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Plumbing a CNG cylinder storage Array

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  • Plumbing a CNG cylinder storage Array



    I'm knocking together a storage array of 7 x cylinders. With 12 years life on them, all are fitted with Emer VBE 474 CNG cylinder valves.

    My question, will these valves allow independent operation? ie independent array filling, one cylinder at a time, as an array. Thus when I fuel my vehicle I intend to fire off one cylinder at a time. Not all seven.

    More usually I know when 2 x cylinders are installed for vehicle use, the cylinder with the higher pressure equalises to the lower. Not an issue when in a car, but not good as an array. Because these valves and tanks came used from a commercial fleet they came fitted vehicle type valves. One manual tap, one solenoid operated on each valve. Fine for that use, but do these usually have one-way valves, to allow for filling with power off. Will the manual valve work as a standard tap, or one way more like a non-return valve?

    I can't get any info out of Emer. I would assume other brand cylinder valves work the same so in essence, how do other brands work?

    If they work as I fear I won't be able to plumb by daisy-chaining the cylinders as shown. Each will require a further valve (on a T) to make independent working possible. Fellas, as shown, will it fly, or do I need to rethink my plumbing?

    Last edited by BritCNGUser; 09-22-2015, 05:15 PM.

  • #2
    I am guessing here. but I think you will have back flow. you could put check valves in between the valves and open the one closest to the compressor first and then move down the line for fast fill.


    • #3

      Now I don\t like you. [sulks] I have a feeling you're right. I was worried someone would say that. ie I have to have external valves, one per cylinder on top of the internal tap and solenoid valve already sitting on each cylinder. I suppose I can pair them up into 3 banks of 2 and one. But valves are pricey and it'll be a right dog's-dinner of joints to plumb the 'kin thing. More joints ain't good. Daisy-chaining as per my first drawing was going to be siimple. What with having to individually switch 7 x solenoids too, this will be a relative cowson to do. It will be as or a variation looking more like the new drawing Thank you for your help,
      Last edited by BritCNGUser; 09-23-2015, 12:15 AM.


      • #4
        I saw a set up similar to what you are doing. Same type tank and valves. Not a finished system.
        Thinking the inlet is controlled by the manual valve and the outlet controlled by the solenoid valve.
        You could fill the tanks as one (buffer) and use the solenoid valves as cascade dispensing.
        My (not a tank specialist) thinking is the solenoid valves need to be energized to be open.
        Tie them into 3 switches, one for each cascade section.
        You should also tie the solenoid valves into an emergency shut down button. That would be code in the US.


        • #5
          If I read you right, and the inlet is controlled by the manual valve on an Emer type valve, I can plumb as the first drawing. You're saying the manual valve is not a directional valve as I feared, but a proper tap. ON or OFF. Lord and master of all it surveys...Thus , I open all for filling and close all but one for dispensing. Firing one solenoid and one manual Emer valve at a time to run as a cascade-array. That'd be brilliant and my original plan.

          No one selling these seems to know how the things work, and Emer don't have a tech sheet. If I'm wrogn the manaul valve operates pretty much the same as the solenoid does, allowing filling even when OFF.

          Even if things are as I would have it, I may have problems with the excess flow-valve on each cylinder. That will kill fast-fill cascading anyway. Methinks I'll cross that bridge when I come to it, but I think a limitign master-valve just before my discharge-hose should solve that issue - to a point.
          Last edited by BritCNGUser; 09-23-2015, 03:43 AM.


          • #6
            It would be nice if I could get an answer more easily. I conclude the only way to have a definitive answer is to plumb one cylinder as a standalone test, then see what happens. I shall let you know.


            • #7
              OK, I can answer my own questions. Using this Emer VBE 474 valve and I suspect others like it, you are able to fill each cylinder individually, even when in an array (as plumbed to my diag) by shutting-off each manual valve. Thus they should be able to operate as a array. Only this fails.

              When filling your vehicle from the storage array, you can’t use them in array fashion, venting individually because as the pressure lowers, there is a safety device to prevent the others venting to pressures much lower than that contained in each respective vessel.

              Thus to vent all the cylinders you have to run them down in unison. If you leave even one cylinder at a higher pressure, you’ll leave it there with no way to vent that vessel’s pressure into you vehicle. So effectively, because of this limitation, despite control over each vessel via both the solenoid and manual valve, you have one large tank, no matter how many cylinders are in your array. So because of the safety factor, to describe this as an array is really a misnomer. It’ll function as one large tank. Not what i wanted, but hey it works.
              Last edited by BritCNGUser; 07-10-2016, 12:59 AM.


              • #8
                I have an array something like yours with three tanks. I have check valves between each tank and individual switches to activate each electro valve in sequence.
                I can do a cascade fill very effectively with this setup.

                It sounds like you are having trouble with the flow limiter in the tank valves. I find if I keep the pressure differential under 700 psi I can get full flow out of a tank valve. I regulate the pressure differential with a throttle valve I need to manually control. It is a bit finicky to adjust and I frequently open it to far allowing more than 700 psi differential and the flow limiter in the tank valve slams shut. I then have to close the "throttling" valve and allow the pressure to build back up in the tubing manifold. I typically hear a thunk as the flow limiting valve pops back open. I then reopen the "throttlng" valve more conservatively and the gas transfers at roughly a gge/minute.
                Once the flow stops (pressure equalizes) I switch to the next tank in the sequence and repeat the process.
                If the cascade doesn't get you up to the desired pressure I have a valve that diverts compressor output to a line bypassing the storage cylinders (with a check valve in it and a shut off valve preventing flow into the #3 cascade cylinder). By diverting the compressor output from the tanks to the fill hose I can top off the tank at the desired maximum pressure quite quickly.

                This is probably not as clear as I intended but the point is you can make your system work as desired, it just won't be quite as automated or hands off as you might hope for .
                Last edited by karl; 07-10-2016, 10:03 PM.


                • #9
                  I think I have yoru general drift... Most definieltey a flow-limiter issue with mine. I too have a valve I can use as a throttle but in my case the differential between flow and the flwo-limiter kickign in is so tight, i find I've in effect got one vessel.