SAFETY BUS SYSTEMS
1University of Kassel
2HIMA Paul Hildebrandt GmbH + Co KG
Abstract
Modern distributed control systems connected via network systems require an effective and uninterrupted communication between all subscribers. It is necessary for the communication to be fault tolerant and safe. For safety related systems, additional safety layers are needed to fulfill these requirements. In a safety related application, a safe protocol alone cannot fulfill this specification without two safe source and destination hardware nodes. Only the combination of a safety related protocol and safety related hardware nodes fulfill the request of safety related bus systems.
Safety related reliability of complex safety network-systems can be achieved with the application of rigorous and analytical processes, incorporating continual verification and testing. The extent of these measurements varies, depending upon the necessary risk minimisation essential for the safety function. Required risk reduction is achieved by a combination of technical and non-technical methods, resulting in a reduced acceptance level for the remaining risk of hazardous plant or equipment.
In addition, the implementation of networking and bus systems as safety technology requires the same consideration of the entire life cycle. Safe communication systems are complex systems consisting of transmitters and receivers of safety-relevant information. Therefore, the design of a safe communication system involves the same prerequisites for risk reduction, fault avoidance, and fault control. However, it is important to note that a safe communication over a network-system alone does not ensure that the transferred safety-relevant function is also safe. The information has to be accurately produced and processed. Nevertheless, it is possible to include bus systems with the development of safe complex electronic systems into the safety system.
