After the variable speed pump absorbs the working oil from the oil pan, part of it will pass through the vertical roller mill, then pass through the radiator for heat dissipation, and finally enter the oil pan; The other part is through the transmission. At this time, if the inlet oil pressure of the system is insufficient, the working oil pressure entering the vertical mill will be too low, resulting in the problem of insufficient inlet oil, so that the transmission oil can not be cooled in time, and finally the transmission temperature will be too high. This problem is mainly caused by three aspects:First of all, the system pressure is insufficient. The pressure regulating valve is the main part of the hydraulic transmission, which can control the working oil pressure in the system. When the valve core of the pressure regulating valve fails or is damaged, the regulating function will not be reflected, resulting in insufficient oil supply and pressure reduction of vertical mill.Secondly, in the process of using the variable speed pump, the gap between the gear and the end cover will become larger, resulting in serious oil leakage. At the same time, the insufficient system pressure and the air suction of the variable speed pump will also cause the vertical mill oil supply can not be met.Finally, it is also possible that the piston in the transmission is worn due to long-term work, which leads to the leakage problem and makes the oil temperature rise.