Good, concise analysis, Jim. I wondered myself if the tank had been properly VIPd, but not until the trip was over. I wondered also what might have happened if a less experienced, more panicky, diver had gotten that tank. It was just luck of the draw who got what tanks on the boat...
Tank Failure in Cozumel
- Thread starter Sandisk
- Start date
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It was likely a debris/drip tube issue.
Especially when I'm working in the tropics, and renting tanks for a period of time, but even in the US, I VIP all the rental tanks that our team will be using and have them marked, we only use those tanks, if the shop or operator doesn't like it ... tough, there's always another who is happy to oblige.
Especially when I'm working in the tropics, and renting tanks for a period of time, but even in the US, I VIP all the rental tanks that our team will be using and have them marked, we only use those tanks, if the shop or operator doesn't like it ... tough, there's always another who is happy to oblige.
If debris or any sort of liquid goo was in the tank it would need to have a lot of debris to clog the dip tube. Which makes me doubt it had a dip tube at all.
As noted before, opening the valve with the reg off will indicate whether gas comes out, but it is hard to quantify if enough gas is comming out.
Generally, with any restiction, the flow will reduce as the supply pressure drops, so it would be "normal" for the problem to get worse as the dive progresses, but not immedaitely with an increase in depth as long as there is enough flow to meet the demand at depth initially. In contrast, a valve that is partially opened may be so restricted that you immediately feel the shortage as you make your initial ascent. Opening the valve will solve that problem but not the other.
Position on the tank can also be critical it may breathe fine when vertical but not deliver in a slightly head down position.
Post dive, I would see if the valve provides gas with the reg off, but then go one step further and invert the tank and see what comes out.
My favorite expereince with tanks in coz was a guy with a reg that delivered almost no gas when he was in a normal swimming position and breathed wet, but did fine when he was vertical in the water. He blamed the reg, but there is nothing in a reg that causes this. The inlet filter however was both wet and discolored - an obvious give away. Inverting the tank and opening the valve slightly produced a spray of nasty looking water, and it was not a surprise, as in addition to the wet filter you could hear water sloshing in the tank before the valve was even opened. Lots of water and no dip tube.
So...if you have reg issues under water, it is always a good idea to check the inlet filter on the reg as well as to check the flow from the tank upright and inverted as well as listen for water or a loose dip tube rolling around inside the tank following an event. Listening for a loose dip tube and large amounts of water in the tank before the boat ever leaves the dock is not a bad idea either to prevent possible problems.
I am most definitely in the rebel "if you rented me this POS and I had a problem, I am going to drain, it remove the valve and look inside" camp.
As noted before, opening the valve with the reg off will indicate whether gas comes out, but it is hard to quantify if enough gas is comming out.
Generally, with any restiction, the flow will reduce as the supply pressure drops, so it would be "normal" for the problem to get worse as the dive progresses, but not immedaitely with an increase in depth as long as there is enough flow to meet the demand at depth initially. In contrast, a valve that is partially opened may be so restricted that you immediately feel the shortage as you make your initial ascent. Opening the valve will solve that problem but not the other.
Position on the tank can also be critical it may breathe fine when vertical but not deliver in a slightly head down position.
Post dive, I would see if the valve provides gas with the reg off, but then go one step further and invert the tank and see what comes out.
My favorite expereince with tanks in coz was a guy with a reg that delivered almost no gas when he was in a normal swimming position and breathed wet, but did fine when he was vertical in the water. He blamed the reg, but there is nothing in a reg that causes this. The inlet filter however was both wet and discolored - an obvious give away. Inverting the tank and opening the valve slightly produced a spray of nasty looking water, and it was not a surprise, as in addition to the wet filter you could hear water sloshing in the tank before the valve was even opened. Lots of water and no dip tube.
So...if you have reg issues under water, it is always a good idea to check the inlet filter on the reg as well as to check the flow from the tank upright and inverted as well as listen for water or a loose dip tube rolling around inside the tank following an event. Listening for a loose dip tube and large amounts of water in the tank before the boat ever leaves the dock is not a bad idea either to prevent possible problems.
I am most definitely in the rebel "if you rented me this POS and I had a problem, I am going to drain, it remove the valve and look inside" camp.
NorthernShrinkage
Contributor
I have always wondered if resort tanks truly get an annual Inspection as is mandatory its rare to see a vis sticker at most resorts and by looking at date stamps doesnt tell you much more than that the tank is older than you:mooner:
I think a lot of resorts just cycle there tanks until theres a problem but thats just my opinion.....Would be happy to be told otherwise but sadly I may be correct
I think a lot of resorts just cycle there tanks until theres a problem but thats just my opinion.....Would be happy to be told otherwise but sadly I may be correct
jhupka
Contributor
Good advice. Thank you.
caseybird
Contributor
Hi Sandisk,
There are some really interesting aspects to your incident I would like to touch on. First of all, the consensus is probably correct, debris in the tank probably blocked air flow. What's important is how you avoid turning an incident into an accident.
