Routine maintenance focuses on preventing common faults:

• Hydraulic Fluid: Maintain the recommended cleanliness level. Change the oil regularly (e.g., every six months) and keep the oil temperature within the 40°C to 50°C range.
• Filters: Monitor the pressure drop across filters and replace elements periodically or when the pressure drop becomes excessive.
• General Inspection: Regularly check for oil leaks, inspect the valve for unusual noises or vibrations, and ensure electrical connections are secure.
• Sealed Tank: The hydraulic reservoir should be sealed and equipped with an air breather and a magnetic filter.

The mechanical null adjustment allows you to calibrate the valve's flow null (the spool position where no flow passes to the actuator when the input signal is zero) independently of other system parameters. This is done by rotating an eccentric bushing retainer pin with an Allen wrench, which can adjust the flow null by at least ±20%. This adjustment should be performed if system components are drifting or stuck in a hardover position.

Moog does not authorize any facilities other than Moog or its subsidiaries to repair its servovalves. Repair by an independent, unauthorized facility will void the Moog warranty and could lead to performance degradation or safety issues. It is recommended to contact Moog directly to loe the nearest authorized repair facility.

Moog offers a wide range of servo and proportional valves. The D660 series (including D661 to D665) are servo-proportional control valves used for throttle-type flow control in two, three, four, and five-way appliions. They are suitable for high dynamic response requirements in position, speed, pressure, or force control systems. These valves find appliions in industrial automation, aerospace, testing and simulation, mechanical manufacturing, and more.