Cleaning out large fuel tank

[Crawdaddy]

I'm not 100% sure if this is the right forum for this, but I recently obtained a 500 gallon metal fuel tank to hold off-road diesel to feed my generators and tractor. However, in its previous life it held less than 200 gallons of gasoline for years. Presumably, the inside of the tank is pretty nasty and should be cleaned before I start dumping diesel in. The drain plug on the tank is also severely rounded off and will probably have to be drilled out. So, I have 2 problems, but they may be able to be solved at the same time.

For the tank holding not a lot of gas for a long time, I'm assuming the walls inside the tank are dirty and rusty from condensation. I've read threads in the Auxiliary Equipment forum from Jimc and others to use a serious of chemicals to clean out 002 and 003 tanks, but, I'm dealing with a tank that's 4 feet in diameter and a few feet long. How can I effectively clean the inside of the tank without huge amounts of chemicals. I can roll the tank around on the ground pretty well to slosh liquids around.

For the drain plug issue, I've put Vice-Grips, pipe wrenches, hit it with PB Blaster and nothing's budging it loose. I'd use heat, except I'm playing with a tank full of gasoline vapors and for some reason that sounds like a bad idea. So, drilling it out sounds like what's going to have to be done, but I still have the heat and potential sparks issue. Does anyone have ideas to try to get the drain plug loose? Perhaps filling the tank with water is the way to go, but that's a lot of water to deal with afterwards.

Should I even worry about the condensation and gas that used to be in the tank? Could I just dump some sort of intermediate liquid in the tank to flush out as much water and old gas as possible and load in diesel? Regardless of what gets done the tank will have filters on the output to catch condensation and small particles.

 

[Cruceno]

Wow. I'd definitely try to drain out as much of the gasoline as possible. Even though its old gas, I'd still be leary of a stray spark sending me to the burn ward. Once empty, make sure that it's been aired out sufficiently to remove the vapors, then I'd drill and retap the drain plug.

Is there an inspection port on the tank? Large enough that you could look inside and tell the condition of the internals? You might actually be able to use gas or diesel as a solvent to clean the inside of it. There are products out there made to coat the inside of fuel tanks, but as long as you'll be keeping the tank topped off regularly, I would think that a good flushing and excellent filtering would be fine.

 

[buggyman]

The long and short answer is to recycle the tank and chalkthe experience up to only buying a clean tank in the future. The tank can becleaned and coated but this will cost you much more than a good used cleantank. Good luck, Paul.

 

[1800 Diesel]

Crawdaddy,

Assuming you can't use the bottom drain fitting on the tank, just fill it with water until the residual liquids in the tank flow out the filler neck. Any petroleum product will float on the water and flow out first. Tilt the tank fore and aft as needed to vent all petroleum product through the filler neck area. Capture fuel into another open container until you get only water. Keep adding water until all solids float out. At his point (with the drain plug area still submerged) you can either weld a bolt (or heavy flatbar) to the head of the drain plug or if that's not possible, go ahead & drill to match the drill size needed for the existing size NPT pipe tap. (Several steps up in drill size will make this a little easier.)

Once you get the existing coupling threads cleaned & chased you can then install a temporary ball valve, add a large box of Tide detergent and about a 5-gallon bucket full of small gravel, set the tank on some rollers (with suitable foundation & in a configuration that will allow 360 degree rotation like a dryer drum), fill about 25% with hot water (if you have access to hot water or can boil some outside), close all fittings and rotate the tank on the rollers. This can be done with some rope wrapped around the tank a few times & with a couple people pulling the rope from each end. I've also seen people get creative with an old dryer motor wired up and with a large belt wrapped around the tank to provide continuous rotation. The detergent will help remove much of the sticky crud and the gravel will work on rust and other stubborn solids.

