1. Internal and external leakage of hydraulic system
The leakage of excavator hydraulic system 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 the pressure pipeline can be easily found because the leaked hydraulic oil can be seen. Maintenance personnel and operators should always check every element of the entire hydraulic system to find the leakage point in time and immediately start to solve the leakage problem. But when When an external leak occurs at the suction port of the pump, it is difficult to detect. If one of the following three phenomena occurs, it is suspected that a leak in the system suction pipe has occurred:
① There are air bubbles in the hydraulic oil;
②The hydraulic system is unstable and has crawling phenomenon;
③ Overheating of hydraulic system;
④ Increased fuel tank pressure;
⑤ The pump noise increases.
If there is any of the above phenomena, you should first check all the suction pipe joints and connections to find the leak point. Do not over tighten the hose joint, because excessive tightening will deform the joint and increase the leakage. At this time, the tightening torque value recommended by the equipment manufacturer should be used, which will ensure reliable sealing, and will not cause distortion and deformation of the pipe joint and the sealing ring, thereby causing 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 generated inside the component will become more and more obvious, and slight internal leakage may not be noticeable, but as the internal leakage increases, overheating of the system will become a problem. When this happens, the other components of the system will start to fail. A simple way to identify internal leakage is to test the duty cycle of the system when it is fully loaded and when it is empty. Pump failure problem.
Once the hydraulic components in the hydraulic system leak, it will not only cause waste of media and environmental pollution, but also cause the entire hydraulic system to malfunction and suspend work, resulting in safety and quality accidents. In order to reduce the failure of the hydraulic system, improve the hydraulic system Efficiency, prevent environmental pollution and reduce the loss of hydraulic media, you must pay attention to the problem of leakage, analyze the cause of the leakage, and take corresponding measures to achieve the purpose of reducing leakage and even avoiding leakage.
2. Factors related to leakage
1) Working pressure. Under the same conditions, the higher the pressure of the hydraulic system, the greater the possibility of leakage, so the size of the system pressure should be consistent with the optimal value required by the hydraulic system, so that it can meet the work requirements , And can avoid unnecessary excessively high system pressure.
2) Working temperature. Most of the energy lost by the hydraulic system is converted into heat energy. Part of this heat energy is emitted into the atmosphere through the surfaces of the hydraulic components themselves, pipes and oil tanks, and the rest is stored in hydraulic oil to increase the oil temperature. The increase in oil temperature will not only reduce the viscosity of the oil and increase the amount of oil leakage, but also cause the accelerated aging and premature failure of the sealing elements, resulting in serious leakage.
3) The cleaning procedure of the oil. The hydraulic oil of the hydraulic system often contains various impurities. For example, the hydraulic components are not cleaned when installed, and the impurities such as iron filings and paint attached to the hydraulic oil enter the hydraulic oil; dust and dust that invade the hydraulic equipment Dirt contaminates the hydraulic oil; colloid, asphaltene and carbon residue produced by the oxidative deterioration of the hydraulic oil. Impurities in the hydraulic oil will cause increased wear on the sliding surface of the hydraulic component, the valve core of the hydraulic valve is blocked, and the small hole is blocked. Damaged seals, etc., resulting in damage to the hydraulic valve, causing hydraulic oil leakage.
4) The choice of sealing device. The correct choice of sealing device is very important to prevent leakage of the hydraulic system. The choice of reasonable sealing device can improve the performance and efficiency of the equipment and extend the service life of the sealing device, thereby effectively preventing leakage. Otherwise , Sealing devices that are not suitable for working conditions will cause the sealing elements to wear or age prematurely, causing media leakage. In addition, the processing accuracy of hydraulic components, the robustness of hydraulic system pipeline connections and their seismic resistance, equipment maintenance, etc. , Will affect the leakage of hydraulic equipment.
3. Prevention of leakage
1) Control the size of the pressure. The working pressure of the system should be determined according to the calculation during design, and should not be adjusted or changed randomly during use.
2) Control the temperature change. Controlling the temperature increase of the hydraulic system generally starts from the design of the oil tank and the setting of hydraulic pipes. 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 out and back inside the oil tank can be increased. The oil is separated by a partition. The temperature of the hydraulic oil in the oil tank is generally allowed to reach 55 ~ 650C, and the maximum should not exceed 70 degrees. When the temperature of the naturally cooled oil exceeds the allowable value, it is necessary to add a cooling water pipe inside the oil tank or set it on the return line Cooler, thereby reducing the temperature of the hydraulic oil. When setting the hydraulic pipeline, the distance between the oil tank and the actuator should be as short as possible, and the elbows of the pipeline, especially 90., should be as few as possible to reduce the pressure Loss and friction.
3) Maintain the cleanliness of the hydraulic oil. The oil filter device is used to filter the hydraulic oil regularly or continuously to reduce the impurity content of the hydraulic oil as much as possible to ensure that the cleanliness of the oil meets national standards.
4) Choose the sealing device reasonably. If you want to choose the sealing device reasonably, you must be familiar with the forms and characteristics of various sealing devices, the characteristics of the sealing materials and the operating conditions of the sealing device (such as working pressure, temperature of the working environment, The speed of the moving part, etc.) When comparing the actual use conditions with the allowable use conditions of the seals, it must be ensured that the sealing device has good sealing performance and a long service life.
5) In daily maintenance, the inspection of the equipment should be strengthened, and the hydraulic oil should be regularly tested to ensure that the oil quality is clean and meets the standard. Choose a durable sealing device that meets the standard, and replace the sealing device regularly or periodically. Strengthen equipment maintenance and minimize leaks to ensure the normal operation of hydraulic equipment.
6) The correct selection of the sealing device is also very important to prevent the leakage of the hydraulic system.
