Since excessively large adjustments to the original roll gap can affect the extrusion effect of the roller press and weaken the improvement of material grindability, although the particle size of the materials entering the mill does not change significantly under the classification effect of the dispersing classifier, it will inevitably have a negative impact on the output of the ball mill system due to material grindability. Our specific measures to adjust the original roll gap should take into account both the complete elimination of torsional vibration and the maintenance of the extrusion effect as much as possible, seeking the best position that balances the two.
The adjustment range of the original roll gap should be determined based on the roll gap difference manifested by the changes in the properties of the materials being extruded, i.e., the change in the working roll gap between normal operation and abnormal operation with torsional vibration. We first measure the fluctuation range of the working roll gap under normal operating conditions of the roller press based on the roll gap value displayed on the digital display of the displacement sensor in the roller press system control cabinet, assuming that the roll gap value is roughly between A1 and A2. Then, we measure the fluctuation range of the working roll gap during abnormal operation with torsional vibration, assuming that the roll gap value is roughly between B1 and B2.
1. A2 – A1 = △A
Where: △A is the change in working roll gap
A2 is the peak value of the working roll gap
A1 is the trough value of the working roll gap
2. B2 – B1 = △B
Where: △B is the change in working roll gap during torsional vibration
B2 is the peak value of the roll gap during torsional vibration
B1 is the trough value of the roll gap during torsional vibration
Estimate the roll gap difference between the two situations:
A1 – B2 = δ
The δ in the above formula is the reference value of the original roll gap adjustment. The final determination of the adjustment amount is based on the operation status of the equipment and fine-tuned as appropriate. The δ value should be the minimum adjustment range that completely eliminates the torsional vibration phenomenon.
3. Stable position without segregation: Although the segregation phenomenon of materials is relatively common, it is not inevitable. When the materials in the weighing bin are at a specific material level with limited fluctuations, there is no segregation phenomenon, and the coarse and fine materials enter the roller press in a uniformly mixed state. At this time, the two main motors operate with normal and stable working currents. The specific measures for stable position without segregation are carried out in two steps. First, adjust the original roll gap to eliminate torsional vibration, as mentioned earlier. Then, slowly raise the material level from low to high. During the gradual change of the material level, we can see that the operating currents of the two main motors change from time to time, with the rule of alternating between normal operating current and low operating current in a short time, and the interval time is in a roughly similar and regular state:
The normal operating current state of the main motor can only indicate that the materials being squeezed are all coarse-grained materials. At this time, the working roll gap is normal, and there is no contact between the movable roller bearing seat and the adjusting pad, but the fine-grained materials in the bin are accumulating due to material segregation. The normal operating time of the main motor is extremely short, and the more fine-grained materials there are, the shorter the normal operating time will be.
The low operating current state of the main motor indicates that the fine-grained materials accumulated to a certain extent in the bin are entering the grinding roller pressure zone in a collapsing manner. Due to the control effect of the adjusting pad, the pulsating change of working torque has been eliminated. The fine-grained materials in the pressure zone between the two grinding rollers are in a relatively loose state with low pressure. At this time, the working roll gap becomes smaller, and the movable roller bearing seat is already close to the adjusting pad. The grinding rollers operate at low torque.
The alternating changes of the above phenomena indicate the ubiquitous segregation phenomenon of materials in the weighing bin. However, when we slowly change the material level in the bin, we find that when the material level is at a certain level segment, the operating currents of the two main motors gradually become stable and normal, and the segregation phenomenon disappears. We can take the material level value in the non-segregation interval displayed by the weighing sensor of the roller press system control cabinet as the system balance section, control the material level in the bin within the non-segregation interval, and strictly control the feed rate to stabilize the material level. On this basis, the original roll gap can be fine-tuned by slightly reducing the thickness of the adjusting pad to enhance the extrusion effect.
Zigong Tianyi Industry Co., Ltd. stands as a preeminent manufacturer and supplier of premium-grade high-pressure roller press machines and their vital components. Our core product portfolio encompasses an extensive range, featuring Hard Alloy Pins, edge blocks, cheek plate, wear-resistant blocks, Rotor Tip Set for sand making machines, Back Up Tip Set, Distributor Plate, tungsten Carbide Cutting Tools, carbide inserts, finish carbide boring heads, and numerous other precision-engineered products.
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