Rexroth A7VO28DR/63L-NPB01 Variable Hydraulic Pump

Rexroth A7VO28DR/63L-NPB01 Hydraulic Axial Piston Variable Pump (MNR: 2011918)

The Bosch Rexroth A7VO28DR/63L-NPB01 (Material Number / MNR: 2011918) is an axial tapered piston variable displacement pump with a bent-axis rotary group engineered for open-circuit hydrostatic power systems. Built on Rexroth’s Series 63 architecture, this bent-axis unit handles high dynamic shock loads and operating pressures up to 350 bar nominal and 400 bar maximum peak.

The integrated DR pressure controller maintains constant system pressure regardless of changing flow demands by destroke regulation. The unit’s tapered piston rings, spherical control plate lens, and heavy-duty rotary assembly make it suitable for marine deck winches, cranes, and heavy offshore machinery where continuous service and thermal stability are required.

Key Features

1. Bent-Axis Swashplate-Free Rotary Architecture: Uses self-aligning axial tapered pistons with solid piston rings in a tilted cylinder block, minimizing mechanical shear and internal leakage under continuous 350 bar duty cycles.
2. High Hydrostatic & Thermal Efficiency: Delivers volumetric efficiencies exceeding 93% across broad viscosity ranges (16 to 36 mm²/s optimal), lowering oil cooling requirements in confined engine and pump rooms.
3. Built-in S-to-A Fluid Dynamic Loop: Optimized suction and working port profiles mitigate localized cavitation during cold starts (down to -40°C start-up limit with appropriate fluid viscosity).
4. Rugged Heavy-Duty Housing (ISO 3019-2 Standard): Includes an ISO 4-bolt round flange mounting interface with a high-strength 25 mm keyed shaft capable of withstanding torsional vibration from direct electric motor or PTO couplings.

Direct Equipment Compatibility

• Marine & Offshore Systems: Hydraulic power units for MacGregor and TTS hatch cover opening systems, mooring line tensioners, anchor windlass units, crane slew/luff drives, capstan hoists, and deck cargo winches.
• Industrial & Material Handling: Injection molding core-pull circuits, aluminum extrusion press auxiliaries, balers, sheet metal press feeds, and continuous-duty hydraulic power units (HPUs).
• Construction & Mining: Rotary drilling drive circuits, trenching attachments, heavy mobile cranes, and transit concrete mixers.

Applications

• High-pressure continuous open-circuit power generation.
• Auxiliary hydraulic supply for marine deck gear requiring localized pressure control.
• Constant-pressure closed-center hydraulic systems requiring zero-stroke idle to avoid oil overheating.
• Variable delivery applications where electrical remote displacement command is not required.

Frequently Asked Questions

What does “DR” control signify on this Rexroth A7VO pump?

The DR control stands for Pressure Control (or Pressure Cut-off). When downstream load resistance drives system pressure up to the DR control setpoint, the pump automatically swivels back from maximum stroke towards zero displacement. It provides only enough flow to compensate for internal leakage and hold line pressure constant, saving power and avoiding heat generation from fluid dumping over relief valves.

Can an A7VO28DR/63L pump be run in a clockwise direction?

No. The rotary group, control lens plate, and internal fluid timing ports are optimized specifically for counter-clockwise rotation (indicated by the “L” suffix in the model code). Running this unit clockwise will draw oil backwards and destroy the valve plate and pistons within minutes. If your drive motor turns counter-clockwise, you must purchase the “63R” clockwise variant.

What is the difference between NPB01 and NZB01 designations?

The letters indicate drive shaft and mounting executions: “P” denotes a cylindrical keyed drive shaft (parallel key according to DIN 6885), whereas “Z” specifies a splined shaft execution. Both feature the “B” 4-bolt metric ISO mounting flange and “01” standard port configurations.

Which hydraulic fluid is recommended for this pump in marine conditions?

High-grade mineral oil-based hydraulic fluids with anti-wear additives conforming to DIN 51524 part 2 (HLP) or ISO 11158 (HM/HV) are recommended. The fluid viscosity should ideally remain between 16 and 36 mm²/s during sustained continuous operation, never exceeding 1600 mm²/s during short cold starts.