The relevant data show that more than 70% of the failures of the hydraulic system are caused by the pollution of hydraulic oil. Therefore, the control of oil pollution is very important to ensure the reliable operation and long service life of the hydraulic system. The control of hydraulic oil pollution should mainly grasp the following links.
1.1 A large number of contaminants will inevitably remain in the newly assembled or overhauled hydraulic system, which needs to be thoroughly cleaned. When cleaning, a temporary cleaning pump is used to circulate the system, and the fuel tank and hydraulic pump of the system can also be used. The cleaning solution can be the oil prepared for use in the system, or the low viscosity oil dissolved with it. Do not use kerosene or gasoline as the cleaning solution. When cleaning, large flow should be used as far as possible in the pipeline in a turbulent state. A high-performance filter should be added to the system, and the components should be activated to knock the welding joints and joints until there is no longer a large amount of pollutants on the filter.
1.2 Prevent the intrusion of pollutants. The main measure to prevent the invasion of solid impurities is to install an air filter in the tank breathing hole.
a. Use reliable sealing device.
b. When the system is filled with oil, it must be filtered, and the filtration accuracy shall not be lower than the system requirements.
c. Special attention should be paid to maintaining cleanliness when removing and repairing hydraulic components.
d. Cleaned components and pipes should be covered with clean silk or plastic cloth. Due to the poor lubricity and rust resistance of the general solvent, the solvent should be cleaned after cleaning the component with the solvent.
e. Clean the oil tank regularly. Do not use fabrics that are easy to retain fibers when cleaning the oil tank, and do not paint the inner wall of the oil tank that may fall off.
f. The main measures to prevent air from entering the system are that the oil tank oil level must be kept within the required range, generally about 23 of the oil level limit of the oil level meter, and the suction pipe mouth of the pump and the system return pipe mouth must be inserted under the low oil level to avoid suction and return oil rush, resulting in bubbles.
g. When the pump is located in the oil tank, it should prevent the leakage of the suction pipe and the blockage of the suction filter, and the closed system should have a high enough oil pressure to prevent the leakage of gas into the low pressure pipeline.
h. When the oil is first filled, the air in the system should be patiently removed. Do not make the pump run for a long time before confirming that the air is exhausted, because the air is difficult to clean after mixing with the oil.
i. The main way for the hydraulic system to mix water is the oil tank and the cooler. The water in the atmosphere can easily enter the hydraulic oil through the tank breathing hole, especially in the tank in a humid environment, so the tank should be placed in a dry room as much as possible. With seawater cooling systems, special attention should be paid to preventing rust through the cooler coils and leakage.
1.3 Strict filtration plays an important role in the reliability of the hydraulic system.
The filtration accuracy is generally selected according to the impurity sensitivity element in the system. The system filter used for the first time should be cleaned in time, and the cycle should be shorter, and the cycle should still be carried out according to the requirements of the manual or according to the extent of the increase in the pressure difference between the front and back of the filter. By analyzing the categories of impurities, it is found that the working condition of the system, such as when there are iron chips, indicates that the components are damaged or excessive wear. The paper filter cartridge of the absorption filter can only be used once, the working life should not be too long, the quality of the hydraulic oil should be checked regularly, and it should be replaced if necessary.
Long-term use of hydraulic oil quality will deteriorate. However, it is difficult to determine the service life of hydraulic oil, it varies greatly with the type of hydraulic equipment system and the materials used and the management, and generally the service life can only be roughly estimated.
Of course, the late oil change will affect the performance and service life of the hydraulic system, and the incidence of failure will increase significantly; And changing the oil too early will cause economic waste. Most systems about two thirds of the oil change once a year, if the maintenance management is good, the actual service life can reach 4-6 years, the working time is not long device may be longer.
In the management of hydraulic oil, whether the oil needs to be changed can be determined according to whether the change of the main performance indicators of hydraulic oil exceeds the limit range. The oil should be sampled every six months to a year. Sampling should be carried out after a period of system operation, taking samples from the line during operation. If this is not possible, samples can also be taken from a depth of 12 below the tank level. Experienced managers can roughly judge the quality change from the appearance, color, odor and viscosity of hydraulic oil. If the oil color becomes lighter, it may be mixed with diluted oil; The color of the oil becomes darker, slightly black, the oil has deteriorated or been contaminated; The color of the oil does not change much, but it is cloudy, often caused by mixing water.
When changing the oil, the hydraulic oil in the oil tank should be discharged first, after strictly cleaning the oil tank and filter, the new oil is added through filtering, starting the oil pump to discharge the old oil in the system using the new oil, the discharged old oil shall not flow back to the tank, but should be led to other oil storage containers, until the old oil in the pipelines are discharged and the new oil flows out. When changing the oil, pay attention to filling the oil tank to prevent the oil pump from being empty. It is strictly prohibited to mix old and new oil, otherwise the life of hydraulic oil will be greatly reduced.
2 Control the working oil temperature when working, the suitable oil temperature should be maintained at 30-50℃.
When the oil temperature is too low, the viscosity of the oil is too large, which not only makes the pump suction difficult, the flow loss is large, but also may make the pump discharge pressure is too large, the motor is overloaded, and even cause the pipeline or joint to burst. Therefore, it is not allowed to start when the oil temperature is below 10℃. When the oil temperature is less than 10℃, the oil should be circulated in the system without load until the oil temperature rises to more than 10℃ before loading. Hydraulic deck machinery must be paid attention to when starting in winter.
The oil temperature is too high, the viscosity decreases, the volumetric efficiency decreases, and it will cause poor lubrication, and even the parts are stuck due to thermal expansion. In addition, the oil temperature is too high will accelerate oxidation, shorten the service life.
Generally speaking, the oil tank inlet temperature is not allowed to exceed 60 ° C, and the hydraulic equipment should not be used when the oil temperature is higher than 70 ° C. When the ambient temperature is outdated and the hydraulic deck machinery is continuously overloaded, special attention should be paid to the oil temperature.
3 Abnormal phenomena such as leakage can cause oil loss, decrease efficiency, and pollute the environment, and make the system not work normally in serious cases. Therefore, the sealing components of each sealing part should be regularly checked, strengthened maintenance, timely replacement of damaged seals, and elimination of abnormal leakage. Regular inspection in use, the oil level of the working tank can help judge the leakage situation, and the phenomenon of a large amount of water can also be found in the work. The management staff is usually found to maintain a rigorous and serious working attitude, develop good inspection habits, hear and see, and the hydraulic system should pay attention to the movement speed of the hydraulic actuator and whether there is abnormal noise and vibration in the use of the hydraulic system. When problems are found, the causes should be identified in time, and the hidden dangers should be eliminated in time.
4 The deactivated hydraulic system shall be inspected monthly. Pay attention to check whether the safety protection device and electrical insulation are normal, and lubricating oil and grease should be added to the hinge bearing pulley and other exposed friction parts according to the time interval and part specified in the manual.
