Youtube vid - free flow

[JeffG]

I think one of the DSAT videos or manuals also says to hook your leg around something to avoid buoyancy changes during drills/gas switches.

or get your buddy to hold you down.

 

[rongoodman]

Yeah, every time I look at that footage it looks uglier and uglier, but it reminds me of stuff to look out for. Our instructor actually gave us the video and encouraged us to post it up.

I'll be very happy when I look "ugly" like that in the water.

 

[PfcAJ]

Question for you - at around the 8 minute mark, the team begins to share gas. After completing the donation, the donating diver goes to the back and the recipient goes to the front. The donating diver then picks up the reel and starts reeling in.

Is that the procedure in tech 1? (It's an honest question. "Go take the class and find out for yourself" is a reasonable response.)

I would have left the reel at that point. Enough was going wrong for that "team" without the need for anything else to deal with.

It should always be the single file procedure.

on a line, you should be single file.

For airshares...the donor is in the rear.
for reeling in a reel....the "reeler" should be in the rear.

Do you mean that when a team is following a line they should always be in single file?

Agreed with donor in the rear on airshairs (unless abreast swimming is possible).

 

[Flightlead]

When the isolator is opened, the the pressure is only reduced in the left tank. The pressure on the right is increasing. This will heat the right tank, and cool the left tank
.

which one free flowed? I didn't watch the vid.

 

[Flightlead]

There will not be much effect on the temperature of the regulator because the pressure is always reduced when gas flows through the regulator.

right. there is only the possibility of a minor change due to conduction of heat between the valve and regulator through the metal-to-metal connection. I suspect that in either case (heating or cooling reg) it would be small and of short duration due to heating/cooling the surrounding water.

 

[Flightlead]

The postulation is if your isolator is closed and you open it "will it contribute to a free flow?"

Now assume your regs are correctly configured and you have been breathing your right post and the left is still at full pressure. You open the isolator. The left tank cools. But the left tank's gas and valve temp isn't relevant as you aren't breathing on it (and the person in the video wasn't either)

The temp of the gas in the right tank will minutely rise as the left tank discharges into it and its pressure rises. Ergo opening your isolator during a dive makes no difference on the likelihood of a primary reg free flow.

ok, we are in violent agreement I was thinking the other reg free flowed. should have watch the vid

 

[JeffG]

Do you mean that when a team is following a line they should always be in single file?

No, when the team is reeling in/out a line. They have to be in single file.

 

[ppo2_diver]

I have the PADI DSAT video. They show the drills on their knees at the bottom of a pool

I love that video!!!!!

 

[rjack321]

Yeah, every time I look at that footage it looks uglier and uglier, but it reminds me of stuff to look out for. Our instructor actually gave us the video and encouraged us to post it up.

You looked fine to me. Looked like #2 in the steel doubles was wearing a 120ft Al80 bottom stage?

I was a little confused about the failures too. #2 had a left manifold failure, shuts right valve and switches regs. Flashes a bit over vigorously and doesn't shut the isolator (I think) but ok that's the way it goes sometimes. Then #1 gets get the iso closed and (I guess) gets the reg switched so they start the return. I'm on board except agree that ditching the reel would be prudent.

Then it seems like there's some missing footage cause #1 (in the AL80s) is OOA and the steel tank diver with the previous manifold failure donates. They are on ascent with #2 now donating to #1.

Did I get something mixed up or what happened??

Ps your video is way way more DIR than the one which started this thread :d

 

[lamont]

the pressure is dropping, but the volume is increasing. to first order that is much more important than the temperature drop (up to around a 20x drop in pressure, less than a 2x drop in temperature).

actually, i may be slightly incorrect there. for a 20x drop in pressure (3000 psi to 150 psi) and a diatomic gas following an adiabat there should be a 8.49x increase in volume and 2.35x decrease in temperature. which implies a temperature drop from 10C to -154C. of course with a delta-T that large there will be a higher rate of heat transfer which is going to make the process much more non-adiabatic.

iceguys: are you more likely to ice up a first stage with full/high pressure tanks?