What makes a high performance diaphragm?

[halocline]

BTW, you can’t get 300 ambient Ft³ of gas past a Scuba cylinder valve on the surface, let alone through a 1st stage regulator.

Absolutely that's true, that's why I said that the weak link in the flow path is the tank valve. The MK25 flow rate is huge overkill.

But I have to disagree with the statement that a regulator with a specified flow rate at the surface could exceed that flow rate by being used at depth. I actually never thought about it before, but in my mind if you have a fixed volume of air in the tank, and a fixed orifice size in the regulator, gas simply will not pass through that at double the rate at 2 ATM simply because we use double the gas to breathe at 2 ATM.

The reason I said it would be slower (theoretically) is because the pressure gradient is lower, and to me it makes sense that flowing gas from say 200ATM to 1 ATM will move faster than gas flowing through the same path into 2 ATM. I'm sure it's a tiny, really just theoretical difference.

 

[JB]

I guess it's safe to say that you will not notice the difference in 1st stages. What you do notice is the second stage. Your perceived work of breathing is entirely accounted for by the second stage performance.
The reason regs are capable of such rediculously high flow rates ( it's not over kill or for bragging rites), is that while your minute ventilation might be 10 to 20 surface liters per minute, during a sudden deep inhalation the peak instantaneous flow rate could be as high as 500 liters/minute for a fraction of a second, but if you didn't receive it you would notice a resistance to inhalation. That's assuming you have fit healthy young lungs!!

 

[Dhboner]

Oh...this ISN'T a birth control thread

 

[herman]

I guess it's safe to say that you will not notice the difference in 1st stages. What you do notice is the second stage. Your perceived work of breathing is entirely accounted for by the second stage performance.
The reason regs are capable of such rediculously high flow rates ( it's not over kill or for bragging rites), is that while your minute ventilation might be 10 to 20 surface liters per minute, during a sudden deep inhalation the peak instantaneous flow rate could be as high as 500 liters/minute for a fraction of a second, but if you didn't receive it you would notice a resistance to inhalation. That's assuming you have fit healthy young lungs!!

The item limiting flow in the reg assembly is the orifice in the second stage which typically is in the 30-60 cfm range...not sure what that is in L/m but in any case, the high flow rates of the first stages are irrelevant because regardless of how much they can flow you can't flow more gas to the diver than the lowest flow element in the system.