A4CSG355 A4CSG355EPD/30R-VZB35F994M Piston Pump | 350 bar | Rexroth

Product Overview

The A4CSG series axial piston variable displacement pumps represent a flagship product line within the Bosch Rexroth hydraulic transmission platform, featuring the proven swashplate axial piston design specifically developed for closed-circuit hydrostatic drive systems. The series offers four displacement sizes — 250, 355, 500, and 750 — covering applications from medium-duty to heavy-duty mobile and industrial equipment.

This product covers the A4CSG355 model, with the complete model code PA4CSG355EPD/30R-VZB35F994M and material number R902437353. The pump features EPD electro-hydraulic proportional control with dual pressure control functionality for both ports A and B — the premium control configuration within the A4CSG 355 range.

100% Interchangeability Guarantee: Our products strictly adhere to Bosch Rexroth A4CSG original mounting dimensions and port layouts, enabling drop-in replacement without modifications to existing piping or brackets. Every unit undergoes 100% simulated duty-cycle testing under actual load conditions to validate performance parameters before shipment, ensuring immediate reliability upon installation.

Quality & Manufacturing Standards: The housing is manufactured from high-strength cast iron, with critical tribological pairs (cylinder barrel/valve plate, pistons/slippers) precision-ground and heat-treated. An integrated charge pump and associated valve groups are built into the pump body, providing stable charge pressure and control oil supply for closed-circuit operation. The compact short-length design delivers an exceptional power-to-weight ratio.

ATEX Explosion-Proof Certification: The A4CSG Series 30 is ATEX-certified for use in explosive atmospheres (II 2G Ex h IIC T4-T1 Gb X and II 3G Ex h IIC T4-T1 Gc X).

Technical Specifications 

Series General Specifications (A4CSG Series 30):

• Design: Swashplate axial piston variable displacement pump

• Circuit Type: Closed circuit (hydrostatic drive)

• Rated Pressure: 350 bar (5,100 psi)

• Peak Pressure: 400 bar (5,800 psi)

• Control Type: EPD (electro-hydraulic proportional control with dual pressure control for ports A and B)

• Charge Pump: Integrated charge pump providing charge pressure and control oil supply

• Mounting Flange: Based on ISO 3019-2 (metric), 4-bolt

• Drive Shaft: Splined shaft DIN 5480

• Main Ports: SAE A and B flange connections (opposite sides, metric mounting thread); SAE S flange connection (offset laterally 90° relative to A and B, metric fastening thread)

• Rotation: R (clockwise)

• Explosion Protection: ATEX II 2G Ex h IIC T4-T1 Gb X / II 3G Ex h IIC T4-T1 Gc X

A4CSG355 (PA4CSG355EPD/30R-VZB35F994M):

• Complete Model Code: PA4CSG355EPD/30R-VZB35F994M

• Material No.: R902437353

• Displacement (Vg max): 355.0 cm³/rev

• Rated Pressure: 350 bar

• Peak Pressure: 400 bar

• Maximum Speed @ Vg max: 2,000 rpm

• Minimum Speed: 800 rpm

• Theoretical Flow (@ 2,000 rpm): 710 L/min

• Drive Power: 414 kW

• Weight: Approx. 235–275 kg (configuration-dependent)

• Control Type: EPD (electro-hydraulic proportional control with dual pressure control for ports A and B)

• Rotation: R (clockwise)

• Mounting Flange: Based on ISO 3019-2 (metric), 4-bolt

• Drive Shaft: Splined shaft DIN 5480

Key Technical Advantages

1. EPD Electro-Hydraulic Proportional Pressure Control — Independent Dual-Port Pressure Regulation
The EPD control utilizes electro-hydraulic proportional solenoids, with pump displacement varying proportionally to solenoid current. The EPD version features dedicated pressure control for both ports A and B, enabling independent pressure limiting for each working direction. This is particularly critical in closed-circuit traction and swing drive applications — forward and reverse pressure limits can be independently optimized, significantly enhancing control flexibility and system safety. A visual swivel angle indicator is standard, enabling quick on-site monitoring of pump status.

