Safety instrumented systems (SIS): Service life

An Safety Instrumented System (SIS) is a new term used in the standards that normally also have been and are known by the majority like: Emergency Shutdown System (ESD), Safety Shutdown System, Interlock System, Emergency tryps System, Security systems, etc. The SIS constitutes the last layer of preventive security and their correct design, installation, tests and maintenance (life cycle) are the guarantee of their suitable operation when, under demand, it is required. If this layer fails the dangerous event will be triggered producing leakages, explosions, fires, etc with the consequences that this can carry in costs and/or human lost. After this last single preventive layer they appear those of mitigation that try to diminish the consequences (fire and gases systems, plans of emergency, etc.). An Safety Instrumented System (SIS) can be defined as: "A System made up of sensors, final logic and elements in order to take to the determmined process to a safe state when pre-established conditions are violated" It is therefore critical and fundamental that the Companies of Process have in consideration in their Projects that the industrial safety of its facilities happens through the strict fulfillment of each step of the life cycle that the modern international standards (ISA and IEC) define. This article tries to expose not only that is a SIS but also to mean its importance, to enumerate the best standards, as well as to as much describe each one of the steps of its life cycle giving finally recommendations and identification acronyms.