1) Set target cleanliness level

The manufacturing clearance in the hydraulic components can be divided into two basic ranges, that is, a minimum of 5 μ m. Maximum 25 for lower pressure elements μ m。 The actual working clearance of a component is determined by the type of component and the working process conditions it experiences. These clearances help determine the fluid cleanliness required for this element. According to engineering data and field experience, the recommended pollution levels of pumps, motors, directional valves, pressure control valves and flow control valves can be selected by referring to relevant design manuals.

The hydraulic system shall have a target cleanliness level clearly indicated in its engineering documents. This target shall be set after considering various factors affecting the system, including oil, operating temperature, starting temperature, temporary load rate, service life of components required by the system and safety issues. Since the actual cleanliness level of the oil varies with the sampling points in the system (i.e. oil tank, pressure pipe, oil return pipe, etc.), unless otherwise specified, it is assumed that the target cleanliness level is set for the oil return pipe and oil return pipe upstream of the filter.

2) Keep flushing off

The most critical time for the life of the hydraulic system or lubrication system is the initial running in period. During this period, various elements produced a lot of debris and mixed with debris in the assembly process, which was washed through the whole system by oil. While the system is operating without load, the pollutant can be quickly captured and removed from the system. The flushing process has three steps. First, drive the pollutants out of the shelter and transport them to the filter; Second, make the machine move so that oil flows through all pipelines and components; Third, use high efficiency filters to catch pollution. The removal and transport of contaminants is best achieved by using low viscosity fluids that flow at high speeds. Special flushing fluid can be used or system hydraulic oil can be used at high temperature. In order to flow through all lines, all valves should be operated several times. In some cases, the component connection line must be bypassed to allow a large flow of fluid to flow through the line. Capture debris fairly quickly and flush the system to the required level of contamination. The target cleanliness level of washing should be two levels lower than the target cleanliness level for system operation. When new oil is introduced into a properly flushed system, it will take less time to reach system balance.

3) Regularly check the oil quality

The oil performance can be selected according to the needs, but it must be strictly controlled that the oil is free of dirt and clean. During refueling, filter to prevent the invasion of dust and fiber debris. Check the oil level frequently. Clean the magnetic rod in the hydraulic oil tank and oil return filter and the magnetic cup of the servo circuit filter frequently for new machines, remove the dust from the hydraulic cooler, and replace the filter element. Regularly check the oil quality, mainly in the following three aspects:

(1) Oxidation degree of hydraulic oil. During the use of hydraulic oil, due to the change of temperature, the role of oxygen in the air and sunlight, it will gradually be oxidized, which will change its viscosity and other properties. The degree of oxidation is usually judged from the color and smell of hydraulic oil. If the hydraulic oil is dark brown and has a foul smell, it indicates that it has been oxidized. The darker the brown color and the stronger the odor, the more oxidized it is. At this time, replace the oil.

(2) The degree of moisture in the hydraulic oil. If the hydraulic oil is mixed with water, its lubricating performance will be reduced and the metal will be corroded. The degree of water mixing in the hydraulic oil is usually judged according to the change of its color and smell. If the color of the hydraulic oil is milky white and the smell does not change, it means that too much water is mixed; In addition, take a small amount of hydraulic oil and drop it on the hot iron plate. If it makes a "bell" sound, it means it contains water. At this time, replace the oil.

(3) The hydraulic oil contains impurities. After the machine has been working for a period of time, take a few drops of hydraulic oil and put them on your hands. Twist them with your fingers to see if there are metal particles, or observe if there are tiny flash points in the sun. If there are more metal particles or flash points, the hydraulic oil contains more mechanical impurities. At this time, the hydraulic oil shall be replaced, or the hydraulic oil shall be drained for sedimentation for not less than 42h, and then filtered for use.