1) Did you have a buddy on the dive? You don't reference getting your buddies attention and getting ready to share air if necessary. By the time you had to switch to your octo, I feel you should made sure to alert another diver to your issue.
I've been in Coz, and I don't travel with a buddy. On small boats there has rarely been another single diver to buddy with. Usually the DM indicates that we will dive as buddies for emergencies. I usually take this to mean that I will dive within comfortable distance of the DM, close enough for me to get to his air in an emergency. In practice, I'm usually farther from the DM than recommended. We're you supposed to be diving with the DM? Did you try to alert him?
2) When you could no longer get air from your octo, you switched to your spare-air. What depth did you switch? What size spare-air? Did it last all the way to the surface? Did you attempt a safety stop? If you were more than 100 feet deep on air, my Nitek duo would have put you into deco after about 16 minutes. I wouldn't want to skip a safety stop from this depth. In fact, you were on the third dive of the day, you could have easily been pretty close to deco at shallower depths.
3) Why didn't you bail out earlier? By the time I needed to get to the octo, I would be getting out of the dive. You might not have been in a position to alert another diver when you went to the octo, But if I were in the caught between trying to get to a distant diver at depth with a failing air supply, or doing a solo ascent with the spare-air, I would immediately ascend, as long as I had no mandatory deco. If you had a deco obligation, you should never had been out of the easy access to another diver and an air-share.
After the safe ascent, checking the tank and regs is important, but assigning blame to the operator for faulty tanks is not a critical issue. Getting to a safe air supply either from another diver or the surface is.
I'm glad this incident had a positive outcome, but you have to be prepared to abort the dive and get assistance. You might have been feeling peer pressure to keep up with the group. Learn to resist it, and when to bail.
Good luck diving
There are some really interesting aspects to your incident I would like to touch on. First of all, the consensus is probably correct, debris in the tank probably blocked air flow. What's important is how you avoid turning an incident into an accident.
1) Did you have a buddy on the dive? You don't reference getting your buddies attention and getting ready to share air if necessary. By the time you had to switch to your octo, I feel you should made sure to alert another diver to your issue.
I've been in Coz, and I don't travel with a buddy. On small boats there has rarely been another single diver to buddy with. Usually the DM indicates that we will dive as buddies for emergencies. I usually take this to mean that I will dive within comfortable distance of the DM, close enough for me to get to his air in an emergency. In practice, I'm usually farther from the DM than recommended. We're you supposed to be diving with the DM? Did you try to alert him?
2) When you could no longer get air from your octo, you switched to your spare-air. What depth did you switch? What size spare-air? Did it last all the way to the surface? Did you attempt a safety stop? If you were more than 100 feet deep on air, my Nitek duo would have put you into deco after about 16 minutes. I wouldn't want to skip a safety stop from this depth. In fact, you were on the third dive of the day, you could have easily been pretty close to deco at shallower depths.
3) Why didn't you bail out earlier? By the time I needed to get to the octo, I would be getting out of the dive. You might not have been in a position to alert another diver when you went to the octo, But if I were in the caught between trying to get to a distant diver at depth with a failing air supply, or doing a solo ascent with the spare-air, I would immediately ascend, as long as I had no mandatory deco. If you had a deco obligation, you should never had been out of the easy access to another diver and an air-share.
After the safe ascent, checking the tank and regs is important, but assigning blame to the operator for faulty tanks is not a critical issue. Getting to a safe air supply either from another diver or the surface is.
I'm glad this incident had a positive outcome, but you have to be prepared to abort the dive and get assistance. You might have been feeling peer pressure to keep up with the group. Learn to resist it, and when to bail.
Good luck diving
Scared Silly
Contributor
If you go to almost any resort it will be rare that you find an inspection sticker on their cylinders. While the industry standard for personal cylinders is to inspect once a year it is every 4 months for those that are heavily used. As to whether this procedure is actually done is always a good question.
I have had a steel 72 where I once pulled my reg off and saw red gunk. I did not need to do anything more to know what happened. Last diver drained it, got water in it, so lots of rust. The dive OP owner ended up scrapping the cylinder.
Another time with an AL80 I saw grey gunk. Same thing, water had been in the cylinder. Like a few others have said, I have no problems taking the valve off a cylinder and checking the inside. You rented it after all and I have never seen a rental agreement that said you can not take the gear apart to fully inspect it.
BTW If you ever get a cylinder that sounds like something is rolling around inside - that probably means the dip tube had fallen off.
I have had a steel 72 where I once pulled my reg off and saw red gunk. I did not need to do anything more to know what happened. Last diver drained it, got water in it, so lots of rust. The dive OP owner ended up scrapping the cylinder.
Another time with an AL80 I saw grey gunk. Same thing, water had been in the cylinder. Like a few others have said, I have no problems taking the valve off a cylinder and checking the inside. You rented it after all and I have never seen a rental agreement that said you can not take the gear apart to fully inspect it.
BTW If you ever get a cylinder that sounds like something is rolling around inside - that probably means the dip tube had fallen off.
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