Scary experience - Any thoughts?

[CamG]

Alfie glad you and your daughter are ok.
Your incident makes a strong case for owning your own regulators and keeping them in service.
I would also suggest possibly getting involved with a local dive club and keep your skills fresh practice them often.
It is a great family activity and I could not think of a better way to share a weekend.
As with any incident it can give us pause and that is a good thing to evaluate the details and work to correct them.

Practice air sharing drills frequently especially at the safety stop it is easy and makes the stops go by very quick.
Again I am very glad you both are ok.

CamG

 

[TSandM]

This could have been something blocking the inlet of your first stage. I have heard of people experiencing this kind of failure and inspecting the first stage and finding the filter blocked with aluminum debris. It might have been the dip tube, but that generally only occurs if you go head down. You could also have run out of gas with a faulty SPG.

I think the reason you had some air to fill your BC is that you emptied the hoses to ambient at 12 feet. By going up to the surface, you gained a few psi over ambient and were able to get air into the BC because the gas in the hoses was still pressurized with respect to the surface, just not at 12 feet.

This wasn't a cracked open valve, because that would have shown up at your maximum depth, early in the dive.

The weird part is the SPG showing 1000 psi. If you had a first stage failure or dip tube blockage, the SPG should have signaled the lack of tank pressure. So it would take a double failure to get both the symptoms you report AND the 1000 psi reading. The only single failure that will do it is the SPG, so by Occam's Razor, it's the most likely explanation.

 

[PfcAJ]

I vote for faulty SPG.

I would expect a 12yr old to use less gas than a grownup (tons of caveats apply), and it seems that she had 'less' gas than you at the end of the dive. That+rental gear+ issue w/ both regs+the BC still being able to be inflated suggests to me that it was the spg.

 

[DivemasterDennis]

Proper equipment maintenance; pre dive gear check, including air is on all the way; pre-dive plane to coordinate response to emergency at end of dive to avoid separation. Follow a buddy in touch distance rule at all times, Those are some preventive things that could have been done. No prevention is fool proff, but I add those suggestions to the conversation.
DivemasterDennis

 

[scagrotto]

I think the reason you had some air to fill your BC is that you emptied the hoses to ambient at 12 feet.

The volume in the hoses would be insignificant, but an AL80 (most likely Caribbean rental tank) sucked dry at 12' would still be pressurized to about 1.36 ATA, and that gas would have an actual compressed volume of about 0.4CF. Ascending to the surface would free up a bit more than 0.14CF (0.36*0.4CF). That's about 9 pounds of buoyancy, which is certainly enough to be obvious and useful, if not enough to fully inflate the BC.

The only single failure that will do it is the SPG, so by Occam's Razor, it's the most likely explanation.

Seems like the logical conclusion. Even without hooking up a different reg it would have been extremely easy to crack the valve a bit and decide if the tank had about 1000 psi or something a lot closer to ambient.

 

[Adventure-Ocean]

You are trying to guess what aspect of your rental gear failed. Clearly you were out of air or the first stage failed. Did you open the tank after all was done to see if it really had 1000psi or nothing? That would have eliminated one possibility. Without knowing if the 1000psi was still in the tank or not makes it hard to guess what failed. If the 1000psi was there you could follow the air to see where it was blocked. A blockage in the first stage is rare. Dove 40 years and never had a first stage fail. Doesn't mean it can't happen. Some rental gear sits around long enough to have insects create homes in them. If the air was not there you know the guage failed.

A very good reason to avoid using rental gear. Adventure-Ocean

 

[AlfieGee]

Thanks to everyone for your answers. It seems to me that the general consensus is either SPG or 1st stage.
I'm don't remember exactly on this dive but I always fully open the valve and then turn it back 1/4 turn so cant be certain but don;t think it was that.

Again I wish I had done a check with another SPG immediately - but just wasn't thinking right.

'Proper equipment maintenance; pre dive gear check, including air is on all the way; pre-dive plane to coordinate response to emergency at end of dive to avoid separation. Follow a buddy in touch distance rule at all times, Those are some preventive things that could have been done. No prevention is fool proff, but I add those suggestions to the conversation.' - I will certainly keep closer to buddy in future and di so on all my 5 remaining dives over the course of the holiday.

Needless to say I am a LOT more aware that things can go wrong, its easy to become complacent after many years of trouble free diving, basically a good 'wake up call'.

My daughter has now signed up at our local dive school for her full certification so the experience hasn't turned her off diving but perhaps given her an experience that could help her in all her future diving.

 

[Diver0001]

Anyone have any idea what might have gone wrong, I’ve no problem if someone says I was at fault. I just want to learn how to prevent/recognise this in future?

Two thoughts come to mind.

1) the tank may have had debris inside it that blocked off the valve or the inlet to the 1st stage. In particular, rust can often be the culprit that causes this if the tank has been drained completely and has had water inside it. The following is a picture of the amount of rust that can form inside a compromised tank, to give you some idea.




2) The SPG may have been faulty. The SPG works as follows. Tank pressure travels down the hose and inside of the SPG into a curved tube called a bourdon tube. That tube straightens out at higher pressures and curves more as pressure reduces. Attached to the tube is a gear that mates with a little gear on the needle and causes the needle to move (see picture below). If water gets inside the guage then it can get cocked up and parts may not move freely anymore, causing faulting pressure readings. In addition, the age of teh meter is important. Bourdon tubes are just little bits of metal that move back and forth on every cycle and are therefore subject to weakening (metal fatigue) over time.

One of the risks of using rental gear is that you often can't know where it's been, if it's been maintained well or if there are "problems" with it.

In terms of the tank what you can try is to hold it upside down and open the valve a bit to see if any water or rust comes out. This is unrealiable though and I don't see people doing this very often unless they already suspect a problem. Another thing you can check is the inlet of the regulator 1st stage. There is a little filter that that's designed to catch anything that comes out of the tank. You can inspect it to see if you see any rust particles or if the filter is wet. Ultimately choosing a consciencious operator is your best protection from this.

To check the SPG is easier. You can charge it (turn the tank on), purge it (tank off) and see if it goes through it's entire range of motion smoothly. IN addition, if there has been water inside, you may be able to see condensation on the inside of it.

As for how you handled it. You made a decision, followed your training and you're still here. That's all that counts.

R..

 

[AlfieGee]

Thanks Diver0001 - very informative and amazing what can be inside a tank!!