DR20-4-4X/100Y | Rexroth Pressure Reducing Valve 315bar 160L/min

Product Overview

The DR20-4-4X/100Y (Material Number R900404826) is a classic model in the Bosch Rexroth DR series of pilot-operated pressure reducing valves, NG20 size. The DR series is designed to limit, reduce, or control system pressure. The valve primarily consists of a pilot valve, main valve with main spool insert, and housing.

The DR20-4-4X/100Y features pilot-operated construction with pilot oil supplied internally and returned externally via port Y. In its default state, hydraulic fluid flows freely from the inlet to the outlet channel, with system pressure regulated by a spring-loaded main control spool. When outlet pressure exceeds the spring setting, the pilot poppet activates, directing fluid into the spring chamber and enabling the main control spool to maintain consistent outlet pressure. This model features mechanical adjustment with a rotary knob.

As an original Bosch Rexroth pilot-operated pressure reducing valve, this product offers complete interchangeability within the same series and size, requiring no modifications to mounting interfaces or piping layouts.

Model Code Breakdown (DR20-4-4X/100Y):

• DR: Pilot-operated Pressure Reducing Valve

• 20: Nominal Size NG20 (flow capacity 160 L/min)

• 4: Pressure grade code (100 bar pressure grade)

• 4X: 4X Component Series (40–49, unchanged installation and connection dimensions)

• 100: Pressure setting (100 bar)

• Y: Pilot oil supply configuration — internal supply, external return via Y port

Technical Specifications 

• Model: DR20-4-4X/100Y

• Material Number: R900404826

• Brand: BOSCH REXROTH

• Product Type: Pilot-operated Pressure Reducing Valve

• Nominal Size: NG20

• Component Series: 4X (40–49, unchanged installation and connection dimensions)

• Maximum Operating Pressure: 315 bar (4568 psi) 

• Maximum Flow Rate: 160 L/min (42 GPM) 

• Pressure Setting: 100 bar

• Adjustment Type: Rotary Knob

• Pilot Oil Supply: Internal

• Pilot Oil Return: External via Y port

• Seal Material: NBR

• Weight: 3.58 kg

• Connection Type: Subplate Mounting

• Hydraulic Fluids: HL, HLP, HLPD, HVLP, HVLPD mineral oils

• Operating Temperature Range: -20°C to +70°C

• Viscosity Range: 10–500 mm²/s

• Recommended Cleanliness: ISO 4406 18/16/13 or better

Key Technical Advantages

1. Pilot-Operated Design — High-Pressure High-Flow with Precise Control

The DR20-4-4X/100Y features pilot-operated construction. Compared to direct-acting pressure reducing valves, the pilot-operated design delivers superior pressure/flow stability, lower hysteresis, and more precise pressure control. Maximum flow reaches 160 L/min with a maximum operating pressure of 315 bar, placing it at the forefront of pressure reducing valves in its class.

2. Internal Pilot Supply with External Y-Port Return

This valve features internal pilot oil supply with external return via port Y. The external pilot oil return ensures stable pilot control circuit performance, preventing return line back pressure from interfering with the set pressure. Pressure at port Y is added 1:1 to the set reduced pressure.

3. 4X Component Series — Proven Standardized Platform

The DR20-4-4X/100Y belongs to the 4X Component Series (40–49). The 4X series represents Rexroth‘s standardized DR valve platform with stable installation and connection dimensions, offering complete interchangeability for convenient maintenance and replacement.

4. Rotary Knob Adjustment for Easy Operation

Equipped with a rotary knob adjustment element. Intuitive operation enables convenient pressure setting adjustment under system operating conditions. The DR series also offers multiple adjustment types including hexagon bushing, lockable rotary knob with scale, and rotary knob with scale.

5. NBR Seals with Multi-Fluid Compatibility

Equipped with NBR seals, compatible with HL, HLP, HLPD, HVLP, HVLPD, and other mineral oil-based hydraulic fluids. For phosphate ester and other specialty fluids, FKM (fluoroelastomer) seals are available.

6. International Standard Compliance for Global Interchangeability

Mounting conforms to Rexroth DR series standard interfaces. Fully compatible with globally adopted NG20 size interfaces for direct replacement of same-series, same-specification products.

Application Areas

• Injection Molding Machinery — Precise pressure control for secondary hydraulic circuits

• Hydraulic Presses and Forging Equipment — Pressure switching and regulation for slide advance and return

• CNC Machine Tools — Precise pressure control for hydraulic clamping and unclamping

• Die-Casting Machines — Pressure staging for high-pressure casting equipment

• General Industrial Hydraulic Systems — Various applications requiring main system pressure reduction for sub-circuits

• Steel and Mining Equipment — Pressure control for rolling mills and heavy-duty systems

Expert Maintenance Tips

1. Installation Guidelines

• DR20-4-4X/100Y is subplate mounting type. Mounting surface must conform to Rexroth DR series standard interfaces.

• Thoroughly clean the mounting surface and all ports before installation to prevent foreign particles from entering and causing spool sticking or seal damage.

• Tighten mounting bolts evenly to the specified torque to ensure proper sealing between the valve body and mounting surface.

2. Y-Port Pilot Oil Return Considerations

• Pressure at port Y is added 1:1 to the set reduced pressure.

• Ensure the Y-port return line has no back pressure or has constant back pressure during system design—otherwise, the outlet pressure setting will be directly affected (every 1 bar increase in Y-port back pressure increases the outlet pressure setting by 1 bar).

• The Y-port return line should be routed directly to the tank, avoiding shared return lines with other circuits.

3. Hydraulic Fluid Cleanliness

• Compatible fluids: HL, HLP, HLPD, HVLP, HVLPD mineral oils.

• Seal material: NBR . For phosphate ester and other specialty fluids, select FKM (fluoroelastomer) seals.

• Recommended fluid cleanliness: ISO 4406 18/16/13 or better.

• Install a return line filter with minimum 10 μm filtration rating.

4. Pressure Setting Adjustment

• DR20-4-4X/100Y factory pressure setting: 100 bar.

• Pressure adjustment is performed via the rotary knob—turn clockwise to increase, counterclockwise to decrease.

• Adjust gradually under system operating conditions to achieve the desired pressure value.

5. Periodic Maintenance Inspection

• Inspect the valve body for external oil leakage every 2,000 operating hours or at least annually.

• If reduced pressure instability or slow response is observed, first check system fluid cleanliness and verify the pilot spool is not sticking.

• Periodically check that the Y-port return line is clear to prevent abnormal back pressure from affecting setting accuracy.

• If required, a subplate mounting version (P version) with check valve is available for free return flow from A to B.