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Why do people buy expired tanks?

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  • Why do people buy expired tanks?

    I have noticed several expired cng tanks sell in the $50 range on a local "want ads" type website in the past few weeks. The ads listing clearly list them as expired tanks and even give the expiration date, yet the tanks seem to sell quickly. I can imagine wanting to sell expired tanks. What I don't get is:

    Why would anyone want to buy an expired tank?

  • #2
    Re: Why do people buy expired tanks?

    possibly for the valves
    sigpichttp://WWW.CNGMOTORS.COM
    SAVE TIME. SAVE MONEY. SAVE THE ENVIRONMENT.

    2003 Hummer H2 bi-fuel
    2000 GMC Yukon XL bi-fuel
    1999 International 4700 dual-fuel
    2007 Chevy Avalanche bi-fuel

    FMQ2-36 Fuelmaker w/ 24 GGE cascade

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    • #3
      Re: Why do people buy expired tanks?

      That is about all since you can't re-use the PRD -- I hope not

      Larrycng

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      • #4
        Re: Why do people buy expired tanks?

        Tanks don't 'self destruct' when they expire like the taped messages on Mission: Impossible. They aren't any less safe the day they expire than the day before, just as food doesn't automatically go bad when it reaches the date stamped on it. I'm sure a lot of people would be willing to accept the small added risk that an expired tank will have a problem in exchange for saving thousands of dollars compared to an 'unexpired' tank. More conventional tanks are inexpensively tested every few years, can remain in service indefinitely and are destroyed when they fail the test.
        02 GX
        01 GX
        03 Crown Vic
        06 GX
        Home Fueler

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        • #5
          Re: Why do people buy expired tanks?

          Probably because we do not believe the ------- pervayed by the EPA and the unfounded planned obsolescense tack from the tank manufactures. BTW. anyone have some undamaged crown vic tanks for sale?
          Last edited by Highmarker; 05-04-2011, 07:39 AM. Reason: Vulgar language is not tolerated on this site!

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          • #6
            Re: Why do people buy expired tanks?

            rtry9a,

            I just sent you a PM about a guy who is looking to get rid of some "expired" crown vic tanks.
            Jared.
            Mountain Green, Utah
            2003 CNG Cavalier
            2003 CNG Silverado 2500HD

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            • #7
              Re: Why do people buy expired tanks?

              One of the reason we went to visual inspection is so that the owner of the tank wouldn't have to pay to have tank vented, removed from the vehicle, taken to a hydrostatic testing facility, re-install the tank and have it refilled; but most important you vehicle wouldn't be out of service for about a week (est). Yes, there are some other tests that could be done in some vehicle but they are also costly. Vehicles being out of sevice are a big deal with fleets and would be detrimental to fleet use of CNG.

              Maybe some one would volunteer run a vehicle until the tank it "blows". However, the people around the vehicle might object when the tank blew -- colatterial damage.

              I would support the manufacturers who have test cylinders and extended their life span. I'm not an engineer, but I do know that materials do fatigue and it not always possible to determine the exact point when they will fail -- too many variables. I'll take my chances with set "do not use after" date

              Larrycng

              P.S. Maybe I'm getting too conserative in my old age -- time for my "shot" of geritol

              Comment


              • #8
                Re: Why do people buy expired tanks?

                I agree with Larry. It is more than a "small added risk". Most people do not understand the forces involved. Your tank is a complex engineered product designed to contain pressures up to 4,500 psi. The stored energy of CNG at 3,600 psi in a 6 GGE tank (Cavalier size) is equivalent to 1.9 lbs of TNT. Using an expired tank, you call that a "small added risk" with your little ones in the back seat?
                Jared.
                Mountain Green, Utah
                2003 CNG Cavalier
                2003 CNG Silverado 2500HD

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                • #9
                  Re: Why do people buy expired tanks?

                  Here are some facts:

                  Part of the rationale of the 15 (or 20) year tank life was the pressurization-depressurization cycles over the life of the tank. How about a 1994 tank from a vehicle with 15,000 miles?

                  Also the number of tanks that have failed due to age (as opposed to damage) is zero.

                  Then is the replacement of low mileage (cycles) tanks a very expensive solution to a non-problem?

                  Is the carriage of 20 gallons of liquid combustible fluid totally risk free? We do it all the time.

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                  • #10
                    Re: Why do people buy expired tanks?

                    Originally posted by jenki_putnik View Post
                    Here are some facts:

                    Part of the rationale of the 15 (or 20) year tank life was the pressurization-depressurization cycles over the life of the tank. How about a 1994 tank from a vehicle with 15,000 miles?

