In the coal beneficiation industry, linear vibrating screen plays a vital role as the key screening equipment. However, in the process of long-term use, linear vibrating screen will also have various failures, affecting the efficiency and quality of coal processing, for example, linear vibrating screen often has excessive vibration of the screen box, overheating of the bearings, abnormal sound and other failures, which seriously reduces the production efficiency of the coal processing plant. Below, we will learn more about the common faults and troubleshooting methods of coal processing linear vibrating screen.

Problem 1: Abnormal vibration

Polarisation: The two opposite corners of the vibration is normal, and the other two corners of the vibration is almost no amplitude. The reason is mostly due to the motor weight block angle change, spring four support points are not in the same horizontal line, spring stiffness is different. Need to check whether the screen frame is a standard rectangular, spring support is at the same level and the same stiffness, the two vibrator self-synchronisation and coaxial plate on both sides of the main, vice eccentric block adjustment of the phase angle is consistent.

Torsion vibration: vibrator vibration force direction shift, spring damping system failure or screen is not placed on the horizontal surface of the screen surface is not level easy to cause torsion vibration. To check whether the spring bracket installation in the same plane and the same amount of tightening, universal shaft joint device on both sides of the phase angle is the same, to ensure that the sieve placed horizontally.

Vibration amplitude is too large or too small: too strong excitation force, damping spring hardness is too large, the installation of the ground is not equal to make the amplitude is too large; while the voltage is insufficient, the eccentric block is less or the angle is small, the feeding amount of large accumulation of material, spring design is unreasonable, the motor or vibration failure will lead to amplitude is small. It can be solved by adjusting the excitation force, replacing the suitable spring, adjusting the installation, stabilising the voltage, increasing the eccentric block or changing its angle, cleaning up the accumulated materials, repairing or replacing the faulty parts.

Problem 2: Damaged parts

Crossbeam failure: mostly manifested as cracks in the crossbeam, mainly due to abnormal vibration parameters, high drop point subjected to prolonged material impact, loose rivets or bolts connected with the longitudinal beam falling, serious accumulation of coal in the crossbeam, severe wear and tear of the crossbeam, and so on. End cracking is treated by welding; h-beam cracking is first welded and then plywood is played on the web and bottom plate; ear plate connection cracking is first welded and then reinforcing plate is added. Daily to check the crossbeam and longitudinal beam plate connection bolts, rivets, to ensure that the connection is solid, clean up the crossbeam coal accumulation and protection, improve the drop point .

Stimulus beam failure: abnormal vibration parameters, shaker foot loose, and side plate connected to the rivets or bolts loose fall, two exciter excitation force or direction is inconsistent with the excitation beam rust and wear and tear will lead to excitation beam cracking. Cracks less than 5mm to play the crack hole, more than 5mm to play the crack hole after welding, location allows but also to play the plywood. Shaker ground bolts should be checked regularly to ensure that the two sets of shaker excitation force and direction of the same, and do a good job of anti-rust and anti-wear work of the exciter beam.

Bearing heat problem

Under normal circumstances, the bearing temperature of the vibrating screen should be 35-6O℃ after 4 hours of no-load test run. If the bearing temperature is too high, it may be caused by the following reasons.

Vibrating screen bearing form error

If the bearing of the shaker part is overheated and there is no improvement after adding lubricant, the bearing model may be unreasonable, and the radial clearance of the bearing is too small, which will also cause overheating and wear. It is recommended to use bearings with large radial clearance, and if the bearings are of ordinary clearance, the outer ring of the bearings can be ground to expand the clearance.

Too little or too much lubricant or the quality of lubricant does not meet the requirements will also cause the bearing to overheat.

If the bearing is not properly lubricated, dry friction will occur, and the heat generated by the dry friction in a short period of time is enough to melt the metal, resulting in bearing damage or even seizure. It is necessary to open the bearing end cover regularly for inspection; fill the lubricant that meets the requirements in time; do not overfill when refuelling.

