1. Internal and external leakage of hydraulic system
The leakage of hydraulic system of Komatsu excavator can be divided into two types: one is internal leakage (internal leakage) and the other is external leakage (external leakage)
(1) External leakage
The leakage of pressure pipe can be easily found because the leaking hydraulic oil can be seen Maintenance personnel and operators should always check each element of the whole hydraulic system, find the leakage point in time and immediately solve the leakage problem However, when external leakage occurs at the suction port of the pump, it is difficult to detect If one of the following three phenomena occurs, it can be suspected that there is a leak in the system suction pipe:
① There are air bubbles in the hydraulic oil;
② The hydraulic system is unstable and crawling;
③ Overheating of hydraulic system;
④ Oil tank pressure increases;
⑤ Pump noise increases
If any of the above phenomena exist, first check all oil suction pipe joints and connections to find the leakage point Do not over tighten the hose joint, because excessive tightening will deform the pipe joint and increase leakage. At this time, the tightening torque recommended by the equipment manufacturer should be used, which will ensure reliable sealing and will not distort the pipe joint and sealing ring, resulting in damage to the surface of the sealing ring.
(2) Internal leakage
Over time, due to the wear of components in the hydraulic system, the leakage inside the components will become more and more obvious. Slight internal leakage may not be detected. However, with the increase of internal leakage, the system overheating will become a problem When this happens, other components of the system will begin to fail A simple way to identify internal leakage is to test the working cycle of the system under full load and no-load. If the action completion time under load is much longer than that under no-load, the pump failure can be suspected
Once the hydraulic components in the hydraulic system leak, it will not only cause the waste of media and environmental pollution, but also make the whole hydraulic system fail and stop working, resulting in safety and quality accidents In order to reduce the failure of hydraulic system, improve the efficiency of hydraulic system, prevent environmental pollution and reduce the loss of hydraulic medium, we must pay attention to the leakage problem, analyze the causes of leakage and take corresponding measures to achieve the purpose of reducing leakage and even avoiding leakage
2. Relevant factors causing leakage
1) Working pressure Under the same conditions, the higher the pressure of the hydraulic system, the greater the possibility of leakage. Therefore, the system pressure should be made to meet the optimal value required by the hydraulic system, so as to meet the working requirements and avoid unnecessary excessive system pressure
2) Operating temperature Most of the energy lost by the hydraulic system is transformed into heat energy. Some of these heat energy is emitted into the atmosphere through the surface of the hydraulic components themselves, pipelines and oil tanks, and the rest is stored in the hydraulic oil to raise the oil temperature The increase of oil temperature will not only reduce the viscosity of oil and increase the leakage of oil, but also accelerate the aging and early failure of sealing elements, resulting in serious leakage
3) Fluid cleaning procedure The hydraulic oil of hydraulic system often contains various impurities For example, the hydraulic components are not cleaned during installation, and the impurities such as iron filings and coatings attached to them enter the hydraulic oil; Dust and dirt invading into the hydraulic equipment pollute the hydraulic oil; Colloid, asphaltene and carbon residue produced by oxidative deterioration of hydraulic oil Impurities in the hydraulic oil will aggravate the wear of the sliding surface of hydraulic components, block the valve core, block the small hole and damage the seal of the hydraulic valve, resulting in the damage of the hydraulic valve and the leakage of hydraulic oil
4) Selection of sealing device Correct selection of sealing device is very important to prevent leakage of hydraulic system Reasonable selection of sealing device can improve the performance and efficiency of equipment and prolong the service life of sealing device, so as to effectively prevent leakage Otherwise, the sealing device that does not adapt to the working conditions will cause premature wear or aging of the sealing elements, resulting in medium leakage In addition, the processing accuracy of hydraulic components, the firmness of hydraulic system pipeline connection and its anti-seismic ability, and the condition of equipment maintenance will affect the leakage of hydraulic equipment
3. Prevention and control of leakage
1) Control the pressure The working pressure of the system shall be determined according to calculation during design, and shall not be adjusted or changed arbitrarily during use
2) Control temperature changes Controlling the temperature rise of hydraulic system generally starts from the design of oil tank and the setting of hydraulic pipeline In order to improve the heat dissipation effect of the oil tank, the heat dissipation surface of the oil tank can be increased, and the oil outlet and return inside the oil tank can be separated by partitions The temperature of hydraulic oil in the oil tank is generally allowed to reach 55 ~ 650C, and the maximum temperature shall not exceed 70 ℃ When the temperature of naturally cooled oil exceeds the allowable value, it is necessary to add cooling water pipes inside the oil tank or set coolers on the oil return road to reduce the temperature of hydraulic oil When setting the hydraulic pipeline, the distance between the oil tank and the actuator should be as short as possible, especially the elbow of the pipeline is 90 Elbows should be as few as possible to reduce pressure loss and friction
3) Keep the hydraulic oil clean The oil filtering device is adopted to filter the hydraulic oil regularly or continuously, so as to reduce the impurity content of the hydraulic oil as much as possible, so as to ensure that the cleanliness of the oil meets the national standard
4) Reasonably select the sealing device In order to reasonably select sealing devices, we must be familiar with the forms and characteristics of various sealing devices, the characteristics of sealing materials and the service conditions of sealing devices (such as working pressure, temperature of working environment, speed of moving parts, etc.) Comparing the actual service conditions with the allowable service conditions of the seal, it is necessary to ensure that the sealing device has good sealing performance and long service life
5) Check the oil quality of hydraulic equipment regularly to ensure that it meets the standard during daily maintenance Select the durable sealing device that meets the standard, replace the sealing device regularly or periodically, strengthen equipment maintenance and minimize leakage, so as to ensure the normal operation of hydraulic equipment
6) Correct selection of sealing device is also very important to prevent leakage of hydraulic system
