A4VG250HD3D1 A4VG250EP2D1 Rexroth Piston Pump 250cc

Product Overview

The A4VG250HD3D1/32R-NSD10F021S, A4VG250HD3D132R-NSD10F00, and A4VG250EP2D1/32R-NSD10F001DH-S are the 250 cc-class core models within the Bosch Rexroth A4VG series 32 of swashplate axial piston variable displacement pumps. The A4VG series is Rexroth’s flagship platform for closed-circuit hydrostatic transmissions, spanning displacements from 28 to 250 cm³/rev with a nominal pressure of 400 bar and peak pressure of 450 bar, widely deployed in construction machinery travel drives, concrete mixer drum drives, and industrial hydraulic systems.

The A4VG series features a swashplate design where flow is proportional to drive speed and displacement and is infinitely variable. The pump is equipped with two pressure-relief valves on the high pressure ports to protect the hydrostatic transmission (pump and motor) from overload, with the high-pressure relief valves also functioning as boost valves. The integrated boost pump acts as a feed and control oil pump, with maximum boost pressure limited by a built-in low-pressure relief valve. The integral pressure cut-off is standard across the range.

Model Code Breakdown (for procurement and engineering reference):

A4VG250HD3D1/32R-NSD10F021S:

• A4VG: Rexroth closed-circuit swashplate axial piston variable pump

• 250: Nominal size (NG), geometric displacement 250 cm³/rev

• HD3: Proportional control hydraulic, pilot-pressure related

• D1: Control variant code

• /32R: Series 32, clockwise rotation (viewed from shaft end)

• NSD10F021S: N = NBR seals; SD = mounting flange and port code; 10 = design variant; F021 = factory calibration code; S = additional configuration identifier

A4VG250EP2D1/32R-NSD10F001DH-S:

• A4VG: Rexroth closed-circuit swashplate axial piston variable pump

• 250: Nominal size (NG), geometric displacement 250 cm³/rev

• EP2: Electric proportional control, with proportional solenoid, 24V supply, with pressure cut-off, without DA control valve

• D1: Control variant code

• /32R: Series 32, clockwise rotation (viewed from shaft end)

• NSD10F001DH-S: N = NBR seals; SD = mounting flange and port code; 10 = design variant; F001 = factory calibration code; DH = additional configuration identifier; S = seal material designation

HD3 Control Function Details:

HD3 is a hydraulic proportional control, pilot-pressure related. Electrical energy is converted to pilot pressure signals via proportional solenoids, driving the servo piston through a hydraulic pilot valve to change the swashplate inclination angle for stepless displacement adjustment. Pump displacement is proportional to the pilot pressure signal, precisely adjustable across 0–100%. HD control offers short control response times and high control precision, particularly suitable for mobile hydraulic systems requiring remote or automated displacement control.

EP2 Control Function Details:

EP2 is an electric proportional control, equipped with proportional solenoids (24V supply), with pressure cut-off function, without DA control valve. Pump output flow is infinitely variable in the range of 0 to 100%, proportional to the current signal. EP2 control uses proportional valve direct control of the stroking piston, offering simple structure and strong contamination resistance. As the stroking piston moves, it drives the feedback lever to rotate around a fixed pivot, which in turn drives the servo balance lever to oscillate, achieving precise closed-loop displacement control.

Drop-in Replacement Advantage: Manufactured to exact Rexroth OEM specifications, these pumps achieve complete drop-in interchangeability with the original A4VG series 32 for SAE J744 mounting flange, shaft dimensions, SAE main port layout, and control module interface. Every pump undergoes 100% simulated load testing prior to shipment, validating 400 bar pressure loading, control response, and volumetric efficiency under conditions replicating real-world duty cycles.

Technical Specifications 

A4VG250 Series General Specifications:

• Series: Rexroth A4VG Series 32 (Closed Circuit, Swashplate Design)

• Nominal Size: NG 250

• Geometric Displacement (Variable Pump): 250 cm³/rev

• Auxiliary Pump Displacement (p = 20 bar): 52.5 cm³/rev

• Nominal Pressure: 400 bar (continuous)

• Peak Pressure: 450 bar (intermittent)

• Continuous Maximum Speed (nnom): 2400 rpm

• Limited Maximum Speed (nmax1): 2600 rpm

• Intermittent Maximum Speed (nmax2): 2700 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (nnom, Vg max): 600 L/min

• Maximum Power (Δp = 400 bar): 400 kW

• Maximum Torque (Vg max, Δp = 400 bar): 1590 N·m

• Torque (Vg max, Δp = 100 bar): 398 N·m

• Moment of Inertia: 0.0983 kgm²

• Maximum Angular Acceleration: 6700 rad/s²

• Filling Capacity: 6.3 L

• Housing Material: High-strength cast iron

• Seal Material: NBR (nitrile rubber), shaft seal FKM

• Weight: Approx. 156 kg

Model A4VG250HD3D1/32R-NSD10F021S Configuration:

