Coal as an important energy resource, its mining, washing and processing process, the treatment of coal slurry is a key link. Coal slurry dewatering screen shoulders the important responsibility of efficiently separating out the water in the coal slurry, so that the coal slurry can meet the requirements of subsequent processing, storage and transport. In addition to the coal industry, in the mineral processing, construction and other industries, the dewatering screen also plays an indispensable role. In the mineral processing industry, tailings dewatering treatment needs dewatering screen to assist in removing excess water, in order to facilitate the tailings of the pile or reuse; in the construction industry, sand and gravel plant washed sand dewatering treatment is also inseparable from the dewatering screen, to ensure that the quality of sand meets the construction requirements, to provide high-quality building materials for construction projects.
However, the coal slurry dewatering screen to continue to play its excellent performance, can not be separated from the careful maintenance and repair. Just as a car needs regular maintenance to maintain a good driving condition, coal slurry dewatering screen can only be properly maintained to extend the service life, reduce the probability of failure, improve production efficiency, and create greater economic benefits for the enterprise. Next, we will discuss the various key aspects of coal sludge dewatering screen maintenance and repair.
一.Daily Maintenance
1.Meticulous inspection before switching on the machine
Sieve screen inspection: the operator needs to carefully check whether the screen mesh is broken, broken wire and so on. In addition, it is also necessary to check whether the tension of the screen mesh is appropriate or not, the screen mesh is too loose will lead to uneven jumping of materials on the screen surface, affecting the dewatering effect; the screen mesh is too tight may increase the stress of the screen mesh, shortening the service life of the screen mesh.
Transport support removal check: in the process of installation and commissioning of coal slurry dewatering screen, in order to prevent the equipment from being damaged during transport, some transport supports are usually set. Before starting the machine, it must be ensured that these transport supports have been completely removed. If the transport support is not removed, the equipment will produce abnormal vibration during operation, which may even lead to equipment damage in severe cases.
Check the connection of each component: check whether the connection bolts between the screen box, vibration exciter, support system and other components are tight, and whether there is any sign of loosening. Loose connection bolts will make the equipment produce abnormal noise and vibration during operation, affecting the stability and reliability of the equipment.
2.Close monitoring during operation
Current monitoring: current is one of the important parameters reflecting the operating status of the coal slurry dewatering screen. By observing the current change of the motor, you can understand the load of the equipment. Under normal operation, the current of the motor should be kept in a relatively stable range. If the current suddenly rises, it may be caused by overloading of the equipment, blockage of materials, failure of the shaker, etc.
Vibration monitoring: the vibration condition of the equipment is a key indicator to judge whether it is running normally. The operator should pay attention to observe whether the vibration of the screen box is smooth and even, and whether there is any abnormal beating or shaking. Under normal circumstances, the screen box should do smooth reciprocating linear vibration, amplitude and frequency should be in line with the technical parameters of the equipment. If you find abnormal vibration of the screen box, it may be caused by the failure of the exciter, damage to the support system, screen mesh clogging or breakage. For example, when the eccentric block inside the exciter is worn or loose, it will make the excitation force change, which will lead to abnormal vibration of the screen box. At this time, the operator should immediately stop the machine, check and repair the equipment to avoid further expansion of the fault . In addition, you can also touch the screen box and other components, feel the intensity and frequency of its vibration, with experience to judge whether the equipment is abnormal.
3.Cleaning and tidying up after shutdown
Screen surface cleaning: after the coal sludge dewatering screen stops, the first thing to do is to clean the screen surface. Use special tools, such as brushes, scrapers, etc., to clean up the residual coal sludge on the screen surface. For some difficult to clean coal sludge, you can use the right amount of water to rinse, but make sure that the screen surface is completely dry after rinsing, so as to avoid the screen from rusting.
Body cleaning: In addition to the screen surface, you also need to clean the screen box, shaker, support system and other body parts. Remove the dust, coal sludge and other debris on the surface of the body to keep the equipment tidy.
Material cleaning and storage: Clean up the coal sludge scattered around the equipment and store it properly. The cleaned out coal sludge can be recycled or reasonably disposed of according to the actual situation to avoid resource waste and environmental pollution. In addition, you can also use the downtime to check the lubrication points of the equipment and replenish the grease to ensure that the equipment is well lubricated and reduce the wear and tear of the components.
二.Maintenance of critical components
1.Vibration motor
Installation and fixation points: the correct installation of the vibration motor is the basis for its stable operation. The mounting surface must be smooth and even, if there is unevenness, it will lead to uneven force on the foot bolt when the vibration motor is running, which will cause the bolt to loosen or even break.
Cable protection: the cable should be natural suspension state, and there should be a greater than 5 – 6 times the outside diameter of the cable bending radius, in order to reduce the cable in the vibration process of the force. At the same time, the cable should be fixed reliably to the vibrating body, the distance between the fixing points is about 500 – 1000mm, in the fixing of the cable clips should be padded with soft insulating material, to prevent the clips on the cable caused by damage. In addition, the appearance of the cable should be checked regularly for signs of wear and tear, ageing, etc., so that potential problems can be identified and dealt with in a timely manner.
