Application of SIWAREX in batching system of plaster mortar

0 Introduction

Nowadays, in the field of weighing automation and process control, electronic weighing systems are widely used to monitor and control various production processes. These applications can range from simple belt tension monitoring or container filling measurement to complex production control of specific formula mixtures. SIEMENS electronic weighing system (SIWAREX) is particularly suitable for these high-precision measurement tasks, or is used in situations where other measurement methods are not suitable, such as the detection of active materials that cause sensor damage and the production of pure substances (such as food, drugs, and chemical products) that are subject to hygienic conditions.

1 Application of SIWAREX system in plaster production

Weighing and proportional quantitative control are key technologies for advanced industrial process control, and weighing technology plays an important role in many industrial process controls. Through electronic weighing systems directly integrated in the SIMATIC automation system, SIEMENS provides a unified weighing solution in centralized and distributed control systems.

SIWAREX weighing modules can be used as central modules for SIEMENS programmable controllers SIMATIC S5 or S7, or as distributed input and output modules for SIMATIC S5, S7, M7 or C7: By using standard hardware configuration SIMATIC components and standard programming software STEP7, the cost of engineering and training can be greatly reduced. In addition, by using SIWATOOL parameterization software, the computer RS ​​232C interface is directly connected to the weighing module, so that users can easily modify all adjustable parameters through the input window without any STEP 7 programming foundation.

1.1 Functions of SIWAREX U and SIWATOOL

SIWAREX U, the most common module in the SIWAREX series, has the following main functions in the plastering production line: executing weighing tasks in all production processes of the production line, signal digital filtering, over-limit detection, short circuit and overload protection, wire break detection, etc. SIWAREX U has two types of modules, single-channel and dual-channel, with a measurement accuracy of 0.05% and a resolution of 65,535 divisions.

SIWATOOL is an application software that can run under Windows and STEP 7 to perform error diagnosis and parameter setting for SIWAREX U. It allows processing of multiple offline weighing modules and one online module at the same time. By connecting the weighing module directly with the computer RS232C interface, we can conveniently perform physical quantity calibration, upper and lower limit setting, digital filter selection, zero point setting and parameter display operations in the plaster production process.

1.2 Example of application in the control of plaster mortar batching system

In the batching system of the newly built wall plaster mortar production line project of Nanjing Yifu Building Materials Industrial Co., Ltd., Siemens SIWAREX weighing system was selected according to the design. Plaster mortar is a plastering finishing material, which is made of natural gypsum through special process to become semi-water gypsum α-CaSO ·1/2HzO.

Plaster mortar is based on α-CaSO4 ·1/2H2O, with appropriate fillers, high-performance admixtures and construction sand of a certain grade added. The above raw materials are prepared under the control of SIWAREX weighing system according to product requirements. The batching system of the production line mainly consists of two large and small scales. The large scale weighs the two main materials of gypsum powder and sand, and the small scale weighs the three auxiliary additives. All the raw materials for production are added to the two scales in turn according to the process formula requirements with the help of five frequency-controlled spiral cutters. After weighing, all the five raw materials in the two scales are put into the mixer for mixing to form the finished product. Then the next batching cycle begins.

The PLC of this system uses Siemens S7-300, the power module is PS3075A, the CPU module is 6ES7314, the digital input module is 6ES7 321, the digital output module is 6ES7322, and the weighing module is SIWAREX U; the sensor uses strain gauge type, the frequency converter is Schneider ATV-28HU72N4; the human-machine interface HMI uses DIGITAL's Pro-faceGP series touch screen.

The control system has two operation modes: manual and automatic. In manual operation, the main functions of the single-machine debugging, fault repair, and weighing module calibration of the plaster mortar production line are completed. In automatic mode, the host computer HMI realizes the setting of the plaster mortar formula, the dynamic display of the instantaneous value and cumulative report of the raw material weighing, and the production line fault alarm. The lower computer PLC performs the engineering conversion of the production process formula value of plaster mortar and accurately realizes the production requirements of each process; the inverter has high, medium and low speed switching, peeling and zero position tracking, out-of-tolerance processing, fault diagnosis and other functions. At the same time, due to the addition of algorithms such as predictive control of production conditions and cumulative error compensation in the program, the production control accuracy and stability of plaster mortar are greatly improved. The process control process of SIWAREX system in plaster mortar production is shown in Figure 1.

Figure 1 Schematic diagram of SIWAREX weighing system control process

2 Conclusion

The plaster mortar batching system uses Siemens S7-300 series PLC, electronic weighing system SIWAREX and DIGITAL touch screen, which is easy to operate, high precision, safe and reliable, and high production efficiency. In addition, due to the good human-computer interaction interface, operators can be competent for production positions without almost any training, which greatly reduces the company's personnel training time and costs. After six months of operation, satisfactory results have been achieved.