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All about loop-checking with new ANSI/ISA standard

“All of the instruments and software that work together to make a process measurement or control a process variable are referred to collectively as a loop. After initial installation and periodically during the equipment life, every loop is checked to ensure that it is performing properly. Hence a loop check,” said Jim Federlein, chairman of the new ISA105 standards committee, Commissioning, Loop Checks, and Factory & Site Acceptance/Integration Tests for Industrial Automation Systems. “

Now that we know what a loop check is, what’s so great about a newly approved standard? The new standard, ANSI/ISA-62382-2012 (IEC 62382 Modified), Automation Systems in the Process Industry − Electrical and Instrumentation Loop Check, provides a better understanding of what a loop check consists of and provides a standard methodology for executing a loop check. It defines procedures and specifications for loop checks, which include activities between the completion of the loop construction (including installation and point-to-point checks) and the start-up of cold commissioning. “Prior to these standards, there were no industry-wide formal requirements or guidance,” Federlein said.

The standard applies to the construction of new plants and to expansion/retrofits (such as revamping) of electrical and instrument installations in existing plants (including PLC, BAS, DCS, panel-mounted, and field instrumentation).

The standard is a US-modified adoption by the ISA105 standards committee of IEC 62382 Edition 1. While the content is largely the same as IEC 62382, this adoption includes an addition of increasing and decreasing directions to tests in order to identify any hysteresis issues. It also adds a category of standard loops and replaces various input/output check forms with a single-loop check form that can be used for all loops, including indicating and control. Another change is the expansion of loop-check examples. Specific loop checks must be established by the user, depending on the specific hardware and software to be verified on the project.

The ISA105 committee is responsible for coordinating ISA standards activities and documents in commissioning of instrumentation and control and electrical systems; instrumentation and electrical loop checks; and factory acceptance, site acceptance, and site integration tests.

For information about obtaining these standards, visit, select “62381” or “62382” from the first drop-down list, and scroll down.

For more information on ISA Standards, contact Charley Robinson of ISA staff, .

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