Tank PSI - Over Filled, Drain or Dive?

[MrChen]

I picked up my tank rental and the guy says, "don't freak out, it's at 4000 psi" with a grin. Umm, ok... According to my dive logs, 3900 psi was the highest pressure I've ever started a dive with and I didn't have any problems. I figured, what's another 100 psi?

We were doing a shore dive at Blue Heron Bridge and I got there early so I could hook up my reg since I was trying out a new configuration. I wanted to make sure I didn't have any leaks and if I did, I had the tools to reverse the config. Once I hooked it up, I left the tank open after checking my gear (which was good to go) so as to not confuse whether it was open or closed. I remember checking the o-ring at the dive shop and it looked pretty good and I definitely had seen worse. My dive buddies showed up while I was playing with my gear. We got to talking and about 20 minutes later I hear a loud pop and hissing noise. I immediately ran over and shut off the tank. The o-ring was visibly not in the groove of the yoke valve. It still looked usable, but to play it safe I replaced it anyways. Now my tank is at 3700 psi which is the pressure I started my dive at.

But this got me thinking, when is the air pressure just too high? So I looked up the specs on my 1st stage regulator and the number was much lower than 4000. I have a Cressi MC9 and according to Cressi:
- Service pressure: 300 bar (4350 psi) DIN version, 232 bar (3365 psi) Yoke version

What do you do when your air pressure is high, dive it or drain it?

 

[Steve_C]

You have not said what your tank is rated for. Is this an AL80 rated for 3000 or a steel rated for 3442?

Don't forget that your tank was sitting in the sun while you were chatting. If your tank was at 4000 in an air conditioned dive shop after it had cooled down and you sat it in the Florida sun you were probably at 4200 or so.

If we are talking 4200 in an AL80 that is way over what I would be comfortable with.

 

[Texasguy]

Dive it. Brag about a cave fill.

 

[chrpai]

Funny, I just had the same thread last fall for 2 AL80's that were filled to bank pressure of 3800psi.

It's well within test pressure so it should be "safe". Any damage done is already done. If you are diving within the next few days, enjoy the nice fill. If you don't plan on diving for a while, drain it down to service pressure.

 

[Teller]

Whats done is done. Enjoy!

 

[MrChen]

You have not said what your tank is rated for. Is this an AL80 rated for 3000 or a steel rated for 3442?

Don't forget that your tank was sitting in the sun while you were chatting. If your tank was at 4000 in an air conditioned dive shop after it had cooled down and you sat it in the Florida sun you were probably at 4200 or so.

If we are talking 4200 in an AL80 that is way over what I would be comfortable with.

The tank was steel 100 rental.

 

[Dr. Lecter]

The tank itself was fine. The A-clamp reg plus sun-heated tank, probably not so much. With a DIN reg, I expect you'd have had an uneventful pre-dive.

 

[MrChen]

Funny, I just had the same thread last fall for 2 AL80's that were filled to bank pressure of 3800psi.

It's well within test pressure so it should be "safe". Any damage done is already done. If you are diving within the next few days, enjoy the nice fill. If you don't plan on diving for a while, drain it down to service pressure.

It wasn't my tank, it was a rental. So we are saying the tank is safe, but what about the reg sitting at that high pressure for an extended time? And steve did make a good point about the pressure potentially increasing. I'll never know if it was climbing up. It didn't increase during the drive to the dive site in which the tank was in the back of my truck exposed to the sun.

 

[spectrum]

The tank was steel 100 rental.

As in HP-100 3442PSI?

I would not be too concerned about the cylinder though I'd avoid storing it that way.

As you identified you were stressing the limits of the youke clamp. Depending on the temp/pressure rise Steve_C described, or if the yoke insert was torqued (they skew if tighened firmly), the exact condition of that oring and how firmly you tightned the yoke screw you probably demonstrated the logic behind the (undocumented?) 3500 PSI cutoff for use of the DIN connection.

With my DIN regulator I would have used it in a heartbeat. In fact I may have been so blessed a time or two. With yoke I may have taken the edge off the pressure simply due to the inaccuracies of the instruments involved, I'd be happy at 3800 but that's more persnoal comfort that science.

Pete

 

[Dr. Lecter]

The reg itself would have been fine--it's the connection between the HP source (tank valve) and reg that's going to be affected by too much pressure. When it gets too high for the connection to handle, it does what you experienced: fails at the weakest point, the oring.

If you had a 100% secure connection between gas source and regulator guts, I have no idea when the reg would cease functioning, but 4000psi ain't it.