Bosch Rexroth A4FO Series Fixed Displacement Piston Pumps

The Bosch Rexroth A4FO Series is a heavy-duty fixed displacement axial piston pump designed for high-pressure applications in open hydraulic circuits. Unlike variable pumps, the A4FO maintains a constant flow proportional to the drive speed, making it the preferred choice for systems requiring simple, robust, and highly reliable power delivery.

These specific configurations—A4FO71/10L, A4FO125/30R, and A4FO250/30R—cover a wide range of displacement needs, from 71cc to 250cc. Built with a swashplate design, these pumps are capable of operating at nominal pressures up to 350 bar and peak pressures of 400 bar, ensuring they can handle the most demanding industrial and mobile environments.

Engineering Configuration Analysis

To ensure a perfect replacement for your existing hydraulic system, it is vital to match the exact nomenclature of these high-performance units:

A4FO71/10L-PZB25N00 & K33: These are 71cc Series 10 units featuring Left-hand (L) rotation. The PZB code indicates a splined shaft and a standard SAE 4-hole mounting flange. The K33 variant includes a through-drive, allowing for the tandem mounting of additional pumps.
A4FO125/30R-PPB25N00: A 125cc Series 30 unit with Right-hand (R) rotation. The PPB designation indicates a parallel keyed shaft, providing a high-torque mechanical connection for industrial drives.
A4FO250/30R-PPB25N00: A massive 250cc Series 30 unit, delivering high-volume flow for large-scale industrial machinery. Like the 125cc model, it features a keyed shaft and right-hand rotation for standard motor coupling.

Exact Technical Specifications Matrix

Feature	A4FO71/10L-PZB25N00	A4FO71/10L-PZB25K33	A4FO125/30R-PPB25N00	A4FO250/30R-PPB25N00
Displacement	71 cm³/rev	71 cm³/rev	125 cm³/rev	250 cm³/rev
Pump Series	Series 10	Series 10	Series 30	Series 30
Rotation	Left-hand (L)	Left-hand (L)	Right-hand (R)	Right-hand (R)
Shaft Type	Splined Shaft (Z)	Splined Shaft (Z)	Keyed Shaft (P)	Keyed Shaft (P)
Through-Drive	None (N00)	K33 (Rear Mount)	None (N00)	None (N00)
Nominal Pressure	350 bar	350 bar	350 bar	350 bar
Peak Pressure	400 bar	400 bar	400 bar

Frequently Asked Questions (FAQs)

Q1: What is the primary advantage of the A4FO series over a variable pump? The A4FO series is a fixed displacement pump, which means it has fewer moving control parts than a variable pump like the A10VO. This results in a simpler, more rugged design that is easier to maintain and often more cost-effective for systems that do not require variable flow rates.

Q2: Can I use the A4FO71/10L on a clockwise-rotating engine? No. The “L” in the model code (e.g., A4FO71/10L) stands for Left-hand (counter-clockwise) rotation. Driving the pump in the wrong direction will prevent it from building pressure and will cause catastrophic internal damage due to a lack of lubrication on the valve plate.

Q3: What is the difference between the N00 and K33 suffix? The “N00” indicates a standard pump without a through-drive, meaning the rear of the pump is sealed. The “K33” designation means the pump is equipped with a rear mounting flange and coupling, allowing you to attach a secondary pump to the same drive shaft.

Q4: Which shaft type is better, Splined (Z) or Keyed (P)? The choice depends on your coupling. Splined shafts (Z) are typically used in mobile applications or when high-torque, direct-drive connections are required. Keyed shafts (P) are more common in industrial settings for use with standard V-belt pulleys or flexible couplings.

Q5: Are these A4FO pumps suitable for use with water-glycol or synthetic fluids? The standard NBR seals (indicated by the “P” in the code) are designed for mineral-based hydraulic oils. If your system uses specialized fire-resistant or synthetic fluids, you should verify compatibility or request a version with Viton (FKM) seals to prevent premature seal failure.