• Model Code: A4VG250HD3D1/32R-NSD10F021S

• Control Type: HD3 — Hydraulic Proportional Control, Pilot-Pressure Related

• Rotation: Clockwise (viewed from shaft end, R code)

• Series: 32

• Factory Calibration: NSD10F021S configuration

Model A4VG250EP2D1/32R-NSD10F001DH-S Configuration:

• Model Code: A4VG250EP2D1/32R-NSD10F001DH-S

• Control Type: EP2 — Electric Proportional Control, 24V proportional solenoid, with pressure cut-off, without DA control valve

• Rotation: Clockwise (viewed from shaft end, R code)

• Series: 32

• Factory Calibration: NSD10F001DH-S configuration

A4VG Series Displacement Size Reference:

• A4VG28: 28 cm³/rev, nnom 4250 rpm, flow 119 L/min, power 79 kW, weight 29 kg

• A4VG40: 40 cm³/rev, nnom 4000 rpm, flow 160 L/min, power 107 kW, weight 31 kg

• A4VG56: 56 cm³/rev, nnom 3600 rpm, flow 202 L/min, power 134 kW, weight 38 kg

• A4VG71: 71 cm³/rev, nnom 3300 rpm, flow 234 L/min, power 156 kW, weight 50 kg

• A4VG90: 90 cm³/rev, nnom 3050 rpm, flow 275 L/min, power 183 kW, weight 60 kg

• A4VG125: 125 cm³/rev, nnom 2850 rpm, flow 356 L/min, power 237 kW, weight 80 kg

• A4VG180: 180 cm³/rev, nnom 2500 rpm, flow 450 L/min, power 300 kW, weight 101 kg

• A4VG250: 250 cm³/rev, nnom 2400 rpm, flow 600 L/min, power 400 kW, weight 156 kg

Key Technical Advantages

1. HD3 Hydraulic Proportional Control with Pilot Pressure Precision
The A4VG250HD3D1/32R-NSD10F021S is equipped with the HD3 hydraulic proportional control, pilot-pressure related module. Electrical energy is converted to pilot pressure signals via proportional solenoids, driving the servo piston through a hydraulic pilot valve to change the swashplate inclination angle for stepless displacement adjustment. Pump displacement is proportional to the pilot pressure signal, precisely adjustable across 0–100%. HD control offers short control response times and high control precision, particularly suitable for mobile hydraulic systems requiring remote or automated displacement control. The HD control module features relatively simple construction with superior contamination resistance and reliability compared to electro-hydraulic servo control.

2. EP2 Electric Proportional Control with Precise Displacement Regulation
The A4VG250EP2D1/32R-NSD10F001DH-S is equipped with the EP2 electric proportional control module, driven by a 24V proportional solenoid, with pressure cut-off function, without DA control valve. Pump output flow is infinitely variable in the range of 0 to 100%, proportional to the current signal. EP2 control uses proportional valve direct control of the stroking piston, offering simple structure, low manufacturing cost, and strong contamination resistance. As the stroking piston moves, it drives the feedback lever to rotate around a fixed pivot, which in turn drives the servo balance lever to oscillate, achieving precise closed-loop displacement control, particularly suitable for mobile equipment applications requiring remote or automated displacement control.

3. Integrated Boost Pump with Closed-Circuit Protection System
The A4VG series incorporates an integrated boost pump with a displacement of 52.5 cm³/rev (at p = 20 bar), serving as both feed pump and control oil pump. The pump is equipped with two pressure-relief valves on the high pressure ports to protect the hydrostatic transmission from overload. The high-pressure relief valves also function as boost valves. Maximum boost pressure is limited by a built-in low-pressure relief valve. The integral pressure cut-off is standard, automatically reducing pump displacement to zero when system pressure reaches the setpoint.

4. High-Strength Cast-Iron Housing with Wide Temperature Adaptability
The pump body is precision-cast from high-strength cast iron, with the material’s damping characteristics effectively suppressing structural vibration and fluid-borne noise. The wide operating temperature range accommodates extreme ambient temperatures from -40°C to +90°C, particularly suitable for mobile hydraulic equipment operating outdoors and in harsh conditions. The low-inertia rotating group design (0.0983 kgm²) and high angular acceleration (6700 rad/s²) ensure excellent system dynamic response characteristics.

