The Design and Implementation of a Graphic Supervisory Control System: A Case Study on Toxic Gas Monitoring of a Chemical Factory

• Main Authors: Hsueh-Li Chiu, 邱學禮
• Other Authors: Da-Chun Wu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/31448389357141296911

碩士 === 國立高雄第一科技大學 === 電腦與通訊工程所 === 95 === As modern technology advances, detection sensors and communication devices have reached enough capacity for high-speed-computing, high-capacity-memory, and high-speed-transmission; it is possible to obtain the operational status of the monitored devices in real time through a Man-Machine-Interface (aka MMI), and by automatically storing accurate monitoring data into a database, it can help to reduce labor cost and enhance working safety. Furthermore, by combining powerful computing speed and accurate design of control sequences, it can help to avoid human errors in operation, increase reliability of automatic monitoring, and enhance production efficiency and quality. Henceforth, it is obvious that Computer Graphic Supervisory Control System play an important role in the area of industrial manufacturing applications. This thesis focuses on such a Computer Graphic Supervisory Control System of toxic gas detection in a chemical manufacturer of sodium hydroxide. These gas detectors are set up in accordance with production processes. In this article, the following topics will be discussed: the fundamental concepts of digital signal transmission and processing via a Programmable Logical Controller (aka PLC), the hardware and software selection criteria when using a PLC, the programming logic, and the application of all these concepts to the target environment for collecting the data from the gas detectors. During the study, the software tool “Wonderware In-Touch” was used to transmit data using a common communication protocol between the PLC and the graphical monitoring system, to build graphical display, to generate dynamic data in real time and to provide functions such as alarms, trend diagrams, and historical data inquiry. The integration of raw data from gas detectors and computer aided system helps to save physical space occupied by traditional equipments, reduce unnecessary labor cost, increase monitoring performance and operational efficiency. In this study, the compliance to environmental protection regulations of harmful gas is taken into consideration by setting up appropriate thresholds. An alarm system is designed to detect and alert when harmful gas goes over a predefined threshold for a certain working area. It may also locate the precise position where the leakage occurs, and reduces the possibility of disastrous leakage events.