Bob3
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Yah, I have some back in CA, I'll be back out there in about a month.
Double Hose Regulators
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ew1usnr
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I know that an unbalanced single stage regulator (Voit 50 Fathom, Mistral, Healthways) breathes fine at a relatively shallow depth, say down to 120-feet. But has anyone reading this post ever taken one down deeper, meaning past 200-feet? I wonder how a single stage regulator would perform at about 220-feet with a tank pressure of 1200 psi. I would suspect that if a diver went deep enough, the inherent limitations of a single stage would eventually manifest themselves. I'm pretty sure (based on the performance of single hose USD Conshelf regulators) that a two-stage USD AquaMaster regulator would work fine at that depth and tank pressure.
I like diving double hose regs but I'm not insane. Why would you ever want to be below 200' at less than 1200 psi with one? That's a pretty good operational definition for being "totally screwed" so I'll assume it's a theoretical argument.
The breathing resistance on a well tuned double hose reg isn't bad but it is no where near the performance of a modern high performance reg. The higher breathing effort of double hose regs at deep depths leave you more prone to elevated CO2 levels which in and of themself can be deadly in addition to the role of high CO2 levels in increasing risk of an O2 hit.
If you took a double hose reg to 200' I suspect you would find that the single versus two stage issue would mean relatively little compared to the balanced versus unbalanced issue. If I had to go to 200' in a double hose reg I would want a balanced reg like the Royal Aquamaster. In any case the limiting factor would be how much air either design could flow at low tank pressures at extreme depths.
The unbalanced double hose reg would need to have a first stage that would flow enough air to maintain a stable intermediate pressure to maintain ease of breathing on the second stage. The first (and only) stage on a single stage reg would need to flow enough air period as there is no IP to worry about. At some point performance onboth designs would begin to fall at some minimum tank pressure where the flow was not adequate for the depth despite a fully depressed demand lever. You'd have to go there with each design to find out at what pressure that occurs. I think the single stage design would offer the same performance right up until the tank presure was too low to provide adequate flow while an unbalanced double hose reg ould suffer a more steady and gradual decline. Personally I think it would be a moot point as if your air is that low at that depth you are gonna die anyway.
J. Cousteau preferred the Mistral and did some fairly deep diving with it so I would defer to his opinion and experience.
ew1usnr
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Hello, AquaMaster. It was a theoretical speculation. I figured a set or double tanks with a starting psi of 2400 psi, with diver swimming down to half, and then coming up. He would reach his deepest point at 1200 psi. This supposes that the diver has a pressure gauge and isn't relyng on his J-valve (just joking).
A single stage design (Mistral) has little pinhole for the HP air to squirt out of. The hole is kept small so as to minimize the amount of spring tension required for the "LP" seat to keep the valve closed. But by keeping the hole small, it's ability to deliver air has a definite limit placed on it. At 220-feet depth the volume of air delivery would be important. And the amount of air flow at 1200 psi would be maybe close to one-half of what would be delivered at 2400 psi.
On a two-stage (AquaMaster), the intermediate pressure might be 110 psi. That would allow a larger outlet with no more spring tension on the LP seat. I don't know if that bigger outlet would give a greater air volume flow because the pressure of the flow would be lower than in the single stage. The maximum flow is limited by the intermediate pressure. The flow to the second stage would also be limited by the flow from the first stage, and that might be similar to the one stage flowrate. Even in an unbalanced two stage, though, it seems that the design would not allow as much variation in air delivery due to declining tank pressure as what would be seen in a one-stage. Maybe a two stage gives a more constant, though not necessarily greater air flow than a single stage. That constancy would be more noticiable at depth.
This is just arm-chair speculation on my part. There are a few divers around who dive below 200-feet. Its probably been a while since very many were doing it with Mistrals and AquaMasters, but I'm sure that it was done.
A single stage design (Mistral) has little pinhole for the HP air to squirt out of. The hole is kept small so as to minimize the amount of spring tension required for the "LP" seat to keep the valve closed. But by keeping the hole small, it's ability to deliver air has a definite limit placed on it. At 220-feet depth the volume of air delivery would be important. And the amount of air flow at 1200 psi would be maybe close to one-half of what would be delivered at 2400 psi.
On a two-stage (AquaMaster), the intermediate pressure might be 110 psi. That would allow a larger outlet with no more spring tension on the LP seat. I don't know if that bigger outlet would give a greater air volume flow because the pressure of the flow would be lower than in the single stage. The maximum flow is limited by the intermediate pressure. The flow to the second stage would also be limited by the flow from the first stage, and that might be similar to the one stage flowrate. Even in an unbalanced two stage, though, it seems that the design would not allow as much variation in air delivery due to declining tank pressure as what would be seen in a one-stage. Maybe a two stage gives a more constant, though not necessarily greater air flow than a single stage. That constancy would be more noticiable at depth.
This is just arm-chair speculation on my part. There are a few divers around who dive below 200-feet. Its probably been a while since very many were doing it with Mistrals and AquaMasters, but I'm sure that it was done.
I know a few divers have dove the Andrea Doria with double hose regs. I know of one diver in partiuclar who even did it with a J-valve. The depths would have been around 180-200 ft. even on a touch dive with no penetration or decent down the deck.
The academic discussion has no basis in reality. The Mistral performs well at depth, and gets easier to breath as the tank pressure drops. The worst conditions for a Mistral single stage two hose regulator is at full tank pressure.
The Cousteau Team, in the Conshelf II undersea living experiment, dove well beyond 300 feet with the Mistral. They were using a La Spiro Technique Mistral (or Royal Mistral), but took it to great depths. They appeared not to have any complaints.
During the same experiments, the two stage, single hose Calypso repulator was also used, but not at depth. This is the same regulator Hans Keller took to over 1000 feet, but it had too small an exhaust valve to qualify for US Navy certification. It wasn't until they re-designed the exhaust, and made it larger, that the single hose regulator began to be allowed by the US Navy into the fleet.
The two hose regulators have easier exhalation resistance, which makes it a very good breathing regulator at depth.
SeaRat
PS--I realize this discussion is pretty old, but perhaps some may see it.
The Cousteau Team, in the Conshelf II undersea living experiment, dove well beyond 300 feet with the Mistral. They were using a La Spiro Technique Mistral (or Royal Mistral), but took it to great depths. They appeared not to have any complaints.
During the same experiments, the two stage, single hose Calypso repulator was also used, but not at depth. This is the same regulator Hans Keller took to over 1000 feet, but it had too small an exhaust valve to qualify for US Navy certification. It wasn't until they re-designed the exhaust, and made it larger, that the single hose regulator began to be allowed by the US Navy into the fleet.
The two hose regulators have easier exhalation resistance, which makes it a very good breathing regulator at depth.
SeaRat
PS--I realize this discussion is pretty old, but perhaps some may see it.
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