Co2 cylinder getting too hot ?

  1. martinez

    martinez Member

    west mids uk
    was welding up my chassis today. Using co2 that local pub gave me which works pretty good, but after a few hours in the sun I heard this hissing sound which was coming from the bottle. On inspection the bottle had got quite warm in the sun and the hissing was coming from the what looks like a pressure release valve on the regulator. I moved the bottle into the shade but noticed one of the pressure gauges was right round at max. The other gauge continued to read the pressure I’d set. What’s going on ? Has it just got too hot, is the gas about to run out ?
  2. piman Member

    Oswestry Shropshire
    Hello Martinez,

    yes, gas pressure in a container is proportional to it's temperature. If there is a safety vent then that appeared to have done it's job.
  3. martinez

    martinez Member

    west mids uk
    But it wasn’t venting from the cylinder, it was the regulator
  4. rtbcomp

    rtbcomp Moderator Staff Member

    Sheffield UK
    I suspect the regulator has a built-in safety device. FWIW pure CO2 gas is stored in liquid form and at normal ambient temperature the bottle pressure will be around 50 bar until all the liquid has boiled off, the drops quickly as the remaining gas is consumed.

    As the gas is used the liquid boils off causing a drop in temperature, sometimes sufficient to cause frosting on the bottle, so if your bottle got warm then I would say it should be kept out of direct sunlight.

    Once the liquid has boiled off the drop in pressure will still causing cooling, but not as much as when the gas is still boiling off, so it could be you're running out of gas too. What is the situation now it has cooled off?
  5. martinez

    martinez Member

    west mids uk
    Tried again today but still the same. The flow gauge reads right round past max and hit the zero stop ! The other gauge still reads decent pressure. I’ll get my mate who I borrowed them off to check on his bottle, could be I’m running out of gas or could be regulator has gone duff. I’ve run out of steel anyway so no more welding until next week
  6. Paul.

    Paul. Moderator Staff Member

    Northampton. UK
    It sounds like the reg has had it, cylinder pressure is getting past the diaphragm, the safety valve is designed to vent it off before it can damage the welder pipework, so its doing its job.
    Last edited: Apr 21, 2019
    Shedendman and brightspark like this.
  7. Shedendman

    Shedendman Member

    east sussex
    Hence why you should back off you reg after a days welding
  8. voipio Member

    Cambridge, UK
    If a CO2 cylinder contains a substantial amount of CO2 (i.e. not close to empty), cylinder pressure will vary quite significantly with temperature. The figures are approximately:


    The original post didn't mention the cylinder temperature, but if it was hot to the touch it might have been around the 50degC mark. What is the max cylinder gauge pressure on the regulator?
  9. slim_boy_fat

    slim_boy_fat Forum Supporter

    Could there be nitrogen mix with the CO2? I've read that some pub suppliers do that stuff now, and not pure CO2. Don't know how/if that would affect the OP's situation, just asking. :dontknow:
  10. angellonewolf

    angellonewolf Member

    bristol england
    when the bloke droped off my co2 i asked what way he knows if it empty he said just open the bottle is should let out a stream of gas and shows white if you know what your lookng for he said its easy to tell if its low on gas

    he did show me but i dout in a years time i will remember

    i just weight the bottle remove the weight of the bottle stamped on it and thats what you have left

    the fourm told me this