welding near a fuel tank

[BrokenBiker]

so, ive got a few bits to weld up on the step fathers rav4. 2 patches are right above the fuel tank, the other 3 are miles away and no issue.

ive never really had cause to worry about the fuel tank on previous welding jobs, usually an exhaust that is on my bench or exterior body work after a bump.

so, do we opt for draining the tank then welding (still very aware that vapour is more explosive than liquid) or do we opt to cover the tank with damp rags.

its currently half ish full with petrol, and around 1.75" clearance between the top of the tank and the floor being welded. Welding a flush fitting plate from the top with mig.

 

[hotrodder]

What's the tank made out of, metal or plastic? Fuel lines in the vicinity etc? As you say vapour is more explosive and fuel tanks typically operate above the explosive limit (not enough oxygen) but if something gets burnt through/cut etc then suddenly all that fuel has access to air...

Don't have enough info to state what i'd do but FWIW a mate of mine got burnt some years back welding/grinding in the engine bay doing an engine swap. No fuel tank or engine in the car but residual fuel in a line flashed off in his face and cost him a large chunk of his hair. To be fair some of his burns were the result of those of us 'helping' him (read standing around drinking) throwing our cups of tea over him during the initial ****, fire, panic reaction

 

[BrokenBiker]

Think its plastic, fuel lines are a reasonable distance away so no worry of cutting through them when opening the rusty holes out to good metal.

if i do drain it, which i probably will given i have a few days to get it done, how do i ensure there is no vapour in the tank?

 

[doubleboost]

Can you put a piece of plate on top of the tank
(between it and the floor you will be welding)
If you drain the tank it could be filled with inert gas (co2 argon ect)

If the tank was drained I would remove it
You have to make the decision
You can get away with a lot but it only takes a little to spoil your day

 

[octo0072000]

Think its plastic, fuel lines are a reasonable distance away so no worry of cutting through them when opening the rusty holes out to good metal.

if i do drain it, which i probably will given i have a few days to get it done, how do i ensure there is no vapour in the tank?

you could fill it with water but if it's a plastic tank there will be no drain hole so maybe just best to leave it
cover top of tank with wet carpet rags soaked in water etc to keep it wet weld one bit check it etc

 

[cumbriasteve]

We had a fuel tank go and the guy was a fair bit away from it (possibly not fully drained or vapour), never did get the full story of what went wrong, it's something you don't forget though.

I know after that if welding close to a tank, it was drained, ensured it was dry and an airline put into it for 10 mins before welding and left running whilst welding, the air purging the tank during welding...no idea if that is a safe method or not though.

 

[BrokenBiker]

if there is a drain point i will drop the fuel and purge with water, if not i will go with the wet rags and check them regularly. From a rough guess the plate welded in Will be about 60x60 dimension thickness to match the floor. Will do the other parts first to get my setting bang on so i can run around them quickly.

would it cause any serious issue if i quench the welds? Nothing is mounted on them, its just floor

 

[dannyp]

fuel tanks are ether best left well alone with fuel in them, or removed and carried out the way imo

 

[brightspark]

id rather weld with a full tank that has no oxygen in it than a part filled or empty one filled with fumes .as said cover the top up with either a bit of tin and damp towel have someone on fire watch with a fire extinguisher and do the job outside

 

[BrokenBiker]

job is being done outside anyway, might get him to fill the tank first to remove the oxygen, will see if i can get some steel to put over the tank and then wet rags as mentioned

 

[rich the mechanic]

My answer is to drain the tank and run a pipe off the/an exhaust to drain the last out that way depending on how long it runs for you need a good 20 minutes of exhaust fumes to purge the tank unless you have loads of cheap inert gas your willing to waste (eventually) and then cover the tank to protect the plastic.

 

[rory1]

Take the tank out, don't be daft, do the job right.

 

[chevy2]

Take the tank out, don't be daft, do the job right.

^^ yeah that, the fact you have concerns welding near the tank justifies removing it,

An hour or so's work is probably all it takes.

 

[Parm]

It's a no brainer if you value the safety of you and your workshop. Remove tank to a safe distance, block lines then commence once your sure there is no residual fuel vapour around

 

[outofthefire]

Just like brightspark says fill the tank to the brim and cover it, and you'll be fine. Empty tanks are dangerous.

 

[RonA]

so, ive got a few bits to weld up on the step fathers rav4. 2 patches are right above the fuel tank, the other 3 are miles away and no issue.

ive never really had cause to worry about the fuel tank on previous welding jobs, usually an exhaust that is on my bench or exterior body work after a bump.

so, do we opt for draining the tank then welding (still very aware that vapour is more explosive than liquid) or do we opt to cover the tank with damp rags.

its currently half ish full with petrol, and around 1.75" clearance between the top of the tank and the floor being welded. Welding a flush fitting plate from the top with mig.

I used to have to carry out explosive tests for welding on Sentinel rail locomotive diesel tanks whilst still working. The tanks often developed cracks due to vibration. Our method was to drain the tank of fuel then refill with water to just below the crack & then fill the void left above with nitrogen & leave a trickle flow of nitrogen on throughout the welding.

My personal view with petrol tanks is they are best removed, petrol being considerably more volatile than diesel. However if you do want to chance it perhaps filling the void above the petrol with welding gas might be an option both Co2 & argoshield type mixtures being inert. Just think the old fire triangle I.e Fuel + Heat + Oxygen = Fire We also used to use a fibreglass woven sheet to cover anything likely to be damaged by the welding sparks

RonA

 

[gordon stephenson]

As Brightspark says eliminate the oxygen,When I cut into propane/butane bottles I don't wash them out now,But leave them on their sides and blow them out with an airline for 5 minutes before cutting.But whatever you decide, do not take risks!!

 

[Rocketman]

I took the easy way out, I got a mobile welder in. Welded right next to a fuel filter and fuel tank.

I chickened out - visions of blowing up in my garage, asked the MOT garage they wouldn't do it without taking the fuel tank out. This mobile guy came out had a look, said it was a piece of **** and don't worry. True to his word the car didn't blow up. To be fair though he had a lot of fire proof blankets covering everything before he started.