Deep thought about Scuba Regulators

[nimoh]

Thats not how regs work...

care to elaborate? are you referring to the claim that the purge will be pushed in by the water pressure?

My initial thought on that was that it wouldn't be pushed in, but without knowledge of the inner workings of a second stage, I don't know why I think that

 

[Firebird4life]

actually i found out the answer after a quick nap and a beer.
Let me know if my logic is correct.

TAnk=3000psi
1 AT=33 fsw (feet in sea water) or 14.7psi
3000/14.7=204.08163 (the amout of atmosphers in a scuba tank)
204.08163*33= 6734.6937 (the depth that i thought i was looking for.)

But i forgot a few things. First is to take off for the presure at the surface (1 ATA). so now were at 6701.6937. But i forgot another thing. The design of a regulator. The regulator is designed to take the presure from a tank (in this case 3000 psi) and reduce it to 140 psi over AMBIENT PRESURE!!! I completly forgot about this. So actually i need to take off another 140psi..

So 140/14.7=9.5238095
9.5238095*33=314.28511
6701.6937-314.28511= 6387.4086

6387.4086 is the depth that a scuba regulator would fail.....

holy crap my brain hurts

 

[dfx]

care to elaborate? are you referring to the claim that the purge will be pushed in by the water pressure?

My initial thought on that was that it wouldn't be pushed in, but without knowledge of the inner workings of a second stage, I don't know why I think that

It's because the "inside" of the second stage (the air-filled part, the part you breathe from) is always kept at the same pressure as the outside (the water). It's what allows you to breathe. The purge would only get pushed in if the inside was at a lower pressure than the outside, but if that was the case, then you couldn't breathe from it. If the pressure outside increases, the second stage lets more air into the inside until the pressure equalizes. Pressing the purge button simulates a higher outside pressure, which is what causes it to keep letting air in: it's trying to equalize to that simulated higher pressure, which obviously doesn't work, because all the additional air goes right out again.

 

[Firebird4life]

so in that case is my thinking correct??????

 

[nimoh]

Sounds correct, except that I don't think 140psi over ambient would be the exact stopping point for delivering air.

After you reached 2860psi ambient and kept going up, the delivery would gradually weaken until you reached 3000psi ambient, so I don't think it needs to be factored in.

Just a theory, I haven't tested this on any of my 6700' dives.

 

[herman]

so in that case is my thinking correct??????

You are close, at 6387ft (roughly) the regulator would not stop "working" but it would stop regulating because it had reached it's minimum range of tank pressure vs ambient pressure. To operate (regulate) the tank pressure must be at least the IP value above ambient, once it drops below that value the reg simply opens fully and remains that way, it has not failed, it is just past it's operating range. Once regulation stops, the "IP" will be equal tank pressure minus ambient, you would still get a flow of air as you breath, just now it's at whatever the tank pressure (above ambient) is and it will continue to drop until it reaches ambient pressure. This is the same thing that happens when you breath a tank dry at any depth, including on the surface. As the tank pressure reaches the IP of the reg, the reg opens fully and stays that way, now the IP is equal to tank pressure and will drop with each breath. This by the way, is the reason that anytime someone claims to have a sudden loss of air due to breathing a tank dry I call BS, that simply can not happen. When a tank reaches the IP of a reg, the reg will open fully and stay that way, basically you now have a second stage connected directly to the tank. With each breath the reg does get harded and harder to breath from but it does not just quit, the last few breaths are quite noticable but you can still get them. If you are paying any attention at all, the reg will tell you that something is not right long before you pull the very last breath out of the tank.