Regulators' rated inlet pressure

  1. Neel New Member

    Messages:
    13
    Location:
    France
    Hello,

    Newbie question I have been searching about for hours already:

    I have an argon cylinder filled at 200bars at 15°C and have bought an argon/CO2 regulator advertised as being "meant to be used with 200 bars cylinders".

    The regulator is a brand new EWO (german brand) 120.470 (good amazon comments made me decide for this model).

    With the argon cylinder at 24°C ambiant temp, the gauge from the regulator reads about 208 bars from the inlet.

    I wonder if I should leak some argon to decrease the inlet pressure down to 200 bars or if it is safe enough to continue with this inlet pressure 4% above 200 bars.

    From another community I was told it is safe as this regulator should have been tested at 1.5 times the 200 bars rated pressure, which would correspond the "200(300) bars" indication in the manual. After what I indeed could check current EU regulations impose a test at 1.43 times the rated pressure.

    Now as I don't want to be anything else than super cautious with this 200 bars cylinder, I have tried to also have this confirmed by the manufacturer but they have not made the effort to answer.

    So before going further I would like to hear about your knowledge about this here. The informations gathered so far tend to indicate 208 bars at the inlet of this reducer will remain safe enough to not want to waste some argon (or cool the cylinder :D) to go down to 200 bars.

    This situation should not be rare (hence why I'm a bit surprised I couldn't find any discussion about this), so it should also not be very likely manufacturers would design their regulators without considering a full cylinder may have a slightly higher pressure than the rated filling pressure, due to the expected temperature range.
     
  2. voipio Member

    Messages:
    1,001
    Cambridge, UK
    Gauge error might be enough to account for the excess, though the cylinder itself might also be slightly overfilled. I wouldn't be trying that regulator on 300Bar inlet pressure, but 208 will be OK.
     
    metalmelt likes this.
  3. Neel New Member

    Messages:
    13
    Location:
    France
    If I do it by maths (Gay-Lussac law) a 200bars cylinder at 15°C will go to 206bars at 24°C (versus approx 208 bars read on the regulator gauge).
    So it may have not been overfilled.
    I will not bother about this small excess of pressure then, as nobody seem to think it could be a danger.
    Time to continue connecting to the welder and do the leak tests :)
     
    metalmelt likes this.
  4. You will be ok, there is a safety tolerance engineered into the regulators manufacture but as said above only use it on 200 bar cylinders
     
    metalmelt likes this.
  5. Matchless

    Matchless I started with nothing, still have most of it left

    Messages:
    1,626
    Location:
    Essex UK
    There are things to worry about and things not to worry about, most ratings are nominal + - , a bit like speed limits, 50kmh, 55kmh... has a 50 in it!
     
  6. mike os

    mike os just a little insane.....

    Messages:
    6,982
    Location:
    North Wales
    There is a healthy amount of headroom designed in , it's fine at that,
     
    metalmelt likes this.
  7. Neel New Member

    Messages:
    13
    Location:
    France
    After 3 days testing (few hours per days) I had a sudden inlet leakage at the regulator (very audible).

    I wonder if I may have tightened too much, or if new threads can take shape over the first days and need to be tightened again to recover a perfect sealing.

    After cleaning the connections and cracking the cylinder, I have used a 38cm long wrench (15") but watched many videos before to get the best idea of the torque to apply. I would say I have tightened moderate-strong (no brute force). After that I have leak tested everything with soapy water and by leaving pressurized for half an hour to check pressure was kept.

    Below are macro pictures of the regulator threads, cylinder threads, and regulator plastic gasket.

    The gasket was enlarged due to the tightening pressure. I have measured the diameter changes VS replacement gaskets (the 3 on the right): outer: 18>19.5mm / inner 11.6>12.8. The gasket picture also shows some wave marks on the gasket surface. Do you think I have tightened too strong ?

    The picture n°2 of the reg threads also seems to show some slight threads damage. What do you think ?

    The cylinder threads seem ok, a bit dirty maybe ?

    Should I retry with a new gasket and applying less tightening torque? (smaller wrench)

    Reg threads (rotated 6 times to view the whole threads):
    [​IMG]

    Cyl threads:
    [​IMG]

    Reg gasket:
    [​IMG]
     
  8. The easiest way to do damage is by over tightening, the spanners supplied are only about 6 inches long for a reason
     
    metalmelt likes this.
  9. minimutly Member

    Messages:
    1,505
    Location:
    Pembrokeshire Wales
    Did I say about the time I used to fill small bottles of oxy from the big boc ones (2800 psi?)using a gutted brass regulator and stainless flexi pipe. After many times of doing this, one day the reg case split and it got blown across the workshop. Oops, lesson learnt..
     
  10. tom2207 Member

    Messages:
    2,513
    Location:
    uk northern ireland
    Never underestimate the force that compressed gasses can exert.

    Lots of welders dont give compressed gasses enough respect , watch a Diver or a Gas Blender at work and you will get a new respect for compressed gasses.
     
    metalmelt likes this.
  11. Neel New Member

    Messages:
    13
    Location:
    France
    I was told the deformation of the gasket clearly indicates way too much tightening.

