DIFFERENCES BETWEEN IEC 61511 AND ISA 84

摘要

The ISA SP84 committee has expressed its desire to migrate from ANSI/ISA 84.01-1996 (ISA 84) to the international standard IEC 61511, when it is approved and published. This migration may take a number of forms, including the following: rewrite ISA 84 to conform with EEC 61511, modify IEC 61511 to reflect US specific issues and replace ISA 84 with the modified contents, or directly replace ISA 84 with IEC 61511. No matter which migration path is chosen, the requirements of IEC 61511 will soon affect the design, implementation, operation and maintenance of SIS in the United States. IEC 61511 has reached final draft international standard (FDIS) status. At this point, only editorial comments can be submitted, so the FDIS provides the final technical requirements. Each country must now submit a single vote for its acceptance of the FDIS, so that the final standard can be released. The final issue of LEC 61511 is expected in early 2003. The ISA SP84 committee has indicated its intent to vote to accept the standard. The majority of IEC 61511member countries have also indicated their intent to vote for acceptance. Of course, this means that IEC 61511 will soon be released as THE international standard for safety instrumented systems for the process industry. When accepted by the member countries, this standard will take the lifecycle concept of ISA 84 worldwide. In the future, SIS design criteria will not be affected by the location of the installation. Rather, all SISs will be specified, designed, operated, and maintained according to the same global standard. Although IEC 61511 uses a lifecycle concept, it is no mirror image of ISA 84. An international standard must harmonize the standards of many countries. Consequently, the standard will add new requirements for component selection, design architecture, software development, pre-startup safety reviews, operation and maintenance, and management of change. This paper will not present an overview of the IEC 61511 standard. Rather, this paper will focus on the most significant differences between IEC 61511 and ISA 84, highlighting what end users need to consider in order to migrate their current ISA 84 programs into IEC 61511 programs.