How to Handle Jamming in a Roller Screen
Introduction
The roller screen, as a screening equipment, is widely used in various fields such as mining, construction materials, and agriculture. With the increase in usage frequency, the roller screen may encounter blockage problems during operation, which will lead to a decrease in screening efficiency, increase the wear and maintenance costs of the equipment, and even cause the production line to come to a standstill. We need to promptly and effectively handle the blockage problems of the roller screen.
Analysis of Roller Screen Blockage Causes
Material Characteristics
High moisture content
When the moisture content of the material is high, its viscosity will significantly increase. For example, in coal mining, if there is rain during the operation, the moisture of the coal will increase. These materials with high moisture content are prone to stick together and form large blocks. During the operation of the roller screen, these blocks cannot pass through the screen holes smoothly and will accumulate on the screen surface, thereby causing blockage.
Uneven particle size
If there are a large number of large particles in the material with diameters far exceeding the screen hole size, these large particles are likely to get stuck between the screen shafts or at the screen holes when moving on the screen surface.For instance, in the screening process of construction waste, large stones are likely to get stuck in the gaps of the roller screen, hindering the normal passage of other materials. At the same time, if there are too many fine particle materials, they may embed in the screen holes, causing the screen holes to become clogged and affecting the screening efficiency.
High mud content
When the mud content in the material is high, the mud has strong viscosity.During the operation of the roller screen, the mud will adhere to the screen shafts and the screen surface.Over time, the adhered mud will increase, gradually reducing the effective size of the screen holes and even completely blocking the screen holes, preventing the materials from passing through normally.
Design and Installation
Inappropriate sieve hole size
The sieve hole size is designed based on the target screening particle size of the material. If the sieve hole size is too small, for materials of normal size, passing through the sieve hole will become difficult, and they are prone to accumulate on the sieve surface, ultimately leading to blockage. For example, when screening a certain mineral, if the designed sieve hole size is much smaller than the actual particle size of the mineral to be screened, the mineral will have difficulty passing through the sieve hole, resulting in blockage.
Inappropriate sieve shaft spacing
If the sieve shaft spacing is set too narrow, for some materials of normal size, when passing through the gap between the sieve shafts, they will be hindered and are likely to get stuck between the shafts. Conversely, if the sieve shaft spacing is too wide, although large particle materials may be easier to pass through, it will reduce the screening accuracy and may also cause some materials that should be screened out to pass directly, while the remaining materials are unevenly distributed on the sieve surface, increasing the risk of local blockage.
Inappropriate installation angle
When installing the roller screen, a certain inclination angle is required to ensure that the materials can move forward smoothly under the effect of their own gravity.If the installation angle is too small, the movement speed of the materials on the sieve surface will be slower, and the materials are prone to accumulate on the sieve surface, increasing the possibility of blockage. On the contrary, if the installation angle is too large, the materials pass through the sieve surface too quickly, which may lead to insufficient screening and also because of excessive impact force, the materials may get stuck at the sieve shaft or sieve hole.
Operation Procedures
Excessive feeding speed
During the operation of the roller screen, if the feeding speed exceeds the normal processing capacity of the screen, a large amount of material will rush onto the screen surface within a short period of time.The screen surface cannot promptly carry out screening treatment for the excessive material, and the material will accumulate on the screen surface, eventually leading to blockage. For example, on some production lines, in an attempt to increase production, operators set the feeding speed too high, exceeding the load capacity of the roller screen, and thus blockage is prone to occur.
Failure to clean in time
After long-term operation, the surface of the roller screen will retain some materials and impurities. These residues will accumulate over time without timely cleaning, gradually affecting the permeability of the screen holes, and eventually causing blockage.
Improper equipment maintenance
The screen shaft, bearings, and other components of the roller screen need to be maintained and serviced regularly.If the lubrication of the bearings is insufficient, it will cause the screen shaft to rotate smoothly. Over time, it will lead to wear or deformation on the surface of the sieve shaft, which will also affect the normal passage of the materials and increase the probability of blockage.
Emergency handling for roller screen blockage
Stop immediately
After discovering that the roller screen is clogged, immediately press the emergency stop button, cut off the power supply, to prevent the continued operation from worsening the clogging situation, and to avoid further accumulation of materials causing greater damage to the equipment, such as motor overload burnout, roller deformation, etc. At the same time, it can also ensure the safety of the operators, avoiding accidental injuries caused by the operation of the equipment when dealing with the clogging.
