leaf from a trucks spring pak and was still in the fuel tank !!! )

If you are modifing a fuel tank to fit in a specific location and the soldering method is not an option because of the amount of area that has to be "welded" then perhaps you would be safer buildin an entirely new tank from new steel.

AGAIN...... This is NOT a job for the home handy man

Kingy

p/s
Years ago we used to fill the tanks with water and freeze them..... this still works but getting access to a large freezer these days is a hard thing to do.... the local supermarket now has a "food safety plan" and petrol just isnt on the list
The freezing method worked a treat but you'll need to keep a close eye on the tank as water EXPANDS when its frozen ...... too much water and the tank will grow in capacity by around 20%.
We also used to freeze tanks to get dents out
and......
it was a sneaky way of adding extra fuel capacity to a standard tank ..... back in the days of real motor racing fuel tanks were often a controled item and by freezing em one could get an additional 10+lits of fuel while still using the "controled fuel tank" ( we also used to increase the actual fuel line size too ) ..... may not seem like much but 15+lits of fuel meant atleast 3 extra laps of Bathurst over other teams.

Cheating ......... depends on how you interprut the rules

[toaddog]

Just for your info I have been to 3 jobs when someone has been trying to weld a tank and its exploded and killed them. THe last one he had a 4 inch piece of tank sticking out the front of his forehead.

Take it in to someone who does them professionally.

They steam the tanks for hours to get any trace of fuel out.

[dumbdunce]

...water EXPANDS when its frozen ...... too much water and the tank will grow in capacity by around 20%....

I call BS!

at atmospheric pressure, water expands approx 9% by volume when frozen. depending on the material properties of the tank, some or all of the deformation caused by the expansion of the water will be elastic deformation, which will be lost when the water is melted - the point is that the maximum increase in volume of a tank filled with water, then frozen, must be mesurably less than 9%. In reality, most of the expansion of the water will be swallowed by oilcanning (bowing out) of the top and bottom of the tank, and this will be almost completely reversed when the water melts. or the tank will split.


anyway back to the welding of tanks, yes filling the tank with an inert gas is a good idea, but diesel exhaust is NOT an inert gas, at idle a diesel only consumes a small % of the available oxygen in the air, and exhaust from an idling diesel will happily support combustion.

[Zute]

It needs to be soap washed and steamed. Dont do it, let a pro take the risk.

[JOHNZ]

Need to remove a section of the petrol fuel tank.

Ive takin it out and drained it but is there any advice for cutting and welding the thing.

Should i just take it to a professional?
If so who would be able to do it?

cheers

flush the tank with water a few time & then run the exhaust from a petrol engine through the tank until the tank is hot. this dries out all the petrol fumes

[ingthorsson]

I did a few tanks twenty-some years ago, and my method was to drain, flush with water for at least an hour, with the filler neck as the highest point, and then I used to blow out the residue fumes by stretching the acetylene welding flame into the opening. Usually there would be a soft "whoosh" as the residue blew. After this the tanks were considered safe to weld. Back in those days it was done with gas, now I´d use MAG.
Maybe this was a stupid way to go about it, maybe I´m lucky to be alive,
but it worked for me!
However, after reading the suggestions others have made on the subject
I think that today I would use some chemical, whatchamIcallit, that you add to the fuel to get rid of condensed water, to help with the flushing and after flushing I´d pump exhaust fumes into the tank for awhile before blowing out the residue.

Ingthorsson.

[sudso]

Some tanks especially aftermarket ones, have an expansion chamber as well that's welded somewhere on top of the tank. They have a small hole into the tank and a small hose fitting on the outside of the chamber where a hose connects to allow the tank to breathe when fuel expands.

Why am I mentioning this?

Because of the small hole into the tank and small hose outlet, fuel vapours can be trapped in there for a very long time and can take a while to remove.

This is the case with my ARB long ranger tank which was badly dented off road.
Like you I have to cut out the dent and reweld it (2mm thick tank and dented along weld seams)
It's been sitting in the shed for 4 weeks now and although I could smell no vapour in the tank last night I used compressed air into the exp. chamber outlet and the petrol vapour was still there as it blew through into the main tank.
BTW I got a new tank thru insurance but I thought I might as well fix the damaged one since I'm a welder, and sell it to cover my excess.

I'll be doing the argon purge thing and mig welding it. Not to try and get rid of all the oxygen though. That wont happen because there will be fit up gaps to start with and oxygen can enter but the purging will minimise this and also help with getting thorough penetration and a nice smooth weld bead on the inside of the tank. Doing this is a must if tig welding it.
I'll flush out the expansion chamber 1st. though with mild detergent and water before any grinder or air chisel goes near it.

As V8patrol said, an air chisel or nibbler would be the go, not only for safety reasons but it will also prevent the need to try and clean out the mess and and bits of metal that and angle grinder would leave behind inside the tank.

[ozrunner]

Are you in HBF

There are many ways that this can and has been done from soapy water to gases etc but it really isn't worth the risk.

Standing there with a gaping hole in your chest will be too late.

I took mine to a accredited tank degasser. They steamed it etc and gave me a certificate. But even then its only valid for 24hours so you need to lock in the actual welding in that time to be safe.

Cost for steaming was $50 and I don't know about you but I considered myself worth more than $50 .

[dogbreath_48]

I had a mate who got the bright idea of filling the tank with water then cutting it with an electric angle grinder. Clever... He gave up after the grinder got soaked, emptied out the water and continued cutting! lucky guy i'd say.

or curse, this guy was cutting the bottom off the tank to use for a bonnet scoop. needless to say that car only lasted 2 weeks on the road before defect.

My vote would be to take it to a pro, or if your good, knock up a custom tank.

-Stu