IEC 61511

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IEC 61511 is a standards document titled "Functional safety - Safety instrumented systems for the process industry sector".

This standard refines the functional safety requirements laid down by IEC 61508 specifically for the process industry sector, for example refineries and chemical/pharmaceutical plants. It provides guidance in the proper application of Safety Instrumented System.

It extends the SIL concept to include environmental damage and asset loss, references studies in ALARP (As Low As Reasonably Practicable) and gives an overview of a Layer of Protection Analysis (LOPA).

[edit] 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 instrumentation system design of both hardware and software. IEC followed up on this standard with many other specific standards dealing with specific industries, the one dealing with the Process Industry was IEC 61511. IEC 61511 is the standard which guides the end users in the application of safety related systems.

In the United States ISA 84.01 was issued in late 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.

[edit] The Standard

IEC 61511 can be considered to be a standard that carries a safety instrumented system from the cradle to the grave. It starts in the earliest phase of a project and continue through startup. It contains sections that cover modifications that come along later along with maintenance activities and the eventual decommissioning activities.

IEC 61511 addresses the total Safety Life Cycle from the sensor to the final elements, regardless of the technology used. Its scope includes: initial concept, design, implementation, operation, and maintenance through to decommissioning.

The standard consists of three parts: