However, it is fairly commonplace for requirements to be split into multiple documents which gather in detail as a project progresses. A specific case is the Application Program software requirements. These will not be available in any depth until logic solver equipment selection has taken place, which often happens much later in a project than would be advisable for the FSA 1 activity to take place. In some cases the number of clauses and associated conformance questions may be limited by the type of project, or by decisions made during a project. For example, if a programmable logic solver system is not part of the SIS scope, then Clause 12 of the standard will not be applicable, and the SRS elements that relate to software will not be needed.
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Food and beverage Why should you use this standard? Safety instrumented systems SIS are engineered controls that protect critical process systems. Its use will help assure reliable and effective implementation of SIS to achieve risk reduction objectives, thereby improving process safety. End users in the process industry should use this standard to develop their internal procedures, work processes, and management systems.
Implementing a SIS lifecycle management system provides a framework for managing people, processes, and systems to improve overall safety and operational performance. The standard also provides implementation examples of requirements outlined in Part 1 and is organized so that clauses correspond with the same clause in BS EN with the exception of the annexes. The main changes are as follows: Clarification of the interpretation of the standard in areas that in the past have been subject to misinterpretation, for example removal of the concept of safe failure fraction SFF , clarifying that reliability data must be derived from the performance in the operating environment.
Enhanced requirements in areas which have previously been poorly addressed, for example the addition of security risk assessment and consideration of errors in the human interface, strengthening of requirements on operations and maintenance particularly when in degraded modes, normative requirements for competence, Factory Acceptance Test and for provision of suppliers functional safety management systems, strengthening of the requirements for Functional Safety Assessment, particularly during Change Management and in conduct of Functional Safety Audits as well as the requirements for analysis and impact assessment during change.
Closer adherence to the Basic Functional Safety Standard IEC , for example the addition of the concept of high demand mode, the provision of an additional route to compliance with hardware fault tolerance, the methodology for handling the highest levels of risk reduction and for allocation of SIFs to a SIS, constraints on the claims that can be made with respect to a BPCS and the independence of protection layers.
In particular, removal of much of the guidance on application programming from Part 1 to Part 2, together with significant enhancement of that guidance and provision of worked examples, provides greater clarity. Safety instrumented systems for the process industry sector.
Guidelines for the application of IEC Status.
BS EN 61511-2:2017
Scope[ edit ] The process industry sector includes many types of manufacturing processes, such as refineries, petrochemical, chemical, pharmaceutical, pulp and paper, and power. The process sector standard does not cover nuclear power facilities or nuclear reactors. IEC covers the application of electrical, electronic and programmable electronic equipment. While IEC does apply to equipment using pneumatic or hydraulic systems to manipulate final elements, the standard does not cover the design and implementation of pneumatic or hydraulic logic solvers. This standard defines the functional safety requirements established by IEC in process industry sector terminology. This document sets the standards for safety-related system design of hardware and software.