The operating temperature of the fluid in the hydraulic-hydraulic hydraulic transmission system is generally in the range of 30-80°C, while the temperature of the oil in the hydraulic system of the machine tool must be controlled within the range of 30-60°C. If the oil temperature exceeds this range, there will be many adverse effects on the hydraulic system. The main effects of rising oil temperature are as follows:

1. The increase of hydraulic oil temperature will reduce the viscosity of the oil, so that the leakage of components and the oil in the system will increase, which will reduce the volumetric efficiency of the hydraulic pump.

2. The increase of hydraulic oil temperature will reduce the viscosity of the oil, which will increase the flow of oil through throttling orifices or slit valve ports. This will cause the original adjusted working speed to change, especially for hydraulic followers. The system will affect the stability of the work and reduce the work accuracy.

3. After the viscosity of the hydraulic oil increases, the viscosity of the lubricating film between the relative moving surfaces will become thinner, which will increase the mechanical wear. When the oil is not clean, it is prone to failure.

4. The increase of hydraulic oil temperature will cause thermal deformation of the mechanical components. The hydraulic valve components will expand after being heated, which may reduce the clearance for fitting, thus affecting the movement of the valve core, increasing wear and even being stuck.

5, the increase of hydraulic oil temperature will accelerate the oxidation of the oil, resulting in deterioration of the oil, reducing the service life of the oil. Precipitates, such as asphalt, which are precipitated in the oil, can also clog the small holes and crevices of components and affect the normal operation of the system.

6. If the oil temperature of the hydraulic oil is too high, the sealing device will quickly deteriorate and lose its sealing performance.