Butterfly Wafer Shutoff Valve with stainless steel disc and pneumatic spring return (SR or One Way - one air line) actuator.
 
Air actuated spring return butterfly valves are used in process automation environments and for controlling water flow on water trucks.

The butterfly valve is closed in its normal state and when air is supplied to the A port the valves opens. When air is released the valve automatically closes due to spring pressure.  Often called single acting,  one way or spring return they only have one airline. 

If you already have double-acting control lines you can simply connect the open line to the A port and the closed line to the B port.
Actuator Type - Air Open & Spring Close
Open & Close Shaft Indicator 
Valve Seat - EPDM
Port Size - 1/4 BSPT Female
Max Butterfly Valve Pressure - 230psi
Max Actuator Pressure - 10 Bar (145psi)
Single Acting - One(1) airline
12 Month Warranty