Safety Instrumented System-Requirements for Successful Operation and Maintenance

In today's world, personal risk posed by hazardous explosive or flammable industry processes depends on the correct functioning of both Safety Instrumented and other technology protection systems. They must be properly designed, operated, maintained and managed in order to achieve a tolerable level of risk on site. IEC 61508 and IEC 61511 standards constitute good engineering practice for safety instrumented systems (SIS) in this area. Based on these standards, this paper will attempt to explore the requirements constituting good practice for operation and maintenance of SIS for the process industry. Good practice for operations and maintenance comprises essentially a number of legs for successful SIS operation: 1. Operation - The SIS is correctly operated within its specified limits for a specified operating time interval. 2. Maintenance - The routine recurring work implemented to keep a SIS in its designed capacity and at optimum efficiency. 3. Management - The coordination of the efforts of people to achieve safety. This comprises planning, organizing, competent staffing, leading and controlling. For each of these three legs a number of key activities have been explored. The following list summarizes those topics which are to be addressed within the following sections of this paper: Essential SIS documentation Action to be taken on detection of SIS fault and SIF bypass SIF device life time SIS security Corrective, preventive and reliability centered maintenance SIF proof test, inspections, Test results analysis and spare parts Organization, planning and staff competency Assessment, auditing and management of change