Hydraulic system leakage and its prevention
1.Internal leakage and leakage of hydraulic system
Hydraulic system leakage can be divided into two types, one is internal leakage and the other is external leakage.
(1) External leakage
Leakage of the pressure line can be easily detected because the leaking hydraulic oil can be seen. Maintenance personnel and operators should always check each component of the entire hydraulic system, find leaks in time and immediately address the leak. However, external leakage is difficult to detect when it is in the suction port of the pump. If one of the following five phenomena occurs, it can be suspected that the system suction pipe leak has occurred:
1) There are air bubbles in the hydraulic oil;
2) The hydraulic system is unstable and has a creeping phenomenon;
3) The hydraulic system is overheated;
4) The tank pressure is increased;
5) Pump noise increases.
If any of the above phenomena exist, you should first check all the suction fittings and connections to find the leak. Do not overtighten the hose fittings, as excessive tightening will deform the fittings and increase leakage. The tightening torque value recommended by the equipment manufacturer should be used, which will ensure a reliable seal and will not make the tube Distortion of the joint and seal causes damage to the surface of the seal.
(2) Internal leakage
Due to the wear of components in the hydraulic system, the leakage inside the component becomes more and more obvious over time, and slight internal leakage may not be noticeable, but as the internal leakage increases, system overheating becomes a problem. When this happens, the other components of the system will begin to fail. A simple way to identify internal leaks is to test the system's full-load and no-load duty cycle. If it takes a lot of time to complete the loaded action than the no-load time, then the pump may be suspected to be ineffective.
Once a hydraulic component in a hydraulic system leaks, it will not only cause waste of the medium and environmental pollution, but also cause the entire hydraulic system to malfunction and stop the work, resulting in safety and quality accidents.
In order to reduce the failure of the hydraulic system, improve the efficiency of the hydraulic system, prevent environmental pollution and reduce the loss of the hydraulic medium, it is necessary to pay attention to the leakage problem, analyze the cause of the leakage, and take corresponding measures to reduce leakage to avoid 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. Therefore, the pressure of the system should be the same as the optimal value required by the hydraulic system, so that it can meet the working requirements and avoid Excessive system pressure necessary.
2) Working temperature. Most of the energy lost by the hydraulic system is converted into heat. Some of this heat is dissipated into the atmosphere through the surface of the hydraulic component itself, pipes and fuel tanks, and the rest is stored in the hydraulic oil to raise the temperature of the oil. The increase in oil temperature not only reduces the viscosity of the oil, but also increases the amount of oil leakage, which also causes the sealing components to accelerate aging and premature failure, causing serious leakage.
3) Oil cleaning procedure. The hydraulic fluid of the hydraulic system often contains various impurities. For example, the hydraulic components are not cleaned during installation. The iron scraps and paints attached to the upper surface enter the hydraulic oil; the dust and dirt invading the hydraulic equipment contaminate the hydraulic oil; Colloidal, asphaltene and carbon residue produced by oxidative deterioration of oil. The impurities in the hydraulic oil can aggravate the wear of the sliding surface of the hydraulic component, the valve plug of the hydraulic valve is blocked, the small hole is blocked, the seal is damaged, etc., thereby causing damage to the hydraulic valve and causing leakage of the hydraulic oil.
4) Selection of sealing device. Proper selection of the sealing device is very important to prevent leakage of the hydraulic system. The selection of the sealing device is reasonable, can improve the performance and efficiency of the device, and prolong the service life of the sealing device, thereby effectively preventing leakage. Otherwise, the sealing device does not adapt to the working conditions, causing premature wear or aging of the sealing element, which may cause leakage of the medium. In addition, the processing accuracy of hydraulic components, the tightness of the hydraulic system piping connection and its anti-vibration capability, and the condition of equipment maintenance also 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 at the time of design, and should not be adjusted or changed during use.
2) Control the change in temperature. Controlling the rise in temperature of the hydraulic system generally begins with the design of the fuel tank and the setting of the hydraulic piping. In order to improve the heat dissipation effect of the fuel tank, the heat dissipation surface of the oil tank can be increased, and the oil discharge and oil return inside the fuel tank are separated by a partition plate. The temperature of the tank hydraulic oil is generally allowed to reach between 55 ° C and 65 ° C, and the maximum temperature should not exceed 700 ° C. When the temperature of the naturally cooled oil exceeds the allowable value, it is necessary to add a cooling water pipe inside the fuel tank or a cooler on the returning oil line to lower the temperature of the hydraulic oil. When setting the hydraulic lines, the distance between the tank and the actuator should be short, and the elbows of the pipeline, especially the 90° elbow, should be as small as possible to reduce pressure loss and reduce friction.
3) Maintain the cleanliness of the hydraulic fluid. The oil filter device is used to filter the hydraulic oil regularly or continuously, so as to reduce the impurity content of the hydraulic oil as much as possible, and ensure the cleanliness of the oil is in line with national standards.
4) Reasonably select the sealing device. In order to properly select the sealing device, it is necessary to be familiar with the form and characteristics of various sealing devices, the characteristics of the sealing material, and the conditions of use of the sealing device (such as the size of the working pressure, the temperature of the working environment, the speed of the moving part, etc.). Comparing the actual conditions of use with the permissible conditions of use of the seal must ensure that the seal has good sealing properties and a long service life.
5) In daily maintenance, it is necessary to strengthen the inspection of equipment and conduct regular tests on hydraulic oil to ensure that the oil quality is clean and in compliance with standards. Choose a durable, standard-compliant seal that replaces the seal on a regular or periodic basis, enhances equipment maintenance, minimizes leakage, and ensures proper operation of hydraulic equipment.
6) Proper selection of the sealing device is very important for preventing leakage of the hydraulic system. The selection of the sealing device is reasonable, the performance and efficiency of the device can be improved, the service life of the sealing device can be prolonged, and the leakage can be effectively prevented. Otherwise, the sealing device does not adapt to the working condition, causing premature wear or aging of the sealing member, which causes the medium. leakage.
In addition, the processing accuracy of hydraulic components, the tightness of the hydraulic system piping connection and its anti-vibration capability, and the condition of equipment maintenance also affect the leakage of hydraulic equipment.