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A long time ago I owned a 2250 ish psi cylinder, but this is a question for modern diving with normal, full cylinders.Just fill your tank to 150 bar before the dive?
So exactly what do you mean by ‘turn’? It doesn’t sound like you are returning the way you came but just using that to mean ‘start to finish’.Start a reefdive with 200 bar, go to 30 meter depth. Go slowly shallower and turn the dive at 100 bar at 18 meter (20-25 minutes divetime) or something like that. Go slowly shallower to 10 meter (40-50 minutes divetime). Do a safetystop. Surface with a tankpressure of 40-50 bar.
Can you give an example? I am wondering if this is a language thing. By ‘turn’ do you mean pressure at which to leave the bottom? Or actually turn back?Rock bottom calculation could easily have 100 bar as turn pressure for a dive profile.