Application of the hottest high-precision direct l

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Application of high-precision direct load-bearing electronic belt weigher in the cement industry

I. preface

Tongling Shangfeng Cement Co., Ltd. is a private enterprise in Tongling City, Anhui Province. It is located on the side of the Yangtze River, has two cement clinker production lines with a daily output of 5000 tons, and has two cargo transportation terminals. Each wharf is equipped with a conveyor belt and a belt scale for trade settlement. One is used to measure the purchase quantity of raw coal (purchase quantity), and the other is used to measure water. In view of the huge utilization prospect of new materials, the shipment quantity (sales volume) of mud clinker is an important cargo measurement point of the enterprise. The accuracy and reliability of belt weigher measurement directly affect the economic benefits of the enterprise. Therefore, it is very important to choose belt weighers with good quality, stable performance and reliable measurement

these two conveyor belts are very long (the total length of the coal conveyor belt is 1100 meters, and the total length of the clinker belt is 600 meters). Affected by many factors such as the strong wind along the river and the variable wind direction, the measurement of the belt weigher used for these two belts has been plagued by the problems of insufficient accuracy, poor stability and large maintenance. This problem has long plagued our company, especially the coal conveyor belt weigher, It has brought great trouble to the normal production of our company. The leaders of the company attached great importance to this, visited the site in person, understood the problems, listened to the problems reflected by the operators and put forward reasonable suggestions. Previously, we have used belt weighers from many domestic and foreign enterprises, including various types of belt weighers such as multi idlers, full suspension, parallel bars, etc., which generally have unstable performance, large fluctuations in measurement values, poor repeatability, and large differences in each calibration, and cannot meet the requirements of trade measurement

II. Solutions

in May and June this year, we saw an article about Siemens belt weighers in the magazine. With a try attitude, we contacted Siemens and invited them to send personnel to the scene to check the situation and analyze the reasons

there are two one meter wide belts on site. We hope they can solve the problem of coal conveying belt first, because the coal conveying belt is long (1100 meters), there are several joints in the middle, the speed is 2m/s, and the normal flow is 400t/h. We hope that the maximum flow can meet the requirements of 700t/h, and the accuracy can meet the requirements of ≤± 0.5%. If the problem of coal conveying belt can be solved, the problem of clinker belt will also be solved. Siemens' technicians soon arrived at the scene. Through on-site observation, they believed that the working condition of the belt conveyor could meet the working requirements of Siemens belt weigher Combined with the actual situation, the modular electronic belt scale solution of Siemens MMI double idler high-precision scale frame integrated with bw500 integrator and md256 pulse speed sensor is finally confirmed

the design of the belt scale frame of Siemens is very distinctive, which is different from the commonly used lever scale frame. It adopts the direct load-bearing scale frame structure called "three noes", that is, there is no lever, no fulcrum, no balance weight, that is, there is no weighing carrier. Compared with other belt weighers we have used, the belt weigher with this design structure has simple scale frame structure, convenient and simple maintenance and installation; The scale frame has modular characteristics and good versatility; The scale frame has the characteristics of high accuracy (see Table 1). Table 1: performance comparison of belt weighers with various design structures

- lever type (single and double) integral suspension type ordinary direct bearing Siemens high precision

direct bearing structure design is complex, simple and simple, the projection area of the scale frame is general/large, very large, very small, and the horizontal friction force

has little influence, depending on the length of the scale frame, depending on the selected carrier structure is very small, The length of the special parallelogram carrier is 1~8 idlers, 2~8 idlers, 1~4 idlers, 1~2 idlers have a large amount of installation/maintenance, and generally require regular professional maintenance. The workload of installation and long-term maintenance is large and small. It is necessary to calibrate regularly to maintain high precision. Whether there are very small movable parts or not, the accuracy can be up to 0.25%, but it is necessary to carry out very strict periodic calibration, which can be up to 0.25%. However, it is necessary to select a structure above 4 idlers, and the installation and maintenance amount is large, with an accuracy of 0.5~1%, Unable to achieve the purpose of settlement, the weight of 0.25% (double idlers)/0.5% (single idlers)

(taking 1000mm belt width as an example) is very heavy: about 110kg (single idlers and single lever); About 210kg (double idlers and single lever); More than 350kg (four idler double lever) is very heavy: more than 320kg (four idler) is light: About 50kg is light: 52kg (single idler, 0.5% accuracy); 104kg (double idlers, 0.25% accuracy) has poor long-term stability, large drift, and large drift, which requires long-term maintenance. Depending on the selection of the carrier, there is basically no zero drift, and the maintenance amount is very low.

