Diaphragm vs. Piston Regulators

[redacted]

You got me to wondering and i found this:

When you exercise and your muscles work harder, your body uses more
oxygen and produces more carbon dioxide. To cope with this extra demand,
your breathing has to increase from about 15 times a minute (12 litres of air)
when you are resting, up to about 40–60 times a minute (100 litres of air)
during exercise. Your circulation also speeds up to take the oxygen to the
muscles so that they can keep moving.

I think my estimates are quite reasonable for a mild to high exercise situation,. The kind we try to avoid while diving.

The reference i hope:.https://www.google.com/url?sa=t&sou...B1E55KmnvRDxxcdnQ&sig2=A8z_WxQNQN0IiJbT2lWzhg

Edit. BTW 2 liters is about halh of our lungs vital capacity. Not really much of a strain.

 

[joshk]

Only way to settle this discussion: Go for a run breathing off an 80 strapped to your back.

 

[tbone1004]

I think those volumes are sprinting type levels of exercise.
Regulation of Ventilation During Exercise | Exercise Physiology
Granted they are from 50 years ago when they did the study, but I don't think we have changed. Sure at max intensity, the graphs top out at 120lpm, but that is max intensity during running. Based on respiratory rate of 45bpm, that's like 5.5 liters per second, which may very well exceed the flow rates of the regulators, but it also equates to a SAC rate of 4.3cfm, which I don't think is something anyone can sustain.

For reference, rebreathers are tested at 75lpm or 2.6cfm as the maximum work rate. ANSTI typically tests 25bpmx2.5l which is half of what is referenced as a theoretical max, and that theoretical max of 120lpm is typically the limits of the ansti machines. 40bpm, 3l per breath

 

[redacted]

I think those volumes are sprinting type levels of exercise.
Regulation of Ventilation During Exercise | Exercise Physiology
Granted they are from 50 years ago when they did the study, but I don't think we have changed. Sure at max intensity, the graphs top out at 120lpm, but that is max intensity during running. Based on respiratory rate of 45bpm, that's like 5.5 liters per second, which may very well exceed the flow rates of the regulators, but it also equates to a SAC rate of 4.3cfm, which I don't think is something anyone can sustain.

For reference, rebreathers are tested at 75lpm or 2.6cfm as the maximum work rate. ANSTI typically tests 25bpmx2.5l which is half of what is referenced as a theoretical max, and that theoretical max of 120lpm is typically the limits of the ansti machines. 40bpm, 3l per breath

I'm sure they are which is why i used a more realistic level

 

[Michael Guerrero]

My flow-by piston regs (XS Scuba compact DIN) are a lot simpler to service than my HOGs (sealed balanced diaphragm) but they get dirtier inside because, as was said, the internals are exposed to the water.I use the pistons for my deco gasses/drysuit because performance isn't an issue and they are easier to clean, but maybe that's sub-optimal since they get more junk in them. No explosions yet though .