D792-5018 G771K227
G771-K226 G771-K201
G771-K620 D664-4009
D631-751C D791-4004
B61042005 G631-3703b MOOG Hydraulic Servo Valve Electro Hydraulic Industrial Flow Control and Pressure

FAQ:

What are the main series of MOOG Servo Valves?

MOOG offers a comprehensive range of servo valves. Some prominent series include :

• G761 Series: A popular two-stage flow control valve with mechanical feedback. Known for fast response and robustness, it is widely used in various industrial applications .

• D630 Series (e.g., D634, D636, D637): These often feature direct drive by a linear force motor (DDV) or advanced control. The D636/D637 series, for example, comes with a fieldbus interface and integrated digital electronics for high flexibility .

• D660, D661, D662 Series: Classic two-stage servo valves with a wide range of industrial uses .

• 72 Series: Standard response two-stage valves with a field-replaceable pilot valve filter and the option for external pilot pressure control .

The table below summarizes the key features of some common series:

Series Example Key Characteristics Typical Applications / Features
G761-3003B Two-stage, mechanical feedback, high response Industrial machinery (e.g., metal forming presses)
D634-341C Pilot-operated, closed-loop spool control with LVDT Precision control systems
D636/D637 Direct Drive (DDV), linear force motor, fieldbus interface No pilot leakage, high dynamics, programmable
72 Series Standard response, replaceable pilot filter Power generation (steam/gas turbines)

4. What are the typical operating parameters for MOOG Servo Valves?

While specifications vary by model, general operating parameters can include :

• Maximum Operating Pressure: Up to 4000-4500 psi (approx. 31.5 MPa) for many models.

• Flow Control Range: From a few liters/minute (e.g., 3.8 L/min) to very high flows (e.g., 3800 L/min), depending on the valve size and type .

• Input Signal: Typically a current signal (e.g., ±40 mA) or a voltage signal. Modern valves may accept digital fieldbus commands .

• Coil Resistance: Typically, each coil in the torque motor has a specific resistance, for example, in the range of 72-88 Ω .

• Operating Temperature: A common range is -20°C to 80°C .

Applications, Troubleshooting, and Maintenance

5. Where are MOOG Servo Valves commonly used?

MOOG servo valves are used in a wide array of industries that require precise motion control :

• Industrial Machinery: Metal forming equipment (press brakes, shears, injection molding machines), wood presses, and plastic machinery.

• Power Generation: Control of steam turbine valves, gas turbine fuel systems, and guide vane control.

• Test and Simulation: Automotive and aerospace test rigs, flight simulators.

• Other Fields: Robotics, material handling, and other applications demanding high-performance hydraulic control.

6. What are the most common failures and how can they be diagnosed?

Common failures can be categorized by the valve's internal components :

• 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.

System-level symptoms caused by these failures include :

• 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.

7. How can I maintain my MOOG Servo Valve and prevent failures?

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. Contamination is the primary cause of servo valve failure.

• System Design: The hydraulic system should be designed to minimize dead spots where contaminants can accumulate. The reservoir should be sized appropriately to allow for air and contaminant separation .

• 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, which may include replacing the valve's internal filter (if equipped) .

Purchasing and Services

Quanzhou Yisenneng Hydraulic Electromechanical Equipment Co., Ltd. has been established for many years and has now developed into an international trading company supplying various hydraulic machinery parts, oil pumps and valves. We are one of the few Chinese companies with multiple products and channels. Main focus: quality assurance! The price is the lowest in the industry! Quality management procedures are implemented in accordance with international standards and are implemented throughout the production process. In terms of channels, we have gathered the most complete variety of products in the world; in terms of quality, all products meet international standards; the lowest price in the industry is the highest; the fastest delivery on credit, and a complete after-sales system; remember Good service is the key to cooperation with customers. We strive to achieve high quality standards, provide competitive prices, and ensure timely delivery. In this way, our products have been recognized by the market and satisfied by customers in the past years. Our goal is to meet the needs of our global customers. Here you can enjoy a one-stop shopping experience, the customer is God, you want all of us, I wish you a happy shopping trip.