Application And Maintenance Analysis of Electronic Belt Scale

Electronic belt scale is a weighing tool, mainly for dynamic measurement of bulk materials. It can measure the instantaneous flow and cumulative flow of materials on the belt conveyor without affecting the flow of materials. It is not only fast, easy to install, but also saves a lot of money. In recent years, the automation level of industrial production in China is getting higher and higher. Electronic belt weigher is widely used in coal, metallurgy, building materials, chemical industry and food industry. We must be familiar with the working principle of electronic belt weigher, eliminate errors through scientific installation and reasonable use, and do a good job in maintenance in time, so as to really play the role of electronic belt weigher, Promote smooth production.

1. Working principle of electronic belt scale

The components of electronic belt scale are divided into weighing scale frame, weighing sensor, speed sensor and weighing instrument. The weighing scale frame uses multi idler type, and the weighing sensor is the most core component. Especially under the development trend of digital sensor technology, its technical performance and measurement accuracy performance have been greatly improved, and the weighing control instrument has also developed into more integrated Scale and miniaturization. In order to make the control operation more centralized, the computer system can automatically complete the control and operation functions of the weighing control display instrument of the electronic belt scale. The measuring personnel only need to use the calculation system to easily complete the operation and control operations such as monitoring, zeroing, automatic interval calibration, linear compensation, maintenance and fault diagnosis. After the electronic belt scale starts, the computer system controls the drive motor to drive the belt conveyor to run, and the weighing display controller and the drive motor are interlocked. After the drive motor runs, the weighing display controller will get the start-up signal and feed the belt for the feeding mechanism. After the material passes through the weighing frame, the gravity of the material is transmitted to the weighing sensor under the action of the weighing idler. The weighing sensor measures the load value signal per unit length of the belt. At this time, the speed sensor measures the belt running speed signal [1]. Then, the weighing signal and speed signal are received by the weighing display controller. After data processing, the instantaneous weight value of the material can be obtained. After receiving by the computer control system, the continuous flow signal can be accumulated, and the accumulated value of the material through the electronic belt scale can be obtained. After the drive motor is no longer working, the weighing display controller will maintain the hot standby state, and the computer system control mode will promote the accuracy, reliability and stability of the electronic belt scale.

2. Installation points of electronic belt scale

2.1 reasonably determine the scale installation position

The scale body should be installed in the place where the belt tension of the conveyor does not change much, and there should be no expansion, joint and longitudinal beam splicing. In the weighing range, the idler and conveyor support should have sufficient strength and stiffness to minimize the influence of external factors, such as vibration, wind, rain and snow, corrosion, vibration and magnetic field. After the scale body is installed on the belt conveyor, it should be separated from the vibration bin to reduce the interference caused by the vibration signal for the weighing signal.

2.2 selection and installation of weighing idler

For the radial runout of symmetrical heavy idler, the tolerance of bearing height and groove angle shall not exceed the national standard range, and the groove angle of idler shall not exceed 35 degrees. If the groove angle is too large, the centrality of idler will be different, and the belt flexibility will also be adversely affected. In the weighing range, the idler should be about 6 mm larger than other idler, and the longitudinal center line should coincide with the center line of hanging roller of conveyor frame, and keep parallel with the longitudinal direction of conveyor.

2.3 installation requirements of electrical part

The power supply should be away from the power line, or the lighting power supply should be selected. If conditions permit, the power regulator should be installed on the power side of the computer integrator. The electrical junction box should be installed on one side of the conveyor to ensure its sealing, so as to avoid water entering into the circuit board or dust entering into the junction box in the process of cleaning the conveyor frame. The computer integrator control room should be kept a certain distance from the site, usually several hundred meters. The weighing signal line and power cable should be separated on the running line, and the shielding end should be connected well at the same time. Because of the large line loss, the weighing signal is easy to be affected by the outside world. When the distance is more than 60m, the 6-wire connection method should be selected for wiring, and both the computer integrator and the scale body need to be grounded, and the grounding resistance should not exceed 4 Ω.

3. Error analysis of electronic belt scale

3.1 Error caused by equipment itself

The equipment has its own defects, which will cause the accuracy of the electronic belt scale to decrease. From the analysis of the structure and principle of the belt scale, its measurement accuracy will be affected by many factors, such as the material quality per unit length detected by the sensor, the running speed of the belt, etc. the selection of the equipment components has a great impact on the accuracy of the electronic belt scale. The errors caused by the equipment itself are mainly reflected in the following points: first, the manufacturing accuracy of the equipment, and its accuracy

It is directly related to the later use effect. In the process of type selection, we must fully consider the accuracy, weighing range, scale type and function. Second, spare parts manufacturing accuracy, this factor also has a great impact on the accuracy of the electronic belt scale, especially reflected in the weighing idler and cross support piece. When purchasing this part of spare parts, the original scale manufacturer should be the main one. The weighing idler must have good concentricity, and the cross support plate should be used

It has good elasticity [2]. Third, the quality of annular belt. Because the annular belt will contact the weighing idler, the uniformity and flexibility will have a huge impact on the weighing fluctuation of the belt scale, so it is necessary to improve the uniformity and flexibility of the annular belt. Therefore, in order to avoid the error caused by the equipment itself, it is necessary to strengthen the quality control of the purchase and acceptance, to select the right type, select the factory, and strengthen the quality control of the incoming factory, so as to effectively solve the above problems.

