Heat is typically introduced via steam running through fin/tube heat exchangers controlled by on/off pneumatic valves.

When a pressure reservoir is present, the flow of air or gas is commonly controlled with pneumatic solenoid valves.

Less common are proportional pneumatic valves or even various electrical actuators.

Controlled by a pneumatic valve, the system required constant attention to ensure correct operation.

Applications for isolated relays include controlling power supplies, turning on motors and annunciator lamps, and actuating pneumatic or hydraulic valves.

The armature is used to provide a mechanical force to some mechanism (such as controlling a pneumatic valve).

On 100 kPa input, you could lift a small car (upwards of 1,000 lbs) easily, and this is only a basic, small pneumatic valve.

It is common practice to lock sites using pneumatic non-return valves during the loading or transferring of chemicals or hazardous waste.

It appears to be a precursor to PL ratings that are now the new requirements which encompass hydraulic and pneumatic valves.