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Folks, I need to remove an old kerosene storage tank (for central heating) from my in-laws back garden. The tank is moulded plastic, and has a 1,000 litre capacity.

The access point it was originally brought through is gone.

The tank has been empty for 10 years or so, the easiest way to remove it is to cut it up, and the easiest way to cut it up would be with an Angle Grinder.

There is a small amount of liquid in the tank, which is (mostly) water, I'm assured the tank was emptied by professionals.

Obviously I'm worried that there may be residual fuel/fumes that the Angle Grinder could ignite.

Is there any way to quantify the ignition risk, or some anti-philostogen agent (i.e. fire retardant) I can add to the tank that will completely negate the ignition risk?

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@Niall C: Thanks for the tags. –  Binary Worrier Jul 7 '11 at 11:58
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It is a health risk to assume the gas is gone. maybe best ask you fire station if they can come out and check the container for any flamable gasses using their special equipment.. other wise i would NOT risk it really.. all it takes is a good enough air-fume mixture and boom.. (Maybe manually cut 2 sections on opposing sides and blast air into the tank from one side while grinding away bigger pieces.. more air is good here) –  ppumkin Jul 7 '11 at 12:17
    
@ppumkin: Thats what's worrying me :) –  Binary Worrier Jul 8 '11 at 7:54
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6 Answers

up vote 6 down vote accepted

Kerosene is not terribly flammable, so it probably is not a problem anyway. I'd pick a windy day, or even simpler, maybe have a fan blowing across where you are working, to keep any fumes away from the motor.

I'd also use a reciprocating saw, not an angle grinder, at least if I had the choice. Even if you have a carbide blade for the grinder, a reciprocating saw may still cut as fast or faster than a grinder, and it will generate less heat when cutting a plastic tank body.

If you are still worried, I'll bet that a good sharp (hand powered) pruning saw, the type that cuts on the pull stroke, will cut up a plastic tank at least as easily as would an angle grinder.

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A reciprocating saw, aka sawzall, will do well with plastic. If you don't already own one, you should consider it, or find a friend, or rent one.

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Just a word of caution, once you have a sawzall, everything will look like a kerosene tank that needs to be cut up. :) –  BMitch Jul 7 '11 at 12:11
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You shouldn't ever use angle grinders on plastic - when cut at such high speeds plastic will melt and evaporate and could start a fire even without kerosene. Your best bet is a plain old hand saw - it will cut plastic rather fast.

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Thanks for the tip, I'm not a "Handy" type of guy (you can probably tell), but rarely refuse a challenge. –  Binary Worrier Jul 7 '11 at 11:52
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It's probably not a problem, but to be safer you can dump in a bunch of dry ice and let the CO2 displace the air. This will work best if the only opening to the tank is at the very top, since the CO2 is heavier than air. See here for a website promoting this idea.

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Interesting suggestion –  auujay Jul 7 '11 at 16:41
    
Very interesting, however I'm not sure it'll work in my case, as I continue to cut into the tank I'm creating an ever larger hole that the CO2 will escape from. Thanks anyway :) –  Binary Worrier Jul 8 '11 at 7:53
    
Well, the idea is that the dry ice is gradually evaporating and replenishing the CO2. If the hole is big enough to remove the CO2 faster than it is produced, then the same hole is big enough to remove the fuel vapours faster than they are produced (since the dry ice is much more volatile than the fuel). –  Lev Bishop Jul 8 '11 at 8:01
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I would take a drill and put a few holes in the tank, first on the top to let fumes escape and then the bottom to allow any liquid to drain out. A would expect for a drill to have a lower spark risk. Wait a bit after making the holes and then come back and cut it up however you want.

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Joel, I now feel incredibly feckin dumb, I hadn't thought to do something so blindingly obviously useful. Epic fail on my behalf :) –  Binary Worrier Jul 9 '11 at 15:43
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If you have access to a welding supply - use C02 or Nitrogen gas and just keep a constant flow of gas into the tank as you work

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