Bosch Rexroth A2FO fixed hydraulic piston pump for the Sermac Concrete mixer truck 2401094 2401111 2401128 2401148 2401188

The A2FO is a fixed displacement axial piston pump built by Bosch Rexroth, one of the most established names in industrial and mobile hydraulics. "Fixed displacement" means the pump delivers a constant flow rate per revolution of its drive shaft — there's no internal mechanism to vary output on the fly, unlike variable-displacement pumps (such as Rexroth's A4VG or A10VG series). That simplicity is exactly why it's so well suited to a task like driving a concrete mixer drum, where a predictable, steady flow is more valuable than adjustable output.

Why Sermac Concrete Mixer Trucks Use the A2FO Pump

Sermac, the Italian manufacturer known for its concrete pumps, mixers, and placing booms, builds equipment that has to survive constant vibration, dust, thermal cycling, and years of near-daily use. The hydraulic drive system for the mixing drum is one of the most heavily worked subsystems on the truck, and it needs a pump that prioritizes reliability over complexity.

Matching Pump Output to Mixer Drum Speed

A concrete mixer drum doesn't need to spin at wildly varying speeds the way, say, a hydraulic excavator's boom needs variable flow. It generally needs to run at a fairly consistent rotational speed while mixing, and at a different but still steady speed while agitating during transport or discharging during pour. Because the A2FO delivers flow directly proportional to shaft speed (usually driven off the truck's PTO — power take-off), Sermac's hydraulic engineers can size the pump precisely for the drum's rated RPM and torque requirements without needing the added cost, weight, and failure points of a variable-displacement unit.

Durability in Harsh Jobsite Conditions

Fixed piston pumps like the A2FO have fewer moving parts involved in displacement control compared to variable pumps — there's no servo piston, no control valve assembly modulating the swash plate angle. Fewer control components mean fewer things that can clog with contaminated fluid or fail from vibration fatigue. On a truck that spends its life on construction sites, exposed to dust, moisture, and rough roads, that mechanical simplicity translates directly into fewer unplanned breakdowns.

How the A2FO Pump Works Inside the Hydraulic Circuit

Axial Piston Mechanism

Power comes into the A2FO through its splined input shaft, typically driven from the truck chassis PTO through a driveline or direct mount. As the shaft turns, the cylinder block spins with it, and the pistons — pressed against the fixed swash plate — are forced to travel in and out of their bores in a reciprocating motion. On the intake stroke, each piston draws hydraulic fluid from the reservoir through the pump's suction port; on the discharge stroke, it forces that fluid out through the pressure port at whatever pressure the downstream circuit demands.

Integration with Sermac's Hydraulic Drive System

On a Sermac mixer truck, the A2FO's outlet feeds into the drum drive circuit, which typically includes a hydraulic motor (often a fixed or two-speed motor) coupled to the drum's ring gear or direct drive assembly, along with the necessary control valves, relief valves, and a cooling circuit to manage heat generated during continuous operation. The pump's case drain line routes leakage oil back to the reservoir, both lubricating the bearings and carrying heat away from the pump housing. Because the pump runs essentially continuously whenever the drum is turning — which, on a job site, can mean hours at a stretch — proper fluid cleanliness and cooling are critical to long service life.

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Q1: How long does an A2FO pump typically last on a mixer truck?

A1: Service life depends heavily on fluid cleanliness, cooling, and duty cycle, but well-maintained units commonly run for several thousand hours before internal wear necessitates rebuild or replacement.

Q2: Is the A2FO pump repairable, or does it need full replacement?

A2: Many A2FO pumps can be rebuilt with new pistons, cylinder blocks, bearings, and seals, provided the housing and shaft are within tolerance. Whether repair or replacement makes more economic sense depends on the extent of wear and the cost of a remanufactured unit.

Q3:What is the price and delivery time of the Rexroth A2FO pump for the Sermac Concrete mixer truck？

A3: The specific price and delivery time will depend on the equipment model or specific product model you provide.

Q4:How to purchase a Rexroth A2FO pump for the Sermac Concrete mixer truck?

A4:You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.