2. Integrated Charge Pump and Valve Group — Highly Integrated Design
The A4CSG series integrates the charge pump and associated valve groups (charge pressure valve, control oil circuit valves, high-pressure circuit valves) directly within the pump body. This highly integrated design drastically reduces external piping and accessory requirements, lowering system leakage risks and installation/maintenance costs while significantly reducing overall installation footprint.

3. Compact Design and Exceptional Power-to-Weight Ratio
The A4CSG355 features an extremely compact short-length design, delivering industry-leading power-to-weight ratio at 355 cc displacement. For mobile equipment demanding high power density with constrained installation space, this translates directly into layout flexibility and overall machine performance improvement.

4. ATEX Explosion-Proof Certification — Safe for Hazardous Environments
The A4CSG Series 30 is ATEX-certified (II 2G Ex h IIC T4-T1 Gb X and II 3G Ex h IIC T4-T1 Gc X). This certification enables safe deployment in explosive atmospheres such as coal mines, oil & gas, and chemical facilities — making it the ideal hydraulic power source for mining machinery and explosion-proof equipment.

5. Long Service Life, High Efficiency and Low Noise
Precision-ground cylinder barrel/valve plate tribological pairs and optimized internal leakage control strategies deliver exceptional overall efficiency. High-strength cast iron housing, high-capacity bearings, and precision heat-treated piston/slipper assemblies ensure long-term reliability under 400 bar peak pressure. Optimized fluid通道 design and precision manufacturing deliver low operating noise characteristics.

6. Through-Drive and Tandem Pump Stack Capability
The A4CSG series supports through-drive design, enabling tandem mounting of additional hydraulic pumps on the same axis for flexible expansion of complex hydraulic systems.

Application Areas

The A4CSG355EPD swashplate axial piston variable pump is widely deployed in closed-circuit hydrostatic drive systems across the following applications:

• Tracked and Wheeled Construction Machinery — traction drive systems (bulldozers, loaders, excavators)

• Mining Machinery — hydrostatic traction drives for underground loaders and haulers (ATEX hazardous environment suitable)

• Agricultural Machinery — hydrostatic drives for large combine harvesters and tractors

• Material Handling Equipment — traction and implement drives for heavy forklifts and reach stackers

• Road Construction Machinery — traction drives for asphalt pavers and rollers

• Specialty Vehicles — hydrostatic transmissions for military vehicles and airport ground support equipment

• Industrial Hydraulic Systems — hydraulic power units for large presses and test benches

Expert Maintenance Tips

1. Housing Priming Before Installation (Critical Step)
Before initial start-up or after extended downtime, the housing must always be filled with hydraulic fluid. Pre-fill through case drain ports prior to start-up. Dry-running at start-up will cause irreversible damage to critical tribological pairs (cylinder barrel/valve plate, pistons/slippers).

2. Charge Pressure Monitoring
The A4CSG series relies on the integrated charge pump for stable charge pressure and control oil supply. Continuously monitor charge pressure during operation — if charge pressure drops below the 8 bar minimum, shut down the system immediately. Insufficient charge pressure will result in sluggish control response, inadequate lubrication, and potential pump failure.

3. Case Pressure Limits
Case pressure during A4CSG series operation must not exceed 3 bar (momentary peaks up to 6 bar, t < 0.1 s, are permissible). Ensuring unrestricted case drain return with zero back pressure is critical for shaft seal life and pump reliability.

4. Filtration and Fluid Cleanliness
Axial piston pumps are highly sensitive to fluid cleanliness. HLP mineral oil per DIN 51524 is recommended, with filtration cleanliness level of ISO 4406 19/17/14 or better. Return line and suction filters should be inspected and replaced regularly.

5. Initial Start-Up and Break-In
For first-time operation, run the pump at low speed (idle) with no load for 5–10 minutes to purge air from the system and allow proper oil film establishment on all tribological pairs before gradually applying load.

6. EPD Control Tuning Considerations
EPD electro-hydraulic proportional control requires PWM (pulse-width modulation) current-regulated control units. During commissioning, systematically set pressure limits for ports A and B per the technical manual to avoid conflicting pressure settings between the two ports. The standard visual swivel angle indicator enables quick on-site verification of pump displacement status.