A4FO22 Rexroth Hydraulic Piston Pump 400bar Fixed Displacement

Product Overview:

The A4FO series from Bosch Rexroth is a fixed-displacement axial piston pump of swashplate design for open circuits. Available in sizes A4FO22, A4FO28, A4FO71, A4FO125, A4FO180 and A4FO250 (example ordering code: A4FO22/31L-NSC12N). Flow is proportional to drive speed and geometric displacement. It offers excellent suction characteristics, low noise and long service life. Manufactured to exact OEM dimensions, interfaces and performance for 100% drop-in interchangeability. Every unit undergoes 100% simulated operating-condition testing to verify pressure, flow and sealing integrity under high-pressure industrial and mobile hydraulic demands.

Technical Specifications 

• Models: A4FO22 / A4FO28 / A4FO71 / A4FO125 / A4FO180 / A4FO250 (example: A4FO22/31L-NSC12N)
• Pump Type: Axial piston fixed pump (swashplate design, open circuit)
• Geometric displacement Vg (per revolution): 22 cm³ (A4FO22), 28 cm³ (A4FO28), 71 cm³ (A4FO71), 125 cm³ (A4FO125), 180 cm³ (A4FO180), 250 cm³ (A4FO250)
• Nominal pressure pnom: 400 bar (sizes 22/28), 350 bar (sizes 71–250)
• Maximum pressure pmax: 450 bar (sizes 22/28), 400 bar (sizes 71–250)
• Maximum rotational speed nnom (at 1 bar abs inlet): 3600 rpm (22), 3000 rpm (28), 2200 rpm (71), 1800 rpm (125/180), 1500 rpm (250; high-speed version up to 1900 rpm)
• Maximum permissible speed nmax (with increased inlet pressure): up to 4500 rpm (size 22) depending on size and inlet pressure
• Flow at Vg and nnom: approx. 79 L/min (22), 84 L/min (28), 156 L/min (71), 225 L/min (125), 324 L/min (180), 375 L/min (250)
• Control method: Fixed displacement (flow proportional to speed, no variable control)
• Weight (approx.): 13.5 kg (22/28), 34 kg (71), 61 kg (125), 76 kg (180), 120 kg (250)
• Other: Through-drive capability for pump combinations; NBR/FKM seals available; clockwise or counter-clockwise rotation

(Data sourced from official Bosch Rexroth data sheet RE 91455/03.2015 and corresponding editions; theoretical values without efficiency losses.)

Key Technical Advantages:

• Precision swashplate and piston-shoe machining: High-wear-resistant materials and tight-tolerance grinding deliver high volumetric efficiency and minimal internal leakage even under continuous high pressure.
• Excellent suction performance and low-noise design: Optimized flow paths and suction port geometry provide strong self-priming capability; low operating noise suits noise-sensitive industrial environments.
• Long-life bearings and high-strength housing: Heavy-duty bearings combined with robust cast-iron/steel housing support continuous operation up to 450 bar, significantly extending service life.
• Through-drive and true interchangeability: Rear through-drive allows mounting of additional pumps of the same or smaller size; mounting flange, shaft end and ports match OEM exactly for 100% drop-in replacement and minimal downtime.

Application Areas

Industrial hydraulic power units, injection molding machines, die-casting machines, metallurgical equipment, marine hydraulic systems, open-circuit drives on construction machinery, material-handling equipment, presses and any fixed or mobile hydraulic system requiring stable high-pressure fixed-displacement flow.

Expert Maintenance Tips

Clean ports and drive shaft thoroughly before installation and ensure system cleanliness meets or exceeds NAS 1638 Class 7. Use HLP mineral oil conforming to DIN 51524 (recommended viscosity range 36–16 mm²/s). Maintain absolute inlet pressure at port S of at least 0.8 bar. Fill the case with hydraulic fluid before first start-up and run at low speed under no load to check for abnormal noise or leakage. Regularly monitor case-drain temperature and filter differential pressure; avoid prolonged over-pressure or cavitation. After replacement, perform flow and pressure verification tests in accordance with RE 91455.