    I was thinking I may have "slightly" overtightened, but wouldn't have imagined it was "that overtightened".
    I have just stopped tightening as soon as I have realized the resistence felt in the wrench was not increasing anymore (=started to feel constant).

    With a plastic gasket that seems that fragile it sounds not easy to find the right torque, and I would have liked a precise torque indication from the manufacturer.
    It should be mandatory from manufacturers given the risk implied.

    My 8" adjustable wrench doesn't fit that nut size, the smaller wrench I own that fits is a 10" one. So I'll just hold it in the middle for my 2nd try after replacing the gasket.
     
  12. Neel New Member

    Messages:
    13
    Location:
    France
    I have looked for diving cylinders videos after reading your comment, indeed the tightening torque used in the video below at 1"50 seems really small !

     
  13. The new 300 bar BOC cylinders use a regulator that is only tightened by hand, no nut to get a spanner on
     
    metalmelt likes this.
  14. Neel New Member

    Messages:
    13
    Location:
    France
    It really depends on the sytem used, the required torque will be different if it is metal to metal or metal to ptfe gasket and maybe other factors depending on the design and materials.

    I have replaced the gasket and have no leak again, but it was necessary to apply some significant torque again (using 10" wrench this time).
    I have done it by steps, tightening about 5° each time with a moderate torque at initial step (wrench hold at the top and applied moderate torque).
    The 3 first steps were leaking at 100bars.
    Next steps allowed more and more pressure before leakage occured.

    It has required almost 10 steps like that to obtain a steady pressure over an hour (cylinder closed).
    Or almost stable, because it is past 1h45 now and it seems to have decreased something like half a bar (again, bottle closed).
    So if it still leaks (= not temperature related, night here and door is slightly open) it is extremely minimal and I will leave it like that to give the best chance to the gasket to survive more than a few days.
    Because the last 2 steps I couldn't tighten more without grabbing the wrench at the middle and applying relatively significant force (more than what I applied with the first gasket and 15" wrench).

    So idk if this gasket system is very picky to tighten correclty, or metal parts are faulty on one or the other side (cyl/reg), or the provided gasket are cheap and barely able to hold 200 bars they are rated for.

    I'll see on the coming days if it starts leaking again or not.
    With that new procedure I'm the closest possible to the minimum torque required for no (or almost no) leakage.
    More precision would require torque measurement tool.
     
  15. Steveblade

    Steveblade Member

    Messages:
    133
    Location:
    West midlands
    minimutly

    Ill happily decant argon ( its inert) into another bottle taking good care of everything in between (mechanicaly speaking) but OXY no, no way its way to reactive and at pressure deadly. Ever seen the digestive biscuit dipped in liquid oxygen video? Use no oil warnings? Ok we might not be taking liquid OXY but it demonstrates the energy than could be released if something goes wrong, not to mention what 200-300 Bar can do. Stuff burns that you would think should not, biscuits explode etc its like the twilight zone. Overfill a Co2 bottle and it can rupture because of the liquid state, not enough room for expansion so ...

    Dont its just not worth the risk.
     
    minimutly likes this.
  16. Just to clarify as this seems to be getting overly complicated, are you shutting off the cylinder valve but leaving the rest of the system pressurised and seeing if the system then looses pressure over a prolonged period of time, or are you wanting to see if it leaks under normal working conditions
     
  17. Neel New Member

    Messages:
    13
    Location:
    France
    Did that to get the correct tightening yes.
    ...and now I expect this of course, as first gasket has failed after 3 days.
     
  18. The gasket shouldn’t fail, it’s either faulty or has been damaged through mis use
    If the system is losing pressure down stream of the cylinder valve have you eliminate all the other places it could leak from such as hose connections, the hose itself (clear braided hose is permeable to a greater or lesser degree dependant upon the make)
    To test the cylinder to regulator joint you should turn off the regulator by fully winding out the PA screw, then open the cylinder valve about 1/2 turn so it is fully open, you are then testing the connection at full cylinder pressure, not at the small pressure that you have down stream of the reg
     
  19. Neel New Member

    Messages:
    13
    Location:
    France
    That`s what I do, I know how it works.
    We are talking about a sudden massive leak when the cylinder was fully open, clearly audible (as when you crack the cylinder), and clearly felt by hand.

    As said it was fixed by replacing the gasket, but given the tightening force I had to apply again (not `that`much less than my first try with the larger wrench) I am now not sure anymore this gasket replacement was really needed.

    I say this because I was surprised by the small force required when I have unscrewed the inlet nut. It seemed much less compared to the force I had applied for tightening, as if the nut got lose by itself over time (3 days).
    So I don`t exclude I could just have re-tightened the inlet nut without replacing the gasket.

    On a french forum I was told the gasket shouldn`t deform like on my picture, and that was indicating a noticeable over-tightening. This is why I have replaced it without even trying to simply re-tighten the nut first.
     
    Jay1st likes this.
  20. That’s good sounds as if you’ve identified the problem then
     
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