Thoughts on using air pressure to push fuel out of transport tank to machine.

kthompson · Aug 16, 2020

If memory is correct have bumped into a post in time past someone used air pressure to push the fuel from their transport tank to the tractor or what ever is being filled. I know the outlet would have to either have a drop tube or be on the bottom of the tank either on a side of the very bottom. Would then use a hose with nozzle to control the flow.

I have thought on it rather than buying an electric pump. Currently using a hand rotary pump. Considering on a diesel and gas tank. My tanks reside on trailer under my shelter with air line with in few feet of them. Both tanks are good metal tanks with standard pipe fittings.

Industrial Toys · Aug 16, 2020

Even a little air pressure can impose enormous stresses on a tank and it's welds. Stresses, it was never meant to see.

Probably many would warn you that compressed air and fluid is a bad combination almost always. I think I wrecked a water heater, by applying compressed air in an effort to drain it quicker once.

In any event. If you are going to do it, obviously use a regulator.

kthompson · Aug 16, 2020

Industrial Toys, been many years back but worked for a company who made heavy machines. Cranes to be exact. We used full air pressure for air tools to push fuel through the lines to bleed them. Never aware of any issue with a tank, filter or any part of the fuel line system. I think 80 psi can be an acceptable pressure for their water lines in some areas. It would seem water heaters would be designed for at least 100 psi but have no idea.

I don't think you would want the air pressure being released into the fluid for that would cause it to bubble and mix with the air. Thanks for your thoughts. I was thinking of something like 50 psi. But that is also one reason for my questions.

grsthegreat · Aug 16, 2020

Are there vents on those tanks? My tank has electric pump, but it must vent to outside air otherwise there would be a vacuum?

crazyal · Aug 16, 2020

I would be a little worried that if the fuel level got too low you would have air going down the fuel line. When that happens you'll have a volatile air fuel mixture. Chances are you'll never have a problem.

Industrial Toys · Aug 16, 2020

I'm not an expert, but was thinking more like 3 or 5 pounds, based on experience doing such things. Certainly, no more than is required to move the fuel.

Another good point. Is it possible to inject air into fuel? That wouldn't be any good at all.

I had a friend that ended up with a bone sticking out of his hand and was almost killed with a little 4" rotten turf tire that exploded on his bench and went into the ceiling. Compressed air can be extremely dangerous.

EDIT: Another Air pressure story. Went to see a customer years ago and he had his broken arm in a cast. Seems his Galvanized weed sprayer blew up. That might have saved me, because I had one that the pump was giving me issues and had in mind to put a schrader valve on the tank to avoid the pump altogether.

kthompson · Aug 17, 2020

grsthegreat, I would have to remove the vent while doing this and install a male air hose fitting to replace the vent when done.

crazyal, very good point. With reasonable amount of fuel in tank don't think that would be a concern but when pushing last of fuel in it just might be. Thank you for this thought. This one causes me concern.

industrial tools, very much appreciate you concerns with air pressure. How low of pressure would work not sure. Have another thought on the gas tank, could mount it on the mower trailer say two or so feet above the deck and let gravity just feed it to mower sitting on the ground. Have seen a few setups like that around.

As to injecting air into fuel, not sure how well you can, but believe you can certainly get air mixed into diesel or gas. Know you certain can have it happen with hyd oil but totally different pressure in a machine with air being sucked into it the system.

Thank each of you and this is why I posted my question. I believe it can be done and safely if pressure is kept reasonable for a fuel pump on a tank is pumping with pressure as it is also pushing the fuel. Seeing how strong of flow many have would believe the pressure is greater than 5 psi but doubt 20 pounds.

Each had good points and have decided to pass on this idea. I know a few years back read someone's post on doing this. My biggest concern would not be my using it but another family member. My oldest two grands this year have taken interest in tractor and mower and no way way think I could reasonable design a setup that would be simple enough for them to push the fuel and then become a vented tank when not fueling. Sincerely appreciate each ones thoughts and yes concerns.

As I finished typing above thought about injector lines that have failed and wonder with their pressure has there been any reported fire or explosion?

Egon · Aug 17, 2020

If the vessel is designed for your maximum air pressure and has a proper relief valve it may be possible but not advisable. Air fuel ratio can easily be within flammable parameters. It would not be allowed in industrial situations.

Best to forget the idea!

beckmurph · Aug 17, 2020

Compressed air is going to have moisture in it.

What psi is your vessel rated for.

Fluid in a drum vs compressed air in a drum is totally different.

fried1765 · Aug 17, 2020

Industrial Toys said:
Even a little air pressure can impose enormous stresses on a tank and it's welds. Stresses, it was never meant to see.

Probably many would warn you that compressed air and fluid is a bad combination almost always. I think I wrecked a water heater, by applying compressed air in an effort to drain it quicker once.

In any event. If you are going to do it, obviously use a regulator.

I can't quite understand how you could over pressurize a water heater.
Unless the pressure relief valve was stuck closed?

Captain Dirty · Aug 17, 2020

Have you considered an accumulator (pressurized air storage tank) and an air driven pump?

Industrial Toys · Aug 17, 2020

Not sure what a pressure relief on a heater is set to. I don't recall it going open. I am not quite that dumb that I would just put my shop air to the tank. Either just give it little shots of air, or I used a regulator. In any event, dumb enough to ruin my tank. Maybe on the verge of starting to leak anyway, so maybe a blessing. Who knows?

DEWFPO · Aug 17, 2020

I agree that 3-5 lbs max. should be you target. Any more than that and you are really asking for trouble in a tank that is not designed for it.

DEWFPO

Industrial Toys · Aug 17, 2020

It always amazes me, how much squish there is in the air, before anything happens. And then having to relieve that pressure. It is a nuisance.

Pressure testing new Diesel Fuel tank Last year with various precautions. Regulator and appropriate bracing.

LouNY · Aug 17, 2020

3 to 5 psi would be getting close to too much pressure;
27.72 inchs of water pressure = 1 psi
or 1 psi will lift water in a column or hose up 27".
Fuel has a density of about 0.9 compared to water so 1 psi will lift fuel approximately 30",
so it you need to lift your fuel 6 ft or 72" you would only need just under 2.5 psi of air to do so,
as long as the volume of air does not exceed the volume of fuel leaving the tank and the tank can handle the pressure it will work.
I have see empty oil drum distort and rupture with 5 psi in them.

tallfreak · Aug 25, 2020

My only concern is the tank. Most likely its not designed for pressure. 3-5 psi is still a lot on a big tank. A 200 gallon tank would have 3900 pounds of pressure on each wall at 5 psi.

In my opinion you should find another way. If you have air pressure available, use it to run a pump.

Industrial Toys · Aug 25, 2020

Those things are super expensive. Like GRACO piston pumps, and some rotary air pumps. Often designed to eliminate explosion hazzards in industrial environments. Did I mention expensive?

PAPPASMURF · Aug 25, 2020

I have a 50 gallon fuel tank on my flatbed with a small air compressor (the type granny would keep in her trunk) and I run 5 to 10 lbs of pressure into the tank and refuel all of my equipment on worksites with it. No problems whatsoever. I do have the filter on it as well, but 10 lbs is more than enough to fuel anything you need. Just my 2 cents. It works great!