Turning air off after equipment assembly

[t-mac]

In training (PADI), I was taught to turn the air off and to purge the system after equipment assembly if I'm not getting directly in the water. In all honesty, sometimes I do and sometimes I don't. I think the reason for my inconsistency is that I'm not sure I have been given a compelling reason to turn the air off. In fact, it seems to me you increase the risk of getting in the water with your tank turned off if you do this (especially if you don't purge it).

I have been told that I could damage my regulator if it is left pressurized in the sun -- compelling, if true! But I would think that if that were such a risk DMs would be running around the boat making sure everyone does this and in the many boat dives I've done in the sun and heat, I've never witnessed this. (Maybe they do it quietly and selectively only with the rental gear in a cynical ploy to increase business?

) It also seems to me that if the sun heats up the tank to such a degree that the pressure exceeds the tolerance of the regulator that as soon as you turn it on after having it off, you are going to do the same problem. And shouldn't a first stage be rated to a pressure that exceeds what would cause the burst disk to blow?

What are your views and experiences?

Thanks.

 

[superspeed]

This risk of getting water in your regulator with the tank on is 0. Having said that, for espically long boat rides I will turn mine off and purge (to eliminate the chance of taking a test breath and thinking my tank is on) just incase I have a slight leak at the tank/1st stage. Leaving your reg pressurized in the sun is not going to damage it, for more or less the reasons you stated.

For me

Short boat ride - setup with tank on/leave on
Long ride - setup and turn tank off and purge line. As I said, im not purging the line for any reason other then making sure I can't "trick" myself into thinking the reg is on and jumping in.

 

[DevonDiver]

One day you might get distracted, be in a hurry etc... you'll skimp on pre-dive checks and jump in the water with your rig pressurized but turned off. A quick descent will see you at ~5m depth and not able to breathe.

I've done it. I know many people that have done it. I was an instructor at the time, circa 3500 dives and tech qualified. I was distracted and rushing because I was supervising/instructing students. Luckily, I have sufficient shoulder flexibility and ingrain responses to reach back and turn the tank on.

Never made that mistake again... kit never gets left pressurized and shut-down.

Have a protocol and stick with it. A pressurized rig can 'slip through the cracks' if your pre-dive measures fail for any reason. If you turn it off, purge it down.

 

[Diver0001]

I have been told that I could damage my regulator if it is left pressurized in the sun -- compelling, if true!

Compelling, but untrue. All modern regs can handle at least 300 bar internally... I´m pretty sure that there´s no way the tank pressure could get high enough in the sun to damage the regulator. The tank would probably fail before the regulator did.

As far as I know, this advice originates from boat diving where people may set up their gear while the boat is enroute to the dive site and then leave it unattended for a while. The idea of turning off the tank in that case is so that the rolling of the boat doesn´t cause your tank to roll up on your regulator and accidentally purge the tank empty.

... and since I don´t boat dive much then I´ll admit to at least one case of turning my tank on during the descent because I had turned it off after setting it up and forgot about it.

R..

 

[tplyons]

Shorter surface intervals, it stays charged.

Heading out on a longer ride, or long surface interval, I'll turn off and purge.

 

[chrpai]

So I've noticed that sometimes for whatever reason I'll leave my reg pressurized overnight. Any potential concerns there? IP is still stable. I know we have a couple thousand nitrogen regulators at work that are left pressurized for months on end ( they are used to locker door hatches in a kiosk scenario ) without issue so I assume it's not the worst sin in the world.

 

[Fishpie]

My preference is to pressurize and not purge.
It's a good way to check for leaks and problems.
I have had a HP hose swage let go on the boat ride.

 

[Bob DBF]

I use the Sherwood "is your regulator leaking" dry bleed reg. It bleeds off a very small volume of air when it is on so, unless the dive starts soon, I turn off the air and purge the line into my BC since, in most cases, I'll need some in there anyway. I never have actually seen any pressure loss from leaving the reg on, but I believe in leaving gear, SCUBA and anything else, in the safest mode pracitical if I'm going to walk away and do something else.

Put the "I have been told that I could damage my regulator if it is left pressurized in the sun" in the Scuba Snopes thread.



Bob
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I may be old, but I’m not dead yet.

 

[uncfnp]

Whichever routine you adopt, always take 3 to 4 breaths from your regulator while looking at your gauge just before your dive. If the pressure is steady, you're ready to go.

 

[chrpai]

Whichever routine you adopt, always take 3 to 4 breaths from your regulator while looking at your gauge just before your dive. If the pressure is steady, you're ready to go.

I personally suggest turning it off, taking a good inhale to test for leaks/vacuum then turn it on and do the SPG needle dance check as you describe.

I caught a bent exhaust valve this way once when I was able to breath when I expected to not be able to.