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The What Cheered Me Up Today Thread

Discussion in 'Off Gassing' started by Doomanic, Jun 11, 2009.

  1. nickb

    nickb Active Member

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    Today, I made a 'Nitrox Stick' from bits and pieces I had in the house.

    [​IMG]

    "What's a nitrox stick?" I hear you ask.

    Well, it's a device that will allow one to continuously blend nitrox (and trimix with some modifications - watch this space) through a compressor. Introduced upstream of the compressor intake, the percentage of nitrox required is 'dialled-in' with the regulator and monitored on the analyser. It enables one to drain an O2 cylinder to a few bar and also to do top-offs when the O2 cylinder doesn't contain enough gas to do partial pressure blending.

    Parts list:

    Vandagraph VN202 oxygen analyser (with T-piece and flow diverter from the DIN kit)
    O2 welding regulator and a length of tubing
    75 cm length of Marley 32mm waste pipe
    Standard Seatec LP nipple (as found on a drysuit inlet valve or BCD inflator)
    50mm length of 33mm glue-lined heat shrink tubing
    2 balls of stainless steel wool (like one uses to scour pans) - this is inside the pipe and acts as a baffle to mix the O2 with the incoming air so that the analyser can get a good average reading

    Not shown is the 20mm OD reinforced hose pipe that connects this to the inlet on my compressor. This was salvaged from a part that came with an old Karcher pressure washer that was meant to scavenge water from a butt.

    The analyser cost me £80 from eBay about 10 years ago. It can take old Sentinel rebreather cells (R17) but I always buy fresh sensors from Vandagraph.
    The regulator was less than £20 on eBay a year or so ago (I bought it to fine-tune the LP flow to my booster but never bothered using it).
    The other stuff was just lying around in my man-cave.
     
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  2. Tribal Chestnut

    Tribal Chestnut Active Member
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    ^^ I won't try to pretend that I understand all of that but it sounds mighty fancy.
     
  3. nickb

    nickb Active Member

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    What don't you understand? Happy to elaborate....
     
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  4. Dave Whitlow

    Dave Whitlow Well-Known Member

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    I went diving the weekend and put another 100 scallops in the freezer. We ate a few too :)
     
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  5. Tribal Chestnut

    Tribal Chestnut Active Member
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    Thanks for the offer @nickb but tbh there's so little that I do know about filling methods/techniques/compressors/etcthat I'm going to have to spend some time educating myself at some point.

    Probably quite soon too given the dire gas situation local to me.
     
  6. jb2cool

    jb2cool Moderator
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    Looks good Nick. Do you have the stick feeding a reservoir/buffer at all (Some people used to use a glorified bin-bag) so that you don't run the risk of starving the inlet side of the compressor?

    I'm surprised more dive centres don't do this and bank 32%. It'd surely make things easier for them and simplify their gas logistics (The empties going back to BOC are really empty).
     
  7. JohnL

    JohnL Well-Known Member

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    Used to work at the BOC world-wide centre and picked up a bit about the UK gas business. Gas in cylinders isn't important unless it is something exotic - you are paying for hiring an expensive and long-lasting asset and the costs of getting it to you.
    The balance of businesses taking and returning cylinders was used by the government statistics dept. When businesses were busy, they tended to ignore the empty cylinders in the yard and just order more; when business started to ease off, they had time to get a few workman to round up the empties and return them to BOC to save a bit of cash. A net return of cylinders from customers was one of the earliest and most reliable sign that the economy was starting to down-turn.
     
  8. nickb

    nickb Active Member

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    No need for the trash bag method with this but I’m working on building something that will allow me to shift helium about.

    Unless you’re selling a lot of nitrox, banking is a bit OTT. If you cascade more than 3 O2 cylinders it’s pretty easy to drain them down to almost empty. I’m hoping to be able to offload some of my cylinders. I currently have 5 Js and 5 ½Js in my garage. It’s getting a bit ridiculous
     
  9. Doomanic

    Doomanic Dinosaur Wrangler
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    Car insurance renewal cheered me up, sort of. TheivingBastardsInsurancedotcom wanted £532. Shopped around and got better cover with breakdown for £370. The same as I paid this year without the breakdown.
     
