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[APD] Re: Ooch

"Is it that the pressure differential with the CO2 set-ups is not great enough for a sonic velocity to be acheived at the metering valve (critical pressure ratio?) or that the metering valve opening in these setups is too large for critical flow?"

Both and neither because we aren't using the valves in a way that any of that applies.

Here's a simple experiment, especially for the Fabco NV-55. Set the regulator to about 25 psi and the valve to a couple of bubbles or so per second. A typical setup. Now apply some suction to the line out of the bubble counter (don't inhale). If the bubble count increases, then by definition it wasn't sonic to begin with. Yet all these needle valves do a perfectly fine job of preventing a dump. Why?


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