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Thread: Making air

  1. #21
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    Quote Originally Posted by NWdiver View Post
    I get paid to do maths... I'd rather not do anymore when I don't have to
    Think the "YAGAMIC" gas blending spread sheet has ability to do it as well

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    I have a couple of American diving magazines where there are articles on using liquid air to supply the divers. I believe the problems with different temperatures when O2 and N2 become gas again led to a number of incidents.
    Probably if looked at now with the control systems available could be a way of extending dive times.

  3. #23
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    Quote Originally Posted by WFO View Post


    Tyres on plant get blown up with a cheetah tank to bang as much air as possible in there as quickly as possible to seat the bead. They are great for making spud guns. The idea of an explosion from the heat involved is preposterous. (and you can literally blast tyres onto the rims with flammable gas explosions and they're fine)
    I guess plant isnít the correct term. If you tried that on a large mining truck, you would probably be off site and never work for that company again. Tyre explosions do happen, and have been known to kill people. Although to be fair it isnít just the heat it is contaminants, maybe compounds released by the rubber or just introduced somehow. The pressure of getting a tyre to bead is a bit lower than that generated on a bad haul road.

    Anyway, anything incoming high pressures and gas can be dangerous. People just get away with so much



    Sent from my iPhone using Tapatalk

  4. #24
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    N2 contaminated? It's exactly the same level of risk as the oxy or helium being contaminated, which we all take as a completely acceptable risk. And very probably much lower risk than the risk of a compressor filter failure.*

    Since helium comes out of the ground as a minor component of a mixture of hydrocarbon gases then it depends on the level of separation which takes place before it can truly be called pure helium. I would imagine helium being suplied for welding purposes is potentially less pure than that for mixed gas blending. Yet I know that some folk do use welding grade to mix their own trimix. Never heard of an incident being attributed to this though, correct me if I'm wrong.

  5. #25
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    Quote Originally Posted by N Bailey View Post
    I have a couple of American diving magazines where there are articles on using liquid air to supply the divers. I believe the problems with different temperatures when O2 and N2 become gas again led to a number of incidents.
    Probably if looked at now with the control systems available could be a way of extending dive times.
    Possibly, but why would you? Where's the benefit in having a complicated cryogenic evaporation system to extend an air dive?! I could be wrong but I don't think even the space programme uses these kinds of gas systems and they have a cold environment right outside thew window!

  6. #26
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    Quote Originally Posted by jturner View Post
    Possibly, but why would you? Where's the benefit in having a complicated cryogenic evaporation system to extend an air dive?! I could be wrong but I don't think even the space programme uses these kinds of gas systems and they have a cold environment right outside thew window!
    The Apollo project which ultimately took man to the moon to begin with proposed using pure oxygen for all phases of the flight. This led to the deaths of the three astronauts, Gus Grissom, Roger Chafee and Ed White when a fire broke out in the capsule during a training exercise on the launch pad in 1967. A major redesign of almost everything associated with the enviroment in the various parts of the vehicle led to an atmosphere of 40% Nitrogen and 60% oxygen at 1 bar in the capsule at launch reducing to 0.35 bar pure oxygen on achieving orbit about 8 minutes later by bleeding off the gas in the capsule and replacing it with 100% oxgen. To prevent the astronauts getting the bends on the ascent they had been breathing pure oxygen for about 3 hours prior to lift-off.
    During the transit to the moon and return they breathed pure O2 at 0.35 bar. On the moon the suits were pressurised to 0.26/0.28 bar with O2, anything higher would have made them too restrictive and this was the minimum for life support. Its all still there, if you are planning a trip take a few bottles of O2 and some spare batteries for the lunar rovers, and plenty of sandwiches.
    Last edited by thistlediver; 20-06-2019 at 07:51 AM.

  7. #27
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    Quote Originally Posted by thistlediver View Post
    The Apollo project which ultimately took man to the moon to begin with proposed using pure oxygen for all phases of the flight. This led to the deaths of the three astronauts, Gus Grissom, Roger Chafee and Ed White when a fire broke out in the capsule during a training exercise on the launch pad in 1967. A major redesign of almost everything associated with the enviroment in the various parts of the vehicle led to an atmosphere of 40% Nitrogen and 60% oxygen at 1 bar in the capsule at launch reducing to 0.35 bar pure oxygen on achieving orbit about 8 minutes later by bleeding off the gas in the capsule and replacing it with 100% oxgen. To prevent the astronauts getting the bends on the ascent they had been breathing pure oxygen for about 3 hours prior to lift-off.
    During the transit to the moon and return they breathed pure O2 at 0.35 bar. On the moon the suits were pressurised to 0.26/0.28 bar with O2, anything higher would have made them too restrictive and this was the minimum for life support. Its all still there, if you are planning a trip take a few bottles of O2 and some spare batteries for the lunar rovers, and plenty of sandwiches.
    IIRC, the astronauts still use low pressure O2 in their suits when outside of the ISS. They also have to have a quick stop-off in the airlock chamber so they don't get bent.

  8. #28
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    Quote Originally Posted by thistlediver View Post
    N2 contaminated? It's exactly the same level of risk as the oxy or helium being contaminated, which we all take as a completely acceptable risk. And very probably much lower risk than the risk of a compressor filter failure.*

    Since helium comes out of the ground as a minor component of a mixture of hydrocarbon gases then it depends on the level of separation which takes place before it can truly be called pure helium. I would imagine helium being suplied for welding purposes is potentially less pure than that for mixed gas blending. Yet I know that some folk do use welding grade to mix their own trimix. Never heard of an incident being attributed to this though, correct me if I'm wrong.
    No you have not looked at the facts of the matter here.

    If you get some verifiable information (for example from BOC) you will find that they sell various grades, the diving grade isn't anything special in terms of purity. (99.95% perhaps). 0.05% which is likely nitrogen, methane and co2, isn't going to do you a lot of harm.
    Various grades mostly used for welding and laser cutting are more pure.


    Can you imagine the furore and legal bill that BAE would present to the gas supplier when the contaminants fk up a few million quids worth of laser welding machine and a few million quids worth of aircraft part?


    Everyone has this idea that "welding grade" is a dirty thing intended for some knuckle dragger with a roll up hanging out of his mouth in a scrapyard and it is a complete myth.

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    [QUOTE=WFO;433244]No you have not looked at the facts of the matter here.

    I did qualify my statement with the words 'imagine' and 'potentially' . If welding grade is a higher purity than that supplied
    for breathing mixtures then why is it more expensive for the latter?
    There must be a cost in it which they would want to recover presumably?

  10. #30
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    [QUOTE=thistlediver;433277]
    Quote Originally Posted by WFO View Post
    No you have not looked at the facts of the matter here.

    I did qualify my statement with the words 'imagine' and 'potentially' . If welding grade is a higher purity than that supplied
    for breathing mixtures then why is it more expensive for the latter?
    There must be a cost in it which they would want to recover presumably?
    Nope, you charge what the market will bear. I have often seen identical products in factories being marked up at different prices. For example, a ladies facial scrub pad (made by a company that makes washing up scouring pads!) priced at either £3.99 or 99p depending on the name of the store on the pack.
    Paul.
    If God had meant us to breathe underwater, he would have given us larger bank balances.
    Human beings were invented by water as a means of moving itself from one place to another.


 
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