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Bleeding GFI Valves

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  • Bleeding GFI Valves

    Hello, I recently received 6 CNG tanks of unknown condition. I plan on making 2 batwing style Earth rollers from them using 3 for each. I know how to properly purge tanks with argon/water etc for welding but I'm not completely certain on how to safely bleed the tanks from the valves. They are all equipped with GFI 1702 valves and have an unknown amount of fuel in them. I was told they were drained but I can't say for certain plus there is clearly rebuilt residual pressure as they have sat for over 5 years. During loading one of the GFI valves hit just right to break it loose and cause a slight and slow leak and a slight pop when it broke loose. I'm guessing from the O-Ring giving way; this caused the pop. Luckily it bled down without incident but I can still see some bubbles when spraying it with soapy water so I haven't unscrewed the valve with the broken seal. I don't want to do the others that way and am wondering what is the best way to bleed off that air pressure inside so i can unscrew the top valve and bottom caps. The solenoid prongs are broken off or damage on most of them so a manual bypass is necessary I'm guessing. After some research it seems this would work?

    I'm a machinist/fabricator and so I'm confident I could make a similar tool without the cost. If I understand it correctly, the bleed off tool is just a manual shut off plug that inserts into the same threaded hole that the manual shut off does and then the screw or T handle compresses some form of plunger in the head which allows gas to flow out the ports of the tank. Would it be correct to assume I could just thread in a bolt with a hole drilled through the center of it and then insert it through the manual shut off to do the same or is there something about the bleeder which has a special design? To also help me clear something, is the override tool of an extra length compared to the plastic faced manual shut off plug that forced the valve open bypassing the solenoid and also destroying the valve? If so, is it possible to just insert a round piece of steel and then tighten in the manual shut off plastic piece accomplishing the same effect or does gas need a hole or port to travel through?


  • #2
    The valve that the link shoes is to be plumbed into the tubing system to relive pressure in a controlled manner.


    • #3
      So you're saying it won't work for bleeding the tank system, it is just for bleeding off fuel lines and such in the system?

      I also got the 1702 valve that broke loose unloading to finally stop hissing after slowly unscrewing it every couple hours. I took it off but don't really see how it works or how to confidently bypass the solenoid. Definitely seems like the design is to keep the pressure in at all costs. I have the tanks in a field where they isn't any machinery or stuff that could cause a flame/spark; I don't suppose it would be a good idea to use a beryllium wrench to crack open the valves and let them all bleed off the same way through the threads? The valve threads are quite substantial on them, I doubt it would shear the threads off and takeoff like a rocket even when full. Of course, it is like playing with fire.


      • #4
        Recommend you take a look at this Safety Forum "sticky" thread and the GFI document provided:

        You will need to get the GFI tool to perform the procedure.


        • #5
          WARNING dont crack any fitting to release pressure. I have a friend did this and got better than 300 stitches. the tubing came out of the fitting and wiped around like a piece of rope and cut his arm. the tubing hangs on his office wall now to remind him not to do stupid things.