Angle grinding a diesel fuel tank!

[oldmanbitter]

I have a very large, very heavy, steel diesel tank on my boat which I don't need for fuel. So I was hoping to cut out one side and use it for storage, as to remove it whole, I'd have to cut the top off the boat and use a crane. Is it safe to use an angle grinder on it?

 

[Lakesailor]

I doubt the sparks could heat up the remains of the fuel enough to ignite.
I remember before the advent of additives, when we had real winters, drivers used to light fires under trucks tanks to get the fuel warm enough to flow. OK, sometimes they caught fire...........

 

[jfkal]

I would use an electric jigsaw on very slow speed to cut an access hole. Clean it out and only then put the angle grinder to it. Alsways have sand and fire extinguisher ready.

 

[sailorman]

purge with exhaust gasses first
petrol tanks can be welded after purging

 

[savageseadog]

I've cut tanks a few times, it will catch fire unless you clean it out. Funnily enough this problem is worse the emptier the tank is especially with debris in the bottom. Purging might not work because the angle grider blade will circulate air into the tank as it cuts through. I would suggest steam cleaning it and fill with water until you've cut a substantial section out.

 

[Guest]

Oh Oh ... here we go again .... flash of diesel coming up !!

Best I would propose is to wash out tank with a mix of detergent and water ..... if you can open an inpsection hatch and spray around the mix to clean walls etc. - then better. To get at top underside .... overflow the tank if you can ... that will also lift oil from bottom and hopefully overflow it out ...

Diesel does not create such volumes of explosive vapours as gasoline or kero does ... and if you are really worried - if you can force vent via inspection hatch while cutting - then that will help.

I see another advocates exhaust gas venting ... fine IF you can keep the venting going all through operation - no good just venting before job. (The system is how an Oil Tanker at sea keeps its tanks out of explosion limits ... funnel gas is cleaned ... cooled and pumped into the tanks to blanket the cargo ... originally it was devised to reduce corrosion in tanks ... then some bright spark realised that explosion problems were reduced ... the original corrosion idea fell flat cause funnel smoke contains sulphur and combined with moisture in tank to form sulphuric acid !! Just thought you'd like to know that !!)

Me ... I work with diesel / well all fuels actually and a diesel tank emptied ... flushed out ... I would grind away ... taking it in short careful steps ... to a) keep workpiece temp down ... b) allow any sparks / metal bits flying around to cool before adding more ... c) keep whole area well ventilated ..... d) have good fire extinguisher ready - preferably one that not only smothers but also cools ... ie Foam .

 

[Guest]

Oh forgot to mention ...

On ships tanks ... diesel is one of the few oils carried that simply venting the tank is sufficient to allow man-entry without need for breathing apparatus / cleaning tank ......... (yes it is on deck as emergency recovery ....)

 

[lydiamight]

Had to take a mild steel tank out of one of my previous boats. An electric jig saw with a metal cutting blade did the job much better and neater than an angle grinder. No sparks at all and no bits of hot metal burning holes in the fibrelglass.

 

[Gordonmc]

I did this job a few months ago using a combination of a grinder and a large flat cold chisel. The biggest problem was the tank had been glassed in before the deck was put on... but if you are leaving the bulk of the tank in situ that won't apply.
The boat had been sunk and the tank was full of marina water... so it may be worth flushing through before the sparks fly.
What was a real pain was getting to the baffle plates inside the tank which meant factoring by four the amount of cutting needed. The chisel dealt with some of the spot-welds.
The tank was eventually halved with the bits exitting through the engine compartment.
As well as fire extinguishers, goggles, and heavy gloves a truss might be worthwhile.

 

[No Regrets]

My mate had the same problem, and carefully washed out all the Diesel residue with unleaded Petrol until it was as clean as a whistle, and then used an angle grinder.

I miss Seamus...... /forums/images/graemlins/tongue.gif

 

[moondancer]

Good informative answer!

 

[vyv_cox]

SBC advice

And accurate, in my experience. I have gas welded diesel tanks several times after flushing out with soapy water. The first time I did this I left the tank almost full of water to reduce the vaour volume, but the second time I didn't bother. No problems.
As others have said, grinding creates a lot of debris that may be difficult to remove. Metal debris from a saw is much lower velocity, is composed only of metal and can be collected far more easily. If mild steel a magnet can be useful.

 

[tross]

Re: SBC advice

Tradition dictates that this sort of operation only takes place on the 5th day of the 11th month

 

[Guest]

[ QUOTE ]
My mate had the same problem, and carefully washed out all the Diesel residue with unleaded Petrol until it was as clean as a whistle, and then used an angle grinder.

I miss Seamus...... /forums/images/graemlins/tongue.gif

[/ QUOTE ]

As Basil Brush used to say ... Boom Boom !

 

[Guest]

Re: SBC advice

[ QUOTE ]
And accurate, in my experience. I have gas welded diesel tanks several times after flushing out with soapy water. The first time I did this I left the tank almost full of water to reduce the vaour volume, but the second time I didn't bother. No problems.
As others have said, grinding creates a lot of debris that may be difficult to remove. Metal debris from a saw is much lower velocity, is composed only of metal and can be collected far more easily. If mild steel a magnet can be useful.

[/ QUOTE ]

I have to say that I would prefer a cold chisel or good jigsaw to a grinder ... not so much for the heat / sparks - but the cra* that gets thrown around all over the place with grinders .... I reckon you'd be finding grinder dust for months after if you used one .... in the upholstery - even if covered over !! in the bilges ... lockers etc.

Theuy are great tools ... but the mess is a serious drawback !!

 

[bobmay]

Remove or open all cocks and access ports and vent with compressed air for 24 hours, or steam until all parts of the tank are hot to the touch. Steaming requires a hole at the bottom so that the residue can be collected.

 

[oldmanbitter]

Many thanks to all for the replies. The boat is completely stripped inside, except for the engine and tanks, so there is no problem with grinding debris. Having looked at all the answers, I'll probably go with flushing the tank through with caustic soda and water and get to work with the grinder. If you here about any boat fires on the west coast of Ireland, then . . . . . . . . . . . . .

 

[sailorman]

carbon monoxide is "inert" & will purge the tank
no mess no fuss no dust
just dont breath it

i have used this process on petrol tanks /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/wink.gif

 

[Spuddy]

Tool available called a Nibbler which is two motorised beaks which, erm, nibble. No anxieties about probability of explosion cos there's no sparks. A bit dear to buy for a one off but try a hire shop.

 

[capn666]

Do you mean carbon DIOXIDE? Carbon Monoxide is flammable!