Created on:2021-09-28 14:21

Lifting and transportation equipment_ Hydraulic steering failure of truck crane

Lifting and transportation equipment_ Hydraulic steering failure of truck crane

The steering of tl-250e truck crane in TADANO was heavy and laborious.

The hydraulic steering principle of the machine is shown in Figure A. It is a split hydraulic power assisted system, which is mainly composed of, throttle valve, safety valve, control valve and power assisted cylinder. The rated working pressure of vane pump is 12.5mpa, the displacement is 17ml / R, and the rotating speed is 370 ~ 3700r / min. Through preliminary inspection, all lubricating parts of the steering mechanism are normal without abnormal sound and wear. Then check the oil tank one by one: the oil quality, oil quantity and oil suction screen are normal. Disassemble and check the safety valve and throttle valve on the vane pump, and the results are also normal; After disassembling the vane pump, the problem cannot be seen by naked eyes due to the lack of standard data and measuring tools; The control valve and booster cylinder were disassembled and inspected, and no problems were found. After reassembly, replace with new oil (No. 8 hydraulic transmission oil), and the fault remains the same. However, when disassembling the vane pump, there is a phenomenon that makes people suspicious, that is, when the rotor is taken out of the vane pump, the blades immediately slide out of the rotor slot, making it feel that the clearance of the blade slot on the rotor is too large and the vane pump fails. To this end, disconnect the oil circuit at a in figure a, connect a pressure gauge at the front end of the disconnection and conduct a pressure test. When the engine speed is rated, the initial oil pressure is 10MPa, 9Mpa after 5min, 6Mpa after 8min, and only 4MPa after 10min, while the standard value shall be 12.5mpa. The above phenomenon that the oil pressure gradually decreases with the extension of time shows that with the extension of time, the oil temperature continues to rise (the temperature was 30 ℃) and the oil viscosity continues to decline. In addition, the serious over tolerance between the blade and the groove intensifies the internal leakage of the pump, resulting in the gradual decrease of pressure. This proves that the previous judgment is correct.

After replacing a new vane pump, the fault disappeared.

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