Is pneumatic control possible without venting high pressure instrumental air?

Consider a hydraulic system where high pressure liquid drives a spring connected load. The movement of load can be controlled by adjusting the flow through the spool valve. But when this system has to be converted into pneumatic system, flow variation by venting the air is not possible since permanent venting of high pressure instrumental air is not permitted.What is the work around?Is pneumatic control possible without venting high pressure instrumental air?
*No more high pressure consumption?


You want to take back to a inlet source through NRV?


or you want to collect back to receiver?





You can use the high pressure air for actuating some other mechanism.Is pneumatic control possible without venting high pressure instrumental air?
Hydraulics require a reservoir to collect the oil. In pneumatics, the reservoir is the atmosphere. In most cases this is no problem.





You say that venting the air is not allowed but within what limits? Can the vent pipes not be piped to an area outside of the prohibited area. This is the same as the return line on hydraulics taking the oil back to the reservoir.
This can be achieved by using an accumulator and controlling the flow by a differential pressure transmitter controlled valve regulating the flow.
The same principals apply. There are many pneumatic valves that control the supply side. This will control the supply to the component being used instead of controlling the exhaust side. Solenoid valves most times have that feature, but it not a flow control valve can be installed. If smooth operation or compression is a problem, consider using an air over oil system.


The venting problem still exist whether the exhaust is controlled or not.
In pneumatic system when you are going to control the speed or movement of the load. Two ways to control it either the vent flow is controlled or the supply flow is controlled. Controlling the supply doesn't mean you have to vent the supply pressure but to control the flow quantity so that it would take some time to fill the cylinder.