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Thread: Stainless MAV mk2

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    Stainless MAV mk2

    When I switched to Miflex hoses on the MAV I bought the new plastic MAV because I didn't realise that the stainless mav could be adapted to SCUBA fittings relatively easily without creating a pile of adapters.

    I did see a thread on this but I can't find it, I even checked the KISS list.

    Can anyone help ?

    I quite liked the stainless MAV and it might be useful as a spare.

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    Re: Stainless MAV mk2

    The threads should be exactly the same as the plastic MAV, IIRC 1/8 NPT. The plastic MAV I had was interchangeable with the stainless MAV's. Whatever adapter fits the plastic MAV will fit the stainless.

    I never understood the Jetsam move to a plastic MAV and rubber hoses, the all stainless O2 supply was one of it's big pluses. The stainless system will survive anything, all HP rated, no o-rings on the connections other than at the 1st stage, totally bombproof. The 2nd gen MAV is great because it takes the same orifice as the plastic one, the 1st gen is limited to 60'ish m. I tried the plastic MAV and thought it was a bit flimsy and the connections would unscrew at random.

    Cheers,

    Stuart
    Last edited by lizardland; 6th February 2009 at 17:07.

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    Re: Stainless MAV mk2

    Hmm, Jetsam told me that the Miflex kit wouldn't fit the Mk2 MAV which is why I changed it.

    What I didn't like was the leaky taper threads and hard as iron hoses.

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    Re: Stainless MAV mk2

    Quote Originally Posted by Scubascooby  View Original Post
    Hmm, Jetsam told me that the Miflex kit wouldn't fit the Mk2 MAV which is why I changed it.

    What I didn't like was the leaky taper threads and hard as iron hoses.
    I thought with the Plastic Mav you had to unscrew the 1/8NPT fittings and replace them with BSP ones?

    Hence you need the plastic body version?

    Janos

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    Re: Stainless MAV mk2

    The plastic MAV uses a 7/16-20M to 9/16-18M adapter, I believe that the SS MAV has 1/8FPT ports on it and used a 1/8MPT to 1/8M CPI
    Two 1/8MPT to 9/16-18M adapters should get you setup.

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    Re: Stainless MAV mk2

    Ahhh... I get it, does the hose fitting attach into the body rather than to the male stems that poke out? The males stems are whatever the Swagelok nut thread is so I was talking bollox earlier anyway. On the stainless MAV I believe the actual threaded part on the body is 1/8-NPT but that might be bollox too.

    Something is badly wrong if the Swagelok fittings are leaking, they are industrial rated, we spec the same components in chemical plants.

    I'd seriously think about replacing the stainless O2 parts with low pressure, if you ever get a 1st stage failure on a dive with a load of deco then you'll be glad of it.

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    Re: Stainless MAV mk2

    Quote Originally Posted by lizardland  View Original Post
    Something is badly wrong if the Swagelok fittings are leaking, they are industrial rated, we spec the same components in chemical plants.

    I'd seriously think about replacing the stainless O2 parts with low pressure, if you ever get a 1st stage failure on a dive with a load of deco then you'll be glad of it.
    Mainly it was the tapered thread adapter at the 1st stage end. No matter what I did it would leak. In the end I lost my rag, overtightened it and split the adapter wide open.

    I bought a complete plastic MAV and Miflex set-up and fitted it. So it is all low pressure now with an OPV on the first stage.

    I'm not clear on your second statement.

    Finding the adapters to re-use the stainless MAV is probably quite hard here in GB.

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    Re: Stainless MAV mk2

    Quote Originally Posted by Scubascooby  View Original Post
    Mainly it was the tapered thread adapter at the 1st stage end. No matter what I did it would leak. In the end I lost my rag, overtightened it and split the adapter wide open.
    Ah... fair enough.

    I'm not clear on your second statement.
    Basically if the HP seat starts to fail then the IP will either start creeping up or just dump the cylinder contents down the line. It will either blow something apart or trip the OPV if fitted, either way you lose a lot of gas and manually running becomes a big hassle.

    The stainless hose and fittings will take 200bar, you don't need an OPV and the whole cylinder can come down the O2 line and it won't make any difference. You can manually control gas into the loop as long as you like fairly efficiently (especially if you have a suicide valve downstream of the MAV so you can shut gas off without touching the cylinder valve).

    I wouldn't have traded the stainless hoses on my KISS for anything, one of the reasons I bought a Mk15 is that everything is stainless and high pressure. It just makes the whole system a bit more survivable and robust.

    It does happen, I had mine do it twice on separate first stages.

    Cheers,

    Stuart
    Last edited by lizardland; 9th February 2009 at 18:17.

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    Re: Stainless MAV mk2

    Right I'm with you.

    I've done the manual control for real when the fibre washer on the orifice disintegrated. It's not too bad for 30-40 minutes but since then I've de-inverted the tanks so it would be a bit more annoying now.

    If the first stage seat leaks now it will pop the OPV (noisily I imagine) and waste a lot of gas. I don't have a flow stop and it wouldn't help here.

    I'm not a caver so my bail out plan would be to ascend (possible on OC) and then flush the loop with O2 to deco. Just to keep the task loading down.

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    Re: Stainless MAV mk2

    Quote Originally Posted by lizardland  View Original Post
    The stainless hose and fittings will take 200bar, you don't need an OPV and the whole cylinder can come down the O2 line and it won't make any difference. You can manually control gas into the loop as long as you like fairly efficiently (especially if you have a suicide valve downstream of the MAV so you can shut gas off without touching the cylinder valve).

    I wouldn't have traded the stainless hoses on my KISS for anything, one of the reasons I bought a Mk15 is that everything is stainless and high pressure. It just makes the whole system a bit more survivable and robust.
    Agreed and I believe this was Gordon's original thinking behind the SS lines.

    For cavers I agree that the original hoses may be better- survival is key in those conditions. As an Open Water/Wreck diver I'm at ease with the Miflex replacements, they provide easier maintenance and are better to access underwater IMVHO.

    As someone once termed it on the old ScubaUK list- ARSE (All the Right Stuff for the Enviroment) ;)

    I have to say the Jetsam Miflex kit was great all round- except the elbow into the head was a b*tch to fit, for some reason it seemed to be a slightly thread and pitch to original, as I tightened it up I was so scared about splitting the head it was tight as anything. With alittle encouragement from Kim I kept going and cupped the fitting with a spanner to ease it in slowly, scary stuff though!

    BEN

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