How common is a rust-clogged 1st stage? (noob question)

[mruseless]

Hi folks, I'm an intermediate level diver (84 dives), and a noob to this board. I did a few searches but didn't turn up much, so I thought I'd post.

I have read a couple accounts (2, to be exact) of people on this board who have experienced a clogged 1st stage during a dive due to rust in a tank.

How common is this? With my measly 84 dives I have not experienced it, nor has anyone I dive with regularly. But it really makes me wonder about "the unexpected" as it relates to things like how close should I stay to my buddy, and pony bottle setups. (Please, let's not rehash the argument of how many cf should be in a pony)

Also, does this type of clog result in an instant OOA situation, or does it just make breathing very difficult? And is there anything that can be done to fix it other than an alternate air source?

Eric

 

[seaducer]

I have never had one either, however I think alot of the trouble could be avoided by proper tank maintenance and making sure you never bleed them dry.

Maybe one reason to own your own tanks and rent only when you have to.

 

[mruseless]

Unfortunately, I only dive on vacation, usually someplace warm. But that pretty much guarantees that I'll have to depend on the operator for tanks with no way to know if they've been taken care of.

BTW, I vaguely remember some kind of markings on a tank when it gets inspected? Is that right?

 

[Guba]

I've had one of those situations you describe (I may be one of the two reports you've seen here on SB before).
In my case, the clog didn't result in total OOA. Instead, it reduced the airflow to about 15-20 percent of normal. I found that if I took my breath reeeeeeeeeeeaaaaaaaal slooooooooow, I could get enough air to survive PROVIDING I didn't move or exert myself. That made it fairly simple to make a controlled ascent (although I summoned help, just in case...). I feel the most important thing this experience emphasized was the absolute necessity to stay completely calm and think the situation through (but do it quickly).
The tank I was using was a rented Al80 on the Riviera Maya in Mexico, so the corrosion that plugged my first stage was aluminum corrosion and not typical rust. I had about 65 dives at the time, so I wasn't in the habit of checking hydro dates and inspection stickers...I'm a lot better at that now, you can bet!

 

[seaducer]

Unfortunately, I only dive on vacation, usually someplace warm. But that pretty much guarantees that I'll have to depend on the operator for tanks with no way to know if they've been taken care of.

BTW, I vaguely remember some kind of markings on a tank when it gets inspected? Is that right?

Yes. Every year the valve must be removed and a visual inspection performed. When this has been done, a sticker with the month and year labeled is placed on the tank. This inspection is looking for rust or aluminum oxide, water, or anything else that does not belong there. Aside from being "VIP'ed" every year, the tank should be opened and inspected if it is completely run out of air.


Every 5 years the tank must go through hydrostatic testing, which tests the strength and integrity of the tank so it does not rupture when filled. The marks for this test are physically stamped into the tank near the neck, they include the code of the test facility, and month and year tested, and if applicable a "+" to indicate the tank may be filled over it's rated capacity. IRRC this only applies to LP steel tanks, not to aluminum tanks.

These are the rules for the US, so if you are traveling outside the US these standards may not apply.

 

[Arizona]

I experienced it upon descent with an instructor on a “fun” dive with two relatively new certified divers. I did my pre dive safety check and all looked good. Upon reaching about 4-5m I felt it hard to breath. It seemed obvious no air would be coming out. Felt just like the OW scenario in the pool when the valve is being shut off. That has been the only real OOA situation for me personally. I signaled to the instructor and took her octo. While surfacing I kept thinking someone might have shut my air off by accident. That was not it. I service my regs on schedule and think it had to be rust or some other crap in the tank. It does happen! IMO, one should be close enough to a buddy that you get to an alternate air source if needed. You see people disregard this all the time. Think of the distance you would need if you felt something like this... 2-3m depending on vis would be my recommendation.

I wound up diving that dive and a subsequent one without any issues. It must have freed up somehow. Needless to say I stayed very close to my buddy. The MSTD who I was with claims she has only seen this once before. Other more experienced divers have also mentioned that this is very rare. Keep in mind, I do dive in Thailand, but it could happen elsewhere.

The AL tank was put on the side to make sure it was not re-used before being serviced.

AZ

 

[mike_s]

Hi folks, I'm an intermediate level diver (84 dives), and a noob to this board. I did a few searches but didn't turn up much, so I thought I'd post.

I have read a couple accounts (2, to be exact) of people on this board who have experienced a clogged 1st stage during a dive due to rust in a tank.

How common is this? With my measly 84 dives I have not experienced it, nor has anyone I dive with regularly. But it really makes me wonder about "the unexpected" as it relates to things like how close should I stay to my buddy, and pony bottle setups. (Please, let's not rehash the argument of how many cf should be in a pony)

Also, does this type of clog result in an instant OOA situation, or does it just make breathing very difficult? And is there anything that can be done to fix it other than an alternate air source?

Eric

the tank valve has a 'dip tube' that goes down into the tank a few inches. this way if the tank becomes inverted and has particles or liquid (moisture or oil), then it won't drain directly into the valve, and then the 1st stage...

of course it could still get in there, but this in theory should stop most things from entering the valve.

of course some times the dip valve is not in place like it should be also...