Actuator motors can be depicted rather poorly on some manufacture's schematics.
Most are fairly simple in their operation. Two coils, one to open and one to close. An internal switch flips between contacts whenever the motor has reached full travel.
As an example: The valve is open. The "close" contacts are ready to receive voltage to drive the actuator closed. When that voltage is present, the motor drives closed, when it reaches full travel, the "close" contacts separate which removes the voltage from the close coil (it keeps the motor from burning itself up). The motor is now closed with the "open" contacts ready to receive voltage to drive it open.