Do you turn the air off or leave it on after setting up on a tank?

[Divin'Papaw]

I always leave it on. I maintain my gear and if I'm somewhere that I had to use a rental tank I pretty much always replace the o-ring on the tank first. Around 200 dives now and I've had zero problems doing it this way. I think problems come in if you've got poorly maintained gear that leaks air.


Are you sure your tx stays active when pressurized but the pressure isn't changing? My scubapro tx definitely stops transmitting after about a minute of no pressure change.

From the Shearwater Perdix AI manual.

If there is pressure it is transmitting. The only way to turn them off is to close the valve and purge.

 

[alex_can_dive]

Is there any risk in leaving the air on while the tank bathing outside in hot sun? (temp could reach ~90F-100F here, ie 30C - 37C)

Would that possibly cause the air to be over pressurized and damage your first stage and gauge?

 

[BoundForElsewhere]

Is there any risk in leaving the air on while the tank bathing outside in hot sun?
would that possibly cause the air to over pressurized and damage your first stage and gauge?

Nope. The sun won't heat the tank up so much that the increase in pressure is going to make much of a difference. I've left tanks in Saudi Arabia sun for a few hours and never had anything pop, wobble, or explode.

 

[tbone1004]

Is there any risk in leaving the air on while the tank bathing outside in hot sun?
would that possibly cause the air to over pressurized and damage your first stage and gauge?

no, the burst discs would go long before that was a problem. Most of the SPG's go to 5000psi/350bar, and the 1st stages are rated for 4500psi/300bar. Burst discs should go around 300bar for any aluminum or HP steel tanks in this country. To get the tanks up to that pressure from working pressure would be impressive.
p1/t1=p2/t2
P1=3000psi/206bar
t1=80f/300k
p2=4500psi/300bar
T2=p2*t1/p1=300*300/206=437K=326F
326 Fahrenheit is bloody hot and the bottle would never get that hot baking in the sun. That's just to get it to where the burst disc would go, much higher than that to get anything else to have an issue.

 

[Divin'Papaw]

To answer the OPs question (I forgot to answer it in my prior post) I typically leave my regs pressurized and my tank on. I am never far from my tank so if anything were to somehow push against one of the regs and start to purge gas, I'd know it. If the boat ride were especially long, which happens with some sites, I will turn the tank off and will often purge the regs.

 

[tbone1004]

To answer the OPs question (I forgot to answer it in my prior post) I typically leave my regs pressurized and my tank on. I am never far from my tank so if anything were to somehow push against one of the regs and start to purge gas, I'd know it. If the boat ride were especially long, which happens with some sites, I will turn the tank off and will often purge the regs.

why purge the regs? increases risk of saltwater intrusion on a bumpy boat as well as o-ring issues if the first stage starts turning.

 

[formernuke]

Leave it on, then double check it when gearing up

 

[Lorenzoid]

For shore dives, I leave it on, even if that means it sits there for half an hour or more.

For boat dives, I keep it off during the ride out, then turn it on at the earliest opportunity after the boat arrives at the dive site.

 

[johndiver999]

why purge the regs? increases risk of saltwater intrusion on a bumpy boat as well as o-ring issues if the first stage starts turning.

Because, if there is no air in the reg. it will be harder to jump in and go down with the valve off, as I explained above.

 

[shurite7]

Open the tank valve to check pressure, then close and purge second stage. Before or after putting the kit on, open the valve and conduct a buddy check while breathing from the second stage to make sure the valve is open.