Cleaning out tank for Avgas use

[svcta]

Hey, all,
we just acquired a 500 gal. tank with the intent of using it for avgas. It has been empty and sealed for a number of years but we are unsure what it contained (mogas or diesel) when it was in use.

Do any of you have any insight on how we may best prep the inside of this tank for our use?

Thanks!

 

[avbug]

What you're going to need to do will depend on the type of tank you have, and it's condition. If the tank was properly preserved with no corrosion, your requirements may be fairly minimal.

You're going to want a new filter, of course, and to make sure that the ability to sump and drain the tank is functional before you fill it. Drains tend to stick or corrode.

If the tank has rust, you're going to end up steam cleaning it, flushing it, going into the tank and scrubbing it and removing the rust, before you returnit to service. What material is the tank? Is it steel? Single wall? Double wall? Prior military (surplus)? Do you plan on taking it on the road and require it to be DoT compliant?

 

[svcta]

It's a 500 gallon tank. Single wall steel. It stored auto gas and has remained empty for a number of years. It has a good drain, so we can clean and rinse. The tank appears to be clean on the inside, but we're going to give it further inspection soon as best we can. The only access to the inside is through the fill hole and where the pump fitting is. Nothing larger than your fist.

Thanks for the info so far.

 

[avbug]

Presumably then this won't be going on the road or used where it needs to be DoT compliant for transportation.

You should have a large enough opening to be able to enter the tank, in the top. Generally such tanks will have a hatch, which may be locked or boltled, but usually secured with a latch, during filling.

If the tank isn't rusted inside, then flushing the tank to ensure it's free of unwanted material is a good idea. If it held autofuel and has been empty, it may be okay. If it held autofuel which sat in the tank for a time, you'll need to replace seals and hoses, and pay close attention to any gum or sludge in the tank.

The best cleaning for a tank is a steam bath, but if you don't have a way to quickly dry the tank, or if it's an older tank that already has oxidized inside or isn't finished, and there's no way to air it out, you may be doing more harm than good and causing rust to form.

Make sure your pump, tank, and mounting structure are thoroughly bonded, electrically.

Check local regulation for requirements on spill barriers or containment. Many jurisdictions have regulations regarding single wall containers, and may require a barrier or containment under the vehicle if it's mounted on a truck. Ensure you have a fire extinguisher mounted near the emergency shutoff, or shutoff valves. If you're buying through a fuel dealership, especially a brand dealership (eg, Chevron, etc) vs a jobber or supplier, often the supplier will have good counsel on the best way to set up your fuel storage. They can also often be a good supplier of parts, including seals, gaskets, nozzles, etc.

 

[svcta]

Thanks for the info, bug. This is indeed a stationary, above ground, single wall tank. Is there any particular kind of liquid that you might suggest to simply "rinse" the thing out? There is no access for a person in to the tank, but there is a drain plug. We could feasible rinse it out, but I don't want to create more of a problem.

We buy from a wholesale petroleum supplier. We'll probably end up with hose and meter at least from them, so i'm sure they'll have some wisdom, too.

Thanks again.

 

[avbug]

The best way to flush a tank is with the same material you'll be putting in the tank. Given that avgas is expensive, you could flush first with stoddard then follow up with avgas. Most tanks have a fill port on top which is big enough to see the inside of the tank; I believe you said you don't have any access to the tank, however. If you've got no means to adequately inspect or flush the tank, and if you reasonably expect the interior of the tank to be in good shape, then fill the tank and run fuel out through your filter, and then inspect the filter.

If the tank has a lot of rust or other contamination,then you've got a problem with a contaminated batch, or you'll have to offload and find a way to clean the tank internally. Tanks which don't have access are unusual.

 

[svcta]

someone today suggested MEK specifically to cut residue left from autogas. Stoddard is just mineral spirits, right?

That was one of my initial thoughts.

I appreciate your help. I've seen several other tanks of similar design at hangars along the way that had two ports, just like this. None bigger than a filler cap. I wish there were a way to get inside, but there sho' isn't .

 

[avbug]

Be really careful if you handle MEK. It's nasty stuff.

MEK leaves very little residue and is useful for cleaning up, but given that there's no way to spray it down inside, you may have to pump quite a bit in there. Then you're stuck with a disposal issue, too. Wear a respirator, eye protection and be careful with contact. Stay upwind. Don't let it get near any paint you want to keep, or rubber or some plastics, or tarmac.

 

[svcta]

Yeah, I've got some experience with MEK in the past and you're right, it's pretty potent.

In your opinion, would mineral spirits to the job well enough? I don't think that there's much to get out of the tank and we plan on many and regular filter changes/inspections in the first little while to be sure we know what's going on.

 

[avbug]

Not having seen the tank, it's hard to say. I think I'd be more concerned about contamination from rust/oxidation than residue from a former fuel. The problem is that even with a strong solvent like MEK, without mechanical agitation, you really have no assurances.

Perhaps some stoddard, roll the tank repeatedly with a few gallons in there to wash the walls, then drain out through the sumps, then do the same with avgas, then fill. If your fuel provider has better ideas or more specifics, I'd go with that.

If it's a private reserve, then you've got less concerns than if you're providing the fuel publically, too...strictly speaking in terms of your duties to inspect the tank.