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Max Helium fraction continuous blend

Discussion in 'Compressors, Boosters and Blending Systems' started by Tyler duran, Nov 8, 2019.

  1. tmassey

    tmassey Barracuda

    # of Dives: 200 - 499
    Location: Shelby Township, MI USA
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    Interesting testing. Better your compressor than mine for now... :) But I too would like to scavenge He too... Could you tell us more about your compressor? brand, number of stages, CFM capacity (or motor HP even). Do you know if your compressor is splash lubricated or pressurized lubrication?

    Compressor head temp measuring seems straightforward. How did you measure oil temp or frothiness?

    And what was your thinking to go with straight He instead of 21/35 in the stick? You mentioned waste, but it’s not that much — especially if you stop the He just a bit early... It does make it easier to change the blend if there’s problems with the He in the compressor (like selectively leaking out...).

    But thank you very much for writing this up! I am enjoying it.
     
  2. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
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    my 3.5cfm alkins has 3 stages and is splash lubed with 751 synthetic oil
    it has a oil sump window for checking the level - and/or bubbles

    I pump 100% because I can do that at much lower pressures. CBing 10/70 up to 3600psi was audibly hard on the pump. I could hear the blowby and the pistons banging around. Just pumping 100% at lower pressure seems friendlier, no banging, no measurable heat.
     
  3. michael-fisch

    michael-fisch Manta Ray

    # of Dives: 2,500 - 4,999
    Location: Germany
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    Take a look on thedecostop.com and search for "Omni Booster". I invented it almost 20 years ago and mine is still going strong.
    When I return He tanks they have 5-10 psi in them and I pump helium to 320Bar.

    Michael
     
  4. taimen

    taimen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Europe
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    Which compressor you use for this and do you see any significant helium loss?
     
  5. Valyngar

    Valyngar Nassau Grouper

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    Actually takes about 12 hours to helium mix stabilize. Have been doing checks with my analyser. Remember to put bottles laying and roll a bit.
     
  6. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
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    These are fancier than I need, I use a wine cork with a hole in it attached to a small grocery bag. The cork goes in my prefilter and I just manually keep the bag partially inflated with a drilled out ebay oxygen regulator.

    Like you I posted about pumping 100% helium over 10 years ago on TDS, seems like SB is just catching up

    There is no loss of helium from any (modern) oil lubed compressor, rig blow-by is routed back to the first stage inlet.

    Don't do this with any oil-less compressor
     
  7. taimen

    taimen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Europe
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    Yes, this is what I have always understood. But a lot of confusing comments always pop up. Some of them confuse loss of efficiency with loss of gas. Others seem to be pure misinformation. Anyway, I haven't yet built my He compressor setup.
    Are there any real life differences between 3-stage and 4-stage compressors for pumping helium (relatively light use)? And now I am asking about small-ish regular scuba compressors, not dedicated helium compressors which are too expensive.
     
  8. Miyaru

    Miyaru Tech Instructor

    # of Dives: 2,500 - 4,999
    Location: EU
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    Here's an example of a Bauer compressor suitable for pumping Helium:
    75429515_393101948242208_4349197975440850944_o.jpg
    Any gas escaping in case of over-pressure is routed back to the first stage.​
     
  9. RayfromTX

    RayfromTX Student Of Gas Mixology Staff Member ScubaBoard Sponsor

    # of Dives: 100 - 199
    Location: Hill Country of Central TX
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    I thought I recalled reading an old thread about this when I started scouring all the historical threads on all the websites about these topics as I was getting my system setup.

    Indeed, you didn't just talk about it on the other website, you also discussed it here ten years ago. Continuous Trimixing Question

    There are some other threads from back then and since then as well.

    Also interesting to learn that @michael-fisch invented the omni-booster.
     
    rjack321 likes this.
  10. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    9,059
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    I gave up on the little hargraves sampling pump pretty quick. It works to route your trimix inlet gas to a helium analyzer (since they rarely have a remote sensor like an O2 cell). but its just not necessary to CB trimix at all when you can pump raw helium and top of with 32%
     

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