According to statistics, 70% of the faults of hydraulic devices are related to hydraulic oil, and about 90% of these 70% are caused by impurities. The inspection contents of hydraulic oil mainly include the following points: cleanliness, color, viscosity and consistency of hydraulic oil; Except the smell. When the hydraulic oil flows from the high pressure side to the low pressure side without mechanical work, heat will be generated in the hydraulic system. If the temperature of hydraulic oil is too high, the expensive seal will deteriorate, the oil will be oxidized and fail, resulting in corrosion and deposition, even blocking the damping hole and accelerating the valve wear. Too high temperature will jam valves and pumps, and high temperature will also bring safety problems. By checking the oil temperature in the oil tank, it is sometimes possible to eliminate system failures before serious harm occurs. In most systems, the safety valve is the main heat source, and the excessive flow through the safety valve is another main reason for generating heat. Because inefficiency is related to energy loss, we can know whether there is inefficiency by checking the working temperature. For the hydraulic system, controlling the pollutants in the oil is a major task, and the sources of pollutants mainly include the following aspects:
1, enter with new oil.
2. During the internal assembly of the system.
3, with the surrounding air.
4. Internal wear of hydraulic components.
5. It enters through a leaking or damaged seal.
6. It was brought in during maintenance.
The removal and control of pollutants need to use filters, and the hydraulic system may be equipped with good filters, and the installation position is also very suitable. However, if it is not carefully maintained in time, the filter screen will not play its due role and waste the cost. So we should do the following work:
1. Make the filter maintenance plan and strictly implement it.
2, check the filter replaced from the system, find out the omen of system failure and potential problems.
3. Do not pour any leaked oil back into the system.
Second, the failure of pumps and valves.
If the pump is installed and used correctly, the hydraulic pump can be used continuously for many years without maintenance. Once a problem is found, it should be found and eliminated as soon as possible. With the hydraulic diagram, it is much easier to diagnose the system fault. The manufacturing precision of hydraulic valve is high. As long as it is properly assembled and kept in good working condition, there is little leakage, and the pressure, direction and flow rate of oil in the system can be accurately controlled. Contaminants in oil are the main cause of valve failure, and a small amount of fiber, dirt, oxide or sludge can cause failure or valve damage. If the products of trusted manufacturers are adopted, the possibility of improper design is very small. The failure of pumps and valves is mainly caused by the following reasons:
1, external conditions
1. 1 The fastening bolt is loose and deformed and damaged due to over tightening.
1.2 The load changes sharply.
1.3 vibration and impact.
1.4 errors in assembly, disassembly and repair, quality of tools, damage and deformation of parts, and injuries and losses.
1.5 Deformation and damage caused by pipeline distortion or pipeline error.
2. Hydraulic oil status
2. 1 mixed with impurities, water, air and deterioration.
2.2 Whether the viscosity and temperature are appropriate.
2.3 lubricity.
2.4 Whether the inhalation conditions are good (to prevent cavitation, excessive positive pressure or negative pressure).
2.5 Abnormal high pressure and pressure fluctuation.
3, the component itself is good or bad
3. 1 structure and strength.
3.2 Quality of parts (bearings, oil seals, bolts, shafts).
3.3 Wear, scratch and sticking of sliding parts.
3.4 Wear, scratch, deformation and deterioration of parts.
3.5 Oil leakage (internal leakage and external leakage).
In order to make the maintenance of valves safe and reliable, the following principles should be followed:
1. Before removing the hydraulic valve, please cut off the power supply, so as to prevent the system from accidentally starting or making tools fly out.
2. Before removing the hydraulic valve, move the valve handle in all directions to release the pressure in the system.
3. Before removing the hydraulic valve, lock all working mechanisms of hydraulic transmission or put them in a lower position.
Third, the accumulator is faulty.
Accumulator is a device for storing high-pressure oil. When the pump is in normal no-load state or idling state, it can be filled with oil. The high-pressure oil stored in the accumulator can be released when necessary to supplement the flow of the pump or supply oil to the system when the pump stops. Most of the accumulators we use now are diaphragm type and airbag type; The accumulator stores energy by compressing inert gas (usually nitrogen), and the actual inflation pressure should not be higher than the critical value. In most cases, the inflation pressure should be in the range of 1/3 ~ 1/2 of the highest pressure of the system, which is the best and the working characteristics of the loop rarely change. In particular, do not use oxygen or mixed gases containing oxygen.
In short, through a deeper understanding and mastery of the hydraulic system and continuous improvement of technology and working ability, we can better solve the main problems faced by users of hydraulic equipment and manage the hydraulic system well. When there is a problem in the system, the real cause of the system failure can be found out. More work should start with routine inspection, pay attention to the details of equipment inspection and maintenance, and exclude all kinds of factors leading to failure in the early stage of failure. Through the continuous improvement and perfection of the working cycle, it is predicted that the maintenance work can go further in the ever-changing working environment, ensure the equipment to play a greater benefit, and realize the goal of zero accidents of equipment.