During the design and development of the Argonaut, I did a lot of flow calculations and testing, but I had the opportunity to do some more flow testing last week, I had several tanks that I needed to empty (for hydro testing) so I had a lot of compress air to use up.
I wanted to get some solid numbers showing how long it took to empty a full steel 72 and a full high pressure steel 80. BTW, this steel 80s actually hold 85 cu ft.
Warning: The two videos below are very boring videos showing the pressure gauge needle moving down while the venturi flow on two different Argonauts is used to bleed the tanks dry. One video is almost 5 minutes long and the other 3.5 minutes. You can fast forward the videos. If you watch the full video, you may regret that you will never get that time back.
My Argonaut regulators are normally tuned hot enough that all I have to do is pull a slight vacuum from the mouthpiece and the venturi flow will continue the flow. I am not doing anything other than initiating an intentional free flow and I am letting it flow.
The bottom line is than an Argonaut can empty a full tank (steel 72 or 85 cuft) in 3.5 to 4.5 minutes. That is a flow rate of 16 to 22 cfm. This type of potential flow rate far exceed the needs of any diving situation. Let me know if you are ever in a diving situation where you need to empty a tank in less than 5 minutes.
I have seen claims of flow through piston first stages than can flow 300 cfm. In theory that first stage would empty a steel 72 in 14 seconds. Impressive numbers, but it is not realistic or practical value. That was only the first stage and I am guessing that it was tested with a high flow valve and constant air pressure source.
My test was for a complete regulator, including the hose loop, attached to a standard scuba valve and tank. The two regulators did flow air at different rates. I can explain more about the difference later.
The tank pressure is obviously dropping. I have taken readings from the videos and plotted the data of time versus pressure drop. It looks fairly linear.