Gianfranco Pellacani writes:
Hi everybody,
I've got the following problem: I need compressed air inlet to a nitrogen generator to be stopped when the pressure within a tank that is to be filled with nitrogen reaches ab. 1 bar less than the inlet pressure to the generator. Since the inlet pressure may vary and setting the threshold pressure based on the minimum accepted inlet pressure would be too disadvantageous for those users who have higher than minimum inlet pressures, a pressure switch is not suitable. Furthermore, I would need the whole control system to be driven only by air and not need any electrical supply.
In my mind a 3/2 pneumatic valve with a double pneumatic pilot, whose two pilots are connected either to the inlet and to the tank, could be used to control a second single-pilot valve that would then open or close connection of the air inlet to the generator, provided that this double-pilot valve can be biased through a spring to have it switching from one position to the other when the pressure difference falls below a given value (I would need 1 bar or less). Alternatively, the double air pilot valve itself might open/close connection of the generator to the air inlet, provided it allows sufficient flow rate.
There are double air pilot valves with different sections of the pilot cylinders achieving a similar function, but these valves typically have a section ratio between the two pilots which is about 1,5:1 to 2:1, and since I have pressures of 8 to 13 bars at inlet this would mean a pressure difference threshold of 4-7 bars, which is far too much.
Do you know of any such component or any workaround for this issue?
Thanks for the helping hand
Gianfranco Pellacani
Nitrogen pressure regulation
