fuel tank

[brightspark]

mythbusters

heres a tank. i put some diesel in it and put the blowtorch on it till it was well smoking out of the orifice then turned the blowtorch on to the open end into the white smoke . all that happened was it ignited into a flame no blast no sudden presurisation of tank or large whoosh does that answer the question of welding a dirty diesel tank . if i was welding one id just powerwash it out with detergent and weld happily away if u want to see a big flame il fill more and stoke it up old co2 tanks have a use after all

 

[mike os]

diesel is not such a big deal, just a common sense approach.... clean well & dooooo it ( assuming you can remove/open all openings in the tank)

petrol is another matter & best avoided unless really necessary eg vintage or no sensible option like an unavailable bike tank

that said, if it has some large openings it is unlikely to explode..... may go bang & scare you to death ( see I'm learning language boss)... bit not really likely to maim or kill.

Do you really NEED to do it? if not i would just leave it if it's petrol & live with it.

 

[syborg]

forgive me for stickin my nose in but.... surely if all the petrol/ diesel is drained completely out, the tank is then filled with water pushing out any excess vapours then emptied out it is fine to weld? as petroleum products float they would be the first to overflow out of the tank??

i could well be 100% wrong but it wouldnt be the first time and im sure it wont be the last, lol

 

[brightspark]

ive welded a few petrol tanks . cleaned them out with a power washer using detergent let them dry out for a day . get the sniffing gear round them EG YOUR NOSE no smell get welding . not a problem its what people are happy with and feel safe and confident to do . most firms wont touch stuff like that because its not worth there while or there not covered by there insurance to repair them health and safety and all that stuff . in home workshop health and safety have no say in the matter as its personal use

 

[Graham S]

When I repaired the fuel tank on my bike (a grey import) I emptied the fuel, syphoned off the remnants with some thin tube (as you can't pour it all out) then filled with water and drained twice, syphoned again and left it in a warm place with the cap off for several days.

I did not explode

Petrol is serious stuff but the fact it is volatile in the sense it evaporates easily is something in your favour if you can at least get the vast majority of it out and wait a good amount of time.

Diesel seems less scary but perhaps tends to cling more.

Graham

 

[scott0031]

Although one always has to treat any fuel tank with full respect, diesel isn't a problem like petrol.

I used to weld many tanks for long distance lorries filling up in Europe on their journey and returning to the uk.


They were jet washed inside and out with detergent, job done and go get welding. As brightspark has proved the dangers, there isn't any if a safe working approach is taken.


Kind regards


Scott (ward eng)

 

[Big Len]

We've ten years of experience with putting aluminium tanks in our single seaters and never had issue with corrosion with gasoline. Simply sheet metal designs, a few baffles and the ports are on a thicker block of aluminium thread etc etc. We've recently started dabbling in bioethanols and a bit of anodising later this isnt a problem either.

To weld our tanks that have already been used we drain them , several rinses with soapy water and then set it on the exhaust of a two stroke engine (lawnmower, genny etc ) the two stroke is pretty key so that the exhaust gas leave plenty of nice residual inert substances on the inside of the tank. This is not the same as flushing it with a shielding gas as there will be none of these residuals. <EDIT> forgot to add the heat of being on the exhaust also evaporates the remaining fuel

We have done this repeatedly without incident but as a further precaution , I have read, to weld the tank as full with water as possible ie to just below where you intent to weld. I should hope the safety implications of this are obvious and remember to not seal the tank as pressure will build up as water is heated and evaporates.

One point about aluminium tanks is if you choose to use a thread aluminium cap be very gentle with it and probably lube it with something. We have have a few coalesce on us and it gets real messy . Anodising even just the cap will more than likely prevent this though.