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First, the common failure analysis causes many reasons for the abnormal operation of the shaker. Generally, there are the following situations:
1. The sound at the exciter is abnormal and the surface is overheated;
2. Breakage, looseness or breakage of the screen plate, resulting in repeated vibration or mixing;
3. The damping spring breaks frequently;
4. Single motor operation or dual motors are not connected in parallel or parallel but do not operate in reverse;
5. The resonance frequency of the screening machine is the same as the fixed frequency;
6. The screen body is not properly installed and the foundation is uneven;
7. The center distance between the exciter axis and the drive shaft deviates too much;
8. Excitation force deviates from screen center of gravity;
9. The exciter or vibration motor is not assembled correctly. The included angles of the two groups of weights are inconsistent.
10. Inconsistent feeding leads to uneven load and raw material discharge is not smooth. Due to the intricate nature of the work site, the abnormal operation of the vibrating screen may be due to coexistence of many factors. Before analyzing and finding out the reasons, we must first understand the use of the equipment on site, whether there is illegal operation or improper maintenance, and the maintenance is not timely. According to the principle of "ease of doing things first, difficulty in the first place, complexity in the first place, first in the future, and the latter in the first place, the reasons are eliminated one by one, and the causes are analyzed so that the problem can be completely solved and the goal of safe, economic, and long-term effective operation can be achieved.
Second, the treatment method and technical improvement measures In the first case, need to replace the big clearance bearing. Due to the vibrating screen work, the temperature difference between the inner and outer rings of the bearing is relatively large. In order to reduce the frictional torque and improve the alignment performance, a large clearance bearing should be used, 0.004mm~0.006mm is appropriate; according to the job site conditions, the general motor runs for about two weeks. A timely lithium- or calcium-based grease (ZL-3) must be added; check the weight loss.
In the second case, the damaged screen or screen strip is replaced, loose bolts are tightened, the relative movement between the screen and the screen strip is eliminated, and repeated vibrations are avoided; the side panels of the screen body can be made of stainless steel plates, and the screen panels are made of The riveting of ring groove rivets not only has good fastening property, but also greatly reduces the internal stress caused by welding. And the sieve plate is easy to install and easy to disassemble.
In the third case, starting from the material: spring material needs to be 60Si2MnA, heat treatment hardness should reach HRC45~50, should also consider increasing the spring diameter; the size of the spring degree stiffness, to affect the working frequency of the shaker, thereby affecting the screening effectiveness. When the working frequency is determined, if the springs with different stiffnesses are used, the amplitude stability of the vibrating screen will be affected. When the vibrating screen is working, the natural vibration frequencies of the two are obviously different. Therefore, it must be ensured that the same spring stiffness consistency of the vibrating screen after replacing the damaged spring;
In the fourth case, single-motor operation is strictly a prohibited behavior, which can easily cause the motor to be overloaded and burn out. During operation, the two motors must be connected in parallel. If the two motors run in the same direction, the direction of rotation of the motor can be changed by adjusting the phase sequence of the power supply to achieve normal operation of the vibration motor.
In the fifth case, the method of increasing the frequency converter can be used to change the operating frequency to avoid resonance; once a resonance condition occurs, it can also be adjusted by changing the number or weight of the weights, and it must be increased symmetrically when the weight is increased or decreased. Reduce to prevent partial load;
In the sixth case, whether or not the vibrating screen is installed horizontally is crucial to the correct operation of the vibrating screen. When installing and adjusting, four legs can be used as a reference, or the screen surface can be used as a reference, and the level meter can be used to measure the support. The method of lowering the pad is repeatedly adjusted until it is horizontal; the technical requirements after adjustment: the verticality between the axis of the leg and the ground is not more than 0.5mm, and the parallelism of the two axes is not more than 0.5mm, and the axis of the exciter is coaxial with the axis of the motor. Not more than 0.25mm;
In the seventh case, the exciter axis is generally 2 to 3 mm higher than the axis of the actuator. Too large values ​​will cause the screen body to twist and cause abnormal parameters. The method of adjustment is to first correct the screen body and make the center of the shaft of the exciter above the center of the driver; the axis of the vibration motor is in the same direction as the longitudinal axis of the screen (not parallel, with an included angle). The two vibration motors are symmetrically arranged on the upper, lower and both sides of the screen body. Linear vibrating screens usually have a screen angle of 8° or less, and the screen surface has a vibration angle of 45°. The screen's screen efficiency and throughput (processing capacity) are the same as the screen's screen angle, screen's vibration angle, and material ejection. Coefficient related. In order to ensure high screening efficiency and large screen production volume, a suitable Ky (projectile coefficient) value must be selected.
