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Maintenance of hydraulic system

- Jun 05, 2018 -

Matters needing attention

A bit of mechanical common sense knows that energy converts to each other, and it is best to apply this knowledge to the hydraulic system to explain the power loss of the hydraulic system, and the power of the hydraulic system will cause the loss of energy on the one hand, and the total efficiency of the system is reduced. On the other hand, the loss of this part of the energy will be the same. It will turn into heat, causing the temperature of hydraulic oil to rise and the oil to deteriorate, resulting in the failure of hydraulic equipment. Therefore, when designing the hydraulic system, the power loss of the system should also be fully considered when meeting the requirements of use.

First, from the power source - pump aspect, considering the diversification of the actuators' working conditions, sometimes the system needs large flow and low pressure; and sometimes it needs small flow and high pressure. Therefore, the choice of pressure limiting variable displacement pump is appropriate, because the flow of this type of pump varies with the pressure of the system. When the system pressure is reduced, the flow rate is relatively large, which can meet the fast travel of the actuator. When the system pressure is increased, the flow rate decreases correspondingly, which can satisfy the working stroke of the actuator. This can not only satisfy the work requirements of the actuator, but also make the consumption of power more reasonable.

Second, pressure loss and flow loss are unavoidable when hydraulic oil flows through various hydraulic valves. The energy loss of this part occupies a large proportion in all energy losses. Therefore, it is an important aspect to reduce the power loss by selecting hydraulic pressure reasonably and adjusting the pressure of the pressure valve. The flow valve is selected according to the flow regulation range in the system and ensures that the minimum stable flow rate can meet the requirements of the use. Pressure valve pressure is as low as possible when it meets the normal work of the hydraulic equipment.

Third, if the actuator has the requirement of speed regulation, when selecting the speed regulating loop, we must not only meet the requirements of speed regulation, but also minimize the power loss. The main speed regulating circuits are throttling speed regulating circuit, volume speed regulating circuit and volume throttling speed regulating circuit. The throttle speed regulating circuit has high power loss and low speed stability. The volumetric speed control loop has neither overflow loss nor throttle loss, and has high efficiency, but poor stability at low speed. If we want to meet the requirements of two aspects at the same time, the differential pressure variable pump and throttle valve can be used to adjust the volume throttle speed control loop, and the pressure difference between the two ends of the joint flow valve is as small as possible to reduce the pressure loss.

Fourth, the rational selection of hydraulic oil. When the hydraulic oil flows in the pipeline, it will be sticky, and when the viscosity is too high, it will produce a larger internal friction force, resulting in the heat of the oil and the resistance to the fluid flow. When the viscosity is too low, it is easy to create leakage, which will reduce the volumetric efficiency of the system. Therefore, the oil with good viscosity and better viscosity temperature is generally chosen. In addition, when the oil is flowing in the pipeline, there is also the loss of pressure and local pressure. Therefore, the pipeline is shortened and the elbow is reduced when the pipeline is designed.

The above is a few work to avoid the power loss of the hydraulic system, but there are many factors that affect the power loss of the hydraulic system, so if a hydraulic system is designed specifically, it is necessary to consider the requirements of other aspects in a comprehensive way.