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Can used cng cylinders be recertified?

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  • Can used cng cylinders be recertified?

    Hello,

    In shopping for used CNG tanks I see that some are only a few years away from their expiration date. Can these tanks be re-certified and get any more life when their expiration date rolls around?

  • #2
    Re: Can cylinders/tanks be re-certified after thier expiration date?

    I have heard that only type 1 tanks can be certified. But in one of my Tank certification classes it was mentioned that no tank can be recertified.

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    • #3
      Re: Can used cng cylinders be recertified?

      Originally posted by pastortw View Post
      Hello,

      In shopping for used CNG tanks I see that some are only a few years away from their expiration date. Can these tanks be re-certified and get any more life when their expiration date rolls around?
      To answer your question - No.

      All CNG tanks must be removed from service once the expiration date has past. There is no re-certification, there is no re-hydrotesting.

      I believe the day will come (and it is closer than you think) when part of the safety/emission inspection of your vehicle will include checking the expiration date on your CNG tank. And if it is "out-of-date", then you will not pass the safety inspection.
      Jared.
      Mountain Green, Utah
      2003 CNG Cavalier
      2003 CNG Silverado 2500HD

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      • #4
        Re: Can used cng cylinders be recertified?

        I assume you can still use a tank after an accident if it is inspected.

        Isn't this a form of recertification?

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        • #5
          Re: Can used cng cylinders be recertified?

          Highmarker is right any fiber wrap tank has to be discarded,the sad part is there companys that collect then up and sell them to foreign countries. I did read a news blog about a person in India that was told ,"Your tank is junk" and don't fill it ,the tank owner said don't worrie about it ,and filled it anyway and you guessed it ,a small explosion the killed the tank owner and left numerious people with hearing loss

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          • #6
            Re: Can used cng cylinders be recertified? - NO

            Thanks must be inspected every 36Kmiles or 3 years, which ever come first.

            As mentioned before, there is no recert after the expiration date.

            As far as accidents, if the tank passes the visual inspection then it's ok, that's not a recert, just an inspection.

            Word of advise, be careful with Type IV (& I think even Type III) tanks, as it was mentioned in a cylinder inspection class I took, if you drop one you can't always tell by visual inspection on the outside that the tank is damaged since the damage can be to the internal layers of the carbon fiber wrap and it won't show on the outside. Just because you didn't drop it doesn't mean someone before you didn't.

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            • #7
              Re: Can used cng cylinders be recertified?

              I would like to know who does the inspection?

              Or better yet who can?

              And if it is some sort of spray on the soap and look for cracks,test.

              I was told by a company that does hydro testing , there is nothing that can be done with any composite (or Fiber wrap tank) it goes in the recycle bin after the date has been expired

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              • #8
                Re: Can used cng cylinders be recertified?

                If you question the integrity of type 4 tanks, and what they can survive, check out this report from Lincoln Composites.
                http://www.lincolncomposites.com/med...ilityFE5F1.pdf
                Your Friendly Nazi Squirrel Administrator

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                • #9
                  Re: Can used cng cylinders be recertified?

                  Hello Pastor...

                  The whole CNG cylinder certification issue is still a work in progress. However, having worked on this issue for over ten years now it's getting a little clearer.

                  The leading certification agency in the US is CSA-America (the old AGA Lab) in Cleveland, OH. Their website describes the process and lists certified inspectors. You can view it at:
                  http://www.csa-america.org/advisory_...certification/

                  They've just Beta tested a new exam at the AFVi Conference in Las Vegas and the results and hopefully the final test should be out soon.

                  Training is available from several organizations that are also listed.

                  Good luck,

                  afvman/Bill

                  Comment


                  • #10
                    Re: Can used cng cylinders be recertified?

                    Originally posted by cnghal View Post
                    If you question the integrity of type 4 tanks, and what they can survive, check out this report from Lincoln Composites.
                    http://www.lincolncomposites.com/med...ilityFE5F1.pdf
                    I don't question their integrity or strength, if I did I wouldn't drive one to work everyday.

                    But....it was mentioned that in certain cases as little as a 6' drop at a certain angle can compromise the wrap. This doesn't mean it's going to rupture instantly when you charge it, but put it through many fueling cycles and the damage can grow over time. If you take the class:
                    http://www.ngvi.com/training_cylinder.html
                    .....and get the Irish guy teaching it he has pictures that prove it.

                    That's why the routine visual inspection doesn't have you remove the tank from the vehicle, it's safer left in place than having people handle them.

                    All I'm saying is be cautious of what you buy used because now you have multiple people handling something and you can't account for every action that took place.

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                    • #11
                      Re: Can used cng cylinders be recertified?

                      i would not worrie about one blowing driving to work ,If made in the usa they are built much stronger than needed,

                      No tank manufactur wants to ever think of one failing,

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                      • #12
                        Re: Can used cng cylinders be recertified?

                        Originally posted by diesel-ongas View Post
                        i would not worrie about one blowing driving to work ,If made in the usa they are built much stronger than needed,

                        No tank manufactur wants to ever think of one failing,
                        The cyclic nature of pressure vessels is the reason why one should not be used past its expiration date.

                        All metals that are subject to stress will fatigue over time.


                        ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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                        • #13
                          Re: Can used cng cylinders be recertified?

                          Yes true ,metals and materals can fatague,I have seen welding cylinders from the 1950's still in use

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                          • #14
                            Re: Can used cng cylinders be recertified?

                            gas bottles are DOT including CNG Only DOT AAA which are hydrostatic tested and recertified every five years until they fail testing. Some ASME cylinders are certified once and if not changed or damaged are good for life.
                            But you can't use either in a NGV.
                            Your Friendly Nazi Squirrel Administrator

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                            • #15
                              Re: Can used cng cylinders be recertified?

                              What is the DOt standard for NGV cylinders?

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