This process can be repeated for several cycles until the tank is cleaned out to an acceptable level. You won't be able to remove all crud (the tank 's interior sides can be a problem without doing another setup or without having a manhole for access) but this will clean up quite a bit. Obviously several rinsing cycles are needed and the gravel has to washed out last by tilting the tank up and washing the gravel through the drain coupling. It sounds like a lot or work but not
too bad.

Once cleaned out, verify all gravel is removed by rolling the tank dry & prior to filling with diesel you may want to conduct a "hydro test" by completely filling the tank up to the top of the filler neck to check for leaks. Then drain & dry tank to allow filling with diesel.

Kevin

Edit: To address concerns over tank wall thickness you can either do a "ring test" with a small ball pein hammer or you can borrow a UT thickness gauge from someone to check wall thicknesses wherever it is suspect. My tanks came off an old fuel barge and they're at least 30 years old and the steel is sound. But steel tanks can rust due to any number of reasons, no doubt about it, so I agree wall thicknesses should be checked prior to keeping a tank.

 

[cuad4u]

Some 5 years ago I also obtained a "used" 600 gallon fuel tank off Craig's List to be used to store "red" diesel fuel for use on my farm. I did most everything mentioned above to clean it out including steam cleaning the inside of the tank. I removed the two bungs on top which gave me access to the innards of the tank so I could insert the steam cleaning wand. 30 years worth of gunk came out of the drain holes during the cleaning.

I dried it out and put it into service and filled it with 550 gallons of diesel fuel, It started leaking within a month or so. The leak(s) started on the bottom of the tank near the 3/4 inch drain outlet in the bottom of the tank. Seems over many years water condenses on the inside walls of most all fuel storage tanks. If not drained regularly this water will accumulate in the bottom of the tank because water is heavier than diesel and gasoline. Over many years the water causes rust and eventually a leak especially when crud and rust are removed during cleaning.

I tried using JB Weld to seal the holes and it worked for a while, but more holes appeared and more leaks started. I considered cutting out a part of the tank bottom and welding in a new curved bottom, but I decided against this for several reasons. One was the cost and the other one was the hazards involved in welding on a tank that has been used to store fuel. I know how to weld fuel tanks safely but when I counted up the money I would be spending purging the tank with inert gas and the cost to have a new bottom "rolled" to fit, I decided it was not worth the money.

Count me in as one who recommends that you sell the old tank for scrap and use the money to get a new tank, especially if this one is 20-30 years old and of questionable origin. Buying a new tank may sound expensive, but a new tank is not nearly as expensive as leaking 600 gallons of diesel fuel on the ground.

 

[Crawdaddy]

The tank has no manhole, but it does have 2 2" fittings up top for filling and venting. The tank sits on a stand and has a 1" fitting about an inch from the bottom of the tank for dispensing using gravity. So, flushing the old gas out with water would be pretty trivial. Then I could weld or drill on the drain plug to be able to drain the remaining water. What should I use to remove the last traces of moisture from the tank?

I don't know if there is any significant cause for concern that the tank will leak once cleaned. The walls are pretty thick and it seems quite solid. I'm working on stripping the paint from the outside to repaint it and the metal is not rusted on the outside. I'll take a peek at the inside with a flashlight when I get a chance. The gasoline I've drained so far from it has a very light amount of particulate in it; nothing a filter couldn't handle.

 

[storeman]

A couple of hair driers (gun type) into the 2" ports for several hours might donthe trick as might a heat gun. I use a hair drier on the smaller tanks. Could boil it out with wood fire also since it needs paint anyway.

 

[4x4 Forever]

The outside being in real good condition gives you a fairly good idea as to the inside, HOWEVER, you have to remember that the main concern will be rusting and scaling on the inside at the bottom. That is where the sludge, water, and nasties have been living and where the deterioration will be the greatest. Also remember that the scale on the inside will hold the product that was in there before and you could wind up with a nice surprise. Someone I know very well almost set a boat on fire while using a torch inside a tank that had scale that was not completely cleaned off...