5. Through Drive and Modular System Expansion
The A4VG series supports through drive, allowing direct mounting of subsequent pumps of same or smaller size on the rear of the main pump for single-motor multi-pump compound hydraulic systems. Modular control designs enable field conversion and upgrade. Standardized SAE J744 mounting flange and shaft require no adaptation for replacement, significantly reducing equipment downtime.

6. Wide Seal Compatibility with Hydraulic Fluid Adaptability
The A4VG series is designed for operation with HLP mineral oil (per DIN 51524). The seal material is NBR (nitrile rubber), with shaft seal in FKM (fluoroelastomer). System cleanliness should be maintained at ISO 4406 20/18/15 or better, with recommended viscosity range 16–36 mm²/s, meeting diverse mobile hydraulic application requirements.

Application Areas

• Excavators: Large excavator travel drive closed-circuit hydraulic systems (A4VG250HD3D1 and A4VG250EP2D1 are widely used in large excavator applications)

• Concrete Mixer Trucks: Drum drive closed-circuit hydraulic systems

• Rotary Drilling Rigs: Rotary drilling rig travel drives and main hydraulic systems

• Road Rollers: Large vibratory roller travel drive hydraulic systems

• Construction Equipment: Large wheel loader travel drives, bulldozer hydraulic drives

• Agricultural Machinery: High-horsepower tractor closed-circuit transmissions, combine harvester hydraulic drives

• Mining Equipment: Mining truck hydrostatic drives, underground LHD hydraulic systems

• Industrial Hydraulic Power Units: Closed-circuit hydraulic power units, test bench hydraulic systems

Expert Maintenance Tips

1. Hydraulic Fluid Cleanliness
The A4VG series HD3/EP2 control spool operates with extremely tight clearances and is highly sensitive to particulate contamination. System fluid cleanliness must meet ISO 4406 20/18/15 or better. Recommended fluids are HLP mineral oils (per DIN 51524) with viscosity grades VG46 or VG68. Install a 10 μm absolute-rated filter element at the pump inlet. Replace elements at 500 hours after first commissioning, then every 1,000 operating hours or 6 months, whichever comes first.

2. HD3 Hydraulic Proportional Controller Commissioning
The A4VG250HD3D1/32R HD3 controller drives the servo piston through pilot pressure signals. During commissioning, confirm that pilot pressure supply is normal and the control pressure setting meets system requirements. The core function of the HD3 controller is to achieve stepless displacement adjustment based on pilot pressure signals. After commissioning, verify the stability and response speed of displacement adjustment under variable load conditions. The minimum required control pressure is 30 bar + (Pn-Ps); ensure the pilot pressure source meets this requirement.

3. EP2 Electric Proportional Controller Maintenance
The A4VG250EP2D1/32R is equipped with the EP2 electric proportional control module, with a proportional solenoid supply voltage of 24V. Regularly inspect the proportional solenoid electrical connectors for corrosion, moisture ingress, or loose pins. Verify the control current signal waveform with an oscilloscope every 2,000 hours to ensure proper PWM waveform and accurate displacement control. The EP2 control features a pressure cut-off function; during commissioning, verify that its cut-off pressure setting is approximately 3 MPa lower than the main relief valve setting to ensure proper system protection.

4. Case Drain Line Requirements
The case drain line must return directly to the reservoir. Maximum permissible back pressure is 2 bar (0.2 MPa). The drain outlet must terminate below oil level at all times to prevent air ingestion. The drain line diameter must not be smaller than the pump case drain port size. Case drain temperature (influenced by pressure and speed) may be higher than the control temperature or circuit temperature, but the temperature at any part must not exceed 115°C. Boost pressure should be maintained between 16–25 bar (static maximum), with permissible pressure peaks from 4–40 bar.

5. Pre-Start Priming and Air Bleeding
Before first start, fill the pump housing with clean hydraulic fluid through the case drain port. After installation, turn the drive shaft by hand several revolutions to confirm free rotation without binding. Position the control at neutral (zero displacement) and run at low speed for 5–10 minutes. Verify continuous bubble-free flow from the case drain. Only after confirming adequate lubrication and boost pressure should the pump be loaded. The suction port absolute pressure must be maintained between 0.8 and 30 bar.

6. High-Pressure Relief Valve and Pressure Cut-Off Inspection
The pump’s built-in two high-pressure relief valves protect the hydrostatic transmission from overload and also function as boost valves. Inspect the relief valve setting pressure every 2,000 operating hours to confirm it remains below the 450 bar peak pressure and that the bypass function operates correctly. The high-pressure relief valve setting range is 100–240 bar (with bypass function); confirm the setting meets system requirements during commissioning. The integral pressure cut-off is standard; during commissioning, verify that its cut-off pressure setting is approximately 3 MPa lower than the main relief valve setting to ensure proper system protection.