The power required by roots vacuum pump to compress gas is directly proportional to the pressure difference. Once the gas pressure difference is too high, the pump may overload and cause motor winding burning. The main methods to solve the problem of pump overload are as follows:

1、 Mechanical automatic pressure regulating bypass valve is adopted

The bypass valve is installed in the bypass pipeline between the outlet and inlet of roots pump, which controls the pressure difference between the inlet and outlet of the pump to not exceed the rated value. When the pressure difference reaches the rated value, the valve will open automatically by the differential pressure, so that the outlet and inlet of roots pump are connected, and the pressure difference between the inlet and outlet is reduced rapidly. At this time, roots pump works under almost no pressure difference load. When the pressure difference is lower than the rated value, the valve will close automatically, and the gas will be pumped out by the front pump through roots pump. The roots pump with bypass relief valve can be started at the same time with the front pump, which makes the unit operation simple and convenient.

2、 Hydraulic coupling is adopted

Professionals believe that: the use of hydraulic coupling can also prevent the overload phenomenon of the pump, so that the pump can work under high pressure difference. The hydraulic coupling is installed between the pump and the motor. Under normal working condition, the hydraulic coupling transmits rated torque from the motor end to the pump. The maximum pressure difference of roots pump is determined by the maximum torque transmitted by the hydraulic coupling, and the maximum torque transmitted by the hydraulic coupling is adjusted by the amount of liquid in it. When the pump works under high pressure difference or starts at the same time with the front stage pump, there is a speed difference in the liquid coupling, that is, sliding. Only a certain torque is transmitted to make the pump work at a reduced speed. With the pumping process, the gas load decreases and roots pump gradually accelerates to the rated speed.

3、 Using vacuum electrical components to control the pump inlet pressure

Pressure sensitive elements such as vacuum capsule relay or electric contact vacuum pressure gauge are installed at the inlet pipeline of roots pump. After the vacuum system is started, when the pressure at the inlet of roots pump is lower than the given value (allowable starting pressure of the pump), the pressure sensing element will send a signal to start the roots pump through the electrical control system (if the bypass pipeline of roots pump is installed in the vacuum system, the valve of bypass pipeline shall be closed at the same time). If the inlet pressure of the pump is higher than the specified value, the roots pump will be automatically closed (or the bypass pipeline valve of the pump will be opened at the same time), so as to ensure the reliable operation of roots pump.