A safety process reference model and tool for the development of machine control systems

This paper presents a safety process reference model for the design of machine control systems. The model follows the new appropriate safety standards as ISO 14121-1 for risk assessment and ISO 13849 standard family for safety related parts of control systems. A safety process realised according to the reference model developed within this study is closely connected to the product development of a control system so that safety related tasks will be carried out systematically and in the right phase. The model was demonstrated using web browser techniques and it includes process stages from Preliminary Hazard Analysis (PHA) to the validation process. The other process stages included are Use Case Safety Analysis (UCSA), Function and Communications Analysis and Performance Level (PL) evaluation according to ISO 13849-1. From the web based user interface it is possible to see the safety engineering tasks relating to different process stages, source documents that are necessary for carrying out the tasks, documents to be processed as results of the tasks and references to safety standards. This web interface offers possibility to link the safety standards so that the relating standards can be opened from the page where the safety requirements relating to the corresponding tasks or phase are given. From the process diagram, which works as a graphical user interface, the tools and instructions relating to the safety engineering tasks can be opened. In addition, all the documents relating to the safety process can be opened from the process diagram of the interface for viewing and editing. For example, Preliminary Hazard Analysis and other worksheets can be opened from the process diagram of the interface. Through the web based user interface it is easy and illustrative to prove how the requirements accordant with the relevant safety standards have been followed within the safety process.