6 On-site detection and diagnosis of hydraulic faults of construction machinery Wang Xuanshang Characteristics of faults in hydraulic system of construction machinery The hydraulic mechanical transmission system is mainly composed of hydraulic pump control valve torque converter transmission and power shift transmission valve, and the fault is usually walking. Weakness or poor hydraulic clutch engagement. The work unit hydraulic system is mainly composed of the hydraulic pump control valve hydraulic motor and the hydraulic cylinder, and its failure is mainly slow back. The common feature of these two system failures is the lack of system pressure.
On-the-spot inspection and diagnosis of faults The initial inspection and diagnosis of the site is based on the fault phenomenon to find out the relevant conditions, and the location of the fault and the preliminary cause are analyzed against the hydraulic system. It should not be overlooked that the inspection process that looks very simple should follow the following steps.
Take the necessary concrete actions. Sometimes, the driver's causal relationship to the machine's fault is not clear, which makes it difficult to diagnose the fault. At this time, the necessary on-site operation will benefit greatly.
Oil quality inspection. This content seems simple and often overlooked when implemented. If the platform 9660 loader travels as a hydraulic transmission system, the transmission oil has been drained when the driver is on vacation. When the assistants came to drive after the site relocation, they found that the machine was unable to walk. It was thought that it was a major problem. However, the maintenance personnel solved the problem only by listening to the sound dipstick at the site and avoided major accidents. In another example, Taiwan Hitachi, 2202 excavator, found that the hydraulic oil was insufficient after repairing the hydraulic cylinder, and the hydraulic oil purchased at the site was a reclaimed oil extracted from the earth, and after being added to the fuel tank, it caused deterioration of the oily quality, resulting in foaming. The machine action is weak, and the fault can be eliminated after replacing the hydraulic oil. Therefore, the consequences for the transmission system of oily oil can be disastrous.
Inspection, various filter elements. The oil filter is a cleaning tool for the hydraulic system. During the fault diagnosis, the contamination degree of the filter and the oil filter, such as the oil filter, can be used as a basis for analyzing failures. Such as Taiwan Garten HD820 excavator, after running the 4000h or so found the whole powerless; dismantled its hydraulic system oil filter, found that the filter element is damaged, blocked the oil return port, replace the filter after the failure can be ruled out.
If the fault cannot be eliminated after passing the above preliminary inspection, the instrument should be used for more detailed inspection.
The instrument diagnosis of the hydraulic system is in general field detection, because the flow rate is more difficult to detect, and the fault of the hydraulic system is often the pressure is insufficient. Therefore, in the on-site inspection, the method of detecting the system pressure is more used. Such as Taiwan 9660 loader, after running 6000,1 found its walking powerless, detecting the torque converter inlet and outlet pressure value, the results are normal; operating power shift transmission valve, measuring the direction of the clutch pressure, the pressure is only 5 Elbow 3, the establishment of normal pressure. After dismantling the transmission, it was found that the oil seal in the direction clutch oil passage was damaged, causing the hydraulic oil to leak, and the fault was eliminated after the oil seal was replaced.
Another example is, Taiwan, 2205 excavator, after running 3000 found walking deviation, detection of walking system pressure found that the left is 32 cubits 3, the right only 26, the heart after adjusting the right walking safety valve pressure, the fault can be ruled out.
With the extensive application of electromechanical liquidation technology in construction machinery, single pressure test can no longer meet the needs of on-site inspection. Now more and more imported engineering machinery, its fault diagnosis must be completed with a special test computer. Detection of computer data measured in a small volume and easy to carry.
Such as Taiwan Hitachi, 2202 excavators, work equipment hydraulic system is weak, when operating the excavator handle, with the engine sound changes and emit smoke. The use of detection computer detection found that no significant changes in the flow of the hydraulic pump, the engine sounds when the pressure increases; after analysis that the hydraulic pump flow is too large, the swash plate can not adjust the flow. The servo valve of the hydraulic pump was disassembled and it was found that the connection pin of the servo valve and the hydraulic pump flow control swash plate was broken, and the failure was eliminated after the pin was replaced.
On-site maintenance is often used in non-instrument replacement diagnostics. This method is often used in the overall test of the same type of machine, ie, if there is no detection device or the device is on site, the components are relatively precise and should not be disassembled, they can be replaced with other components of the same model and then checked, that is, quickly. Diagnosed as faulty. Such as Taiwan. When the digging 320 excavator did not work at 500, the work unit hydraulic system was weak. At the time, there was no testing equipment on the site. According to experience, the primary safety valve was initially judged to be faulty; however, the main safety valve on the site was disassembled. The pilot needle cone was found to have no obvious wear and scratches, and the owner of the 320 model excavator on the site The safety valve is exchanged with the safety valve, and the malfunction is eliminated after the test machine. This method of swap diagnosis is simple and easy, but it must be accurate.
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