Addtime： 2020-07-18 Browse times： 2768
It is widely used in vacuum press and web press. The output of roots pump directly affects the output and quality of paper. When the flow rate drops and the vacuum degree decreases, it will cause the moisture change of the paper sheet and form the paper diseases such as sticking roller and embossing in the consumption process. Therefore, the use of roots pump is very important.
1、 Adjust the clearance between impeller and rotor frequently
As is known to all, roots pump is a kind of pump which produces vacuum due to volume change caused by the meshing of two "8-shaped" rotors, so it is also called positive displacement pump. In the process of operation, there must be a continuous contact line at the position where the rotor of the pump is required to engage, so as 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 service time, the impeller is worn for a long time, and restricted by the directional rotation, resulting in the uneven meshing gap between the two impellers, resulting in collision, resulting in the concave surface of the impeller. As a result, the two impeller rotors have different levels of wear in the outer diameter and length, and the clearance between the impeller rotors and the shell also increases. Therefore, the vacuum degree of roots pump is reduced, and the time is large and the time is small. It is necessary to timely repair and adjust the clearance between impeller and end cover and pump shell.
If the impeller rotor clearance is too small, it will increase the contraction ratio in roots pump, causing the air in the pump to heat up, which will quickly lead to the gearbox and motor heating. The reason why the clearance between the two impellers becomes smaller is that the additives, fillers and rubber materials are attached to the surface of the impeller. When this phenomenon occurs, the engagement of the two rotors becomes too tight and even gets stuck. It is very difficult or basically does not rotate when it is started again after shutdown. The problem of burning out the motor sometimes occurs. Therefore, it is necessary to clean the inner wall of pump shell and the surface of impeller rotor. The cleaning solution can use 5% sodium hydroxide solution or 5% hydrochloric acid solution. After pickling, rinse with water to avoid corrosion.
2、 Check the sealing condition of pump shaft frequently
The sealing function of the pump shaft is to avoid the leakage of the compressed gas from the pump shaft and the pump housing, and to avoid the external air immersion into the pump. Mechanical seal and counter spiral seal, asbestos packing seal and rubber seal ring are often used. The mechanical seal has the best effect. Recently, the sealing effect of magnetic powder newly developed by Northeast University of technology is very good.
3、 Reasonable selection of rotation number of roots pump
In the use of roots pump, it is necessary to adjust its speed according to practical needs. Obviously, the improvement of revolution can increase the theoretical displacement, increase the volumetric efficiency and output significantly, but the resulting increase in noise will worsen the operating environment. When it is necessary to increase the number of revolutions to improve the ability of the pump in consumption, it should be adjusted within the allowable range of workshop noise. Generally, the progressive revolution method is not used. When the pumping speed of the pump is higher than the rated operating value, the speed should be reduced and the reactive power consumption should be reduced. In this way, for the equipment itself, it can reduce defects, reduce vibration, increase power storage, improve overload ability, and at the same time improve the 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 pump can not reach the request. The high efficiency working area of ordinary roots pump is between - 300 mm Hg and - 400 mm Hg column. To reach above - 500 mm Hg column, the vacuum degree of single pump is difficult to complete, so two pumps can be used in series. In accordance with this process, the series mode adopted should make the pump in front of it play a pre pumping role, and the pumping speed of the latter pump must be 1.5-2 times higher than that of the front suction pump. Only in this way can we give full play to our due effectiveness.
Overseas Roots pumps not only use two pumps of the same type and different sizes, but also often use two pumps of different models. The former suction pump capacity is small, and the rear suction pump capacity is large. It is designed to be coaxial transmission. In this way, the coaxial compensation makes the current change of two pumps small and the operation is easy.
Attention should be paid to the backflow of white water when using series units. When the series pumps are shut down, there will be a lot of white water from the paper machine flowing into the pump cavity, especially the back suction pump of the unit. The suction inlet is under the pump body, and the accumulated water cannot be swept away, sometimes the water level is more than 250mm higher than the pump rotor. If it is started consciously under such conditions, the working medium of suction is changed from gas to water, the motor must be overloaded and trip. The treatment method is to install a one-way valve on the inlet pipe to avoid white water flowing into the pump, and clean up the accumulated water at any time after shutdown.
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