SM4-20 Vickers Servo Valve 210bar 76L/min

Product Overview

Models such as SM4-20, SM4-20(15)57-80/40-10-S182 (Assy 3025047) and SM4-40 belong to the Vickers (now Eaton/Danfoss) SM4 series of high-performance electrohydraulic servo valves. Featuring a two-stage design (nozzle-flapper pilot + sliding-spool main stage), they provide precise flow control. Every unit undergoes rigorous 100% simulated operating-condition testing and offers excellent drop-in interchangeability with equivalent servo valves. Low hysteresis and high dynamic response make them ideal for closed-loop position, velocity and force control in precision hydraulic systems.

Technical Specifications 

• Model examples: SM4-20(15)57-80/40-10-S182, SM4-40(40)151-80-40-10
• Valve type: Two-stage electrohydraulic servo valve (four-way flow control)
• Rated flow: up to 76 L/min (at 70 bar Δp for SM4-20)
• Maximum supply pressure: 210 bar (standard); up to 350 bar on certain designs
• Minimum supply pressure: approx. 14 bar
• Hysteresis: ≤3% of rated current
• Symmetry error: <10%
• Threshold: ≤0.5%
• Weight: approx. 2.1 kg
• Mounting: Subplate or manifold
• Coil options: Multiple resistance/current combinations (e.g. 80 Ω / 40 mA)

Key Technical Advantages

1. Two-stage high-precision design: Nozzle-flapper pilot stage plus precision sliding-spool main stage delivers excellent resolution and dynamic response.
2. Low hysteresis and high linearity: Hysteresis ≤3% supports precise closed-loop position, velocity and force control.
3. Excellent drop-in interchangeability: Standard mounting interface allows direct replacement of equivalent Vickers/Moog servo valves, minimizing modification costs and downtime.
4. Wide flow coverage: SM4-20 series covers rated flows from 3.8 to 76 L/min, flexibly matching different actuator requirements.
5. Modular design: Optional filter modules and flushing valves improve system contamination resistance and ease of maintenance.

Application Areas

Injection moulding machines, die-casting machines, test and simulation equipment, mill automatic gauge control (AGC), hydraulic press brakes, precision presses and other hydraulic systems requiring high-accuracy closed-loop control.

Expert Maintenance Tips

1. Ensure mounting surfaces are clean and flat before installation; fit seals correctly and tighten specified bolts to the recommended torque.
2. Maintain very high fluid cleanliness (NAS 5 or better recommended); use high-cleanliness mineral oil.
3. Observe correct electrical polarity and shielding; ensure compatibility with the servo amplifier; flush the system thoroughly before first start-up.
4. Periodically inspect filters and the valve body for contamination or leakage; clean and protect during long-term storage.
5. Do not disassemble the torque motor or spool assembly. Service must be performed only by technicians experienced with servo valves in a clean environment; always re-check null and performance after service.