Motorised operated valve MOV

March 4, 2021 4instrumentation20

The motorized operated valve is widely used in most of the industry. The motorized valve is called in many ways according to its application. The motorized valve, which is used to control a damper is named a motorized control damper (MCD).

They are used in both on/off and control type valves nowadays. They have a set of electronic components to control the motor to operate towards the desire limits.

List of components

Analog control unit
Digital control unit
Power unit
Display unit
Encoders
Limit switches
Torque switches
Terminal connection unit
Motor

According to the type and manufacture, some circuit cards will not be available. In an on/off valve, there is no need for analog cards it will be eliminated.

Analog control unit

This unit takes care of the incoming and outgoing signal from/to dcs. We can operate the valve linearly by giving a 4–20 mA signal from the control room and the valve will operate 0%-100% according to the command. Furthermore, it will send the current valve position as feedback to the control room. So we can able to track the real-time valve status.

Digital Control unit

Here all kinds of digital signals are handled. The open or close command from the control room is fetched to this unit and it contains a set of the relay to implement the operation and send back the full opened/closed position feedback to the control station.

Power unit

It consists of a set of the transformer and other equipment to convert a 440 V power to a lower range to power our control units. A 24 V supply is required to power up the control cards.

Limit switches

Nowadays limit switch is not found separately in a MOV they come along with the digital unit and encoder feedback are fetched and concluded into position feedback. However, in some valves, you should manually set limits using a switch.

Torque Switches

It is used as a safety mechanism to stop the valve in the event of a valve jam or any abnormality caused while MOV tries to operate a valve. It will help cut off the motor immediately to safeguard the health of the motor and the process line attached.

Terminal connection unit

Here all the cable from the panel room is connected according to the standard to order to achieve proper maintenance for a long time.