3.2 Errors caused by environmental factors

The equipment installation environment also has a great impact on the accuracy of electronic belt scale, but the environmental factors can not change in a short period of time. Therefore, the equipment installation environment should be reasonably selected to minimize the impact of temperature, humidity, vibration and electromagnetic interference. Temperature has a great influence on the belt stiffness, which will make the belt tension change, so the accuracy of the belt scale will gradually reduce, and the temperature will also affect the measurement characteristics of the load cell and speed detection instrument. If the humidity is high, it will reduce the reliability of the detection components, shorten its service life, and cause the belt slip problem, reduce the accuracy of measurement. Vibration and electromagnetism will direct the instrument

In order to solve these problems, we should fully consider the installation environment, so as to effectively eliminate its impact on the weighing accuracy.

3.3 human error

First, belt sticking. Sticky materials are easy to bond on the belt during transportation. If it is not cleaned, the empty weight of the belt scale will be gradually increased, and eventually the accuracy of the belt scale will be reduced. Therefore, it is necessary to clean up in time, improve the ingredients and reduce the viscosity of materials. Second, the belt scale accessories are damaged. Including cross reed aging and fracture, signal circuit fault, belt idler wear and belt idler operation problems, etc., all of the above have instantaneous characteristics, which must be checked one by one, and the problem can be solved by replacing spare parts. Second, the correction of zero and slope coefficient is not in place. Electronic belt scale belongs to dynamic scale, which will inevitably change when transporting materials, and the zero point and slope coefficient will change, so it is necessary to correct the zero point and slope coefficient, so as to improve the weighing accuracy [3]. Usually, it is necessary to make regular systematic correction or sporadic individual correction. For periodic system correction, it means that the calibration scheme of batching scale is defined according to the planned maintenance cycle of equipment, so that all equipment maintenance cycles can make system calibration for belt scale. For sporadic individual correction, it means that after the temporary inaccuracy of the electronic scale, if it is caused by the key measuring parts of the belt scale, it can be reused after the relevant parameters are corrected.

4. Use and maintenance measures of electronic belt scale

4.1 regularly check the running parts of the electronic belt scale

It is necessary to regularly check the condition of each running part of the electronic belt scale, so as to avoid the problem of loose fasteners of the weighing scale frame, so as to affect the measurement accuracy. After the above problems, the zero value of the electronic belt scale weighing display control instrument will appear unstable. It is necessary to comprehensively check the relevant parts of the weighing scale frame, and timely fasten them, including the weighing sensor connector, weighing idler and other key parts. For the accumulated materials on the scale body of the electronic belt scale and the adhesion on the belt, it is also necessary to check and clean them regularly. If the material jam is found at the fulcrum, it will be removed immediately to avoid the change of the weighing benchmark. Moreover, if there is adhesion on the inner surface of the belt of the speed sensor of the electronic belt scale and the residual material of the speed measuring roll is out of round, the speed sensor will jump and the speed signal will not be detected normally, so the measurement accuracy of the electronic belt scale will be improved

It will also be affected. In this regard, the electronic belt scale belt should be carefully checked to solve the problems of deviation, slip and so on. After the electronic belt scale is installed, in the first few months of use, the tare weight value and zero point of the belt scale should be detected regularly to ensure real-time monitoring of the operation of the electronic belt scale. If the measurement deviation occurs, it needs to be verified or calibrated again.

4.2 maintenance of electronic belt scale carrier roller

The measurement accuracy of electronic belt scale is easily affected by many factors, mainly including the motion flexibility and radial runout degree of the carrier roller of the weighing scale frame. Therefore, the rotation of the heavy carrier roller should be strictly checked. If there is any problem, it is necessary to make targeted adjustment, and add lubricating oil in time, and then verify or calibrate the electronic belt scale [4]. During the long-term operation of the weighing roller of the electronic belt scale, it is easy to cause problems such as damage, out of round and inflexible rotation, which will greatly increase the running resistance of the belt of the electronic belt scale and cause measurement deviation. Therefore, it is necessary to repair or replace the damaged roller in time. Under the action of external force, the weighing frame of electronic belt scale will appear mechanical damage, which will make the weighing frame of electronic belt scale deform and eventually cause the change of weighing force, resulting in inaccurate measurement. The measurement deviation is very obvious, which is a sudden change and is easy to be found. The damaged parts should be better checked as soon as possible, and they should be re checked after they return to normal, and then put into use after they are qualified.

4.3 seriously overhaul the electronic belt scale system

In the maintenance process of electronic belt scale system, it is not allowed to conduct electric welding operation on the scale body installed with load cell, otherwise the load cell will be damaged. Under special conditions, the power supply of the electronic belt scale should be disconnected first, and the grounding wire should be led to the scale body. In the welding process, attention should be paid to avoid the current loop passing through the load cell. In addition, if the maintenance personnel must stand on the scale frame for maintenance, it is necessary to disconnect the load cell overhead to avoid overload problem and damage of the load cell. When using the electronic belt scale, it is necessary to strengthen the flow control, and it is better not to exceed the maximum flow value. This method is conducive to improving the measurement accuracy and reliability of the electronic belt scale, and also can effectively extend the service life of the electronic belt scale.

5. Conclusion

In short, in the process of using the electronic belt scale, we should not only master the correct application method and reduce the measurement error, but also do a good job in maintenance to ensure that the electronic belt scale is in normal working condition. In the future, we need to further improve the design and manufacturing level of the electronic belt scale, install it under the best conditions, and strictly do a good job in daily detection and maintenance, so that the function of the electronic belt scale can be brought into normal play.

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