Manifolds on Twins: It's an open and shut case

[Padowan]

But you all realise that diving with twins, normal, inverted, manifolded, indipendant, open, closed, or any combination of the above is a bit old fashioned - you all want a Yellow Box at the end of the day - and Juz and I (in 6 days) will win on that front too!

I think I made my point! Rep (good, please) to me......

[Digger]

Originally Posted by Padowan

OK, to play devils advocate here, I can think of 1 situation when you might be better keeping things permanently equalised - here it is:

You are diving valve shut - you have 1 tank drained more than the other, perhaps by 50bar or so. You have a catastrophic failure of a neck O-ring or something which means you lose a whole tank of gas - and this is on the tank which was fuller - you now only have the less pressured tank. If you were running half a turn open, you'd have the same pressure in each, but this also implies that the pressure you lose shutting the isolator is less than the pressure "gap" that you have between the 2 cylinders.

Personally I think this is SO unlikely I'd take the risk. Also bear in mind I should have a buddy who should have a bit of spare gas, which should more than make up for the defecit.

So NO vote for the half a turn crowd, just a possible, but very unlikely event that might give you a benefit other than convenience.

Fair, but I find I can isolate before I'm going to lose more than 10 bar. It literally takes a second. Any doubt, I isolate, and start shutting down valves.

My criticism was of someone breathing one down a LOT, and then a major failure screwing you up. Obviously you guys will have to open and close at least every 50 bar, personally I'd want it to be more often.

[Padowan]

Originally Posted by Digger

...personally I'd want it to be more often.

I do it just before each time I look at the SPG - probably every few minutes, certainly less than 50 bar.

[Juz]

I'd say I typically equalise 5-6 times in a dive, so that would be every 30 bar or so.

Juz

[Digger]

I've taken the lead! Oh, and JUz, posting it twice doesn't make it more right. It's task loading throughout the dive, when you should be thinking about monitoring dive time and deco info etc., not relying on that poxy VR3 thing to do the thinking for you. That said, it's probably cleverer than my pea-sized brain. And you can't play games with my brain, unless you're really really clever.

[MATTBIN]

None of that new fangled open all the way DIR stuff for me my boy!
I know which way is closed whenits a bit open cos I is an Engineer and it dont matter if its right way up or not.

I wouldnt open and shut during a dive as I have seen all sorts of kit go phut (or worse) when put under pressure and if its going to do that I'd like to be on the surface when it does.

Matt

[Juz]

Originally Posted by Digger

not relying on that poxy VR3 thing to do the thinking for you

Now now, that's a different argument altogether, but lets not forget you said on saturday you'd have one if you won the lottery, and also let's remember that Juzzy is a thinking diver and the VR3 is a tool to be interpreted not relied upon!

Juz

[Padowan]

Originally Posted by MATTBIN

...I wouldnt open and shut during a dive as I have seen all sorts of kit go phut (or worse) when put under pressure and if its going to do that I'd like to be on the surface when it does.

What about if it goes "phut" when you really need it?

This is the same reasoning I put on the slob knob debate - it's a tool and if you need one fine, BUT accept it's a potential failure point and therefore use it in such a way that means if it DOES fail, then it's only an inconvenience, rather than another disaster, that IT was supposed to get you out of. ie, use a slob knob in an equalising, rather than a shutting off capacity.

[Juz]

Originally Posted by Padowan

ie, use a slob knob in an equalising, rather than a shutting off capacity.

Hey! that's a good idea, so you dive with the manifold closed then, and equalise at convenient times during the dive!

Juz

[Padowan]

Originally Posted by Juz

Hey! that's a good idea, so you dive with the manifold closed then, and equalise at convenient times during the dive!

Juz

Exactly, and when we reel in all the votes from the Slobknobbers out there, that we'll have converted with this fabulous reasoning, we'll take the lead back.