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  • Tank temperature question.

    Anyone ever check their tanks outer skin temperature after a drive of 1 or 2 hours? My tanks get cold and the drop in temp seems related to the amount
    of psi pulled off and I suspect it is also related to the rate that fuel is used from the tank. I shot infared temp of tanks the other day after driving home from Broken Arrow OK. The surrounding area was 55 degrees but the tanks
    were 46 degrees. I suspect the gas inside is actually cooler. I also think
    that is why the psi doesnt go down on a long drive in a linear fashion. If your tank temperature was static then the psi use would be a straight line. But the tanks cool off alot at first and then begins to slow down on the temperature differential as you continue to drive and so the psi change slows down also. The temperature to pressure ratio is linear it is the tank temperature that isn't. I hope to install a remote sending psi gauge in the Impala soon so I can directly watch the psi drop. If I could get a cold fill of gas to 3600 psi right before starting a trip I would get at least one extra gallon and still be in the specification of the tank, or is the tank rating based on the temperature being at 70 degrees and would a 3600 psi fill at a lower temp compromise the tank safety? I know it would if you let the tank warm up after a cold fill. I think you are only allowed a 10% overage of the tank
    pressure rating and then you begin to enter danger of compromising tank safety. But what if you never let tank pressure exceed 3600 and you stay at a lower temperature?

  • #2
    Re: Tank temperature question.

    Physics supports your observation but I doubt that the amount of pressure drop from driving could make that big a difference in the temperature of the tank. You can see this effect dramatically if you charge a soda syphon with a CO2 cartridge -- the cartridge gets very cold very fast. I saw a news story about an inventor who is using this effect to make a self-chilling soda can -- gas is released when you open the can, chilling the soda. Assuming it was daytime I think the sun had a lot to do with your observations. I bet it would be a lot different at night.

    You can safely fill a tank to 3600 at any temperature but if it warms while that full the pressure could rise potentally opening the pressure relief device. These components are tested to 1.5x operating pressure or more so a 10 or 20 percent overfill is nothing to be worried about.
    02 GX
    01 GX
    03 Crown Vic
    06 GX
    Home Fueler

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    • #3
      Re: Tank temperature question.

      NGV2 has a design qualification test that pressure cycles the cylinder at -40°F for 4000 cycles. It also pressure cycles the cylinder at 185°F for 4000 cylces.
      Jared.
      Mountain Green, Utah
      2003 CNG Cavalier
      2003 CNG Silverado 2500HD

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      • #4
        Re: Tank temperature question.

        A co-worker of mine likes to put his Walmart brand carbonated, fruit flavored water in the freezer. Once it gets good and cold he'll twist the cap off and watch it turn to slush. The slush starts at the top and quickly sinks to the bottom.

        When he twists the cap off it releases the extra pressure. By dropping the pressure suddenly, it drops the temperature below freezing and turns the water to slush.

        Try filling your tank and measure its temperature before and after. I'll bet its warmer just after you've filled it.

        Bill

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        • #5
          Re: Tank temperature question.

          Oh, it definitely gets hotter, I knew that from my old scuba diving days. I'll usually go eat or kill a little time somewhere while the tanks cool and then come back and top off again if the high pressure station has a good final bank
          pressure. I just wasn't aware that a slow consumption rate by the engine was
          enough to drop tank temperature. Interesting on the juice slush.

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          • #6
            Re: Tank temperature question.

            Originally posted by freedml View Post
            Physics supports your observation but I doubt that the amount of pressure drop from driving could make that big a difference in the temperature of the tank. You can see this effect dramatically if you charge a soda syphon with a CO2 cartridge -- the cartridge gets very cold very fast. I saw a news story about an inventor who is using this effect to make a self-chilling soda can -- gas is released when you open the can, chilling the soda. Assuming it was daytime I think the sun had a lot to do with your observations. I bet it would be a lot different at night.

            You can safely fill a tank to 3600 at any temperature but if it warms while that full the pressure could rise potentally opening the pressure relief device. These components are tested to 1.5x operating pressure or more so a 10 or 20 percent overfill is nothing to be worried about.
            this is why we have a temp comp chart a tank with 2100 lbs at 0 will have 3600 at 70 and over 4000 at 100 dont hold me to ex #s my temp comp chart is glued to my compresser and not here but I think Im close might want to look at go farther in the lounge at a thought of mine to do with this and add what you think and over pressure will stress tanks cowboy

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