The handling of the fault where the concrete pump fails to pump

A Niigata 11FB concrete pump experienced a phenomenon of weak pumping during operation. At this time, the pressure on the pressure gauge slowly rose to one-third of the maximum pressure and then slowly dropped to 0. This pump truck is equipped with an electrical limit switch (commonly known as a reed switch) at the terminal of the main hydraulic cylinder for concrete pumping. After the main hydraulic cylinder is in place, the reversing signal is controlled by the limit switch, and the electrical signal is transmitted to the reversing solenoid valve of the main hydraulic cylinder through the electrical control system to implement reversing. The hydraulic oil pressure of the main hydraulic cylinder is controlled by the main safety valve. After analysis, the possible causes of this malfunction may include: failure of the main hydraulic pump; The main safety valve is malfunctioning and leaking. Leakage of the reversing solenoid valve; The position of the electrical limit switch is incorrect. Conductive circuit failure. Upon inspection, it was found that the reed tube inserted at the end of the main hydraulic cylinder was pulled out too much outward, shortening the piston stroke. The piston returned to operation before reaching the very front end, that is, unloading and reversing, thus causing the oil pressure to fail to rise to the maximum value. After adjustment, the fault was eliminated. The adjustment steps are as follows: ① Open the oil replenishment valve, replenish oil to the closed oil circuit of the main hydraulic cylinder, and then tightly close the needle valve; ② Run the piston for several strokes, at which point the engine speed is approximately 1000r/min. ③ Apply a thin layer of grease at the outlet of the concrete cylinder. ④ Conduct a maximum pressure test on each of the left and right pistons once. Move the pistons to the terminal and apply grease at the stop position of the pistons. ⑤ Draw at an engine speed of 2200r/min and adjust the reed switch until the piston can retract approximately 50mm at the terminal position (switching action).

Another Chutian brand HBT60 concrete drag pump suddenly saw the gate move and the pumping completely disappear during normal operation, with the pressure gauge showing 0. The gate cylinder and the concrete conveying cylinder of this pump are all supplied with oil by the same main pump. The hydraulic oil pressure is controlled by the main safety valve, which is controlled by the unloading solenoid valve. The unloading solenoid valve is a two-position four-way solenoid valve. When unloading is required, the right side is energized, the solenoid valve is in the right position, and the unloading is carried out through the overflow port. After analysis, the causes of this malfunction are as follows: ① Failure of the main hydraulic pump; ② The main safety valve and the unloading solenoid valve are malfunctioning and leaking. That is: First, there are small particles of debris on the conical surface of the main safety valve core mating, or the conical valve returns to its original position and gets stuck during the overflow process, causing the oil circuit to overflow and unable to establish pressure. This kind of fault mostly occurs during the running-in stage of newly purchased equipment. Secondly, if the unloading solenoid valve gets stuck when returning to the left position during use or fails to return to the left position, simply gently push the indicator rods installed at both ends of the solenoid valve to open or close the solenoid valve switch, and you can check whether the solenoid valve is working properly. If the circuit malfunctions and the solenoid valve cannot move, and it is urgent to pump at this time, the lock nut can be tightened to put it in the working state when the solenoid valve is in the left position. After completing the work, maintenance can be carried out. If it is necessary to stop the pumping, loosen the lock nut until it is in the right position of the solenoid valve.