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  • jblue
    replied
    Re: All about tanks

    Originally posted by cnghal View Post
    As far as I know from NGV Cylinder Inspector Certification Class, NGV-2 cylinders are no longer pressure tested due to it's destructive nature and are certified by the manufacturer for 15 years (20 years on some Canadian cylinders) from date of manufacture and that's it.
    cool. Thanks for rehashing that for me!



    I think what they did is use a 3AA sticker and filled in NGV2 info ...
    Last edited by jblue; 07-17-2008, 01:06 AM.

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  • cnghal
    replied
    Re: All about tanks

    Jblue,
    Do you have this tank or know it's date of manufacture? 1999?
    This sticker has many levels of confusing information. Is it an inspection sticker or retest/recertification sticker? Is the tank Dot 3AA or NGV2-2?
    As far as I know from NGV Cylinder Inspector Certification Class, NGV-2 cylinders are no longer pressure tested due to it's destructive nature and are certified by the manufacturer for 15 years (20 years on some Canadian cylinders) from date of manufacture and that's it. They are required to be visually inspected every 3 years or 36,000 miles, which ever comes first.
    DOT 3AA cylinders or bottles which are used in stations, storage trailers and boats for use on stoves are pressure tested and recertified every 5, 10 or 12 years, depending on type of use. If certification stamp or marks are no longer visible, a stamped metal plate may be used for identification. DOT 3AA cylinders are no longer certified for use in NGVs in the United States.

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  • jblue
    replied
    Re: All about tanks

    Originally posted by Larryect View Post
    It looks like a service company made it as advertisement/documentation the they inspected (tested?) the tank. CNG tanks are supposed to be inspected every three years or 36,000 miles.
    Did you look at the sticker?

    An inspection was done in 03 and the retest date is 2014. A wee bit more than the 3/36 spec.

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  • Larryect
    replied
    Re: All about tanks

    I am only guessing as well.

    Any company can have any sticker made. Re-Test is not Re-Certify.

    It looks like a service company made it as advertisement/documentation the they inspected (tested?) the tank. CNG tanks are supposed to be inspected every three years or 36,000 miles.

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  • freedml
    replied
    Re: All about tanks

    Some steel CNG tanks can be recertified.

    Leave a comment:


  • CNGfamily
    replied
    Re: All about tanks

    Originally posted by jblue View Post
    I am not trying to debate your statement, but if what you say is true, why does this sticker exist? It clearly specs a retest date ...
    Might it be the re-cert sticker is from a previous era when you could recertify tanks?

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  • jblue
    replied
    Re: All about tanks

    Originally posted by cnghal View Post
    To clarify, no NGV-2 cylinders (Types I, II, III, and IV) can currently be recertified for another 15 years.
    I am not trying to debate your statement (as if to say you do not know what you are talking about), but explain why this sticker exists? It clearly specs a retest date ...
    Attached Files
    Last edited by jblue; 07-16-2008, 05:11 PM.

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  • cnghal
    replied
    Re: All about tanks

    With as many illegal shops and shadetree mechanics as there are at work in Utah these days, I'm thinking this Fourth of July could be a doozie.
    "And the rockets red glare, CNG tanks bursting in air......"

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  • CNG MOTORS
    replied
    Re: All about tanks

    I agree this really doesn't prove anything. The car next to it looks pretty good, was burnt a little from the fire but does look like explosive damage to it. And this was arson. If this was in the real world hopefully the driver was smart enough to get out of the car when it's was on FIRE. This explosion occured because the PRD failed. The same thing can happen to a gasoline vehicle or maybe I've seen one too many films. Don't think your gas tank has a PRD.

    Do not play with matches and Smokey says only you can prevent forest fires.

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  • Highmarker
    replied
    Re: All about tanks

    Curtis,

    The 25 year life is new only to NGV2-2007. It was published in July 2007. I haven't seen any tanks with the new 25 year life. You are right about the manufacturer designating the life of the tank.

    Originally posted by Curtis View Post
    While they can have a 25 yr service life, that is a function of the tank manufacturer, right? The manufacturer can set 15, 20, or even 25yrs on the expiration. I've seen 15 & 20's, I'm not aware of anyone doing 25 yrs yet. That's still a fairly new standard, do you think it may be a while before we see the 25 yr tanks available

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  • Aaragorn
    replied
    Re: All about tanks

    So who benefited from that attack? What political agenda was behind it? I don't see how a terrorist act like this proves anything about the technology except that it can be exploited for destructive purposes like so many other things. The human factor of intention is what failed here, not the technology.

    Leave a comment:


  • Andy-Paul
    replied
    Re: All about tanks

    Originally posted by Highmarker View Post
    I am of the opinion that the reason for the expiration date on composite overwrapped tanks (Type II, Type III, and Type IV), is because nobody really knows the "long term" effects of composite materials. Steel has been around for a long time (thousands of years). Using carbon or glass fibers as reinforcement on tanks is fairly new technology (1960s). It takes time to trust the materials. Besides the processes of fabricating a composite tank is much different than fabricating an all steel tank.
    You're right in stating that steel has been around for a much longer time, therefore it is much more clearly understood, and we have a much better understanding of what will lead to catastrophic failure (the driver killed when the owner did not have the proper safety check) versus a gradual failure. There is also a well-understood microstructure (crystallline structure of the atoms involved) upon which strength of materials estimates can be based.

    In the case of fiber reinforcements--either glass or carbon fibers--the composite structure is strong up to a point beyond which it fails (look at the pictures from the link that is a few posts down from here--that shaggy doghair on the tanks is fiber material that has snapped out of its manufactured position.) There is no real middle ground, like a green stick from a tree has. The microstructure of the overwrap is reasonably well understood, but because we are talking about amorphous substances (--remember hearing that glass is a super-cooled liquid? That just means that it does not have an overarching microstructure--) there is more variability in the calculation of material strength.

    Aging is a factor in both metals and composites, but that's way too much for me to think about at this late hour, much less try to explain. If yer interested, shoot me an email and I'll try. Compression/depressurization of the tank does effect the microstructure, however.
    Last edited by Andy-Paul; 06-06-2008, 06:41 AM. Reason: extra data

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  • Curtis
    replied
    Re: All about tanks

    Originally posted by Highmarker View Post
    FYI, the new NGV2 specification (NGV2-2007) now allows for tank life of 25 years on new designs.
    While they can have a 25 yr service life, that is a function of the tank manufacturer, right? The manufacturer can set 15, 20, or even 25yrs on the expiration. I've seen 15 & 20's, I'm not aware of anyone doing 25 yrs yet. That's still a fairly new standard, do you think it may be a while before we see the 25 yr tanks available

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  • Aaragorn
    replied
    Re: All about tanks

    Originally posted by Highmarker View Post
    FYI, the new NGV2 specification (NGV2-2007) now allows for tank life of 25 years on new designs.
    if you under pressurize when filling does it extend the life? a 25 year life is likely longer than I would want to own the vehicle.

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  • Aaragorn
    replied
    Re: All about tanks

    I've been measuring the Pathfinder. Looks like the back end has about 44" width and 16" depth when the seats are in the upright position. So how big a tank would that accommodate? 16" dia. and leaving enough room for the valves on the end. How do I figure gge from these dimensions? What would a tank weight of the different types? I II III IV?

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