Model Structures Of Dangerous Chemicals Monitoring System Based On Functional Safety

With the basic standard of functional safety, IEC 61508, released and implemented in China, "Functional Safety" becomes a hot topic and a technology hot spot. The standard advocates a new concept of safety with the requirements both in technology and management, personal and environmental.Functional safety is still a new theory now in China. In this paper, a model of mobile dangerous chemicals monitoring system is built with Siemens S7-300F PLC, buttons and lamps, in which functional safety related concepts and theory are used according IEC 61508, IEC 61511 standards.First, the origin and development in China and abroad of functional safety is introduced, the basic theory and requirements in relative standards is illuminated.Second, the functions of the model, such as overrun alarm and emergency alarm, are determined whose Safety Integrated Level (SIL) should be SIL 2 after risk analyze of dangerous chemicals monitoring system.Third, the model is built, PLC is configured and programmed by STEP 7, PC program for monitoring the model is made by WinCC.Fourth, functions of the model are tested.And last, SIL of the model is validated to ensure that it is satisfied with the requirements requested in the risk analyze. During the verification, formulas for calculating PFH value of 1oo1D and 1oo2D structure are presented.