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Cryo jets trouble shooting

Discussion in 'Special Effects' started by pickles, Jan 13, 2018.

  1. pickles

    pickles Member

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    Location:
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    Ran a gig last night with some cryo jets. They tested just fine and we shut off the tank to preserve fluid. Came time for the show and they made a lot of noise, and no plume. Went to fire the second cue, and same thing. All the noise, none of the effect. After the house cleared we fired them again and held the valve open for 5-6 seconds and still no plume. The hoses and tank weren't particularly warm, and the tank was cool to the touch so it's not like the fluid evaporated or whatever.
    System spec:
    4 Sigma services valves
    1 50 LB siphon tank of liquid C02
    about 15' of hose to 4 way maniofld
    Then another 10' to each valve

    Any thoughts are appreciated.
    Thanks!
     
  2. DanH

    DanH Member

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    It's normal for the liquid in the hose to turn to gas if it's left in there for more than 30-60 minutes; but usually once it's cleared, you'll get gas again.
    I've typically seen a 1:1 ratio of tanks-to-jets, or even two tanks per jet on heavier-use shows, so it's very possible that your one tank just doesn't have the pressure to feed four jets.
    I've also had one of a bank of tanks quit delivering liquid for no apparent reason, well before the others - sometimes we've speculated that the siphon tubes just aren't that well attached, and sometimes just come loose inside the tank, so you get gas off the top rather than liquid from the bottom...
     
    RonHebbard likes this.
  3. Amiers

    Amiers Lighting Phoenix 1 Lamp at a Time

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    I would also say not enough tank. Best way to test this is shut down 3 jets and test and rinse and repeat til you recreate the problem.

    But ideally you should 1:1 but if you can test it 1:2 then do that to save ya some coin.
     
    RonHebbard likes this.
  4. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @pickles A minor swerve you likely wouldn't think of. The Stratford Shakespearean Festival used to use a lot of liquid nitro and found it convenient and cost effective for one simple, but likely rarely considered, reason. The city of Stratford is in south western Ontario, Canada and in the heart of farming and pig breeding country. Pig breeders are large users of liquid nitro, they use it to flash-freeze pig sperm for cross-breeding and artificial insemination of female pigs. Don't go there. It's not something you want to spend much time thinking about. The good part of being in the heart of pig rearing country is being able to be on the regular weekly delivery routes of more than one competitive liquid nitro provider. Stratford being Stratford and running rotating repertory plots in, during my time, three separate venues in three locations across the city, ALWAYS kept a reasonable stock of liquid nitro on hand in each theatre. This occasionally became useful when a neighboring pig farmer found himself un-expectantly in need of just one more container of liquid nitro. You could often easily trade a partial cryo tank for a refillable empty tank AND a whole lot of fresh pork for your barbecue when the timing worked out. Our crews had some mighty fine barbeques over the course of my years there.
    Just an application, and source, you MAY not have thought of.
    Toodleoo!
    Ron Hebbard.
     
    MarshallPope and EdSavoie like this.
  5. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @pickles One more dumb thought / query for you: You are using a two-hole stopper in the top of the Dewar (Sp?) flask and forcing air, or an inert gas, under pressure into the tank as an aid to pushing the liquid nitro out on cue, right?
    Toodleoo!
    Ron Hebbard.
     
  6. DanH

    DanH Member

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    They said they're using a 50lb siphon CO2 tank, not a dewar...
     
  7. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @DanH Boo! Hiss!! My apologies for missing that.
    Toodleoo!
    Ron Hebbard.
     
  8. pickles

    pickles Member

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    Thank you all so much for your responses. Our current theory is that there's something silly with the siphon tube. But seeing as we can't return the tank today (MLKJ Day) We are going to take @DanH and @Amiers advice and try it in the shop with one or two hooked up.
    Thanks!
     
  9. Olddog

    Olddog New Member

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    The jets require up to 1 pound per second. You have 4 so 50/4 = 12.5 seconds of run time. restrictions and temperature drop in the tank will slow the flow giving a bit more time.
    Once the dip tube gets uncovered you will still get gas pressure for awhile but no liquid. I expect you just ran out. You should have a bust disk on the lines somewhere and it's good practice to let off the pressure if you close the tank valve, this prevents the liquid trapped in the hose from over-pressuring.
     

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