Fault analysis and troubleshooting of hydraulic transmission system

Hydraulic transmission uses hydraulic oil as the working medium for energy conversion and power transmission. It has the advantages of large energy transmission, easy layout, compact structure, convenient commutation, smooth and uniform rotation, and easy to complete complex actions, so it is widely used in the field of construction machinery. However, it is often difficult to accurately determine the location and cause of the fault from the external surface phenomenon and sound characteristics of the hydraulic transmission fault, but accurately and quickly find out the location and cause of the fault and eliminate it in time. It is very important in the use, management and maintenance of construction machinery.

1、 Main faults of the hydraulic system: leakage, high oil temperature, noise and failure of the electro-hydraulic combination part are often found on the surface of the relatively moving hydraulic components, hydraulic oil seals, pipeline joints and control components. Specific performance: First, the leakage of pipes, pipe joints and sealing surfaces not only increases the oil consumption of hydraulic oil, dirties the surface of the machine, but also affects the normal operation of the actuator. The second is the slow and weak execution action, which is manifested by the slow lifting of the bulldozer blade, the difficulty in cutting the soil, the weak digging of the excavator, the inability of the oil motor to turn or the low rotation speed. Third, the hydraulic system produces vibration and noise. Fourth, other components are abnormal.

Fault inspection:
1. Direct inspection method
Based on the feeling, experience and simple tools of the maintenance personnel, the cause of the fault is qualitatively analyzed and judged, and solutions are proposed.

2. Instrument detection method
On the basis of direct observation, according to the characteristics and experience of the failure, various inspection instruments and meters are adopted to detect the flow, pressure, oil temperature and rotational speed of hydraulic components of the hydraulic system, and to quantitatively analyze the vibration noise and wear particles.

3. Element replacement method
Replace the components that may fail with spare components one by one, observe whether the faults of the hydraulic system are eliminated, and then find out the location and cause of the faults and eliminate them. At the construction site, this method is not suitable for components with large volume, difficult disassembly and less spare parts. However, for components such as balance valve, overflow valve and one-way valve that are small and easy to disassemble, it is convenient to use replacement method.

4. Regular and timely monitoring and diagnosis: according to the regulations of various mechanical models, inspection contents and time, and according to the time and position required by the factory, the technical condition of components and parts can be detected through professional detection, monitoring and diagnosis, and possible abnormal hidden dangers can be found in time. This is a scientific and technical means to eliminate the failure of hydraulic system before it occurs. Of course, to implement the regular inspection method, first of all, it is necessary to train some professional and technical inspection personnel, so that they can not only be proficient in the structure and principle of hydraulic components of construction machinery, but also master and study various diagnostic techniques for detecting hydraulic transmission systems. While continuously accumulating the experience of judging faults by human intuition, gradually develop the non-disassembly diagnosis technology to complete the technical data collection, and use computers to analyze and determine the causes of faults and troubleshooting methods.

Fault prevention of hydraulic system
1. Ensure the cleanliness of hydraulic oil
Correctly use the calibrated and required hydraulic oil and its corresponding substitutes (see the Engineering Machinery Oil Manual for details) to prevent the invasion of dirt and impurities in the hydraulic oil. Because hydraulic oil is both the working medium and lubricant in the hydraulic transmission system, the cleanliness of the oil has a great impact on the performance of the system and the reliability, safety, efficiency and service life of the components. The fitting accuracy of hydraulic components is extremely high, and it is more sensitive to the deposition, blockage, scratch and corrosion caused by dirt and impurities in the oil.

The main reasons for dirt and impurities invading the hydraulic oil are as follows: first, the exterior of the actuator is not clean; Second, pay no attention when checking the oil quantity; The third is that the 120 mesh filter is not used for filtering during refueling; Fourth, the containers and utensils used are not clean; Fifth, the severely worn and damaged seals cannot be replaced in time; Sixth, during the inspection and repair, the rust scale and impurities produced by the hot bending pipeline and joint welding repair are not cleaned; The seventh is improper storage of oil. During use, inspection and repair, attention should be paid to solving these problems to reduce and prevent the occurrence of hydraulic system faults.

2. Prevent air from mixing in hydraulic oil
The hydraulic oil in the hydraulic system is incompressible, but the air compressibility is very large. Even if there is a small amount of air in the system, its impact is also very large. The air dissolved in the oil will escape from the oil to produce bubbles and form cavitation when the pressure is low; In the high pressure zone, under the impact of pressure, these bubbles are quickly broken and compressed sharply, making the system produce noise. At the same time, when the gas is suddenly compressed, a large amount of heat energy will be released, which will cause local heating, damage hydraulic components and hydraulic oil, unstable operation, and sometimes cause shock vibration.

Therefore, air must be prevented from entering the hydraulic system. Specific measures: First, avoid oil pipe fracture, joint looseness and seal damage; The second is to avoid improper dumping when refueling; Third, the oil return pipe is inserted below the oil level; Fourth, prevent the blockage of the oil filter at the inlet of the hydraulic pump from increasing the oil suction resistance and from separating the air dissolved in the oil.

3. Prevent excessive temperature of hydraulic oil. The working temperature of the oil in the hydraulic system is generally within the range of 30 ℃~80 ℃. Pay attention to prevent excessive oil temperature during use. If the oil level in the oil tank is not enough, the heat dissipation performance of the hydraulic oil cooler is poor, the system efficiency is too low, the component capacity is small, the flow rate is too high, and the viscosity of the selected oil is incorrect, they will make the oil temperature rise too fast. High viscosity increases the energy loss when the oil flows, and low viscosity will increase the leakage. Therefore, pay attention to and check these problems in use to prevent excessive oil temperature. In addition, regular filtration of hydraulic oil and regular physical performance inspection can not only ensure the working performance of hydraulic system, but also reduce the wear and corrosion of hydraulic components, and extend the service life of oil and hydraulic components.

Source: Network