Control Valve Accessories

1.Handwheel

• It is used for manual operation of control valve during start up or event failure.

• They are frequently used when lockup or bypass valves are not provided.

2.Limit switches and solenoid

• Limit switches are mounted on top to operate signal lights for valve position, valve operation or alarm.

• Solenoid valve may be provided for remote loading and unloading of valve.

3.Booster relay

• They are used to reduce lag time resulting from long transmission lines or to actuate large diaphragms.

4. Lockup Valve

• Certain applications require valve to remain in it’s last controlled position in event of air supply failure.

5.Capacity tank

• The valve position tends to drift depending on plug forces in event of air supply failure.

• Thus understanding necessity an airlock utilizing capacity tank is used.

• This stored pressure in cushion provides positive or negative valve opening.

6. Transducers

• Electronic control loops require I/P converter when control valve is pneumatically operated.

• If control valve is subjected to vibrations they must be mounted on rigid support.

7. Jacketed bodies

• They are required when valve body needs to be heated.

• They provide efficient and uniform heating using copper tubing tracing.

8.Airsets

• Most common accessory is air filter regulator.

• Filter removes air-particulates.

9.Ratio & reversing relays

• A ratio relay is used to multiply or divide inlet pressure

• Reversing realy is used when control action needs to be reversed

E.g. Split range valve may be operated where one is air to open and other is air to close.

• A reversing relay might be used with one of the valves to achieve desired action.