• By Jim Federlein, PE
  • Standards

The most widely used of all ISA standards, ISA-5.1, Instrumentation Symbols and Identification, has been published in a 2022 version that provides clarifications and corrections to the previous 2009 version. 

Originally published as ISA Recommended Practice RP-5.1 in 1949, the document was revised and expanded to become an ISA and American National Standard in 1984, and then reaffirmed without change in 1992. Most of the identification letter and symbol meanings or definitions that were contained in ISA-RP5.1-1949 and ISA-5.1-1984 became and remain accepted practice across the worldwide process industry sectors.

In 2009, a major revision and update of the standard was completed in which the symbology and identification systems as described accommodated various advances in technology and reflected the collective industrial experience gained. That 2009 revision involved a detailed review by a large, multi-industry group of practitioners in the field of instrumentation and control, with an emphasis on the use of identification and symbol systems as a means of communicating the intent of measurement and control systems to all that need such information.

The 2022 revision of ISA-5.1 is intended to provide usage clarifications and to correct typographical and technical errors that have been uncovered over the years since the 2009 version. As such, this 2022 revision will serve as a basis on which the ISA5 standards committee can begin a more regular maintenance/revision cycle for this widely used international standard.

To that end, a new working group is now forming to begin work on the next revision of ISA-5.1. The overriding goal will be to continue strengthening the role of the standard as a communication tool in all industries that depend on measurement, control, and automation systems to operate and safeguard their manufacturing processes, machines, and other equipment. This standard and future versions will build on that foundation to serve the global process industry sectors.

All who are interested in actively participating in the new working group to begin the next revision of ISA-5.1 are asked to email Charley Robinson, ISA Standards. Access ISA-5.1-2022 here.

This update was provided by Jim Federlein, retired PE and principal of Federlein & Associates, Inc. He is an ISA Life Member and a director on the ISA Standards & Practices Board. He is chair of the ISA5.1 working group and of ISA105, Commissioning, Loop Checks, and Factory & Site Acceptance/Integration Tests for Industrial Automation Systems. Federlein also serves on IEC SC65E WG3, Commissioning. 

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About The Authors

Jim Federlein, PE, is the chair of ISA105 and director of the ISA Standards & Practices Board. He is the principal at Federlein & Associates, LLC.