I agree with everything Jack said about propane tanks, I would only differ
in one aspect - I would not want more than 3 PSI air to move oil. A friend
of mine had small tractor tire explode with 12 PSI air pressure, threw him
about 30 feet and did some serious damage to him. Tire and wheel landed on
top of two story building next to Service Station. I unloaded a tank cars
full of oil and they had relief valve set at 5 PSI. Because of volume of
tank it took a while to get air built up to 3 PSI but one you did I could
turn compressor off and car would unload 8,000 gallons and at last pressure
would be down to less than a pound but oil would still flow.
----- Original Message -----
From: "Jack Rabon" <rabonj@bellsouth.net>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Thursday, December 06, 2001 9:26 AM
Subject: Re: [MV] Propane Tank
> The pressure in a propane tank depends on the temperature, as long as
there
> is any liquid left in the tank. A tank with a little slosh in the bottom
> will have the same pressure as a full tank, if both are at the same
> temperature.
>
> I have seen quite a few air tanks made from old propane tanks. They
differ
> from purpose built air tanks by having much thinner walls. Plenty strong
> enough for use, and fatigue through pressure cycles is not the problem -
it
> is rust.
>
> When used for propane, there is little chance of internal rust, but the
> tanks are required to be inspected regularly to check for rust. "Portable
> tanks that have a DOT number stamped on them are required to be
recertified
> twelve (12) years after the date of manufacture and every five (5) years
> thereafter." This involves looking into the interior with an inspection
> tool, and perhaps removing light rust by steel shot & a rotating fixture.
> External paint touch up is done. A new date is then stamped on the
> cylinder.
>
> When used for air service, they will be much more likely to have
condensate
> collect in the tank. And there is no drain valve to release the water.
> The walls will begin to rust.
>
> Portable air tanks also collect water, and begin to rust. They just have
a
> longer way to go before releasing the contents.
>
> Still, I think the idea of using an old propane tank for oil delivery is a
> great idea. So lets manage the risk:
> * keep the pressure down, like 30 psi instead of 100
> * use dry shop air to pressurize
> * check for external rust
> * keep that safety release valve on your conversion
>
> If your shop air compressor runs at 180 psi (common for 2 stage units) it
> will wring out a lot of moisture in its storage tank. When it expands
> through the regulator, it will have less moisture than the discharge of a
> single stage system. Better for painting, too.
>
> I live in Florida, so do not see cold, thick oil. Perhaps one of you cold
> weather maintainers will try the setup with 30 psi & report the results.
>
> Jack
>
>
>
>
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