What are the methods to control hydraulic oil contamination?

1) Set a target cleanliness level

The fabrication gap in hydraulic components can be divided into two basic ranges, namely 5μm for high-pressure components and a maximum of 25μm for lower pressure components. The actual working gap of a component is determined by the type of component and the working process conditions it undergoes. These gaps help determine the desired oil cleanliness of the component. According to the engineering data and field experience, the recommended pollution level of the pump, motor, direction valve, pressure control valve and flow control valve can be selected by referring to the relevant design manual.

Hydraulic systems should be clearly stated in their engineering documentation of the target cleanliness level, should take into account the various factors affecting the system including oil, operating and starting temperature, temporary load rate, system required components of the service life and safety issues, set this goal. Since the actual cleanliness level of the oil varies with the sampling point in the system (i.e. tank, pressure line, return line, etc.), unless otherwise indicated, it is assumed that the target cleanliness level is set for the return line and the return line upstream of the filter.

2) Rinse off well

The most critical time for the life of the hydraulic system or lubrication system is the initial running period. During this time, the components generate a lot of debris and are mixed with debris during assembly, which is washed through the entire system by oil. This contaminant is quickly captured and removed from the system while the system is operating without load. There are three steps to the flushing process. To drive pollutants out of the den and transport them to the filter; To make the machine operate so that the oil flows through all pipes and components; Third, use high-efficiency filters to capture pollution. Removing and transporting contaminants is achieved by using a low-viscosity fluid that flows at high speeds. Special flushing fluids can be used or system hydraulic fluids can be used at high temperatures. In order to flow through all lines, all valves should be operated several times. In some cases, the component connection line is bypassed to allow a large flow of oil to flow through the line. Catch debris fairly quickly and flush the system to the desired level of contamination. The target cleanliness level of the wash should be two iso codes 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 equilibrium.

3) Check oil quality regularly

The performance of the oil can be selected according to the specific needs, but the oil is strictly controlled without dirt and clean. Filter when refueling, prevent the intrusion of dust and fiber debris, check the oil level frequently, the new machine should frequently clean the hydraulic tank, the magnetic rod in the oil return filter and the magnetic cup of the servo circuit filter, remove the ash of the hydraulic cooler, and replace the filter element. Regular inspection of oil quality, mainly in the following three aspects:

(1) The oxidation degree of hydraulic oil. Hydraulic oil in use, due to changes in temperature, oxygen in the air and the role of sunlight, will gradually be oxidized, so that its viscosity and other properties change. The degree of oxidation is usually judged from the color and smell of the hydraulic oil. If the hydraulic oil is dark brown in color and has a foul smell, it has been oxidized. The deeper the brown and the stronger the odor, the more severe the degree of oxidation, and the new oil should be replaced at this time.

(2) The degree of moisture in the hydraulic oil. If the hydraulic oil is mixed with water, it will reduce its lubrication performance and corrode the metal. To determine the degree of water mixed in hydraulic oil, usually according to its color and smell changes, such as the color of hydraulic oil is milky white, the smell has not changed, it means that too much water is mixed; In addition, a small amount of hydraulic oil is dropped on the hot iron plate, and if it makes a "horn" sound, it indicates that it contains water. New oil should be replaced at this time.

(3) The hydraulic oil contains impurities. After mechanical work for a period of time, take a few drops of hydraulic oil on the hand, twist it with your fingers, and see if there are metal particles, or observe if there are small flashes in the sun. If there are more metal particles or flash points, it means that the hydraulic oil contains more mechanical impurities. At this time, the hydraulic oil should be replaced, or the hydraulic oil should be released, and the precipitation of not less than 42h is carried out, and then the filter is used.