Too much pressure in BCA Float canister

**alias_rice** · 11-13-2015, 05:32 PM

I tested my BCA Float a few days ago and took it in today to the local dive shop for a refill. Problem is the dipshit wasn't paying attention and filled it to 2900 psi. He said it was a one way valve so there is no way to bleed it down to the required 2700 psi. Anything I can do other than deploy the bag again and refill? Will it cause a problem to the bag by deploying at too high of a pressure? I guess I could refrigerate it to bring the pressure down before deploying.

**idahospud** · 11-13-2015, 07:05 PM

Refrigerating it won't really do anything for you. There's still the same amount of mass in the canister whether the pressure is 2900 psi at room temperature or 2700 psi at some lower temperature and when it's released it'll expand to the same volume no matter what pressure it started at.

I don't know enough about the bag construction to comment on that, but if it were mine I'd look for a way to release the gas in the canister without going into the bag.

**japanada** · 11-13-2015, 07:53 PM

Hook the canister up to the pull/deploy cord, but do not hook it up to the airbag if youre afraid of blowing out the bag. The gas will just rush out into the thin air.

**1000-oaks** · 11-13-2015, 10:58 PM

I'd expect the venturi to backflow once pressure in the bag reaches a certain level, but that's just speculation on my part. If you activate the cylinder without the bag attached, wear earplugs.

Better yet, do it under your buddy's blanket while he's sleeping off a night of heavy drinking. Have a good grip on the cylinder while wearing a glove (it'll get cold quick), so it doesn't get airborne.

**Lindahl** · 11-13-2015, 11:15 PM

2900 is fine... sleep soundly

**alfajores** · 11-14-2015, 10:28 AM

Originally Posted by Lindahl

2900 is fine... sleep soundly

If this weren't true, but good to know it is, the volume to pressure to temp ratio you would need to employ is basic physics. Good to see you thought of it. One thing to identify is that while the particles are cold from chilling the canister, the act of moving them out into the bag will give them movement and activity. As they move around one another and leave the valve, the friction would warm the particles of air and as they reach the bag and air around the bag, they would warm greatly as well. Conceptually, you would need a very cold (-40*C) freezer, undergoing a high barometric pressure, likely some atmospheric time greater than sea level, and would see the escape velocity from the canister reduce dramatically as volume would fill slower, resulting in less force and possibly not depleting the canister in full if intense enough.

Fun. We could do the math, but I wanted to keep it light on the weekend.

Thanks Lindahl for the answer!

**idahospud** · 11-14-2015, 10:49 AM

Originally Posted by jcolingham

One thing to identify is that while the particles are cold from chilling the canister, the act of moving them out into the bag will give them movement and activity. As they move around one another and leave the valve, the friction would warm the particles of air and as they reach the bag and air around the bag, they would warm greatly as well.

That's the exact opposite of what would happen. With very few exceptions, gases cool as they expand since temperature is inversely proportional to pressure.

Like 1000-oaks said, wear a glove if you're holding it. It won't be warm.

**whyturn** · 11-14-2015, 11:05 AM

Pull it remotely in case it explodes. If not refill. If it does film it and go after dive shop? Lash to a tree with para cord or similar and pull trigger from at least 50 feet. Of course no calculations implied since I'm not an ME. Deployment video would be good

**1000-oaks** · 11-14-2015, 11:17 AM

^ Lol, actual max pressure for the bottle is a whole a lot more than 2900 PSI, and the burst valve will vent well before the cylinder ruptures. If it was going to pop, it would have during filling.

**PNWbrit** · 11-14-2015, 11:36 AM

Originally Posted by 1000-oaks

I'd expect the venturi to backflow once pressure in the bag reaches a certain level, but that's just speculation on my part. If you activate the cylinder without the bag attached, wear earplugs.

This.

**406** · 02-25-2016, 01:30 PM

deployed mine the other day after they filled it to ~2900 psi and didn't seem to have any issues, but let the air out of the bag very soon after pulling trigger.