Evaluate the clogging situation
Observe the location of the clogging. If the clogging occurs at the feed inlet, it may be due to the feed speed being too fast, the particle size of the material being too large, or the presence of foreign substances mixed in; if the clogging occurs on the screen surface, it may be due to the high viscosity of the material, the small size of the screen holes, and the mismatch between the particle size of the material and the screen holes; if the clogging occurs at the discharge outlet, it may be due to poor discharge or malfunction of the conveying equipment.
Check the degree of clogging. A slight clogging may only involve partial screen holes or local areas with material accumulation, while a severe clogging may fill the entire screen surface or discharge channel with materials. This helps determine which treatment method to adopt subsequently.
Clean the feed inlet
If the clogging occurs at the feed inlet, use appropriate tools, without damaging the structure of the feed inlet, carefully remove the accumulated materials at the feed inlet. At the same time, check if the feed system is abnormal. If the feed speed is too fast, adjust the parameters of the feed equipment appropriately to reduce the feed volume to prevent further clogging.
Handling screen surface blockage
After the equipment has completely stopped, for loose surface materials, non-metallic tools such as wooden sticks and rubber hammers can be used for removal to avoid damaging the screen surface. If severe adhesion occurs due to wet and sticky materials, manual cleaning is required. In such cases, the confined space safety regulations must be followed. The fundamental solution lies in controlling the moisture content of the materials at the source and installing effective comb-type cleaners on the screen shaft. Additionally, the principle of starting and stopping without load should be adhered to to prevent material hardening.
Inspect other components
After clearing the blockage, check the temperature and sound of the motor, the oil level of the reducer, and whether there is any abnormal noise or overheating in the bearings. If any abnormalities are found, they should be dealt with promptly to prevent equipment failures during subsequent operation.
Restore equipment operation
After confirming that all blockages have been cleared and all components of the equipment are normal, connect the power supply, start the roller screen without load, observe the operation, and after running without load for a period of time, if the equipment operates normally, gradually resume feeding.
How to prevent roller screen clogging
Material characteristic control
Particle size control
Before entering the roller screen, larger particle-sized materials can be processed using crushing equipment to break down the large pieces into smaller particle sizes, making them more suitable for screening by the roller screen. At the same time, the materials should be screened to remove any oversized particles mixed in, such as branches and iron blocks, which can be achieved by installing grilles or magnetic separators at the feed inlet.
Humidity control
For materials with high humidity, drying measures can be taken to reduce the humidity. For example, in the coal processing industry, before the coal enters the roller screen, it can be dried through a hot air drying equipment to reduce the stickiness of the materials.
Adhesion control
For materials with high adhesiveness, some anti-adhesion agents can be added before feeding to reduce the adhesiveness of the materials. At the same time, it is necessary to avoid mixing materials of different adhesiveness into the feed to prevent the adhesion from intensifying and causing blockage.
Equipment parameter adjustment
Screw shaft rotation speed adjustment
If the screw shaft rotation speed is too slow, the materials will stay on the screen for a long time, which is prone to accumulation and blockage; if the rotation speed is too fast, the materials may pass through the screen before they can be screened. The screw shaft rotation speed should be adjusted reasonably according to the material characteristics and the mesh size of the screen.
Sieve plate gap adjustment
If the gap is too small, the materials are prone to get stuck in the gap and cause blockage; if the gap is too large, it will affect the screening effect. The sieve plate gap should be adjusted according to the average particle size of the screened materials.
Inclination angle adjustment
If the inclination angle of the screen is too small, the materials move slowly on the screen, which is prone to accumulation and blockage; if the inclination angle is too large, the materials move too fast and the screening is not sufficient. The inclination angle of the roller screen should be adjusted according to the material characteristics and screening requirements, generally controlled between 10° – 25°.
Equipment maintenance and servicing
Regular cleaning
Regularly clean the roller screen to remove the adhered materials on the screen shaft and screen plates. The cleaning cycle is determined based on the material characteristics and equipment operation conditions. Generally, a comprehensive cleaning is carried out once a week.
Component inspection and replacement
Regularly inspect the wear condition of components such as the screen shaft and screen plates. Replace severely worn components in a timely manner. At the same time, check the sealing condition of the equipment to prevent material leakage into the equipment interior and cause blockage.
Conclusion
The clogging problem of the roller screen not only affects the screening efficiency, but also may aggravate equipment wear and even lead to the risk of equipment shutdown. Considering various factors such as material characteristics, equipment design and operation, take targeted preventive and handling measures to reduce the occurrence rate of clogging.