Pressure cover and bearing outer ring firmly affixed. There should be a gap between the gland and the bearing outer ring to ensure heat dissipation and axial movement. Adjust the gap by adjusting the gasket between the end cap and the bearing housing.

Sticky mud entering the bearing end cap will also cause the bearing to heat up.

Clean dirty bearings; replace seals and check seals frequently to ensure good sealing.

Problem 3: screening quality problems

Screen clogging: screen debris into the screen more, material moisture, uneven feeding, thick layer of material is easy to cause screen clogging, resulting in poor screening quality. To reduce the load of the vibrating screen, change the angle of inclination of the screen frame, adjust the feeding volume and uniformity, tighten the screen, and clean or replace the screen when necessary.

Sieve mesh breakage: it may be due to the screen mesh quality, tension is not enough to cause it to flutter, so that along the edge or the edge of the package compression strip at the fracture damage. Choose a good quality screen material, check and adjust the screen tension frequently.

Problem 4: Abnormal coal flow

Sometimes the coal is not evenly distributed on the screen surface. If there is no coal in the front section of the sieve, the eccentric block will be adjusted forward appropriately; if there is no coal in the middle section of the sieve, the quality of the eccentric block is too light, and the amplitude is not up to the requirement, and the quality of the eccentric block should be increased; if there is no coal in the back section of the sieve, the eccentric wheel will be adjusted backward. In addition, improper placement of the screen flushing pipe will also cause the phenomenon of no coal on the screen surface.

It can be solved by adjusting the position of the flushing pipe and speeding up the running speed of the material on the screen, but this method is only applicable to the screening or dewatering of 0-3mm material.

Problem 5: Cracked side panels

The amplitude of the vibrating screen box is inconsistent, resulting in stress concentration and cracking of the side plate or side wall. The main reasons are: the height difference between the vibrating screen springs on both sides of the vibrating screen is too large, resulting in inconsistent amplitude of the screen box. It should be necessary to install the spring in strict accordance with the installation standards; replace the damaged or failed spring in time. Improper welding between the side plate, reinforcement plate and wing plate causes welding stress. When the vibrating screen works, the vibrating screen exciter generates high frequency excitation force, and under the action of welding stress and excitation force, the side plate of the screen box cracks. The side plate, reinforcement plate and wing plate are connected by riveting.

The eccentric block angle is inconsistent, and the counterweight block specification, model, material and quality are different.

The inconsistent angle of the eccentric block will cause the direction of the excitation force to be inconsistent, resulting in abnormal vibration of the vibrating screen, which will lead to cracking of the side plate in serious cases. Usually, the counterweight block will be added according to the need to change the quality and amplitude of the vibrator, if the counterweight block is not added properly, it will also cause abnormal vibration.

When disassembling, repairing and assembling the vibration exciter, we must ensure that the eccentric block has the same specification, model, material and quality, and the clamping angle of the eccentric block must be the same when installing, and the counterweight block with the same specification, model, material and quality should be installed symmetrically on both sides of the screen machine.

 

Other faults

Noise: screen box or side plate vibration cracks, bearing damage, screen box side plate and other thin plate structure vibration, screen mesh is not pressed or loose bolts, spring damage, vibration of the exciter bearing itself, material and chute collision will produce large noise. It is necessary to weld or replace the cracked parts in time, lubricate and replace the bearings, apply constraint damping materials to the plate surface, tighten the screen mesh and bolts in various parts, replace the springs, add a soft soundproof cover to the outside of the shaker, and lay rubber lining boards on the inner wall of the chute or make it into a box.

Unable to start or difficult to start: the motor or electrical components are damaged, insufficient voltage, vibrator failure, too much material will lead to unable to start or difficult to start. Damaged motors or electrical components should be checked and replaced, the supply voltage should be tested and the power supply changed, the vibrator grease and fault conditions should be checked and dealt with, and the screen surface and sieve hopper should be cleaned of accumulated material.

Sieve machine swing: spring height difference or stiffness difference is the main reason. Measure the height and stiffness of the springs, replace the springs if necessary, clean up the dust around the springs, and adjust the top wire of the buffer damping block.