The hottest SIWAREX weight loss scale based on the

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SIWAREX weightlessness scale based on the concept of full integration

Abstract: This paper introduces the working principle, system composition and characteristics of weightlessness scale, and briefly describes the concept of Siemens' fully integrated control, as well as SIWAREX based on the concept of full integration, but they are all used as some parameter technologies, weightlessness scale schemes and applications that eventually form the effect ranking during the query validity period

key words: weight loss scale SIWAREX is fully integrated and maintenance free

I. Introduction

in the plastic, chemical, metallurgical, pharmaceutical, cement and other process industries, the batching system of raw materials is a key link in the process industry, which can directly affect the product quality, efficiency, energy consumption and other indicators of production. In recent years, with the continuous development of process industrial control system, new requirements are put forward for field equipment: not only the field equipment is required to achieve accurate measurement function, but also to meet the continuous production requirements of high efficiency, high intensity and strong real-time,; It not only meets the high reliability requirements of 7/24, but also has the characteristics of low maintenance and even maintenance free; Not only to reduce the failure rate, but also to achieve the effect of energy saving

compared with electronic belt weighers, weighing feeders, screw feeders, punching flow meters, disk feeders and other metering and batching equipment, weight loss scales have received more and more attention in recent years. After it was introduced to China in the late 1980s, its advantages in metering and batching have been widely recognized

II. Basic principle, system composition and characteristics

loss in weight scale is a continuous weighing and measuring equipment that has been applied to various process industry fields since the mid-1980s. It combines the different advantages of dynamic weighing and static weighing, and gradually replaces continuous weighing equipment such as belt scale and screw scale. It is applied to more and more industrial fields

2.1 basic principle and system composition

take the weighing bucket and feeding mechanism as the whole scale body, continuously sample the weight signal of the scale body through the instrument or upper computer, calculate the change ratio of weight in unit time as the instantaneous flow, and then process it through various software and hardware filtering technology to obtain the "actual flow" that can be used as the control object

the basic composition of weight loss scale can be divided into two parts: equipment system and control part

the equipment is mainly composed of metering bucket, feeding feeder, unloading feeder and suspension device. The control part is mainly composed of weighing sensor, signal amplifier, input and output interface, host computer (upper computer), etc. (as shown in Figure 1)

Figure 1: typical weight loss scale body and structure diagram

the batching process of weight loss scale is divided into two stages: feeding and unloading. After batching, first start the feeding feeder, and the controller will detect and sample the material weight of the metering bucket. When the material weight of the metering bucket reaches the upper limit set for batching, stop feeding. At the same time, the controller detects and samples the material weight of the metering bucket, and stops feeding when the material weight (feeding amount) of the metering bucket reaches the upper limit value set for batching. In the unloading stage, the controller starts the unloading feeder to unload the materials in the metering bucket to the next level of conveying equipment. During unloading, the controller detects and samples the weight of the material in the metering bucket. When the weight of the material in the metering bucket reaches the lower limit set for batching, it feeds the metering bucket again. However, after the start of the second feeding stage, the unloading feeder still continues to unload without stopping

the weight loss scale continuously weighs the whole feeding system, including the metering bucket and the feeding mechanism, which is equivalent to a static scale; At the same time, the discharge flow of the feeding mechanism is controlled by variable frequency speed regulation

weight loss scale measures the reduction of material weight per unit time in the bucket Δ d/Δ T corresponds to the feeding flow of the weight loss scale. The weight loss scale controller compares dv/dt with the preset feeding flow and automatically corrects it by adjusting the speed of the feeder, so it can maintain an accurate feeding flow (as shown in Figure 2)

Figure 2: weight curve of weight loss quantitative feeding and feeding

when the weight of material in the metering bucket is lower than the preset value, the weight loss scale control module will lock the feeder speed, keep the feeding mechanism feeding in volume mode, and open the feeding valve for rapid feeding. When the weight of the material in the metering bucket reaches the high preset value, the feeding valve will close automatically. At the same time, the weight loss scale controller automatically switches the blanking mechanism to the weighing mode for feeding

2.2 technical features

from the perspective of working principle and structure, the weight loss scale has the characteristics of both static scale and dynamic scale

for the traditional dynamic weighing measurement methods, such as belt scale, punching flowmeter, screw scale, etc., although they have the characteristics of continuous weighing and high efficiency of the process, there are also problems such as low system accuracy (generally lower than 0.5~1%), large maintenance, etc; Although the static weighing method greatly improves the measurement accuracy of the system (up to 0.1%, or even higher), it can only meet the intermittent batch feeding (dispensing) application, and can not be disposed of by the processor to the greatest extent, so as to meet the requirements of high efficiency and high output of modern process industry. Moreover, some industrial applications require continuous feeding (dispensing) without interruption

the emergence of weightlessness scale just combines the advantages of these two and makes up for their shortcomings. Its main advantages are:

