A11VO for concrete pump truck

The A11VO series plunger pumps are the heart of a concrete pump truck’s hydraulic system. Typically used as the main oil pump, they are responsible for transmitting hydraulic energy to the delivery cylinders to enable high-pressure concrete pumping. In the high-impact, high-frequency directional change operating conditions typical of concrete pump trucks, the A11VO has become the industry standard thanks to its exceptional power density and response speed.

First, Key Advantages of A11VO for concrete pump truck

1. High-Pressure Shock Resistance: Sudden directional changes in concrete pump trucks generate severe pressure pulsations. With a rated pressure capacity of 350 bar and a peak pressure capacity of 400 bar, the A11VO effectively withstands directional change shocks, reducing the risk of pump body cracking.

2. Extremely High Power-to-Weight Ratio: Concrete pump truck chassis have limited space and strict weight restrictions. The A11VO’s compact design delivers the immense power required to support pumping with booms spanning tens of meters within a small footprint.

3. Excellent Self-Priming Capability: Due to installation constraints on the concrete pump truck chassis, the hydraulic pump is often positioned above the oil level. The A11VO’s optimized cylinder block design ensures it maintains good oil suction efficiency even during high-speed rotation, thereby reducing cavitation.

Second, Hydraulic Circuit Logic of the Concrete Pump Truck (A11VO Layout)

1. Power Input: The engine’s transfer case drives the main shaft via a flexible coupling; due to the significant vibrations of the concrete pump truck, rigid direct coupling is prohibited;

2. Rear End of the Drive Shaft: A series-connected gear pump supplies oil to the boom pilot control, mixing motor, and cooling fan;

3. High-Pressure Outlet Port A: Divided into two lines to the main pumping cylinder and the boom multi-way directional control valve, simultaneously enabling concrete delivery and boom extension;

4. LS Load Feedback Circuit: Load pressure from the multi-way valve is fed back to the pump’s LS port to dynamically adjust the swashplate displacement in real time;

5. Dedicated Drain Port (T): Use a separate line from the pump’s highest drain port that extends directly below the oil tank’s liquid level. Sharing this line with the main return line is strictly prohibited, as high return backpressure can destroy the skeleton oil seal and cause the pump body to overheat;

Third, Specific Installation Guidelines for Concrete Pump Trucks

1. Strict Requirements for Drive Coaxiality

Due to continuous vibration during driving and pumping, the radial coaxial deviation of the flexible coupling must be ≤0.1 mm; inspect the splines and rubber buffer blocks every 200 hours to prevent shaft breakage and resonance-induced noise from the pump body.

2. Prevent Air Leaks in the Suction Line (Most Common Failure Point in Concrete Pump Trucks)

For A11VO models with displacements of 40–145, the suction vacuum must be ≤0.8 bar; use short, straight suction lines with minimal bends, and replace flange seals regularly; air leaks can cause weak pumping performance, a sharp screeching noise from the pump body, and rapid piston scuffing; for 190/260 models, the A11VLO model with oil replenishment must be used.

3. Mandatory Housing Oil Filling and Bleeding During Pump Repair or Replacement

After prolonged downtime or after changing hydraulic oil or the pump unit, clean hydraulic oil must be added through the drain port. Manually rotate the pump more than 10 revolutions to completely bleed out internal air. Never start the pump directly, as this can cause dry grinding and burn out the distribution plate.

4. Upgrading Hydraulic Fluid Cleanliness

Due to severe cement dust contamination at construction sites, use a suction filter with a rating of ≥100 μm and a high-pressure line filter with a rating of 20 μm. Maintain hydraulic fluid cleanliness at NAS Class 7 (exceeding the NAS Class 8 standard for general construction machinery) to extend the pump’s service life.

Fourth, Common Faults and Causes in Concrete Pump Trucks

1. Weak pumping performance, system pressure fails to rise: Low LS pressure differential, air leaks in the suction line, clogged suction filter element, or internal pump leakage caused by contaminated fluid;

2. Persistent high-pitched screeching noise during pumping: Use of standard A11VO pumps without oil replenishment on 190/260 models, low tank fluid level, or cavitation due to high oil viscosity during cold starts at low temperatures;

3. Engine stalling and black smoke emission during high-head pumping: Constant power regulation set too high, or maximum displacement limit fully open;

4. High pump housing temperature and leakage from the skeleton oil seal: The drain line shares the system’s return line; drain backpressure exceeds limits; prolonged no-load overflow causes overheating;

5. Uneven speed during combined boom and pumping operations: Blockage in the LS feedback oil circuit; the constant-power curve is not matched to the engine.

For vehicles with frequent combined operations and intermittent pumping conditions, balance pumping speed with fuel economy;

Rexroth A11VO series hydraulic piston pump