Concrete Pump Truck Malfunction Troubleshooting Cases

Malfunction 1: Main System Pressure Too Low

A 37-meter concrete pump truck experienced a main system pressure build-up issue, with the maximum pressure only reaching 21 MPa after pressure relief. Tightening the adjustment screws of the main relief valve and the constant pressure valve of the main oil pump did not resolve the problem.

Fault Analysis

Troubleshooting Process

1. Removed and inspected the spool of the main relief valve cartridge valve; no abnormalities were found. To rule out a fault in the main relief valve, a new one was installed, but the pressure still could only be adjusted to 21 MPa. Therefore, the failure of the main spool of the relief valve was eliminated.

2. Due to the lack of equipment to detect the fault of the constant pressure valve of the main oil pump, several circular blocking pieces (matching the size of the cartridge valve spool on the main valve block) were processed. The cartridge valve spool was blocked with the blocking pieces, the screw of the constant pressure valve was loosened, and then the pressure was built up. The constant pressure valve was adjusted slowly, and the pressure could rise to 34 MPa. Thus, the failure of the main oil pump was ruled out.

3. Under the condition that both the main oil pump and the main relief valve spool were normal, it was suspected that the DT1 electromagnetic directional valve on the main relief valve had internal leakage. After replacing the DT1 electromagnetic directional valve as a whole, the system pressure returned to normal.

Malfunction 2: Main System Pressure Loss After Pumping Concrete

Fault Analysis

1. Reversing pressure fault;

2. Electrical fault;

3. Main relief valve fault;

4. Main four-way valve fault;

5. Main oil pump fault.

Troubleshooting Process

1. Observed that the reversing pressure fluctuated between 12-16 MPa, which was normal.

2. Measured the voltage between terminal 20 and terminal 37 with a multimeter, and tested the proportional electromagnet with a small screwdriver, which showed strong magnetism. It was preliminarily judged that the proportional electromagnet worked normally, and DT1, DT3 and DT2 could be energized normally.

3. During the disassembly and inspection of the main relief valve, it was found that the cartridge valve spool of the main relief valve was stuck in the upper position. After polishing the spool with sandpaper and reinstalling the main relief valve, the system operated normally.