  10. Dave Whitlow

    Dave Whitlow Well-Known Member

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    :eek: Getting?
     
  11. Cornish Joss

    Cornish Joss New Member

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    Thought I would expand my tank collection, now have three 12l and two 15l cylinders waiting to be breathed from!
    (Tis a shame I need to have four of them serviced though) do people find the cost of servicing stays the same wherever you go?

    Sent from my PLK-L01 using Tapatalk
     
  12. jb2cool

    jb2cool Moderator
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    Servicing does fluctuate a bit so have a look online to fine some typical costs and then as long as your local place isn't too much more then suck it up. If your local place is way more expensive then maybe shop around but then you have to factor in travel time and inconvenience.
     
  13. Wibble

    Wibble Fish don't talk
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    They sure do breed in that garage; I'm sure I heard them rutting at night.:sheep:

    Seems that testing & cleaning is roughly the same sort of price. My LDS is about £47 for a hydro & O2 clean (plus £15? for a twinset breakdown). I know it's a bit cheaper elsewhere but I tend to support my LDS as it's in my interest -- ye cannae get gas fills on t'internets.

    There are some places which seem to be much cheaper. However I've not heard great things about some of them -- to be fair though, some of the moaning was from their competitors...
     
  14. Cornish Joss

    Cornish Joss New Member

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    I'm always up for supporting the local companies. And after looking around this morning, it turns out the closest to me is the cheapest and who most people I know use! So that's a bonus. Hyrdo at £30 and O2 at £18. Doesn't seem a lot.. until I remember it's 4 tanks need doing.

    Sent from my PLK-L01 using Tapatalk
     
  15. Wibble

    Wibble Fish don't talk
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    I wish they wouldn't price it like that as most people need a clean with the test. That's £48 all in. Same(ish) price as my LDS.
     
  16. JohnL

    JohnL Well-Known Member

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    My LDS has stopped filling Nitrox - not enough sold to make it worthwhile. So, I've found another in the opposite direction - Ipswich. Typical grumpy guy did the filling (probably the owner :whistling:). I went off for a coffee and an hour later two cylinders filled with 32%. Well.... maybe - as they start with oxygen and top up with air, you cannot analyse as they won't have mixed enough*. How much is an oxygen analyser and what sort is recommended?

    * As they will likely be used for North Norfolk with a maximum depth of 10m, the risk is minimal.
     
  17. Dave Whitlow

    Dave Whitlow Well-Known Member

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    Analox is the most common one and often come up second hand. You need to factor in the age of the cell as they have about a 5 year life and replacements are around £50.
     
  18. Doomanic

    Doomanic Dinosaur Wrangler
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  19. jb2cool

    jb2cool Moderator
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    Analox O2EII are the most common (As said by @Dave Whitlow), they are nothing more than a glorified multimeter, all the cleverness is done by the O2 sensor/cell that is expensive to replace (These look closer to £100 these days).

    As for not mixing enough, they seem to have mixed enough at my LDS and at NDAC to analyse straight away. Sure, this might not be 100% precise to the decimal point but as long as you can see it's 32ish and not way too low or way too high then I'd be happy enough to take it away.
    Having said that, I do have my own analyser and I analyse my cylinders the day I'm going to dive them to confirm exactly what's in there.
     
    #1979 jb2cool, Aug 8, 2017
    Last edited: Aug 8, 2017
  20. Dave Whitlow

    Dave Whitlow Well-Known Member

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    This is the replacement cell if they have stock.
    Most dive shops normally have an analyser available so you can check the gas you are buying is what you asked for.

    A mistake I've seen is forgetting to add the air. I once saw someone on a boat discover he had 32 bar of oxygen and a couple of years ago my diluent bank was delivered with a partial fill of 14/70 and needed the air top to become 15/50.
     

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