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.

1、 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 vacuum pump. This valve controls the pressure difference between the pump inlet and outlet not to 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 vacuum pump are connected, and the pressure difference between the inlet and outlet is reduced rapidly. At this time, roots vacuum 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 away from the front stage pump through roots vacuum pump. Roots vacuum 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) The hydraulic coupling can also prevent the overload of the pump and make the pump 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 vacuum 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 vacuum pump gradually accelerates to the rated speed.

(3) Vacuum electrical components are used to control the pump inlet pressure, and pressure sensitive elements such as vacuum diaphragm relay or electric contact vacuum pressure gauge are installed at the inlet pipeline of Roots vacuum pump. After the vacuum system is started, when the pressure at the inlet of Roots vacuum pump is lower than the given value (allowable starting pressure of the pump), the pressure sensing element will send a signal to open the roots vacuum pump through the electrical control system (if the bypass pipeline of Roots vacuum pump is installed in the vacuum system, the valve of bypass pipeline shall be closed at the same time). If the pump inlet pressure is higher than the specified value, the roots vacuum 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 vacuum pump.

2、 Repair method

With the increasing application of roots pump, due to the impact of harsh environment such as high temperature, high pressure, strong corrosion and cavitation erosion, the equipment often appears wear, corrosion and leakage, which restricts the normal production of enterprises, and even leads to serious safety accidents such as fire, explosion and pollution. At the same time, the unexpected shutdown caused by roots pump failure also affects the production efficiency and product quality, and increases the cost investment of enterprises. The common faults of roots pump are mainly divided into the following two categories:

1. Wear of bearing position

The wear of transmission parts is a common problem of roots pump, and the number is large and the damage is frequent, including bearing position, bearing seat, bearing chamber, keyway and thread. The traditional repair welding machine processing method is easy to cause material damage, resulting in deformation or fracture of parts, with greater limitations; brush plating and spray machining methods often need outsourcing, which not only has a long repair cycle and high cost, but also can not fundamentally solve the cause of wear and tear because the repair material is metal material.

The latest method is to use polymer composite materials, which have super strong adhesion, excellent compressive strength, wear resistance and corrosion resistance and other comprehensive properties. 2211f polymer composite repair material can be used in the case of relatively small wear size of transmission parts, which can avoid mechanical processing, thermal stress and thermal influence of repair welding, and repair thickness is not limited. At the same time, the wear resistance of the product and the yielding property of metal materials can ensure the 100% contact and coordination of the repaired parts and reduce the impact shock of the equipment It can avoid the possibility of wear and tear, and greatly extend the service life of equipment components (including bearings), save a lot of downtime for enterprises, and create huge economic value.

2. Repair steps:

1. Mold processing: making standard split mold.

2. Surface treatment: degreasing, grinding, cleaning, thoroughly removing the surface oxide layer, cleaning the surface with acetone.

3. Blending materials: strictly in accordance with the proportion of blending, and stirring evenly, until there is no color difference.

4. Coating material: apply a thin layer of material to ensure bonding and complete coverage, and then evenly apply the material to the repair surface to reach the required repair thickness.

5. Installation mold: Brush release agent, install and fix to ensure that surplus material is extruded.

6. Demoulding: after curing, remove the mold to clean up the surplus materials. The materials can not be knocked, but can be removed by polishing machine, file and other tools to meet the installation requirements.

Corrosion, erosion.

The forms of metal corrosion can be divided into overall (uniform) corrosion and local corrosion. The former occurs more evenly on the whole surface of the equipment, while the latter occurs only locally. Corrosion, crack, crack, corrosion, crack, corrosion, etc.