BC Failure Mode

[aquaregia]

I recently came across a 30 year old BC that I don't quite trust. I'd like to test it out, but I'm curious about how it's likely to fail. The most catastrophic thing I can imagine is the bladder rupturing under higher pressures. Can I check for something like this by diving the pool a bunch, checking for wear, diving 20' a bunch, checking for wear, etc? Or is it likely to just blow up on me without warning @ 60'?

Followup question: In my OW classes we were taught to ditch weight pretty much any time it occurred to us. However, if I consider ditching 25# of weight @ 40' with a 7mm and an AL80, I'm not sure I could flare hard enough to not shoot to the surface. Would it be stupid to wear two weight belts so I could ditch 10# separately? I can come up with a bunch of reasons it's a bad idea, but I can't come up with something better.

 

[miketsp]

Inflate it until the dump valve(s) pop then leave it inflated for a couple of days to see if it's leaking and goes soft. You may well need to replace the rubber sealing disks in the dump valves.
I have 2 BCs that have 10 years of use and one with 15 years of use. I replaced various disks with pieces cut from car inner tubes - work perfectly.

At depth the situation is no worse. The springs on the dump valves mean it can only be inflated to a fixed absolute pressure above ambient pressure. Although the internal pressure will increase as you descend so does the external pressure on the bladder.

As for dumping weight, unless you're grossly overweighted the only time you should ever actually need to dump weight would be at the surface.

 

[herman]

First off, you are placing too much emphasis on the importance of a BC. It is a buoyancy COMPENSATOR, its purpose is to compensate for buoyancy changes during the dive which should be the compression of your wetsuit and the slight changes in the buoyancy of your tanks. If you are inflating it more than a little then you are likely way overweighed unless you are doing some serious technical diving, at which point it really becomes a neutral buoyancy achieving device with a secondary function of a BC. Even with a thick wetsuit it's unlikely you can't swim yourself to the surface with a total BC failure to hold air. The real failure you should worry about is the inflator valve sticking open, inflating the BC to the point you cannot control your accent.
More to your question, I would first inflate it fully and inspect it for leaks and signs of damage or excessive wear. If it holds air for an hour or so, then I would dissemble, clean and reassemble all of the inflate and deflate valves. If it does not hold air, look for the source of the leak before assuming it's bad, leaking dump valves and minor seam leaks are common and can be repaired. Often the problem is nothing more than a grain of sand or salt in the wrong spot. Once everything was back together I would again inflate it to its max and make sure the overinflate dumps work. If all goes well and it will hold most of it's air for an hour or 2, dive it.

 

[redacted]

A 30 year old BCD, if it holds air at all, is likely to have "pin-hole" leaks where the waterproofing material has degraded and is failing. While you might patch a few such leaks with aquaseal, the degraded material will not miraculously heal. Seams and creases will be the first to go. It will look like a fish tank aerator.

I would not expect much more use from that BCD. Eventually you will probably end up harvesting a tank strap, inflator, hoses and maybe some accessories and trash the rest.

Good luck.

 

[aquaregia]

Awesome, thanks.

 

[aquaregia]

Right on the money awap. I inflated it, and within two hours it was noticeably lower. I assume that means I shouldn't even bother testing it in the pool as even if it doesn't create more bubbles that my lungs do, I'll end up pumping more air into the BC than I do into my lungs?

Is there likely to be any vintage freaks that would want this? It's an old Seatec. Or should I just dumpster it?

 

[Diver0001]

Right on the money awap. I inflated it, and within two hours it was noticeably lower. I assume that means I shouldn't even bother testing it in the pool as even if it doesn't create more bubbles that my lungs do, I'll end up pumping more air into the BC than I do into my lungs?

Well you're right about one thing. You shouldn't use it if it's leaking.

But you still might want to try it out in the pool to see *where* it's leaking. If the bladder has (pin) holes in it, then there isn't a lot you can do. However, it might be leaking from a valve, and that can be fixed.

R..

 

[Zung]

Actually 2 hours is not that bad: there's not a lot of people who do recreational diving that's 2 hours long!

I'd throw it in a pool or a bath tub to see where it leaks; I wouldn't be surprised if it's the inflator or the valve: hopefully a little cleaning'll do.

I still dive a SP jacket style BC that's 20 years old. Last October in Egypt, on the day before the last dive day, there were some big big bubbles (what's the english word for bubbles that's bigger than bubbles?), more like a burst, coming out of the lower inside of my BC. I shifted it a bit and it stopped and I didn't pay further attention, finished the dive and the following day's dives; didn't even bother to tell the wife and the kids. Only when I was back home did I realize the CO2 inflator has broken off and there's a hole the size of a dime! A bit of Aquaseal and it's good to go.

 

[herman]

Right on the money awap. I inflated it, and within two hours it was noticeably lower. I assume that means I shouldn't even bother testing it in the pool as even if it doesn't create more bubbles that my lungs do, I'll end up pumping more air into the BC than I do into my lungs?

Is there likely to be any vintage freaks that would want this? It's an old Seatec. Or should I just dumpster it?

Check to see where it's leaking, may be just a loose connection or a bit of junk in a valve. An old Seatec most likely had an internal bladder that you can get to, if so and it's a small pinhole leak (very common) or a little tear in a seam, Aquaseal will fix it. If it's a standard jacket type, not too many vintage divers want/use them. If on the other hand it's a horse collar....where do I send money for shipping ?

Wait a minute.......freak.....who you calling a freak....I prefer weird old dude in that old junk, thank you very much. :mooner:

 

[redacted]

If not repairable, I harvest any usable or interesting parts and trash the rest.