Range of Roller Screen Shaft Rotational Speed and Application in Coal Mines
Introduction
Different from other screening equipment, the Roller Screen relies on the synchronous rotation of multiple Screen shafts to drive the movement of materials and completes the classification of materials through the gaps between the screen plates. The rotational speed of the screen shafts is the core parameter that determines the screening efficiency, processing capacity and service life of the Roller Screen. Unreasonable setting of the rotational speed can easily lead to problems such as material accumulation, screen shaft jamming, incomplete screening, and excessive wear of the screen plates.
Roller Screen Speed Range
Combined with the production conditions of the coal mine and the technical parameters of the equipment, the working speed range of the Roller Screen shaft is 3-20r/min. The suitable speeds are subdivided for different working conditions:
For the screening of dry blocky raw coal, 15-20r/min is preferred to increase the material conveying speed and enhance the processing capacity of the equipment. For the screening of damp and sticky raw coal, control the speed at 3-15r/min, extend the material screening residence time, and avoid the problem of screen blockage. For fine-grained powder removal operations, the rotational speed should be controlled at 10-15r/min to ensure the screening rate of fine materials. Special customized large processing capacity mobile Roller Screen. The rotational speed can be moderately increased. However, in the fixed coal conveying and washing scenarios of coal mines, it is not recommended to exceed 20r/min to avoid material splashing and decrease in screening accuracy.
The Relationship Between Screening Efficiency And Rotational Speed
When the rotational speed of the Roller Screen is too low, the material pushing speed is slow, the material on the screen surface accumulates, the fine material in the lower layer is difficult to pass through the screen, and the screening efficiency is relatively low. When the rotational speed is too high, the material stays for insufficient screening time. Large pieces of material quickly pass over the screen surface, mixed with fine materials, causing screening waste and simultaneously intensifying the vibration of the equipment. The rotational speed needs to be adjusted to the optimal range to meet the continuous production requirements of coal mines.
Factors Affecting Roller Screen Shaft Rotational Speed in Coal Mine Conditions
The Inherent Characteristics Of The Material
The moisture content, viscosity and particle size distribution of raw coal in coal mines are the primary factors affecting the regulation of rotational speed. Raw coal with high moisture content and high viscosity is prone to sticking and caking. If the rotational speed is too fast, the caked materials cannot be broken up and are very likely to adhere between the screen shafts, causing screen blockage. The rotational speed needs to be reduced in coordination with the cleaning device to complete the screening. Dry and loose lump coal and fine coal have good fluidity, which can increase the rotational speed and improve the operation efficiency. At the same time, for raw coal with uneven particle size distribution, it is necessary to compromise and adjust the rotational speed to take into account the screening effect of coarse and fine materials.
Screen Surface Structure And Screen Plate Shape
The plum blossom-shaped and toothed screen plates have strong material grasping capacity, are suitable for large pieces of raw coal, and are compatible with medium and low rotational speeds. Elliptical and parabolic screen plates can form sinusoidal wave disturbances, providing excellent material stratification effects. They are mostly used in fine particle powder removal operations and are suitable for medium and high rotational speeds.
Driving Mode
At present, Roller screens in coal mines are mainly divided into two modes: independent drive and gearbox linkage drive. The gearbox linkage drive has a fixed rotational speed and simple operation and maintenance, making it suitable for mines with single working conditions and stable raw coal properties. The rotational speed is mostly locked at 10-15r/min. The independent drive adopts a variable frequency motor, which can independently control the speed of each single screen shaft, adapt to the complex and changeable raw coal working conditions, and flexibly adjust the speed range.
Typical Application Scenarios Of Roller Screen In Coal Mines
Raw Coal Grading Operation
It is mostly used in the pre-process of coal conveying and crushing in thermal power plants and coal washing plants of coal mines. The raw coal after mining is conveyed to the Roller Screen. Through the rotation of the screen shaft for screening, the materials are divided into the upper and lower screen materials. The large upper screen materials are conveyed to the coal crusher for crushing treatment, and the fine and qualified lower screen materials directly enter the production system. This mode can reduce the operating load of the coal crusher, avoid repeated crushing of fine materials. Meanwhile, the anti-clogging material feature of the Roller Screen is perfectly adapted to the working conditions of high humidity and high viscosity raw coal in the south, eliminating the failure of screen clogging and shutdown, and ensuring the continuous operation of the production line.
Fine-Grained Powder Removal Operation
The coal powder and fine soil mixed in raw coal are very likely to adhere to the surface of large pieces of coal, increasing the load on subsequent washing and impurity removal equipment. By taking advantage of the low-speed disturbance screening characteristics of the Roller Screen, the adhered materials are broken up, the surface dust and fine materials are removed, and the purity of raw coal is optimized. Compared with traditional vibrating screens, Roller Screen has no high-frequency vibration, the screen plates and bearings wear less, the operating noise is small, the maintenance cost is low, and it is less likely to have screen hole blockage. It has stronger long-term operation stability and is suitable for long-term continuous production in coal mines.
Common Faults And Solutions
The Screen Shaft Is Stuck
It is mostly caused by large debris and sticky wet coal materials getting stuck on the Screen shaft. The modern Roller Screen is equipped with an overload protection system and automatically alarms and stops when the resistance exceeds the standard. When handling faults, the machine should be shut down to clear the clogged materials. Afterwards, the rotational speed should be moderately optimized, and the coal sticking condition should be raised to 12-15r/min, combined with a cleaning scraper to reduce material adhesion.
Screen Plate Wear
Long-term friction of raw coal can cause deformation and wear of the screen plates, resulting in an increase in the screening gap and a decrease in screening accuracy. It is recommended to use manganese 13 cast steel and NM400 wear-resistant material screen plates to enhance wear resistance and impact resistance. Regularly check the wear and tear of the screen plates and replace damaged parts in a timely manner.
Bearing Housing Failure
Long-term high-load operation of the bearing housing is prone to problems such as insufficient lubrication, abnormal noise and jamming. It is necessary to formulate a regular lubrication and maintenance plan, check the sealing condition of the bearing to prevent coal dust from entering the wearing parts and extend the service life of the bearing.
Daily Basic Maintenance
Daily operation and maintenance should focus on cleaning the lower sweeping device of the screen shaft, promptly scraping off the coal slime adhering to the screen plates to prevent material accumulation and solidification. Regularly inspect the elastic pin coupling. The nylon pin has an overload cut-off protection function. Replace it immediately if any damage is found to protect the drive motor and the screen shaft. For the independently driven Roller Screen, the operating current and rotational speed of each screen shaft are monitored in real time to eliminate potential hazards of abnormal vibration and jamming.
Conclusion
The general optimal rotational speed range of the Roller Screen shaft in coal mines is 3-20r/min. Combined with the dryness and wetness of the materials, particle size and production requirements for detailed regulation, the optimal screening effect can be achieved. The four major elements, namely material characteristics, screen surface structure, inclination Angle layout and drive mode, mutually restrict each other and jointly affect the speed adaptation standard.
