4WRH25W6-325-7X//V

The 4WRH25W6-325-7X//V proportional directional valve is part of the WRZ Proportional Directional Valves series produced by Bosch Rexroth for closed-loop hydraulic automation where spool position controls actuator speed and direction. The main flow path handles up to 870 l/min so high-capacity cylinders or motors can be driven without excessive pressure drop. During normal operation at 10 bar differential, the valve delivers a nominal flow of 325 l/min, giving predictable linear control around the mid-stroke. A maximum operating pressure of 350 bar allows connection directly to high-pressure supply manifolds used in heavy machinery. The pilot circuit tolerates 25 bar, enabling use with standard low-pressure pilot pumps while safeguarding the control edges. Pilot oil is supplied externally and is also drained externally, letting the designer isolate the pilot loop from system back-pressure for consistent modulation. A pilot oil volume of 10 cm³ moves the spool from 0 to 100 %, which influences response time and sizing of the pilot lines. The manifold interface follows ISO 4401-08-07-0-94 so the valve bolts to common size 08 subplates without extra adapters. Ports A, B, and T have a 25 mm diameter to keep velocity losses low on both work and return lines.

The pressure inlet P uses a 24 mm passage, providing slightly thicker wall sections that withstand inlet pulsation. When the return flow leaves through the external T port, the circuit may build up to 250 bar, making the valve suitable for accumulator-charged regeneration loops. If the T port is piped internally, admissible back-pressure falls to 30 bar to avoid overstressing internal galleries. Port Y is limited to 30 bar, protecting the pilot drain cavity from pressure spikes transferred through the housing. Mounting surface flatness must stay within 0.01 mm per 100 mm so the housing seats evenly on the subplate. A surface roughness not exceeding Rzmax 4 supports reliable sealing by eliminating micro-channels along the interface. FKM seals are fitted, allowing the unit to operate with high-temperature mineral oils and many synthetic fluids. Together, these limits and material choices let the proportional spool maintain precise positioning even under variable load, pressure, and return conditions.