In the 8th situation, the ideal working condition of the vibrating screen should be that the whole machine works steadily, the amplitudes are the same everywhere, and there is no swing. As shown in Fig. 2, the horizontal distance of the excitation force to the center of mass C is the offset e, the line of action is negative on the left side of C, the right side is positive, coincidence is zero;
The negative (positive) deviation of the excitation force from the center of gravity will increase (or decrease) the amplitude at the feed end, decrease (increase) the amplitude at the discharge end, and increase (decrease) the high stress amplitude at the side plate. The person has a significant influence on the beam stress. The greater the offset, the greater the effect on stress. Distinguishing and calculating the size and positive and negative offsets can be determined by testing or calculating the amplitude and direction angles at both ends of the shaker. Exciting force deviates from the center of gravity, which is the main reason for the rotation of the vibrating screen in the xoy direction. It has a great influence on the motion parameters and structural strength of the vibrating screen. Such deviations can be caused by design, manufacturing errors, or uneven material distribution. This type of displacement causes the screen body to move not only with the translation of the center of mass in the direction of vibration but also with the rotation around the center of mass. To change the deviation of the exciting force, measures such as changing the screen mass distribution can be adopted;
In the ninth case, vibrational anomalies may be caused by the different excitation forces or the inconsistent directions of the two groups of exciter. In fact, the direction of the resultant force of the exciting force depends entirely on the eccentric position of the weight. If the counterbalance angles of the two groups of exciter are different, the vibration direction angle and the vibration force are also different. The screen body will generate torsional vibration, and the size and direction of the material speed in different parts of the screen body will also be different. The phenomenon of deviation, rotation and stagnation of the material will result in a decrease in the screening efficiency, the amount of processing, and the strength of the screen body. The inconsistency of the vibrational directions on both sides of the screening body may be due to: (1) The included angles of the counterweights of the exciter on both sides of the screen body are inconsistent and the counterweights on both sides must be adjusted so that the included angles are the same. (2) The vibration at one end of the exciter is damaged, resulting in inconsistent excitation force on both sides. The exciter must be disassembled. Note the following points: 1. The disassembly and assembly of the exciter should be performed on a clean site; 2. All parts before assembly are Must be cleaned to remove burrs; 3. Can not directly hit the bearing inner and outer ring; 4. All assembly surfaces must be coated with lubricating oil before assembly, such as lithium grease; 5. Carefully check the seal ring, if there is aging or damage, timely replacement; Into the appropriate amount of lubricants such as lithium grease, etc.; 7. When assembling Y-rings, pay attention to the end face inwards; 8. Fasten all bolts as required, fasten once every two days in the initial stage of installation, three times in a row. Above, check once every two days;
In the tenth case, changing the equipment feeding method and evenly feeding can ensure that the design's screening efficiency and throughput can be achieved.
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Vibrating screen has the advantages of stability and reliability, low consumption, low noise, long life, stable vibration mode, high screening efficiency, simple structure and easy installation, so it is widely used in mining, coal, smelting, building materials, refractories, light industry, Chemicals, pharmaceuticals, cement and other industries. When the vibrating screen is working, the reverse oscillating force of the exciter is generated by the synchronous reverse rotation of the two motors, forcing the screen body to drive the screen plate to perform the longitudinal movement, so that the materials on the screen are excited to periodically throw a range forward. In order to complete the classification of the material, desliming, dehydration, removal and other screening operations. At present, there are many types of screening equipment in use in the country and there are many problems in the process of design, manufacture, installation and user use. In addition to some mechanical failures, there are abnormal operating parameters, improper maintenance and other reasons caused by the vibrating screen body screening efficiency, reduced processing capacity, and even lead to sieve body, shaker base and broken beam, bearing damage and other fatal problems.