Original MOOG servo valves from Germany for precise flow and pressure control in industrial applications.

• Torque Motor Issues:
  • Broken Coils: Result in no current, valve does not respond
  • Contamination in Air Gap: Causes the armature to stick, preventing valve movement
  • Loose Fasteners or Worn Parts: Can lead to increased null bias or instability
• Nozzle/Flapper Stage Issues:
  • Clogged Nozzles or Orifices: Often caused by oil contamination, leading to reduced frequency response, poor resolution, and system instability
• Spool Amplifier Stage Issues:
  • Spool Sticking: Caused by contaminated oil or a deformed spool, resulting in distorted response or complete seizure
  • Cutting Edge Wear: Increases internal leakage, causes null shift, and reduces stability

• Cylinder Refusal to Move: Often due to a stuck servo valve
• Uncontrolled Valve Movement: Sudden full opening/closing of a cylinder without a command change, often due to a clogged nozzle
• Cylinder Oscillation ("Cylinder Hunting"): Can be caused by high internal leakage, poor resolution, or instability in the valve's null zone
• High Cylinder Lag

The most critical factor for reliable servo valve operation is maintaining clean, dry hydraulic fluid:

• Oil Filtration: Use high-quality filters and adhere to a strict oil analysis and replacement schedule
• System Design: The hydraulic system should be designed to minimize dead spots where contaminants can accumulate
• Regular Inspection: Periodically check the valve and system for leaks, unusual noises, or changes in performance
• Preventive Maintenance: Follow the manufacturer's recommended maintenance intervals

MOOG can provide custom solutions by modifying product components to enhance performance or meet specific application requirements.

A detailed test report is provided with new valves or after professional repair, verifying performance specifications including:

• Flow Characteristics
• Null Bias and Hysteresis
• Internal Leakage
• Frequency Response