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Thread: Cutting a BIG propane tank?

  1. #1
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    Default Cutting a BIG propane tank?

    This is a mostly hypothetical question but I'd like to hear what your thoughts are on the matter.

    Suppose I had a 30,000 gallon propane tank and I wanted to cut a section out of it and weld it back together to make it shorter and use it for something other than propane. For reference, a tank of this size is about 9' in diameter and about 67' long. Apart from the obvious difficulty of moving this thing around, there is the question of how to cut it without accidentally blowing up the neighborhood. I'm familiar with the various techniques for cutting up smaller tanks where you fill them either with an inert gas or with water (or water vapor), but filling a 30,000 gallon tank is a bit impractical. The only thing I can come up with is cleaning it really well - power wash the interior with a degreaser and hope for the best?

  2. #2
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    Quote Originally Posted by Fasttrack View Post
    This is a mostly hypothetical question but I'd like to hear what your thoughts are on the matter.

    Suppose I had a 30,000 gallon propane tank and I wanted to cut a section out of it and weld it back together to make it shorter and use it for something other than propane. For reference, a tank of this size is about 9' in diameter and about 67' long. Apart from the obvious difficulty of moving this thing around, there is the question of how to cut it without accidentally blowing up the neighborhood. I'm familiar with the various techniques for cutting up smaller tanks where you fill them either with an inert gas or with water (or water vapor), but filling a 30,000 gallon tank is a bit impractical. The only thing I can come up with is cleaning it really well - power wash the interior with a degreaser and hope for the best?
    It would make a heck of a compressor tank. Pump would only run once a month, but for three days. LOL.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  3. #3
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    The first step in cutting something like that up is to make sure the video camera is running for the YouTube clip, or maybe liveleak

  4. #4
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    We've reused a few propane tanks and the way I "inertize" it is by openig 2 opposing connections and connect a hose to a running diesel engine. Ussualy our big diesel forklift. 15 to 20 minutes is enough to clear all propane residue
    Helder Ferreira
    Setúbal, Portugal

  5. #5
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    I believe that the proper steps would be to first notify NORAD that there may be a new satellite orbiting the earth, they would want to track it.
    Second I would notify the Chinese govt. that there may be an earth quake.

    JL.............

  6. #6
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    Quote Originally Posted by oxford View Post
    The first step in cutting something like that up is to make sure the video camera is running for the YouTube clip, or maybe liveleak
    Yes, most definitely have the camera running, but from a good distance so the footage could be sent to the Goddard Space Flight Center.

    JL............

  7. #7
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    power wash the interior- what do you do, cut an access hole first?

    Something that large- the key is probably to use CO2 to purge it and to maintain a small pressure so air wont get in through the cut you'd be making. I don't think you'll get rid of all the propane because it will continue to diffuse out of the metal for some time, so you might have to just eliminate the oxygen instead.

    How to know when all the oxygen has been eliminated? Well, I could suggest holding a lit match in the escaping air stream and when the match goes out you're there- Yeah right- Kaboom! You won't have to worry about anything after that, except your wife having to deal with the mess. I don't know how much CO2 it would take- probably a full tank or maybe more.

    I can't think of any really practical way to do this. If the tank is in the sun a lot, it might bake out if there's holes to allow the propane to fall out from a lowest point. Can you drill holes safely- I don't know. Drilling isn't generally a spark-forming operation, but chips can be very hot- would they be hot enough to ignite a combustible mixture? I don't know.

    Propane tanks are not coated inside as far as I know. With propane there's no moisture to rust the steel, so it's probably just bare steel. Just add water to start the rusting process, or leave it open to the air which will also start the rusting. Whatever your second use might be, it might require that you coat the steel- and that's a big operation with a tank that size, not to mention the cost of the coating material.

    Makes me wonder if any company makes use of old tanks for other applications- if so, they would probably have a procedure to handle everything safely. It would probably be a water fill.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  8. #8
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    I'd get it close to a pond/river/creek and rent a pump to fill it from the water source and purge all the gas out. Free except for the pump rental. I don't know how much 30,000 gallons of good water costs, but i wouldn't want it on my bill.

  9. #9
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    I would purge it with CO2. Simple math will tell you the quantity. One mole, (44 lbs,) is 454 cu ft of gaseous CO2. Determine the volume of the tank, fairly accurately, and order as much dry ice as you think you need. Personally, I would go for 50% extra since it is cheap. Evaporating it is simplified if you put water in the tank. It will take a while, quicker on a hot day. If you seal the tank and install a low-range pressure gauge, you will know when the it is a gas. Then slowly vent the tank, REALLY SLOWLY, and get cutting.
    There will be NO propane desorbing from the tank walls-that is an old wive's tale. The ONLY gas that difuses significantly into steel is helium, and then at HIGH pressure. I would be much more concerned with oil accumulated in the tank over time. Apparently all propane carries a small quantity of light oil, which condenses out on the tank walls.
    Duffy, Gatineau, Quebec

  10. #10
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    Darryl, these tanks have access holes large enough for a man to get inside. So you could, theoretically, get inside to pressure wash. I've done that before in diesel and water tanks. Not a fun job.

    Filling from a pond or river is an interesting idea, as is the dry ice.

    As a fun piece of trivia, propane tanks are also radioactive. The light oil which condenses and accumulates typically includes traces of radium and the gas itself contains radon. Propane tanker trucks trip the radiation portals at ports of entry all the time due to this naturally occurring radioactive material!

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