high system accuracy

when the weight loss scale works, the measurement of the silo is actually completed under static state, and it is one after feeding and one after feeding Measure once, and calculate the flow according to the difference between the two weights measured under the two working conditions. The error between the difference and the given value of flow can also be compensated in the next cycle, and the two weight measurement times can be completed in a few minutes, without the influence of zero drift and temperature drift of the sensor. Therefore, quite high measurement accuracy can be obtained, and the measurement accuracy of the system can reach 0.5%, or even 0.2%

fully enclosed stainless steel structure, suitable for all kinds of harsh sites

all the equipment and systems are made of steel (Siemens weightlessness scales are generally made of stainless steel), which is suitable for occasions with poor environmental conditions, but many people in the industry believe that it has the characteristics of durability, small maintenance, and fear of high-temperature materials

many industrial and mining enterprises are large power consumers, so how to save energy is also a very important topic. Because the weight loss scale adopts a fully enclosed structure, no dust is generated in the batching process, and the dust removal device is omitted. The structure is simple, and there is no need to equip with belt scales, which not only saves equipment investment, but also saves electric energy and improves production efficiency

maintenance free, simple calibration

since the weight loss scale is a material measurement method that calculates the flow by measuring the weight difference, there is no influence of factors such as zero drift (caused by belt deviation, sensor displacement, material impact and vibration, belt slipping, belt sticking, etc.), material adhesion, scale body mechanical structure deformation, etc. in dynamic scales such as belt scales, which can ensure long-term stable system measurement accuracy, There is basically no need for maintenance and a lot of calibration work

according to its measurement principle, it can not only calibrate the physical object, but also calibrate in the production operation. That is, the calculation accuracy is compared according to the difference between the upper and lower weights of the materials in the metering bucket and the flow display value of the weight loss scale. This calibration method is simple and convenient, saving money and labor

III. fully integrated design concept

totallyintegratedautomation is the core idea and leading concept of Siemens' automation system technology and products. TIA integrates a high degree of integration unity and unprecedented openness. The standardized network architecture, unified programming configuration environment and highly unified data integration make TIA realize horizontal and vertical information integration for enterprises; Leading communication standards, component-based automation technology (CBA) and it integration make TIA truly open to the range of products and services in the global automation market

in 1996, Siemens Automation and drive group proposed the conceptual system structure of "fully integrated automation" TIA (as shown in Figure 3). This new concept revolutionizes the knowledge and experience in the field of "manufacturing" and "process", and provides an excellent solution for the production line. For users, in the whole life cycle of the production process, TIA technology with S7 Series PLC as the core helps enterprises to maximize productivity. From the initial planning and design, project implementation, installation and commissioning, operation and maintenance, to system upgrading and transformation, TIA enables enterprises to obtain the highest productivity and product quality in the whole life cycle, and significantly reduce project costs. In addition, TIA can greatly shorten the time of product launch and system operation, so as to comprehensively enhance the core competitiveness of enterprises

due to the relatively complex structure and large amount of maintenance of the weighing system, the leading weighing technology manufacturers have been considering how to design a solution that can not only reduce costs, simplify the weighing system structure, but also improve the overall performance of the weighing system. Based on the design concept of TIA, Siemens designed and launched the Siemens SIWAREX weighing scheme with simatics7 as the core, which is undoubtedly a feasible solution to meet the new requirements

Figure 3: schematic diagram of Siemens fully integrated control structure

IV. SIWAREX system

as mentioned above, the batching process of the weight loss scale is divided into two stages: feeding and unloading, and the control part is relatively complex. The batching accuracy of the weight loss scale is mainly determined by the weighing accuracy and batching speed. These two parameters are two contradictory control quantities. To improve the weighing accuracy, the more stable the scale body is, the better, that is, the slower the feeding (or unloading) speed is, the better, but it is bound to increase the batching time and low efficiency; On the contrary, if the feeding (or unloading) speed is too fast, the scale body vibrates greatly, and the accuracy is difficult to ensure

therefore, the use of a suitable control system is the key factor to ensure the batching accuracy of the weight loss scale. This control system should not only ensure the perfect combination of the control system and the equipment to achieve synchronous work, but also ensure good real-time, stability and reliability, so as to ensure smooth "communication" between the scale part and the control part

Siwarexftc (flexible continuous weighing technology) is a high-precision and high-speed weighing control module, which is directly integrated into Siemens PLC control system and can be used for weighing control application of weight-loss feeding equipment

in the production process, the accurate control of feed flow plays an important role in ensuring product quality. Siemens swarexftc weighing module can accurately control the feeding flow of powder, particle, sheet, strip and block solid materials in the production process

Figure 4: the control system composed of SIWAREX FTC and S7 controller

siwarex weight loss scale standard configuration includes siwarexftc weighing module and PLC or upper computer (HMI), weighing sensor, metering bucket, feeding valve, blanking mechanism, motor drive part, etc. (as shown in Figure 4)

siwarexftc fully integrated weightlessness weighing scheme advantages:

1) by integrating into the SIMATIC system (as shown in Figure 5), you can directly manage the formula and set the preset value of the weighing system

2) for different materials, it is convenient to set the parameters of quantitative feeding remotely. Through the use of automatic acquisition of characteristic curve, simple remote adjustment of metering parameters can be realized

3) it is easy to install and can read weighing data and set weighing through various communication modes

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