Application and Practice of Revamping Speed of Metering Belt Scale

1 Introduction

With the continuous expansion of the company's production scale, the unloading capacity of the raw material wharf (the original design annual unloading capacity is 4 million tons) has seriously restricted the rapid development of the company.At the same time, in order to further enhance the market competitiveness of the enterprise, reduce the logistics and transportation costs of the company, we must give full play to the cost advantage of water transportation, increase the proportion of water logistics.Therefore, based on the original hardware of the raw material wharf, the company has implemented the systematic transformation of "improving the unloading capacity of the raw material wharf", so that the running speed of the unloading belt has been increased from 1.2m/s to 1.6m/s, and the annual unloading volume has been increased from the original 4 million tons to 8 million to 10 million tons.With the improvement of the speed of the metering belt, and the change of the measuring environment such as the in-place lifting of the metering belt, it will also greatly affect the measurement accuracy of the original metering belt scale, and then affect the company's foreign trade settlement (according to the requirements of the company's foreign trade settlement, the maximum allowable error of the metering belt scale is ±0.3%).Therefore, on the basis of fully tapping the potential of the original measuring equipment, we have also carried out technical transformation on the metering belt scale of the raw material dock.In with the original belt scale equipment manufacturers scheme demonstration and technical seminars, based on the final decision on the original measuring belt use scale body shift, improved the original scale body mechanical structure, increasing the scale body weight, expand the sensor range and other multi-pronged scheme, to ensure that the technical transformation application practice safe, in order to realize the long-term stability of the belt scale measurement, and accuracy.

2.Composition and working principle of metering belt scale

Metering belt scale is generally composed of belt conveyor, scale frame, weighing sensor, speed sensor and weighing display controller.

When the material is conveyed by the belt, the material quality on the weighing section acts on the scale frame through the metering idler set and is transmitted to the weighing sensor. The weighing sensor converts the material weight into MV signal and sends it to the weighing display controller, which is converted into digital signal through the process of operational amplification, filtering, A/D conversion and so on.At the same time, speed sensors mounted on the return belt convert the speed of the belt into a pulse signal.The arithmetic device carries out integral operation on the two signals to obtain the cumulative quantity and instantaneous quantity of the material, which is displayed on the weighing display controller.

3. Technical transformation and application practice

3.1 Comprehensive improvement of mechanical structure of scale frame

The scale frame design of the original belt scale is double lever 2 roller structure, the weighing section length is short, the weighing precision is not high, the influence of the belt tension, the belt deviation is big.In order to ensure the accuracy and stability of measurement, we changed the original 2 rollers to 6 rollers in this transformation, increased the weighing length, and replaced the original inflexible roller with high precision double-sided sealed bearing.Taking into account the original nylon trunnion support point shock resistance is poor, easy to wear, the use of rubber trunnion as the support point of the scale body, so that the scale body free return, avoid mechanical return insensitive situation.

At the same time, the use of balanced frame structure, the use of 180mm×100mm×8mm rectangular steel pipe and the diameter of 75mm round steel combined to increase the rigidity of the scale body frame, the weight of the scale body, the length of the frame from the original 4m long extended to 6m.

3.2 Shift of belt scale

Because the metering belt of the original belt scale installation position is raised in situ, the horizontal Angle of the scale body reaches 35°, the inclined Angle is too large, the belt scale is not uniform, and easy to lead to the material backflow in the process of conveying, affecting the measuring accuracy of the electronic belt scale.Therefore, we moved the original belt scale back to a relative horizontal position.However, after the shift of the belt scale under the base beam spacing is too large, and the electronic belt scale as a metering equipment, in the installation process need to have an independent installation bracket or platform, and the installation bracket or platform must be strong and horizontal.If the position of the electronic belt scale installation is unstable, it will affect the metering of the material of the belt conveyor above the electronic belt scale. Therefore, when installing the electronic belt scale, we reinforce the bottom beam to avoid the impact of the toughness of the platform on the metering accuracy of the electronic belt scale.

3.3 Increase the range of the weighing sensor

With the increase of the weight of belt scale, the lengthening of the weighing section and the increase of the flow, the original capacity of the weighing sensor is no longer applicable.According to the maximum force value of the scale, the number of weighing sensors, the weight of the scale body, the weight of the material line and other factors, we use the S type 1000kg weighing sensor.The calculation formula of the range of the weighing sensor is as follows: the material weight G on the single length =Q/ (3.6×V) =173.6kg/m, where Q=1000t/h, V=1.6m/s;The force arm of the sensor L =3000mm, the force arm of the roller 1 L1=500mm, the force arm of the roller 2 L2=1500mm, the force arm of the roller 3 L3=2500mm, the force arm of the scale frame L =1500mm,Unit length belt weight G leather =26kg/m, single roller weight G support from =23kg, roller spacing L support =1000mm, weighing frame weight G scale =380kg;Single roller force G support =G material ×L support +G skin ×+L support +G support from =222.6kg;Sensor force F= [G support × (L1+L2+L3) +G scale ×L self] /L transmission =523.9kg;The range of the sensor is C=F×K=785.85kg, where K=1.5 (safety factor).Therefore, the standard range of the weighing sensor is 1000kg.

4 check

4.1 Preparation before calibration

(1) first use the belt balance to run for a period of time under full load, the purpose is to make the belt tension to reach a stable state and the running in of all parts of the belt balance.

(2) Check the state of weighing frame, speed sensor, weighing roller, weighing sensor, etc.

4.2 Physical verification of belt scale

(1) Zero calibration

After the belt runs 3 laps without load, the accumulative value of the weighing display controller is less than the percentage of the accumulative load under the maximum flow rate in these 3 laps. In 5 tests, the zero value is stable.

(2) physical calibration

The materials used are first weighed and tested in the standard check hopper scale. The indicated value of the hopper scale is taken as the standard value and compared with the cumulative indicated value of the belt. The error is within ±0.3%.After the transformation of the metering belt scale at the raw material wharf of the company has been put into use, it is in good condition and the metering accuracy is stable after more than one year's operation.After several random checks, the results are within the error range.

5 conclusion

Through the improvement of the mechanical structure of the scale frame, the selection of the range of the weighing sensor and the adjustment of the installation position of the belt scale, the accuracy of the measuring belt scale has been improved and the reliable data support has been provided for the foreign trade settlement of the company.At the same time, the cost of logistics and transportation is reduced, and the working efficiency is improved (the speed of conveyor is increased to 1.6m/s ~ 1.8m/s, and the flow range is increased to 800t/h ~ 1000t/h).The practice proves that the application of this transformation is successful and the experience can be popularized.

 NOTICE: This site is reproduced by the editor of this website. The purpose of the reprint is to transmit more information. It does not mean that this website agrees with its views and is responsible for its authenticity. If you are involved in the content, copyright and other issues, please contact us within 30 days, we will delete the content in the first time! [Declaration] The copyright of this article belongs to the original author. The content is the author's personal opinion. This site is only for reference and does not constitute any investment and application advice. This site has the final interpretation of this statement.