Roots vacuum pump of correct use

Roots vacuum pump is widely used in the key parts of paper consumption, such as web, vacuum couch, vacuum press and wool cloth dehydration. The output of roots pump directly affects the output and quality of paper.

When the flow rate and vacuum degree decrease, it will cause the moisture change of the paper page and form the paper defects such as sticking roller and embossing in the consumption process. Therefore, it is very important to use roots pump well.

1、 Adjust the clearance between impeller and rotor frequently

As we all know, roots pump is a kind of vacuum pump caused by the change of volume caused by the meshing of two “8-shaped” relative rotating rotors, so it is also called volume vacuum pump. There must be a continuous contact line at the place where the rotor of the vacuum pump is required to engage during the operation to prevent the gas from the exhaust port from flowing back to the vacuum pump. Therefore, it is necessary to check the engagement of the two rotors frequently. With the extension of operation time, the impeller has been worn for a long time, but also limited by the directional rotation, resulting in uneven meshing clearance between the two impellers, resulting in a collision, resulting in a concave surface of the impeller. as a result, two impeller rotor has different levels of wear in outer diameter and length, and the gap between impeller and impeller rotor and shell also increases.

Thus, the vacuum degree of roots pump is reduced, and the time is large and the time is small. It is necessary to maintain and adjust the clearance between the impeller and the end cover and the vacuum pump housing in time. If the clearance between the impeller and rotor is too small, the contraction ratio in roots pump will increase, which will cause the air in the vacuum pump to heat up, and soon lead to the heating of gearbox and motor. The reason why the gap between the two impellers becomes smaller is that additives, fillers, rubber and other substances are attached to the surface of the impellers. When this phenomenon occurs, the two rotors become too tightly meshed and even stuck. It is very difficult or basically does not rotate when it is restarted after shutdown, and the motor is burnt out sometimes. Therefore, it is necessary to clean the inner wall of the vacuum pump casing and the surface of the impeller rotor. The cleaning solution can be 5% sodium hydroxide solution or 5% hydrochloric acid solution. After acid cleaning, rinse with clean water to avoid corrosion.

2、 Check the sealing condition of vacuum pump shaft frequently

The sealing function of the vacuum pump shaft is to prevent the compressed gas in the vacuum pump from leaking out between the vacuum pump shaft and the vacuum pump housing, and at the same time to prevent the external air from entering the vacuum pump. Mechanical seal and anti spiral seal, asbestos packing seal and rubber seal ring are often used.

The mechanical seal is the best. Recently, the magnetic powder seal newly developed by Northeast University of technology has a good sealing effect.

3、 Reasonable selection of rotations of roots pump

In the application of roots pump, its revolution must be adjusted according to the practical demand. Obviously, the improvement of revolution can increase the theoretical exhaust volume, increase the volumetric efficiency, and increase the output significantly, but the resulting increase in noise will worsen the operating environment. When it is necessary to increase the number of revolutions in consumption to improve the ability of the vacuum pump, it shall be adjusted within the allowable range of workshop noise. Generally, the method of progressive revolution is not used. When the pumping speed of the vacuum pump is higher than the rated operation value,

In addition to stop adjustment with bypass valve, speed shall be reduced and reactive power consumption shall be reduced. In this way, for the equipment itself, it can reduce faults, reduce vibration, increase power storage, improve overload ability, improve operating environment and reduce noise.

4、 Series application of Roots vacuum pump

In consumption, two pumps are often used in series because the output of the vacuum pump can not meet the requirements. the ordinary roots vacuum pump’s high efficiency working area is between -300 to -400mmHg column, and it needs to reach more than -500mmHg column. The vacuum degree of single vacuum pump is difficult to complete, so two pumps can be connected in series. In accordance with the series connection mode adopted in this process, the vacuum pump placed at the front should play a pre pumping role, and the pumping speed of the pump at the back must be 1.5-2 times higher than that of the vacuum pump at the front. Only in this way can we play our due role.
the roots vacuum pumps abroad do not only use two vacuum pumps of the same size and size, but also adopt different types of two vacuum pumps. They still make the volume of the front suction vacuum pump small, and the capacity of the rear suction vacuum pump is large. The coaxial transmission is designed, so that the coaxial compensation is made, and the amplitude of the two vacuum pump current changes is small, so that the operation is convenient.

Pay attention to the backflow of white water when using series units. When the tandem vacuum pump unit is shut down, a lot of white water from the paper machine often flows into the vacuum pump chamber, especially the back suction vacuum pump of the unit. The suction port is below the vacuum pump body, and the accumulated water cannot be removed. Sometimes the water level is more than 250mm higher than the pump rotor. If in such a case, the motor starts automatically, and the working medium is changed from air to water, the motor must be overloaded and trip. The treatment method is to install a one-way valve on the inlet pipe to prevent white water from flowing into the vacuum pump, and clean the accumulated water at any time after shutdown.

Roots vacuum pump of correct use