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Question Skipping 1st stage Maintenance?
- Thread starter Pearlman
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halocline
Contributor
Is this statement supposed to be applicable to all scuba regulators? If so, there might be a little bit of semantics at work. I guess what happens is that with enough depth ambient pressure would exceed tank pressure. At that point the first stage valve would remain open, and I’m guessing that water would force its way into the tank through the 2nd stage, if it too were open.
Remember that IP is the force that closes the valve on the 1st stage. On a piston reg, you have the spring pushing the valve open, assisted by ambient (water) pressure. That open valve allows air to flow into the IP chamber until enough pressure builds up to push the piston closed. But that pressure can only be supplied by the tank, so if ambient (plus the spring force) is greater than what’s in the tank, the 1st stage will remain open.
On a typical diaphragm reg, the geometry is a little different but I think the result is more or less the same. Ambient pressure on the diaphragm (plus the spring) pushes the seat off the orifice (via the pin) and if there’s not enough tank pressure to counter-act that, everything stays open.
So it might be just a little tough to breathe off a 2nd stage! I guess the depth at which this happens depends on how much pressure is in the tank.
But surely your comment must have something to do with a specific sealed regulator, because I think in my scenario we’re talking about thousands of meters, not hundreds.
Hello halocline
In metric units ist's very easy .
Vor exapmble : your tank pressure is 170 bar , your IP is 10 bar over ambient .
Substract 10 bar from the tank pressure = 160bar
One bar equals 10 m water colume , 160 bar equals 1600 m water deephs .
Right , that what you said .
The reason that the IP don't stay constant is that the mechanical stress in the closed design raises with the ambient pressure and if the parts are not strong enought they fail . As far as I know only the Mares and the Poseidon are certfied for 200 m . For 50 m will al do well .
In metric units ist's very easy .
Vor exapmble : your tank pressure is 170 bar , your IP is 10 bar over ambient .
Substract 10 bar from the tank pressure = 160bar
One bar equals 10 m water colume , 160 bar equals 1600 m water deephs .
Right , that what you said .
The reason that the IP don't stay constant is that the mechanical stress in the closed design raises with the ambient pressure and if the parts are not strong enought they fail . As far as I know only the Mares and the Poseidon are certfied for 200 m . For 50 m will al do well .
admikar
Contributor
Also some of Apeks regs (FSR and FST, not sure about DST) are certified to 200 msw.
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