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Thread: CO2 fire extinguisher

  1. #1
    Hello Roboteers.

    Can you please help me! I just want to make sure I have interpreted the rules correctly…

    I am running a low pressure system…
    I was unable to find a screw in isolation valve for the co2 extinguisher so I have left the lever type and plan to bolt this open with a wing nut (lever clamped shut)

    This then goes into a compression fitting adaptor using the nut that came with the extinguisher, (I couldn’t identify this thread)
    Attachment 6498 Attachment 6499
    Then into a hydraulic elbow, then to a ball valve to act as an isolation valve for the cylinder.

    This will leave the adaptor, and elbow pressurised (until the wing nut can be removed and the lever shut)
    I had planned to use the quick release so that I can remove the canister and also use this for filling, however, I realised that I cannot use the quick release, as this has the potential to leave the quick release to ball valve pressurised, so I plan to replace this with *something* (probably just a screw fitting) to join to the regulator.

    After the regulator I have an air fuse for the low pressure side, and a ball valve tee’d in for a dump valve.
    I currently do not have a way of quickly dumping the whole cylinder, as it would have to run through the regulator and escape through the low pressure release.

    I have really struggled to do this will off the shelf parts, as I do not have access to pressure testing facilities!

    Is this correct??

  2. #2

  3. #3
    Hello Dave,

    I'm not sure if that is a general comment or for me specifically, but I do not think I have done anything that is not safe.

    I am a mechanical design engineer, and design pneumatic handling assistors as a profession. Where this has lead me to areas outside my expertise I have the sought the support of experts.
    I am concerned that I have done something not in line with the rules.

    I'm literally on here asking for advice from people with more knowledge than me.

  4. #4
    The tread on the fire extinguisher valve is a kind of a hybrid. Based on the BSP idea, 5/8 but with higher TPI.

    Your setup needs a dump valve in between the FEV and the isolation ball valve.

    For the rest, it's just heavier than most setups, but not unsafe.

    I would fix the ball valve in the robot, and make the connection between bottle and that ball valve with a flexible hose.

  5. #5
    I thought I might, thank you.

    I will need to add another ball valve for the dump?
    Then I will do just that, mount it all to the baseplate and use small hydraulic hosing.

    is there anywhere I can lose some weight in this?

  6. #6
    You could opt for a 3way ball valve.

    And weight, you can lose weight on every part, commercial parts ain't build to the lightest possible, but to the easiest to manufacture with the least material involved.

  7. #7
    Thank you for your help,

    I went to Hopespare hydraulics and pneumatics yesterday, and the screw in elbow is in the process of being replaced with a compression fitting and a flexible, thermoplastic hose. The fire extinguisher valve small thread was also identified as a 7/8 unf 14tpi if anyone is struggling with this! (The larger thread into the bottle is an M25 x 2, though i couldnt find anything commercially available to fit this.)

    The hose will then attach to a 3 way T ball valve, to isolate or dump the bottle, which can be clamped onto the chassis.

    He has also supplied me with a quick release that does not seal when released, so no pressure will be stored.

  8. #8
    We had someone use this system on RW last series, I failed them because of it. No part of the system can be pressurised until it is in the arena, the above photo doesn't allow for the system to be dumped. Also part of the system is pressurised without a pressure relief device in it, this would also be a safety failure point. I know the rules are being tightened up on this aspect so, we will have to see on Monday.
    What most people do is modify the lever valve on the CO2 bottle, with a screw and knob to close the valve slowly this would mean you could lose the isolation ball valve and the additional dump and relief valve otherwise required. If the regulator goes straight on to the bottle with the short solid pipe to the CO2 nut then it doesn't need a Full pressure relief valve, won't hurt to have one on the reg though.

    Also I would advise against using the quick release, no one else uses them this must be for a reason. I would assume it's too likely to come undone with the shocks of 40mph collisions.

  9. #9
    Thank you Ed.

    I have had quite a lot of conflicting advice on this so far!
    I was initially told i could not use the lever on the FE as the isolation valve, but having spoken to james cooper, this is not the case and i am fine to do this.
    I will do as you say and add a hand screw to the lever.

    The quick release does not hold pressure, so the busrt disk on the FEV would cover the short pipe run to the ball valve, but the de-coupling risk is a good point so I will re think the QRV.
    Does everyone else just undo the bottle fitting each time they want to fill/ inspect the bottle?

    The reg came with a burst disk so I will just leave it on there. It saves trying to plug up the port too.

    Do I need a dump valve directly after the bottle (before the reg)?

    Thank you for your help

  10. #10
    Yes that's the standard, to remove the CO2 nut. The filling rig will screw straight on to the bottle valve. This is the case a live events and robot wars.

    The dump can be anywhere in the system as long as all pressure is vented from the system, usually we will close the bottle first to save gas. But sometimes this isn't possible for safety and we will vent the whole system including the main tank. I would put it after the reg, not knowing what reg you are using, it will always allow downstream so it will still vent the system.

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