another question about manifolds.

[diving_moose]

Hi,
Just got myself a twin set, rec wing and twin 10's. quick question regarding setup of gear. I know that i will be diving with the manifold fully open, (the only way) but with regards to pressure gauges i have noticed in the past people will dive with two so that they always no what each cyclinder has in it but is this realy needed as i always thought you would just double what ever your single pressure gauge was reading and that would give you your total content of both cyclinders. Any advice would be nice and also and input on twin set configuration etc. I am taking it to the pool first to make sure evrything is okay but and info would be good.
Cheers Lee

[TDave]

Lee

Diving with the Manifold open equalises the pressure across the cylinders, so the reason to place a guage on each post to me seems completely irrational (granted, diving the manifold closed also seems irrational...).
I personally dive with Wing Inflation and Long Hose (Primary Reg) off the right post, SPG, Drysuit Inflation (if not using Helium Mix) and Necklaced Backup reg off the left post. If the Manifold is for whatever reason closed I will realise as my left post guage will not change its reading at all (no, I'm not just having a 'good gas day'...).
If there is a bigger problem and I need to close the manifold then I'm thumbing/turning the dive anyway. At that point knowing the amount of gas I have left after the failure is effectively irrelevant. If I'm going to go completely OOG it's going to happen anyway, whether I have a 'backup guage' to check or not. The rest of the team would of course be aware that I'd had the problem and in any case are prepared for if I should go OOG, as we have prepared for it in the Dive Plan.

Hope that helps.

TD

[Phoenix]

Having two SPG's gives no benefit and simply introduces yet another point of failure into your rig, particularly the O-ring on the SPG swivel so best avoided.

Ian

[Jules]

as said earlier, you only need one pressure gauge which tells you the pressure across both tanks when the manifold is open ,you dont need to double it!

Good idea to practice your shutdown drills in a safe environment. and if you cant do it get some training
Good luck


jules

[diverdman]

Twin indepentants-2 SPGs
Twin manifolded-1 SPG, and no fancy maths stuff like doubling or tripling.