                    Also the number of tanks that have failed due to age (as opposed to damage) is zero.

                    Then is the replacement of low mileage (cycles) tanks a very expensive solution to a non-problem?

                    Is the carriage of 20 gallons of liquid combustible fluid totally risk free? We do it all the time.
                    Especially in a car where the CNG tank is inside the car and totally protected from the elements, the lifetime based on time seems very conservative.

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                    • #11
                      Re: Why do people buy expired tanks?

                      Originally posted by jenki_putnik View Post
                      Here are some facts:

                      Part of the rationale of the 15 (or 20) year tank life was the pressurization-depressurization cycles over the life of the tank. How about a 1994 tank from a vehicle with 15,000 miles?

                      Also the number of tanks that have failed due to age (as opposed to damage) is zero.

                      Then is the replacement of low mileage (cycles) tanks a very expensive solution to a non-problem?
                      You are making the assumption that low mileage in a car means low cycles in a tank. There is no relation between the two. You don't know the history of the tank. You don't know if the tanks on the car now are the same tanks that were installed in the auto factory. You don't know if the fleet company removed the tanks and put them on another vehicle for a while only to reinstall them back on your car before they sold it. You may think that it is a "small added risk", but when 1.9 lbs of TNT goes off in your car with your little ones buckled in, you will be thinking differently.
                      Jared.
                      Mountain Green, Utah
                      2003 CNG Cavalier
                      2003 CNG Silverado 2500HD

                      Comment


                      • #12
                        Re: Why do people buy expired tanks?

                        Originally posted by larrycng View Post
                        One of the reason we went to visual inspection is so that the owner of the tank wouldn't have to pay to have tank vented, removed from the vehicle, taken to a hydrostatic testing facility, re-install the tank and have it refilled; but most important you vehicle wouldn't be out of service for about a week (est). Yes, there are some other tests that could be done in some vehicle but they are also costly. Vehicles being out of sevice are a big deal with fleets and would be detrimental to fleet use of CNG.

                        Maybe some one would volunteer run a vehicle until the tank it "blows". However, the people around the vehicle might object when the tank blew -- colatterial damage.

                        I would support the manufacturers who have test cylinders and extended their life span. I'm not an engineer, but I do know that materials do fatigue and it not always possible to determine the exact point when they will fail -- too many variables. I'll take my chances with set "do not use after" date

                        Larrycng

                        P.S. Maybe I'm getting too conserative in my old age -- time for my "shot" of geritol
                        As a construction worker, I use tanks that have fuels and accelerants that been in service since the 1940's. They re-certify the tanks every few years. This is existing technology and the tank in your car is no more dangerous (perhaps less) than tanks of oxygen and acetylene sitting at your local welding supply shop. They can all be violently explosive.

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                        • #13
                          Re: Why do people buy expired tanks?

                          Well if you buy a GSA vehicle you can pretty much be sure CNG was never used. :0)
                          sigpichttp://WWW.CNGMOTORS.COM
                          SAVE TIME. SAVE MONEY. SAVE THE ENVIRONMENT.

                          2003 Hummer H2 bi-fuel
                          2000 GMC Yukon XL bi-fuel
                          1999 International 4700 dual-fuel
                          2007 Chevy Avalanche bi-fuel

                          FMQ2-36 Fuelmaker w/ 24 GGE cascade

                          Comment


                          • #14
                            Re: Why do people buy expired tanks?

                            As long as a tank is not damaged, Id imagine the chances of a catastrophic failure are pretty small regardless of age. A leak is much more likely from older fittings and lines. Until I see some real verifiable data to the contrary, I see no reason to change my opinion; everything else are SWAGS, and then mostly from vested interests who want to sell you parts and services.
                            Last edited by rtry9a; 05-05-2011, 10:15 AM.

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                            • #15
                              Re: Why do people buy expired tanks?

                              I've found that people who are selling expired tanks either don't know anything about cng, or know that they aren't worth much expired.

                              I looked at two tanks with no expiration date on them in December. They were from a bus that this guy parted out. He thought he had a gold mine because they were both full of fuel. He kept telling me that it was the same as propane and propane was so expensive. I laughed, attempted to educate the man, told him cng in Oklahoma wasn't expensive at all. He told me if he didn't sell them, he would hook the tanks up to his home and heat his home for the entire winter. I guess he went through a lot of trouble to hook those tanks up for heat, because he didn't sell them.

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