January/February 2011

ISA12 to drive proposals for the U.S. National Electrical Code

By Ellen Fussell Policastro

ISA12 Electrical Equipment in Hazardous Locations will meet in March to cover draft comment resolution and new project initiation (original documents, adoption of IEC standards, and co-publications with other Standards Development Organizations [SDOs]). Prominent on their agenda is putting together proposals for the 2014 U.S. National Electrical Code (NEC). Proposal areas of particular interest include nonincendive field wiring installation requirements, fiber optics, gas detectors, ignition systems, limitations on short circuit current in hazardous locations, plug-and-play cable connector assemblies, process sealing, and type of protection "mc."

The acceptance of most of the 2011 NEC proposals sets a positive precedence for future proposals. The NEC proposals related to combustible gas detection (Article 500.7(K) and Article 505.8(K)) "provided further guidance on recommended practices for the use of combustible gas detection equipment as a method of protection," said ISA12.13 Subcommittee Chair Jon Miller. "The NEC proposals recommended inclusion of a footnote for reference to ANSI/ISA-TR12.13.03-2009, Guide for Combustible Gas Detection as a Method of Protection, as a recommended practice document directly based upon API practices that have been applied for 30+ years in the petroleum industry," he said. "The recommended practice document will provide a safe and consistent approach for using gas detectors as a method of protection in hazardous (classified) locations."

In addition, ISA12.20 Chair Dave Burns said, "Ignition systems have seen use on reciprocating engines driving natural gas compressors in hazardous (classified) locations for many years. Operators of these compressor stations have only had general guidance (NEC Article 501, API RP 14F, local authority having jurisdiction [AHJ] requirements) for proper source of ignition control for these hazardous (classified) locations in the past.

"Review of these general requirements led to the use of shielded ignition systems in which the primary high-tension leads interconnecting the spark plugs for each power cylinder of the reciprocating engine to the ignition system were completely encased in grounded metallic sheathing materials. This was to prevent any inadvertent arcs and sparks on the exterior of the ignition system that may lead to ignition of a small flammable gas leak or release associated with the gas compressor. The use of these shielded systems soon resulted in dielectric failures in the primary leads that led to ignition system misfiring, misoperations, and engine damage.

"As these issues became more prevalent with compressor station operators, higher quality primary leads were developed, but were not able to resolve the high stresses associated with the shielded primary lead design. As most compressor station buildings can be classified as Class I Division 2, the use of explosion-proof or flame-proof protection techniques that were utilized in the shielded ignition systems design may not be required. Recognizing this, ISA12 organized an effort to establish a fit for purpose performance standard that would employ Class I Division 2 protection techniques utilizing non-shielded technology for ignition systems in these applications. The ANSI/ISA-12.20.01-2009 performance standard for ignition systems for use on reciprocating engines driving natural gas compressors installed in Class I Division 2 or Zone 2 hazardous (classified) locations provides specific details and performance test procedures for non-shielded ignition systems for use in Class I Division 2 (Zone 2) installations. As the standard was not published in time to make the 2011 edition of the NEC, we will propose a reference to ANSI/ISA-12.20.01 in the 2014 code cycle," Burns said.

The upcoming ISA12 meetings will take place 7-11 March. For more information on the meetings or ISA12, contact Eliana Beattie at ebeattie@isa.org.

ABOUT THE AUTHOR

Ellen Fussell Policastro (efussell@isa.org) is an ISA Standards administrator.