Differential pressure driven pneumatic valve
Pellacani Gianfranco - TECO S.r.l.
I've got the following problem: I need to stop
compressed air inlet to a nitrogen generator to be stopped when the pressure
within a tank that is to be filled with nitrogen reches 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 disadvantegeous for those users who ahve hiher 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 thorugh a srping 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 genrator 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 betweenthe two pilot-cylinders 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?
Please forward any reply to my personal address too (remove SPAMNO and
NOSPAM from address).
Thanks any helping hand
Gianfranco Pellacani