Product Overview
The 4WRZ25W1-220-5X series pilot-operated proportional directional valve (model 4WRZ25W1-220-5X/6A24NZ4/D3M) is manufactured to original Bosch Rexroth technical standards. Belonging to the 4WRZ series with size 25 (NG25 / ISO 4401-08), this valve features a pilot-operated two-stage design conforming to ISO 4401 mounting standards. The valve receives an analog input signal via proportional solenoids to precisely control the main spool displacement, achieving continuous, proportional regulation of hydraulic flow direction, flow rate, and pressure. Without electrical position feedback, it is specifically designed for open-loop control applications in medium-to-high flow hydraulic systems.
The 4WRZ25W1-220-5X employs spool type W1 with a nominal flow rate of 220 L/min (at 10 bar pressure drop) and maximum operating pressure of 350 bar (5075 psi). The main stage maximum flow capacity is 870 L/min. This product is dimensionally and functionally identical to the original Rexroth 4WRZ series valve, offering true drop-in interchangeability for direct replacement of same-specification OEM valves. Every unit undergoes 100% bench testing under simulated working conditions, including rated pressure holding, spool position accuracy, flow linearity, and dynamic response characterization.
Technical Specifications
General Specifications
Model: 4WRZ25W1-220-5X/6A24NZ4/D3M
Product Series: 4WRZ (Size 25 / NG25 / ISO 4401-08 / CETOP 08)
Component Series: 5X
Spool Symbol: W1
Design: Pilot-operated two-stage proportional directional valve, without electrical position feedback
Mounting Pattern: ISO 4401-08-08-0-05
Installation Position: Any
Hydraulic Parameters
Nominal Flow Rate: 220 L/min (at Δp = 10 bar)
Maximum Main Stage Flow: 870 L/min
Maximum Operating Pressure: 350 bar (5075 psi)
Rated Pressure: 315 bar (4568 psi)
Hydraulic Fluid: Mineral-based hydraulic oil (HL, HLP, HLPD, HVLP, HVLPD) and HFC fluids
Fluid Temperature Range: -20°C to +80°C
Filtration: ISO 4406 19/17/14
Electrical Parameters
Supply Voltage: 24 VDC (6A24N)
Command Signal: 0-10 V voltage input / 4-20 mA current input (external amplifier required)
Solenoid Type: Proportional solenoid
Integrated Electronics: Without OBE (external amplifier required)
Electrical Connector: D3 type plug (per DIN EN 175301-803)
Protection Class: IP65 (with standard connector)
Materials & Construction
Valve Body: High-strength cast iron
Control Spool: Carburized steel, precision ground
Seals: NBR (standard) / FKM (optional)
Surface Treatment: Phosphating / anti-corrosion coating
Weight
Key Technical Advantages
1. Pilot-Operated Two-Stage Control with High Flow Capacity
The 4WRZ25W1-220-5X employs a pilot-operated two-stage control structure where the pilot stage is actuated by proportional solenoids and the main spool is positioned by pilot pressure, achieving flow capacity up to 870 L/min. The main stage features spring-centered design; with de-energized solenoids, the main control spool is held in the central position by the centering spring. The main control spool is controlled by the pilot control valve and proportionally moved to the electric input signal, with connection from P to A and B to T via orifice-type cross-sections with progressive flow characteristics. Pilot oil supply can be internal via port P or external via port X, offering high flexibility.
2. High Contamination Tolerance for Industrial Environments
Compared to servo valves with stringent fluid cleanliness requirements, the 4WRZ25W1-220-5X offers excellent contamination tolerance, making it particularly suitable for industrial field environments. The pilot-operated structural design and optimized spool metering notches provide high-accuracy flow control while maintaining tolerance to particulate contamination, effectively reducing downtime risks caused by spool binding and lowering maintenance frequency and operating costs.
3. Precision Spool Machining with Progressive Flow Control
The control spool is precision-ground from carburized steel. Metering notches are precision-machined on the spool lands, delivering progressive linear flow characteristics during spool shifting. Combined with precision-machined spool and bore, the clearance is controlled at micron level, maintaining low internal leakage and responsive shifting performance at 350 bar operating pressure. The nominal flow of 220 L/min (at 10 bar pressure drop) meets the precise flow control demands of medium-to-high flow hydraulic systems.
4. Manual Override and System Safety Assurance
This model is equipped with a concealed manual override (Z4 option) that allows the spool to be manually operated in case of power failure or solenoid malfunction, ensuring safe system shutdown or emergency operation. With de-energized solenoids, the main control spool is automatically returned to the central position by the centering spring, ensuring a safe system state. Caution is advised as accidental activation of the manual override may lead to uncontrolled machine movements.
5. 100% Simulated Working Condition Testing and Drop-in Interchangeability
Every 4WRZ25W1-220-5X/6A24NZ4/D3M valve undergoes 100% bench testing prior to shipment, covering 350 bar rated pressure holding, spool position accuracy calibration, flow-signal linearity verification, internal leakage measurement, and solenoid response characterization. Mounting dimensions, port positions, electrical interfaces, and performance curves are strictly matched to the original Rexroth valve, enabling direct drop-in replacement without modifying piping or control programs.
Application Areas
Injection Molding Machines: Injection speed and holding pressure proportional control, mold closing and injection action precise control
Hydraulic Presses: Proportional speed and direction regulation for medium-to-high flow systems
Die Casting Machines: Shot speed and intensification pressure precise regulation
Metallurgical Equipment: Continuous casting machines, rolling mill auxiliary hydraulic control
Construction Machinery: Excavator and crane hydraulic drive system direction and flow control
Testing Equipment: Force-displacement closed-loop control for material testing
Wind Power Generation: Pitch control system hydraulic directional control
Marine & Offshore: Offshore platform hydraulic control systems
Expert Maintenance Tips
Installation Guidelines
The 4WRZ25W1-220-5X series can be mounted in any position. Mounting surface flatness must be ≤ 0.05 mm. Tighten mounting bolts diagonally in stages to the specified torque value. The mounting surface conforms to ISO 4401-08, facilitating quick installation and system integration with hydraulic manifolds or subplates.
Thoroughly flush all piping circuits before installation. Ensure no welding slag, metal chips, or particulate contaminants remain. Prior to first operation, circulate the system through a 10 μm filter element for a minimum of 30 minutes.
Electrical connections must use a D3 type plug (per DIN EN 175301-803) to maintain IP65 protection. This valve does not include OBE and requires an external proportional amplifier. Control signal cables should be shielded, with the shield grounded at one end.
Routine Maintenance Procedures
Fluid Cleanliness Management: Maintain system fluid cleanliness at ISO 4406 19/17/14 or better. Check fluid particulate contamination every 500 operating hours and replace filter elements and hydraulic fluid when contamination exceeds limits. Although this valve offers better contamination tolerance than servo valves, maintaining fluid cleanliness remains key to extending service life.
Electrical Zero Point Verification: Periodically check the electrical zero point for drift with the power supply disconnected. If zero point deviation exceeds ± 2%, re-calibrate via the external amplifier.
Coil Resistance Verification: Measure solenoid coil resistance every 1,000 operating hours. Deviation from factory value should not exceed ± 10%.
Internal Leakage Monitoring: Due to the design principle, pilot-operated proportional valves have inherent internal leakage which may increase over the life cycle. An annual internal leakage test is recommended. If leakage exceeds 150% of the factory standard, seal replacement should be scheduled.
Manual Override Precautions: Periodically check that the manual override is in the non-activated state to prevent accidental activation leading to uncontrolled machine movements. If manual operation is required, proceed cautiously after system depressurization.
