Product Overview
The Parker R4R03-59511P2G0RB110 (also referenced as 026-66128-G) is a pilot operated pressure reducing valve from Parker’s R4R series of industrial hydraulic pressure control valves. It is designed to maintain a constant, precisely regulated outlet pressure regardless of fluctuations in inlet pressure or changes in downstream flow demand. The valve operates on a two-stage pilot principle: an adjustable pilot stage senses outlet pressure and modulates the main spool, which throttles the flow from the high-pressure inlet to the reduced-pressure outlet port. This design delivers accurate pressure regulation, fast response to dynamic load changes, and excellent stability across the full operating range. The R4R03-59511P2G0RB110 is a direct-fit, drop-in replacement for OEM part 026-66128-G and is engineered for continuous duty in demanding industrial hydraulic circuits.
Technical Specifications
| Parameter | Specification / Feature |
|---|---|
| Component Type | Pilot Operated Pressure Reducing Valve (Pressure Control Valve) |
| Model Designation | R4R03-59511P2G0RB110 / 026-66128-G |
| Manufacturer | Parker Hannifin |
| Series | R4R Series — Pilot Operated Pressure Reducing |
| Operating Pressure | Standard Industrial Grade (up to 350 bar rated inlet) |
| Regulation Principle | Two-stage pilot operated, adjustable spring-loaded pilot stage |
| Mounting & Connection | Standard ISO / Manufacturer Interface (subplate or manifold mounting) |
| Adjustment | Manual adjustment via protected set screw / adjustment knob |
| Fluid Compatibility | Mineral-based hydraulic oils (HLP / HM), standard industrial viscosity range |
Engineering Features & Advantages
- Precision Performance: The two-stage pilot operated design maintains a constant reduced outlet pressure with minimal deviation, even under widely varying inlet pressure and downstream flow conditions, ensuring repeatable process control.
- Stable Regulation: The pilot stage isolates the main spool from pressure surges, delivering smooth, chatter-free operation and protecting downstream actuators, cylinders, and instrumentation from pressure spikes.
- Industrial Reliability: Built for continuous operation under severe industrial conditions, with hardened spool and sleeve components for long service life and consistent metering performance.
- Direct Fit Replacement: Exact dimensional and functional compatibility with original OEM standards, allowing drop-in replacement for Parker 026-66128-G without modification to the manifold or piping.
- Direct Fit Replacement: Precision-manufactured to original PARKER specifications for direct replacement, minimising downtime and eliminating fitment issues.
Typical Industrial Applications
The R4R03-59511P2G0RB110 is a direct-fit, drop-in replacement for OEM part 026-66128-G and is engineered for continuous duty in demanding industrial hydraulic circuits.
PRODUCT IMAGES




PARKER R4R03-59511P2G0RB110 / 026-66128-G Pilot Operated Pressure Reducing Valve
⚡ Emergency Plant Maintenance & Ready-to-Ship Notice:
- Authentic & Fully Tested: 100% bench tested for hydraulic response, pressure rating, and null-bias stability before dispatch.
- Fast Dispatch: In-stock units ready for same-day dispatch via DHL / FedEx Express directly to your plant.
- Pre-Shipment Verification: High-definition photos, video testing runs, and serial number verification provided prior to shipment.
- Peace of Mind: Covered by our 12-Month Replacement Warranty.
Shop the genuine PARKER R4R03-59511P2G0RB110 / 026-66128-G Solenoid Directional Control Valve. This Germany-made 110V AC hydraulic component features a robust spool design, delivering leak-free, reliable fluid control for heavy-duty industrial systems.





