Installing New Hatches In Fuel Tanks

[s/v Jedi]

This is how it was when I learned this; may be they now put stuff in diesel that changes it but I don't think so:

- diesel fuel flash point is well above 50 Celsius.
- standing diesel fuel below that temperature (without being atomized by injectors inside cylinders etc.) will not ignite by spark or flame. Only when the liquid diesel fuel becomes warmer than 52 Celsius or so, it starts creating vapors that can ignite.

that is how it was and I believe still is.

p.s. Also, OP has an aluminium tank, not a steel tank, so when drilling this there should not even be any sparks.

p.p.s. I believe many are confusing this with welding on a diesel tank, which process can heat the liquid diesel above it's flash point.

[Ofer]

Originally Posted by s/v Jedi

This is how it was when I learned this; may be they now put stuff in diesel that changes it but I don't think so:

- diesel fuel flash point is well above 50 Celsius.
- standing diesel fuel below that temperature (without being atomized by injectors inside cylinders etc.) will not ignite by spark or flame. Only when the liquid diesel fuel becomes warmer than 52 Celsius or so, it starts creating vapors that can ignite.

that is how it was and I believe still is.

p.s. Also, OP has an aluminium tank, not a steel tank, so when drilling this there should not even be any sparks.

p.p.s. I believe many are confusing this with welding on a diesel tank, which process can heat the liquid diesel above it's flash point.

My vote goes to the Jedi. I would follow his advice.

[GordMay]

Originally Posted by s/v Jedi

... - diesel fuel flash point is well above 50 Celsius.
- standing diesel fuel below that temperature (without being atomized by injectors inside cylinders etc.) will not ignite by spark or flame. Only when the liquid diesel fuel becomes warmer than 52 Celsius or so, it starts creating vapors that can ignite...
... p.p.s. I believe many are confusing this with welding on a diesel tank, which process can heat the liquid diesel above it's flash point.

Indeed.

Flash point is determined by heating the fuel in a small enclosed chamber until the vapours ignite when a small flame is passed over the surface of the liquid. The temperature of the fuel at this point is the flash point.

Diesel Flash point 40° - 62°C (144 °F)
Biodiesel Flash point >130 °C (266 °F)

[dannobee]

Remember, those flash points are in AIR. If you fill the tank with argon or carbon dioxide first (both of which are heavier than air), the tank won't ever go boom, even if you cut the hole with a plasma cutter.

We routinely weld diesel fuel tanks without much more than filling them with argon and/or CO2. But they are emptied of fuel.

[s/v Jedi]

Originally Posted by dannobee

Remember, those flash points are in AIR. If you fill the tank with argon or carbon dioxide first (both of which are heavier than air), the tank won't ever go boom, even if you cut the hole with a plasma cutter.

We routinely weld diesel fuel tanks without much more than filling them with argon and/or CO2. But they are emptied of fuel.

Yes correct, it is all about reaching the explosive limit with right amount of oxygen in the vapor. However, the OP is not going to weld or use plasma cutters. He is going to use a drillbit to drill a hole for a pickup into the top of an aluminium diesel tank in cold England. Unless he puts propane burners under the tank, he is never going have diesel at 50 degrees Celsius with this project, nor is he going to have sparks.

The safest thing to do is to fill the tank with sand before drilling. It is also the most time consuming method.

p.s. with some grease or other sticky stuff on the drillbit, most if not all chips should stick to that instead of dropping in the tank.

[Dockhead]

Originally Posted by s/v Jedi

This is how it was when I learned this; may be they now put stuff in diesel that changes it but I don't think so:

- diesel fuel flash point is well above 50 Celsius.
- standing diesel fuel below that temperature (without being atomized by injectors inside cylinders etc.) will not ignite by spark or flame. Only when the liquid diesel fuel becomes warmer than 52 Celsius or so, it starts creating vapors that can ignite.

that is how it was and I believe still is.

p.s. Also, OP has an aluminium tank, not a steel tank, so when drilling this there should not even be any sparks.

p.p.s. I believe many are confusing this with welding on a diesel tank, which process can heat the liquid diesel above it's flash point.

Indeed.

I'm sorry to have offended the sensibilities of the marine school graduate, but I do think he is confusing the protocol for welding tanks with that for merely cutting one. I am pretty confident that just cutting holes in alu plate does not require any special anti-explosive precautions.

Before actually doing so, I will read up on it again, to be absolutely sure.

[David_Old_Jersey]

............and get someone to shoot some youtube - just in case!

[Bambolera]

I just cut access holes in my aluminium tanks. Although most of the fuel was pumped out, there must have been fumes present. No problem.

I used a 4" hole saw, an electric drill and a shop-vac. If you remove the chips (w/shop-vac) as you drill, there will be very little debri in the tank.

Good luck

[Bambolera]

Since I also needed to add fittings to the tanks, I had them welded to the access plates with pickup tubes.

Hope that helps