Structure And Characteristics of Weight Reduction Scale
The reduction scale dynamically and accurately measures the materials according to the reduction rate of the materials on the scale body. It is suitable for the control and batching of granular materials, powder, calcium carbonate, talc powder, resin film powder, flour, starch and other types of materials, such as cement, lime powder, pulverized coal and other fine materials. The domestic reduction scale has the advantages of reliable performance, accurate measurement, low failure rate, moderate price With the characteristics of saving raw materials and high cost performance, it is suitable for a variety of industries, and it is predicted that it will grow rapidly in the next few years.
The weight loss scale includes continuous weight loss scale and intermittent weight loss scale, of which the continuous weight loss scale is one with high technical level. The continuous weight reduction scale can continuously detect the conveying rate of materials, and maintain the constant discharge flow by adjusting and other parameters of the conveying system (such as valve opening and discharge speed). From the perspective of accuracy evaluation method, the continuous decrement scale is similar to the continuous accumulation automatic scale.
Typical continuous weight reduction scale structure
The hopper part includes a base, a supply hopper, a clamp and a weighing hopper: store materials and discharge them to the feeding parts to prevent material blockage.
The metering part includes a metering platform: real-time dynamic weighing of materials in the hopper.
The vibrating plate part includes the main vibrating plate: the power for the blanking of production materials, the uniform movement of materials to the hopper, and the guidance of materials.
The feeding part includes a discharge cylinder, an air outlet pipe and a feeding port: the materials are transported outward from the reduction scale.
The electric box part includes alarm light, electric box and junction box: analyze and calculate the relationship between the weighing result of the sensor and the motor speed, and control the operation of the whole machine.
The driving part includes reducer, motor: power drive of screw and agitator.
1 working principle of weight reduction scale
The weight reduction scale is a measurement method to calculate the instantaneous flow of the silo by detecting the reduction rate of the silo weight. A load cell is installed on the discharge bin. During the production process, the load cell transmits the signal to the controller by detecting the reduction rate of the bin weight. The controller calculates the instantaneous discharge flow of the bin, and then compares it with the pre calibrated set value, Send a control signal to the frequency converter to control the speed of the discharge screw (impeller) motor under the silo to adjust the powder output until it is consistent with the set value and runs stably. When the powder in the silo reaches the lower limit, the controller sends a feeding command to the feeding motor under the silo, and the silo replenishes materials until the powder reaches the upper limit
2. Analysis of control characteristics
In terms of structure, the volume of its own discharge bin is limited. In the production process, the discharge bin has a process of replenishing materials after working for a period of time. In the process of replenishing materials, the weighing sensor on the discharge bin cannot detect the reduction rate of bin weight, Therefore, during the feeding process, the system locks the motor speed of the discharge screw (impeller) to the motor speed controlled by the frequency converter at the moment before feeding. At this time, the weighing system of the reduction scale is discharging
The constant speed discharge of motor and the weighing system of reduction scale are actually a volumetric feeding system. The condition of stable feeding of the volumetric feeding system is that the density of the discharged material remains unchanged, which requires that the pressure of the material at the bottom of the silo cannot change. However, the process of replenishing materials is a process of adding materials from the lower limit of the silo to the upper limit of the silo. With the continuous increase of cement in the silo, the pressure of materials at the discharge port also increases, thus changing the density of materials. Therefore, when the speed of the discharge motor is locked when the materials in the silo are the least, the actual discharge volume of the system will continue to increase during the feeding process. After stopping feeding, the load cell re detects the reduction rate of bin weight, and the controller re adjusts the speed of discharge motor until the discharge is stabilized within the control range again. From the above analysis, it can be seen that the control of the reduction scale is a cyclic process of adjustment → stability → feeding → adjustment → stability.
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