valve shut down drill

[SOCAL_CELT]

I recently completed the PADI Tec40 course & we were initially taught to do it one valve at a time but on our final dive we were told beforehand we could do 2 valves at the same time to speed things up.

Quick question is there a standard on how many turns on a valve for it to go from fully closed to fully open? I felt like the tank I had took a long time to shut down/open up compared to some of the other tanks, or maybe it was just the pressure of performing the drill...

 

[grassgreen]

Ah right, interesting, thanks for that Ste wart.

Funny enough the Cave method felt the most straight forward and easiest

 

[DevonDiver]

Quick question is there a standard on how many turns on a valve for it to go from fully closed to fully open? I felt like the tank I had took a long time to shut down/open up compared to some of the other tanks, or maybe it was just the pressure of performing the drill...

It depends on the make/model of the valve. They have different turns to close/open.

 

[TSandM]

As Ron said, the valve shutdown drill is simply to practice being able to access and turn all of your valves. The order, in my view, is unimportant.

I have seen the drill where the diver shuts down right post and isolator simultaneously. It's not pretty. It's very difficult to do it, especially under major time pressure, without losing other important things, like trim and buoyancy, and awareness of the team.

When it comes to failures management, there are two basic approaches: One is to isolate first, on the theory that no matter how things go from there, you can't lose more than half your gas. The other is to try to localize the leak and address it first, since that minimizes the total gas loss during the incident, if you are right. If you dive in a tight team, by the time you're halfway through closing a valve, you will have at least one and probably two other divers looking at your manifold, who will immediately know if you have misidentified the problem.

 

[TONY CHANEY]

Humm...there is only a few reasons why to even address the isolator valve (tank /valve o ring rupture, burst disk failure or the manifold o rings fail). Burst disk being the most likely to happen. Outside of those 3 (and maybe something else I forgot) there is no reason to isolate unless you have no idea as to where the bubbles are coming from.
As for valves being longer or shorter to shut dowm...it depends of the maks and model as stated before. I broke the left side valve handle off during my cave training. We changed it out but the valve could be shut down in about 3 twist. Well that seemed to be the next problem. The cave ceiling can shut it down very fast only after a few bumps (still in training). So I switched the left and the right. So now the right can be shut down in about 3 twist and the left can be shut down in about 6-8 twist. I figured that the right will more than likely be the free flow or other complications due to that being the one I am breathing from. so fast to shut down. While the left takes several additional twist to shut it down...should there be (God forgive me) contact with the ceiling of the cave.

 

[rongoodman]

Also why purge it? that air will be lost, wasted, better just leave it in the hose????

If you don't breathe down or purge the hose, when you still hear bubbles after shutting down the post, you won't be able to tell if it's just residual air in the hose or a continuing leak from someplace else.

 

[GrimSleeper]

I have seen the drill where the diver shuts down right post and isolator simultaneously. It's not pretty. It's very difficult to do it, especially under major time pressure, without losing other important things, like trim and buoyancy, and awareness of the team.

When I did DSAT Tec Deep and Tec Trimix way back before PADI decided they did like technical diving after all, we were drilled to shut down right post and isolator simultaneously, breathe down primary, switch to backup. Re-open right post and isolator, close left post and isolator. Breathe down backup, switch to primary reg. Re-open left post and isolator. In 40 seconds or less. Without changing depth by more than 20cm (about 8 inches). In trim. It was bloody difficult, but perfectly possible given enough practice. I did feel kind of abused when I discovered later that lots of other people do much less hectic shutdown drills...

Absolutely useless as a diagnostic method or for solving any imaginable real problem, of course, but good training for reaching everything and manipulating it fast, while keeping control of the other parameters of your dive. I still practice it every dive. And in the real world, if the source of the bubbles isn't immediately obvious, why wouldn't you isolate straight away as well as closing down the valve you suspect? If your team-mates don't understand the sudden wild flailing of your primary light as you turn either the right post or the isolator to mean that something's wrong, taking the time to signal between each step of a shutdown probably isn't going to help much either...