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Thread: Pneumatic safety issues

  1. #21
    Bit of info about Water testing and Gas testing, much safer to test stuff with water rather than put it in your robot and gas up.

    Pressure testing of pipelines should normally be carried out using water. Only in exceptional circumstances should pneumatic pressure testing using compressed inert gas or air be used, and then only under carefully controlled conditions. The reason for this is because water is virtually incompressible (as are other liquids) and only a small quantity of energy needs to be introduced to increase the pressure significantly. Air, however, (like all gases) is compressible and, as a result, much more energy has to be put into the gas to raise its pressure. In fact, at the pressure ranges normally used for testing water-piping systems 200 times more energy is stored in compressed gas compared to water at the same pressure and volume. So, should a joint, pipe, or any other component fail under test pressure when using compressed gas, the energy can be released with deadly force

  2. #22
    I think the rule's it's quite clear what's supposed to be tested and how, but be totally honest there's only a select few that can afford to do that.
    My other concern would be that any certification would be invalid legally as it's used in an combat situation where a slight dent by a spike or axe that has no ill effects would deem it not safe for use in a commercial environment.

    That being said, my personal opinion is that the main CO2 bottles need to be off the shelf and always in good condition as they do now, but the custom parts after the bottle/regulator should not need full certification. Obviously we need to keep a close eye on things so that people aren't being stupid with material thicknesses etc - but that's no different to how things are at the moment.
    The arena's are built to take any misshap's with these sorts of systems.

  3. #23
    kane's Avatar
    Roboteer

    Quote Originally Posted by maddox10
    I believe Behemoth suffered from that rulechange too. In Series 5 600 gram paintball bottles were used.
    We didn't suffer, just had to get some approved cylinders. It was a sensible and logical approach, especially given the number of competitors and the high levels of HSE participation.
    Kane Aston
    http://www.makerobotics.com

    Co-owner and builder of BEHEMOTH

  4. #24
    What do the Americans do? I believe they run Nitrogen at well over 1,000psi so it may be worth looking at how they deal with the safety and regulation issues.

    They also run flame throwers, and Li-Pos & Spinners in the HW category.
    Perhaps taking a look at how they run could answer some questions, provide some inspiration for solutions.

  5. #25
    Quote Originally Posted by kane
    Quote Originally Posted by maddox10
    I believe Behemoth suffered from that rulechange too. In Series 5 600 gram paintball bottles were used.
    We didn't suffer, just had to get some approved cylinders. It was a sensible and logical approach, especially given the number of competitors and the high levels of HSE participation.
    Ok, you adapted. Just like Team Warlock did. We replaced the frame-main tanks with recertified 2L Oxygen bottles, rerated as 1.5 kg CO2 bottles , but restamped as 1.1 kg bottles to satisfy Mentorn.

    BTW, the main bottles that were welded in the frame untill the rulechange hit us. Here are the relevant test sheets.

    http://users.telenet.be/P3/2012-06-01/001.jpg
    http://users.telenet.be/P3/2012-06-01/002.jpg

  6. #26

  7. #27
    I would be a little cautious with the idea of using pressure vessels that have been used for more than say 5 years.
    I think you may find over their life the bottles being filled and exhausted many times may suffer from material fatigue, they may appear OK. But on a microscopic level may have started to break down undermining their integral strength.
    This in turn means they could fail with disastrous consequences, when they are in the process of being filled after a fight when they are still very cold! This is when the material would be most brittle, and when you people are holding the things. and I could be standing close to you at the time. :shock:

  8. #28
    Quote Originally Posted by craig_colliass
    I would be a little cautious with the idea of using pressure vessels that have been used for more than say 5 years.
    I think you may find over their life the bottles being filled and exhausted many times may suffer from material fatigue, they may appear OK. But on a microscopic level may have started to break down undermining their integral strength.
    This in turn means they could fail with disastrous consequences, when they are in the process of being filled after a fight when they are still very cold! This is when the material would be most brittle, and when you people are holding the things. and I could be standing close to you at the time. :shock:

    That is why main pressure vessels need to be certified; if one blows up then, it's the fault of the certifier.

    How many times did we have a catastrophic failure with a commercial CO2 bottle? (most btw, are 200 bar bottles, pressure tested at 300 bar, equipped with a 195 bar burst disk)

    Also, not many steel tanks around anymore. Most are ali. Surprise, gas bottle ali doesn't get brittle at -80°C, that is why it is used for LNG tanks on large tankers....


    And, with 6 events a year, 4 fights an event. 24 fillings a year. Even doubling that...
    Avarage Scuba tanks get more use. And people carry those on their backs, in constantly changing pressure regimes. I don't get a lot of exploded scubadiver stories , not even on the internet as a spoof or Darwin Award nominees.

  9. #29
    Thanks for the reply I'm not sure dose that mean you agree? also is your computer OK as some times the words go really small.

  10. #30
    The thing I agree upon is that storage bottles need to be certified. By the book preferably.


    But fatigue seems not the foremost of our concerns.
    How many fights has a robot before a full overhaul or even retirement?

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