Centrifugal fans, as a commonly used fan in most ventilation systems, need to be balanced and corrected before they are officially used and after a period of use. Otherwise, it will directly affect the ventilation efficiency of the centrifugal fan, and even cause premature damage to the fan. How to balance the centrifugal fan?
1) Dynamic balance correction method of centrifugal fan
1. Dynamic balance correction of critical speed
This kind of balance correction has high precision and needs to be carried out on a special dynamic balancing machine. The dynamic balancing mechanism is complex and the equipment cost is high, so it must be operated by professional personnel. Therefore, this method is generally only used in centrifugal fan manufacturers, but is rarely used in factories that use and overhaul centrifugal fans.
2. Dynamic balance correction of working speed
This method is generally carried out at the site of use, which is simple to operate and easy to master, and does not require the purchase and installation of a dynamic balance machine. Although the accuracy of its balance correction is not high enough and it takes a long time, it is widely used in the maintenance of centrifugal fans because it is simple and easy to implement, and can meet the requirements of centrifugal fan maintenance. However, when using this balance method, that is, when finding dynamic balance on the centrifugal fan body, the following matters should also be noted:
(1) Before finding dynamic balance, all the parts on the rotor must be installed, cover the bearing cover and fix it, and take out the sealing device in the casing. If the upper part of the casing is covered, for a general centrifugal fan, the gas pipeline valve must be opened by 1/2~1/4; for a centrifugal fan that transports gas, the gas pipeline valve must be closed tightly, and the bypass valve leading to the atmosphere must be fully closed. Open. So as not to generate gas eddy current in the casing and affect the correctness of the balance work.
(2) The vibration measurement should be measured once every time the vehicle is driven, and a special person should be responsible for the measurement after the rotational speed is stable.
(3) The detachable connection method must be used to firmly fix the test weight in the balance slot or special balance hole to avoid flying out at high speed to hurt people or damage the equipment.
(4) When performing rotor dynamic balance correction, sometimes only one end of the rotor needs to be corrected (such as the arm-type rotor driven by the coupling); sometimes it needs to be performed alternately at both ends of the rotor (such as the belt-driven rotor). The method at this time should be: when one end is calibrated, then calibrate at the other end; when the other end is calibrated, then calibrate at the upper end, and repeat this several times until both ends meet the requirements. Therefore, to correct the dynamic balancing machine according to these simple methods, sometimes it takes a dozen to dozens of times to complete. The common methods of dynamic balance correction on centrifugal fan body are: Circumferential weight method, marking method and comprehensive method
2) Static balance correction method of centrifugal fan
The static balance correction method of the centrifugal fan mainly adopts the guide rail static balancing machine, which is a kind of equipment with high sensitivity, simple structure, convenient operation and common use. Balance operation method:
Place the rotor lightly on the track of the balancing machine (or within the included angle of the disc), so that the horizontal axis of the rotor is perpendicular to the track axis. Turn the rotor by hand to stop it at will. Make a mark “1” under the rotor, as shown in Figure a. To eliminate friction torque errors, rotate the rotor 90°. Make the mark “I” horizontal with the center line of the rotor, and then release it. After it stops swinging, mark “2” at the bottom of the rotor at this moment, as shown in Figure b. Then turn the rotor 90 in the opposite direction. , also make the mark “1” and the center line of the rotor into a permanent flat position, release it, and after the swing stops, mark “3” at the bottom of the rotor at this moment, as shown in Figure c. If the marks “1”, “2”, and “3” coincide, the biased position is at the coincident point; otherwise, the biased position is in the middle of the marks “2” and “3”, as shown in Figure d.
After the eccentric position is found, use putty or plasticine to stick it in the symmetrical direction of the eccentric position (the position where the balance block will be arranged) by trial addition. Then it is considered that the mass-diameter product of the counterweight is equal to the mass-diameter product of the partial weight. It can also be used on the heavy side to reduce the weight by drilling or scraping, peeling and other methods to achieve the purpose of balance. After the static balance operation of the rotor of the centrifugal fan achieves the purpose of balance, two processes of inspection and correction are required.