Motor-operated valve, MOV.
A valve body topped by a small circle with the letter M denotes motor-operated actuation. MOVs handle large block valves, ESD service, and remote isolation where a manual operator is impractical.
How it's drawn.
A valve body with a small circle on top carrying the letter M for a motor actuator. Motor-operated valves handle large block valves and remote isolation where a handwheel is impractical. Position feedback is usually drawn alongside, showing open and closed status.
Typical usage.
Pipeline block valves, large-diameter isolation, ESD valves on hydrocarbon service. Tags carry ZSO, ZSC position-feedback switches on top of the actuator status. Each MOV consumes 2-3 DI channels just for position feedback.
Telling it apart.
- The M marks a motor actuator. A handwheel in the same position would mean manual operation.
- A motor-operated valve is usually an isolation valve driven open or shut. Throttling service is the exception, not the rule.
- Open and closed position signals shown with the actuator are status feedback, separate from the drive command.
Related.
Get the P&ID symbol cheat sheet.
One page of valve and actuator geometry, including the motor operator and the fail positions drawn with it.