ISA S12.2 subcommittee meeting report
Spring, 2012
The work of harmonizing the Hazardous Area national standards of the United States with those of the international community continue in earnest. The ultimate goal of this harmonization is that products produced and approved in the US can be exported and installed in other countries, and vice versa. We are many years away from this goal even though the harmonization process started with the release of the 1999 edition of the National Electrical Code (NEC). This report will primarily discuss the current efforts to correlate our standards with those of the NEC, but first, some background.
Prior to the adoption of the 1999 NEC, the US was the only major country that had not yet adopted the Zone system of area classification for hazardous locations. (Canada adopted zones in 1998.) In the US, we can now choose to use either zones or divisions for area classification. One remaining obstacle in the harmonization effort is that we cannot use equipment that is only listed for use in one category in the other one. For example, if something is listed for use in a Class I, Zone 1 area, it may not be installed in a Class I, Division 1 area unless it also carries that listing. The reason for this is that what we allow in the Division 1 area is covered by both Zones 0 and 1 in the IEC area classification scheme. It could be understood this way: The area that could be classified as Zone 1 would be a subset of the area that could be classified as Division 1. As an additional point of reference, Zone 2 areas are essentially equivalent to Division 2 areas.
There is a major distinction between Zone 0 and Zone 1, but in the historical system in the US, they are lumped together so that everything must meet the stricter “Zone 0 equivalent” of our Division 1 classification. With the adoption of the 1999 NEC, we put in place the framework for harmonization with the inclusion of Article 505, Zone 0, 1, and 2 Locations. Incidentally, there are relatively few installations that use the Zone system of classification in the US due to the inherent barriers that were built into its adoption. How do you get equipment listed for the zone system when there are no zone classified areas in existence, and how do you use a zone area classification when there is no equipment listed for use in such an area?
We are getting both closer to harmonization as we adopt and mold the IEC standards, and further away as the IEC standards evolve to include new material that we, in the United States, have dealt with differently over the years.
The Spring 2012 Meeting of the ISA S12.2 subcommittee, the group that is charged with developing and maintaining the intrinsic safety standards for the United States, was spent in the ongoing discussions of how to adapt our national Intrinsic Safety standard, ANSI/UL 60079-11 to the IEC’s equivalent document. Specifically, how do we implement the new ‘ic’ level of intrinsic safety for use in Zone 2 areas? In most of Europe, for example, the IEC 60079-11 standard on Intrinsic Safety is the “national code”. In the United States, the ANSI/UL 60079-11 is the national standard, but it is then implemented by the National Electrical Code. While the ISA S12.2 subcommittee is working on the national standard, ANSI/UL 60079-11, it is the National Electrical Code that gets adopted by jurisdictions in the United States and becomes the legal requirements for electrical installations. The ISA S12 committee is working together with the NEC code making panels to “harmonize” this process.
The ‘ic’ level of protection being added to the definition of intrinsic safety is a welcome development in the United States. Historically in the US, we have used the concept of non-Incendive wiring and circuits for Division 2 areas. Since the hazards are lower in a Division 2 area than in a Division 1 area, the wiring methods required for safety do not need to be as robust. A wiring method that is less robust will naturally be less costly to install. This is a major consideration for users of hazardous area equipment. These existing lower cost non-Incendive wiring methods are not widely understood, so often Division 2 equipment is ‘over designed’, just to make sure it is safe. The introduction of ‘ic’ intrinsic safety for Zone 2 will provide us with an excellent opportunity to not only introduce this concept, but also to instruct our hazardous area electrical system users in the cost saving methods that will become available.
The focus of the spring meeting was how to incorporate the ‘ic’ concept into our standards so that the NEC can give guidance for its installation. Intrinsic Safety has a well defined body of practice as it is applied in the Division 1 hazardous area. With the ‘less robust’ requirements of ‘ic’ in Zone 2, there will be a modest need to change how we refer to intrinsic safety. If NEC Article 504 were to stand unchanged, we would not see all of the potential economic benefits of the ‘ic’ method of protection because it would need to conform to all of the rules designed for and required by the Division 1 implementations of intrinsic safety.
I hope this report whets your appetite for the upcoming introduction of ‘ic’ intrinsic safety for use in Zone 2 areas here in the US. Watch your next revision of the National Electrical Code for information on implementing this protection technique.
The background required for understanding this topic made this report longer than I wished for, and I did not include all of the information that I wanted to. Please continue to watch this blog for updates on electrical safety in hazardous areas. It is set up to be interactive. Please leave your questions and comments!
Final Notes:
1) In this report, I’ve stated that the United States is working to adapt our standards to those of the international community. I do, however, want to also express that the US members of the IEC standards body are also endeavoring to move that body in the direction of incorporating US best practices into the IEC documents as well.
2) The NEC Article 504 is the primary Intrinsic Safety section, but there are provisions throughout the NEC’s Chapter 5 (and elsewhere) that apply.