Buy in-line progressive starters by Metal Work
The in-line progressive starter is a valve that regulates the flow of air until the outlet pressure reaches a certain value, at which the valve opens and allows air to flow at full rate.
This valve can be used to control a group of valves or a single valve, or it can be mounted between another valve and an actuator.
The air that enters inlet 1 passes through a choke that has a knob adjustment to control the flow. The valve opens completely when the outlet pressure reaches about 60% of the inlet pressure.
If the air supply is switched off, the valve discharges air from outlet 2 to inlet 1.