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On-Off Valves and Regulators

On-Off Valves and Regulators

1. On-Off Valve

On-off valves are primarily used to open and close the system’s main air supply lines. However, they have two other important functions:

a. Exhaust

In order to prevent unexpected motion or forces within a system that has been shut down, the valve exhausts the system when supply air is shut off. Thus "residual air" escapes which might otherwise have dangerous consequences.

b. Safety Lock

For safety reasons, manually actuated on-off valves can be locked in the closed position with a commercially available padlock.

 

2. Air Regulator 

Compressed air regulating valves are used to limit a system's operating pressure, and at the same time to compensate for small pressure fluctuations.

a. Directly Actuated Diaphragm Regulator

With these regulators, force is applied to a diaphragm by means of a mainspring. This force can be adjusted by manually turning a knob.

A sealing element is located at the middle of the diaphragm, which initially seals the front end of the regulator piston as a result of the selected force applied by the mainspring, and the regulator piston's spring.

b. Input Pressure Range

This is another expression for primary pressure.

The knob must be pulled up before it can be turned in order to adjust pressure. The knob snaps into place when it’s pressed back down, thus preventing inadvertent changes to the selected setting.

c. Primary Pressure Compensation

Output pressure at the valve is independent of input pressure fluctuation.

When the mainspring is adjusted, the regulator piston is pressed down and the lower sealing seat is opened, while the face of the regulator piston continues to close the sealing element in the diaphragm.

Flow from the supply port to the exhaust port, for pressurizing and venting the system, is thus open. In this position, minor pressure fluctuations, as well as associated changes in flow rate at the lower sealing seat, are compensated for by means of a slight movement of the regulator piston.

If pressure at the working port is increased to a level that exceeds the selected working pressure, it applies a force to the bottom of the diaphragm which pushes it up and distinctly compresses the mainspring.

The spring pushes the regulator piston up and completely closes the lower sealing seat, but no longer reaches the sealing seat in the diaphragm.

Air escapes through the sealing element in the diaphragm, as well as an exhaust port on the housing of the pressure regulator. This process is called secondary venting.

d. Secondary Venting

If the pressure increases at the working port from the consumer via the value selected at the regulator, this “excess” pressure can also be relieved via the pressure regulator.
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