Roots vacuum pump compressed gas required power is proportional to the pressure, once the gas pressure is too high, the pump may be overloaded, causing the motor winding burn. There are several ways to solve pump overload problems: (1) The use of mechanical automatic pressure regulating bypass valve. The by-pass valve is mounted on the by-pass line between the outlet and inlet of the Roots vacuum pump. This valve controls the pressure difference between the pump inlet and outlet does not exceed the rated value. When the differential pressure reaches the rated value, the valve opens automatically by the differential pressure effect, allowing the Roots vacuum pump outlet to communicate with the inlet port, thereby rapidly reducing the pressure difference between the inlet and outlet. At this moment, the Roots vacuum pump works with almost no pressure difference. When the pressure drop below the rated value, the valve automatically shut down, the gas through the Roots vacuum pump from the foreline pump. The Roots vacuum pump with bypass relief valve can be started simultaneously with the forepump to make the unit easy to operate. (2) the use of hydraulic coupling The use of hydraulic couplings also prevents overloading of the pump, allowing the pump to operate at high differential pressure. Hydraulic couplings are installed between the pump and the motor. Under normal working conditions, the hydraulic coupling transmits the rated torque from the motor end to the pump. The maximum pressure difference of Roots vacuum pump is determined by the maximum torque transmitted by the hydraulic coupling, and the maximum torque that can be transmitted by the hydraulic coupling is adjusted by the amount of liquid in it. When the pump is working under high pressure difference or starting with the fore-stage pump, there is a difference in rotation speed within the liquid coupling, that is, sliding. Only a certain torque is transmitted to decelerate the pump. As pumping proceeds, the gas load decreases and Roots vacuum pumps gradually accelerate to the rated speed. (3) using vacuum electrical components to control the pump inlet pressure Roots vacuum pump inlet pipe at the installation of vacuum diaphragm relays or electrical contact pressure gauges and other pressure-sensitive vacuum components. When the vacuum system is started, the pressure sensitive element sends out a signal when the pressure at the Roots vacuum pump inlet falls below a given value (the pump allows the start-up pressure) and the Roots vacuum pump is turned on by the electrical control system Through the pipeline, then turn off the bypass pipe valve). If the pump inlet pressure is higher than the specified value, then automatically close Roots vacuum pump (or at the same time open the pump bypass line valve), thus ensuring the Roots vacuum pump reliable operation.