IEC 61511 | Wikipedia audio article


IEC standard 61511 is a technical standard
which sets out practices in the engineering of systems that ensure the safety of an industrial
process through the use of instrumentation. Such systems are referred to as Safety Instrumented
Systems. The title of the standard is “Functional safety
– Safety instrumented systems for the process industry sector”.==Scope==
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 61511 covers the application of electrical,
electronic and programmable electronic equipment. While IEC 61511 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 61508 in process industry sector terminology. IEC 61511 focuses attention on one type of
instrumented safety system used within the process sector, the Safety Instrumented System
(SIS).==History==
In 1998 the IEC, which stands for International Electrotechnical Commission published a document,
IEC 61508, entitled: “Functional safety of electrical/electronic/programmable electronic
safety-related systems”. This document sets the standards for safety-related
system design of hardware and software. IEC 61508 is generic functional safety standard,
providing the framework and core requirements for sector specific standard. Three sector specific standards have been
released using the IEC 61508 framework, IEC 61511 (process), IEC 61513 (nuclear) and IEC
62061 (manufacturing/machineries). IEC 61511 provides good engineering practices
for the application of safety instrumented systems in the process sector. In the United States ANSI/ISA 84.00.01-2004
was issued in September 2004. It primarily mirrors IEC 61511 in content
with the exception that it contains a grandfathering clause: For existing safety instrumented systems (SIS)
designed and constructed in accordance with codes, standards, or practices prior to the
issuance of this standard (e.g. ANSI/ISA 84.01-1996), the owner/operator shall determine and document
that the equipment is designed, maintained, inspected, tested, and operated in a safe
manner. The European standards body, CENELEC, has
adopted the standard as EN 61511. This means that in each of the member states
of the European Union, the standard is published as a national standard. For example, in Great Britain, it is published
by the national standards body, BSI, as BS EN 61511. The content of these national publications
is identical to that of IEC 61511. Note, however, that 61511 is not harmonized
under any directive of the European Commission.==The Standard==
IEC 61511 covers the design and management requirements for SISs throughout the entire
safety life cycle. Its scope includes: initial concept, design,
implementation, operation, and maintenance through to decommissioning. It starts in the earliest phase of a project
and continues through startup. It contains sections that cover modifications
that come along later, along with maintenance activities and the eventual decommissioning
activities. The standard consists of three parts: Framework, definitions, system, hardware and
software requirements Guidelines in the application of IEC 61511-1
Guidance for the determination of the required safety integrity levelsISA 84.01/IEC 61511
requires a management system for identified SIS. An SIS is composed of a separate and independent
combination of sensors, logic solvers, final elements, and support systems that are designed
and managed to achieve a specified safety integrity level (SIL). An SIS may implement one or more safety instrumented
functions (SIFs), which are designed and implemented to address a specific process hazard or hazardous
event. The SIS management system should define how
an owner/operator intends to assess, design, engineer, verify, install, commission, validate,
operate, maintain, and continuously improve their SIS. The essential roles of the various personnel
assigned responsibility for the SIS should be defined and procedures developed, as necessary,
to support the consistent execution of their responsibilities. ISA 84.01/IEC 61511 uses an order of magnitude
metric, the SIL, to establish the necessary performance. A hazard and risk analysis is used to identify
the required safety functions and risk reduction for specified hazardous events. Safety functions allocated to the SIS are
safety instrumented functions; the allocated risk reduction is related to the SIL. The design and operating basis is developed
to ensure that the SIS meets the required SIL. Field data are collected through operational
and mechanical integrity program activities to assess actual SIS performance. When the required performance is not met,
action should be taken to close the gap, ensuring safe and reliable operation. IEC 61511 references IEC 61508 (the master
standard) for many items such as manufacturers of hardware and instruments and so IEC 61511
cannot be fully implemented without reference to IEC 61508. IEC 61511 is the process industry implementation
of IEC 61508. IEC61511 is updated with Edition 2.0==References==

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