If you want to weld or perform hotwork on the tank, there are several ways to go about it:
1. Fill it up with water to just below the level you are going to work on and then throw dry ice in, the vapors from the dry ice will form CO2. Continue with the dry ice while working.
2. Connect the exhaust from your car or truck and fill up the tank and perform your activity. Keep the car/truck running and purging the whole time you are working.
3. Some people use CO2 or Argon cylinders and purge the tank while working, again, purge throughout the job. .
4. Fill the tank up with water, detergent, rocks and rock and roll it around. Even using this method is questionable as the scale/rust hold the previous product.

As you can see, it is not for someone who might have doubts. If you have any, get a professional...

FYI, Ships, boats, and barges are issued a "Hot work Permit" for someone to perform hotwork. The permit is valid at the time the tanks/area was inspected. It is up to the permit holder to verify the tank/area still complies with the permit (sniffers, etc.). If ANYTHING changes, the permit is null and void...

If you have any doubts, please do not do it!

 

[zoltarp]

The scale you are referring too is it whitish in color? My MEP-002A fuel tank is full of what looks like calcium scale and I was wondering what in the heck it was. Make me concerned for the fuel pumps on this thing.

 

[1800 Diesel]

The scale you are referring too is it whitish in color? My MEP-002A fuel tank is full of what looks like calcium scale and I was wondering what in the heck it was. Make me concerned for the fuel pumps on this thing.

I suspect he was referring to rust scale or flakes--these can trap pockets of fuel vapors which can ignite while performing hot work. That's the reason I recommended doing the welding on the plug while water was in the tank. That would eliminate any possibility of ignition. For any other hot work on the tank skin, using engine exhaust for inerting the tank interior air is an effective method that only costs in setup materials (hoses, clamps etc.) This is something you don't want to rush and the exhausted gas needs to verified prior to any hot work.

Kevin

 

[Crawdaddy]

I suspect he was referring to rust scale or flakes--these can trap pockets of fuel vapors which can ignite while performing hot work. That's the reason I recommended doing the welding on the plug while water was in the tank. That would eliminate any possibility of ignition. For any other hot work on the tank skin, using engine exhaust for inerting the tank interior air is an effective method that only costs in setup materials (hoses, clamps etc.) This is something you don't want to rush and the exhausted gas needs to verified prior to any hot work.

Kevin

I am referring to very fine rust or dirt that's the size of a grain of sand or smaller. When I get home I'll take a picture of what I got out of the tank in 5 gallons worth of gas.

 

[1800 Diesel]

I am referring to very fine rust or dirt that's the size of a grain of sand or smaller. When I get home I'll take a picture of what I got out of the tank in 5 gallons worth of gas.

That sounds better than rust flakes...sounds like the tank interior is in pretty good shape...

 

[4x4 Forever]

I am referring to very fine rust or dirt that's the size of a grain of sand or smaller. When I get home I'll take a picture of what I got out of the tank in 5 gallons worth of gas.

You cannot go by what you took out of the tank that is in the bucket. A visual inspection of the tank is required to verify that there is no spots that would hold the previous product. I've pumped tanks dry and the product looked good and clean, but after doing a visual inspection the rust scale/flakes were all over the sides and bottom.

 

[goldneagle]

I got an inspection camera if that would help you.

 

[Crawdaddy]

This project's been on hold for a while, but I'm about to get started on it again. I bought some oil-based primer and paint to re-paint the tank with and I also drained the last bit of old gas out the tank.

When I picked the tail end of the tank up and dumped the rest out, it was pretty brownish, which was a stark difference from the perfectly clear fuel that was at the level of the valve and above. I'm satisfied in the cleanliness of most of the tank that I'm thinking I should just flush 20 gallons or so of a solvent through the tank while sloshing it and call it a day.

The question is what solvent can I use that's cheaper than gas to clean the tank with? When I fill the tank with diesel, I will be filtering the output from the tank through a water-block filter and as fine of a filter as I can find.

