More than 70% of hydraulic system failures are caused by hydraulic media (mainly hydraulic oil). In addition to the contamination of the medium, the high temperature of the hydraulic oil is also one of the important reasons that affect the normal operation of the hydraulic system, especially in the case of high temperatures in summer. The hydraulic system has a normal operating temperature of 30-50 ° C, a maximum of 70 ° C, and a minimum of 15 ° C. What is the effect of excessive oil temperature on the performance of the hydraulic system, and what are the causes of excessive oil temperature? How to prevent it?
1. Influence on hydraulic oil viscosity
In the general industry, the working pressure of the hydraulic system is below 20MPA. Because under this pressure, the influence of pressure factors on the viscosity of hydraulic oil can be neglected, mainly considering the influence of temperature on viscosity; when the temperature rises, the cohesive force of oil molecules decreases, and the viscosity decreases.
The effect of the viscosity reduction of the hydraulic oil on the system is the increase of the leakage. The leakage principle of the hydraulic oil gap is known: the leakage is proportional to the reciprocal of the viscosity of the hydraulic oil, and the temperature increases, and the leakage increases exponentially.
2. It is more prone to cavitation
In the case of an increase in temperature, the air separation pressure and the saturated vapor pressure in the hydraulic oil increase, making cavitation more likely to occur. For example, a general hydraulic pump works when the vacuum is 0.5 MPA. Cavitation caused by cavitation can seriously damage the surface of components (especially power components), which can greatly shorten the service life of components, and at the same time reduce the working efficiency of the entire hydraulic system, such as the oil absorption capacity and volumetric efficiency of hydraulic pumps.
3. Accelerate the aging of hydraulic oil
Oxidation reaction is the first cause of aging of hydraulic oil, and the occurrence of oxidation reaction is closely related to oil temperature. It has been proved by experiments that when the oil temperature reaches the temperature zone (55-60 °C), the oil temperature rises by 10 °C, hydraulic pressure. The oxidation of the oil is doubled and its life is reduced by 50%. When the hydraulic oil is contaminated, it will accelerate the wear between the components, resulting in a vicious circle.