On the one hand, when the oil level of vertical roller mill is too high, the high-speed rotating parts in the transmission will increase the rotation resistance because of too much oil, resulting in the rise of oil temperature. 

On the other hand, when the oil level is too low, it will accelerate the oil circulation speed in the transmission work, resulting in the short residence time of the transmission oil in the oil pan, resulting in poor heat dissipation effect, and the pressure in the hydraulic system is reduced due to the absorption of air by the variable speed pump.