 

[zoltarp]

This project's been on hold for a while, but I'm about to get started on it again. I bought some oil-based primer and paint to re-paint the tank with and I also drained the last bit of old gas out the tank.

When I picked the tail end of the tank up and dumped the rest out, it was pretty brownish, which was a stark difference from the perfectly clear fuel that was at the level of the valve and above. I'm satisfied in the cleanliness of most of the tank that I'm thinking I should just flush 20 gallons or so of a solvent through the tank while sloshing it and call it a day.

The question is what solvent can I use that's cheaper than gas to clean the tank with? When I fill the tank with diesel, I will be filtering the output from the tank through a water-block filter and as fine of a filter as I can find.

I just did my tank a few months ago, I took some advise I got on here and used a pressure washer to remove the scale and crud. The insides ended up looking pretty darn good, then I stuck it out on the sidewalk and let it bake in the sun for a while. No fuss no muss.

 

[jd426426]

This project's been on hold for a while, but I'm about to get started on it again. I bought some oil-based primer and paint to re-paint the tank with and I also drained the last bit of old gas out the tank.

When I picked the tail end of the tank up and dumped the rest out, it was pretty brownish, which was a stark difference from the perfectly clear fuel that was at the level of the valve and above. I'm satisfied in the cleanliness of most of the tank that I'm thinking I should just flush 20 gallons or so of a solvent through the tank while sloshing it and call it a day.

The question is what solvent can I use that's cheaper than gas to clean the tank with? When I fill the tank with diesel, I will be filtering the output from the tank through a water-block filter and as fine of a filter as I can find.

You may want to try ZEP, All purpose Degreaser available at your Auto Parts Store.. one gallong makes easily 40 gallons of solution . I have used this stuff to remove some pretty nasty Industrial Grease and it worked great. Maybe pick a really HOT day (so it air dries fast) , and put some in the Pressure washer to mix with the water ? or just slosh some around with a HOT water mix.. have honestly never done a big Fuel tank with it ,but for like cleaning parts it is even better than gasoline or even Dawn Dish liquid which is an excellent De Greaser.. Im ripping out my 500 gal inground #2 tank as well, because if i need to sell my house, i wont be able to close, noone is writing insurance on them anymore.
Would be curious to find out how you make out with this.

 

[Jeepsinker]

You need to get 5 gallons of purple power or castr super clean and pour that in with some water. Let it sit overnight. The purple power has alkali in it which helps to clean off the rust and scale. Then drain and flush, and try to find some evapo-rust. It's about $20 a gallon, but that is the only solvent that will clean the rust out to bare steel. You can probably do the cleaning you need with three or four gallons.

 

[Jeepsinker]

I'm sure that zep cleaner would cut the fuel and stuff well too but I have no experience with it.
Crawdaddy, also note that if you want to you can load the tank up and bring it over here. We'll spend a full day on it and get it clean. I have a LOT of experience doing this.

 

[Crawdaddy]

I'm still working on my diesel storage tank and I'm ready to build the dispenser system. I'm aiming for the dispenser pump to pull fuel out of the tank, but also be able to offload barrels of new diesel into the tank. I am currently planning on using 2 Wix 24001 spin-on bases with a 24027 water-block filter and a 24006 10 micron final filter.

I was trying to figure out how to lay out the components for optimum operation. Should the filters be before or after the dispenser pump? I think plumbing-wise it would be smarter and easier to put them between the tank and the pump, but I don't know if the average barrel pump can pull fuel through filters like that. I usually see them after the pump on the auxiliary tanks in pickup trucks, but that seems that it's easier to put them there on that application.

To achieve the barrel offloading into the tank, I think a T-fitting and a couple of ball valves between the filters from the tank and the pump would fit the bill and use the dispenser nozzle to dump the fuel in the top of the tank.

Am I off in my design?