Quote: (Originally Posted by
UKSteve)
Not sure what the classic's controller software does however...or if AP is upgrading its software in line with the vision algorithm.
Not sure about the statement on intermediate pressure however. During ascent, the interstage pressure would stay the same until either the solenoid fires or until the over-pressure valve which is fitted to the first stage vents some gas. If it stays constant while the diver ascends fast then there would indeed be an increase is the differential pressure across the solenoid. However I am not sure what the lift setting on the over pressure valve is vs the maximum differential pressure that the solenoid will operate at. Anyone know?
Steve
The Classic does the 6 second O2 injector pause.
The intermediate pressure issue is quite interesting. The "over-pressure valve" is not fitted to most O2 first stages, especially in Europe, and they generally blows at a much higher pressure than the APD solenoid sticks at anyway. This means if the O2 solenoid is programmed not to fire for a period, and the ascent is fast enough (350ft/min is what some divers manage to achieve in uncontrolled ascents), then the intermediate pressure increases relative to ambient. That is, the differential pressure across the solenoid increases.
The APD O2 injector operates over an extremely narrow range for a safety critical system. The increase in differerential pressure across the injector in 6 seconds in an uncontrolled ascent is enough to jam on an APD injector if the intermediate pressure were near the top end of its range to start with.
Just to highlight the differences between a safety critical injector and a modified machine automation injector, attached is the Test Plan for the DL Open Revolution submission O2 Injector (Edit: Upload failed: 1.9MB limit, file is 3MB. Will put it onto the DL web site when I have time next week).
Cheers,
Alex