15 July 2008
Global unity sought for hazardous location standards
The ISA12 standards committee for electrical equipment in hazardous locations continues to build continuity in global standards. The committee is working to reduce the number of national differences in U.S. adoption of the IEC standards used for U.S. certification.
By eliminating regional standards, it will allow manufacturers to produce equipment suitable for global use. It also allows multi-national users to improve efficiency and productivity as they specify, install, and maintain common equipment in all the plants around the world.
ISA12, in cooperation with Underwriters Laboratories (UL) standards technical panel (UL STP 60079) is responsible for the development of U.S. adoption of IEC standards related to hazardous location equipment, including the IEC 60079 series of standards. The 5th edition of the general requirements standards (IEC60079-0) includes the concept of equipment protection levels (EPLs), intended to give users a better understanding of which protection concepts can be applied in which situations. Beginning with the 5th edition, IEC 60079-0 also includes a new equipment Group III for dust applications. As this 5th edition of IEC 60079-0 is implemented, the committee will start to see international products being marked with the EPLs and Group III.
“EPLs are designated as G for gas, D for dust, or M for mining, and then followed by a letter (a, b, or c), which indicates to the user whether the equipment provides either (a) very high, (b) high, or (c) enhanced levels of protection against ignition of an explosive atmosphere,” said Evans Massey, manager of standards and certification at Baldor Electric Co. in Greenville, S.C., an ISA12 and IEC committee member and representative for Code Panel 14 for ISA.
Various protection concepts (flameproof, intrinsic safety, encapsulation, and the like) defined in IEC 60079-0 are assigned a specific level of protection depending on the likelihood of the equipment causing an ignition. Flameproof equipment such as an Ex d IIC motor would additionally be marked with the EPL of “Gb” to indicate it affords a high level of protection. Intrinsically safe equipment, such as an Ex ia IIC temperature transmitter would additionally be marked “Ga” to indicate the equipment affords a very high level of protection. Group II is subdivided based on the characteristics of the dust into IIIA (combustible flyings), IIIB (non-conductive dust), and IIIC (conductive dust).
ISA60079-0 (the U.S. adoption of IEC 60079-0) is undergoing revision to address EPLs and Group II. “These revisions create a need to make corresponding changes to the National Electrical code (NFPA 70),” Massey said. The NFPA is currently accepting proposals to revise the NEC for the 2011 edition. ISA12 has established a working group to draft NEC updates as they revise standards.
Anyone who has worked with hazardous locations in the European market should be aware of the ATEX Directive (94/4/EC), which implemented new requirements, including those for manufacturing quality systems and mechanical risk assessment for equipment used in explosive atmospheres. The European Committee for Standardization (CEN) TC305 developed standards for this process called European Norms (ENs). A new subcommittee, SC31M, will start taking the concepts from these EN standards from CEN TC305 internationally in new standards with dual logos, International Organization for Standardization (ISO) and IEC.
The first international meeting of SC31M occurred last fall in conjunction with IEC TC31 meetings in Kuala Lumpur, Malaysia.
“This is an historic event because the committee represents a joint effort between IEC and ISO to work together using a common process and common experts to develop the international requirements for non-electrical systems used in hazardous locations,” Massey said.
The work program for SC31M will start with the quality system requirements, presently found in EN13980 and in parallel form within the IECEx Scheme as OD005. In order for the U.S. to participate in this process, the U.S. National Committee of the IEC, sponsored by ANSI, has established a parallel 31M technical advisory group (TAG) to provide experts and participate nationally in the review, comment, and ballot cycle of standards development.
As in the case of USNC TAG TC31, ISA will be serving as the administrator.
A new mining working group under ISA12 is developing standards for equipment used in potentially flammable locations within underground mines. Their work will cover equipment to detect materials within their combustible ranges.
The group reviewed U.S. adoptions of IEC 60079 series standards to determine the impact of reinstating references to and requirements for Group I. The working group is also comparing other provisions of these standards to current requirements in U.S. standards for mining equipment. They will use this analysis to recommend to ISA12 appropriate direction to adopt international requirements for hazardous locations mining equipment for U.S. markets.
—Ellen Fussell Policastro
For related information, go to www.isa.org/safety.