mmi multi idler belt scale is a high-precision type. The scale frame is composed of two MSI single idler scale frames, so it is equipped with four load cells, and the accuracy index is ≤± 0.25% within the range of 20% ~ 100%

bw500 is a powerful integrator designed for belt weighers and weighing feeders. The real dual PID function can be used for flow control of weighing feeders, which can control constant load or feeding volume. It has the following main features:

it has the balance function of patented dual weighing sensors (up to four sensors), which can eliminate the influence of uneven lateral load and does not need the sensor to match the mechanical balance

the high-tech waterproof experimental machine products have the functions of calibration, batch processing, humidity compensation, tilt compensation and so on

dual PID regulation function, which can set the response time and regulation range of PID according to whether there is bubble in the quantitative tube or not according to different process needs

it can effectively solve the problem of sensor characteristic matching, and can significantly improve the long-term stability of the system compared with the external potentiometer

the scale frame of Siemens MMI belt scale was delivered to the site, and the exquisite appearance and compact structure of MMI electronic belt scale left a deep impact on us. The installation work is completed under the guidance of Siemens' technicians. The installation of this electronic belt scale with direct load-bearing scale frame structure is very simple: the original installation usually requires four to six people to complete this work, but this time it only needs two to three people to complete it (as shown in Figure 1). Our electric repair team and machine repair team worked together to complete the installation of Siemens belt weigher frame and speed measuring roller. After Siemens technicians came to the site to guide our installation, they found the following problems:

1) six sets of idlers could not be installed in place and were not in a straight line

2) the speed measuring roller is not perpendicular to the belt

3) the installation position of the anti rotation rod and spring of the speed sensor is incorrect

Figure 1: MMI electronic belt weigher installed on site

after rectifying the above problems as required, we began to calibrate the belt weigher. The calibration procedure of Siemens electronic belt weigher is also different from that of other products. A weighing sensor balancing procedure is added to ensure the consistency of the output of the four weighing sensors and improve the anti eccentric load capacity. This is very important for us, because in practical work, belt eccentric load often occurs. If the belt weigher cannot measure accurately when the belt weigher is under eccentric load, it will certainly affect the final measurement result

in the process of calibration, the bw500 integrator has corresponding prompts at each step, as long as you operate according to the prompts. Although the bw500 integrator displays an English interface, it is difficult to operate for the first time, and you get used to it when you use it more. In the future, if the bw500 integrator display interface can be Chinese, the operation will be more convenient

the second step is to calibrate the zero point. We have done it three times, and the repeatability is within ± 0.02%

the third step is to calibrate the range. We have also done it three times, and the repeatability is within ± 0.04%

there are hotkeys on the panel for the operation of zero point and range calibration, which is very convenient. During range calibration, the instrument also has automatic error correction function. If the relevant operations are not done, the next operation cannot be carried out

through calibration, we feel that the performance of Siemens belt weigher is significantly better than the belt weigher products we have used before, especially its repeatability index is particularly prominent. Moreover, Siemens has very strict requirements on repeatability, and believes that there is no concept of accuracy without repeatability, which has not been explained by other weighing product manufacturers

in the next period of time, we compared the measurement results of water gauge and belt weigher, and the measurement results of Siemens belt weigher are always relatively stable

in the process of use, we also found that the company's remote cumulative input was different from the output data displayed by the bw500 integrator. Under the guidance of Siemens' technicians, we adjusted the parameter settings of the bw500 integrator and replaced the relevant electrical components, which quickly solved the problem

III. application effect

since Siemens belt weigher was put into use, we have conducted peeling operation every day, and the zero point change is ≤± 0.05%; It was predicted and determined by experts with 65kg/m chain code for three times before and after, and the error was ≤± 0.15%; It fully shows the outstanding performance of Siemens electronic belt weigher in stability, repeatability and reliability

our leaders are very satisfied with the use of Siemens belt weigher, which solves the problem of inaccurate raw coal measurement. After the study of the company's leaders, it is decided to implement the renewal and transformation of the belt scale for loading cement clinker, and it is proposed to add a belt scale in the raw coal bunker. (end)

Copyright © 2011 JIN SHI