Excitation force adjustment skills: when adjusting the excitation force, first of all to ensure that the equipment is in a power-off state to ensure operational safety. For horizontal vibration motor, usually by changing the size of the eccentric block angle to adjust the excitation force. Specific steps are: open the dust cover of the vibration motor, loosen the outer eccentric block to tighten the bolts, and then the two sides of the eccentric block in the same direction, so that the axis of the line aligned with the eccentric block on the excitation force value to the required value of the excitation force, and check whether the two ends of the same angle. It should be noted that the adjustment of the eccentric block at both ends must be consistent, otherwise it will lead to equipment vibration imbalance.
Lubrication and maintenance cycle: the bearing of the vibration motor will produce wear and heat due to friction during long-term operation, so it needs to be lubricated and maintained on a regular basis to prolong the service life of the motor. Generally speaking, the lubrication cycle of vibration motor bearings is to add grease once every 1000 – 1500 hours of operation and replace grease once every 2500 – 3000 hours of operation. When replacing the grease, the motor bearings should first be cleaned with petrol or special cleaning agent, and then add an appropriate amount of high-quality grease after drying.
2.Bearing
Daily cleaning and rust prevention: Regular cleaning of bearings is an important measure to maintain their good working condition. When cleaning, special cleaning agent or petrol should be used. After cleaning, the bearings should be wiped dry with clean rags and coated with appropriate amount of antirust oil (grease) to prevent the bearings from rusting.
Lubrication and replacement cycle: the replacement time of bearing grease varies under different working conditions. Generally speaking, under normal working conditions, the replacement cycle of bearing grease is once every 2000-3000 hours of operation; in high temperature, high humidity, dusty and other harsh working environment, the replacement cycle should be appropriately shortened, can be shortened to once every 1000-1500 hours of operation. When replacing the grease, it is necessary to pay attention to the selection of the appropriate type of grease, according to the operating temperature of the bearing, speed, load and other factors for comprehensive consideration.
三.Common Problems and Solution Strategies
1.Abnormal vibration problem investigation
In the operation process of coal slurry dewatering screen, vibration abnormality is one of the more common problems. When it is found that the screen box appears to be violently shaking, uneven beating or abnormal vibration direction, it is necessary to investigate the reasons in time. Improper installation of screen mesh is one of the common causes of abnormal vibration. If the tension of the screen mesh is not consistent during installation, and some areas are too loose or too tight, it will make the screen mesh unevenly stressed during vibration, thus causing abnormal vibration of the screen box.
Shaker failure is also an important factor in triggering vibration abnormalities. The eccentric block inside the shaker is worn, loose or bearing damage, etc., will change the excitation force and vibration frequency of the shaker, resulting in abnormal vibration of the screen box. When the eccentric block is worn, its mass distribution will change, so that the size and direction of the excitation force is unstable; if the eccentric block is loose, in the high-speed rotation process will produce additional impact force, exacerbating the vibration of the screen box. For shaker failure, the shaker needs to be disassembled and inspected to replace worn or damaged parts. When disassembling the shaker, pay attention to marking, record the installation position and angle of each component, so that it can be accurately restored during installation. At the same time, select reliable quality parts for replacement to ensure that the performance of the shaker is restored to normal .
2.Motor fault diagnosis and repair
Motor heating is one of the more common failures, and its causes may be manifold. Prolonged overload operation is one of the main causes of motor heating. When the feeding amount of the coal slurry dewatering screen is too large and exceeds the rated load of the motor, the motor needs to output more power to drive the equipment, which leads to an increase in current and motor heating.
Abnormal motor speed is also a common failure. Low speed may be caused by insufficient supply voltage, short circuit of motor winding, bearing damage and other reasons. When the power supply voltage is insufficient, the output power of the motor will be reduced, resulting in a decrease in speed; motor winding short circuit will increase the current of the motor, the magnetic field distribution is not uniform, thus affecting the speed. For the problem of low rotational speed, the first thing to do is to check whether the power supply voltage is normal or not, and you can use a voltmeter to measure it. If the voltage is insufficient, it is necessary to check whether the power supply line is faulty, such as poor line contact, wire aging, etc., and repair it in time. If the power supply voltage is normal, it is necessary to further check the motor winding and bearing. For motor winding short-circuit failure, it is necessary to use professional testing instruments, such as multimeter, megohmmeter, etc., to test the winding, determine the location of the short circuit, and repair or replace the winding. If the bearing is damaged, it should be replaced with a new bearing in time .
On the contrary, the high speed may be due to the failure of the motor’s control system, such as the inverter parameter setting error, the controller is damaged. In this case, the control system of the motor needs to be checked and debugged. First of all, it is necessary to check whether the parameter settings of the frequency converter are correct, such as the frequency setting value, acceleration time, deceleration time and so on. If the parameters are set incorrectly, they should be adjusted according to the technical requirements of the equipment. If the parameters of the frequency converter are normal, it is necessary to check whether the controller is faulty, such as whether the components on the circuit board are damaged, whether the connecting lines are loose and so on. For controller failure, need professional maintenance personnel to repair or replace .
