Defining hazardous locations on a global scale - Now the same products can be used around the world

By Paul Kelly, Engineering Services, Northbrook

EXPLOSION. It can happen anywhere in the world. A piece of electrical equipment installed in a refinery, grain silo or factory, or on an oil rig, generates a tiny spark. And that tiny spark ignites the hazardous atmosphere present with a loud bang or a muffled whoosh -- with potentially catastrophic results.

It's not a new problem. Requirements for products for use in hazardous locations have been in existence in the United States for more than 75 years. It's hard to say which organization wrote the first requirements, but the National Electrical CodeŪ (NECŪ) first addressed the installation of equipment for use in hazardous locations in 1920. And UL's first published Standard to address equipment for use in these areas is the 1930 edition of UL 698, the Standard for Industrial Control Equipment for Use in Hazardous (Classified) Locations. What's important is that over the years these requirements for the United States evolved around a single area classification system known as the Division system. Today, the Division system addresses the design, manufacture, installation, maintenance and inspection of hazardous areas and the equipment and wiring used in them.

Meanwhile, European countries, as well as other countries around the world, were developing their own area classification systems to address hazardous locations safety issues -- but the development was independent from the U.S. approach.

This independent development resulted in systems for these countries or groups of countries based on the International Electrotechnical Commission (IEC) Zone system, with deviations to meet each country's national codes. While other countries do accept and use the Division system (most notably Canada and Mexico), the majority of the world's hazardous locations are classified using the concepts of the IEC Zone system. This is mainly because the IEC Zone system is an international system and many countries prefer to use international requirements as the basis for their installation and product classifications.

Because of this dual approach to the classification of hazardous locations, two major markets -- North America and Europe -- are regulated by these two different hazardous area classification systems, the Division system and the Zone system, respectively. And, while these systems have many similarities, they also have significant differences that impact the ability of manufacturers to sell products and the ability of users to install these same products in hazardous locations around the world. It is often very difficult for a product or installation to comply with both systems because of the differences in the requirements of the two systems.

U.S. ADOPTION OF THE IEC SYSTEM

As a result of these Division/Zone differences, internationally oriented manufacturers and users found it increasingly more difficult to conduct business in the emerging world market. This global business challenge made it critical for the United States to examine the Zone system closer and find a way to integrate it into its codes. In 1995, the United States completed this review and adopted the IEC Zone system into the 1996 edition of the NECŪ. As a result, the United States has joined Asia, Australia, Canada, Europe and South America in accepting the Zone system -- in applications from on-shore refineries to off-shore oil rigs. This acceptance has increased significantly the potential for global marketability of a common product and installation design.

A new Article 505 in the 1996 edition of the NECŪ allows for a second, parallel classification system to the traditional U.S. Class I Division system -- the new U.S. Class I Zone system. This new Zone system for the United States is based on the IEC Zone system, with U.S. national deviations. While it was necessary for the U.S. Zone system to deviate from the IEC Zone system (as is done by most countries), the key concepts of the IEC system have been incorporated into the new U.S. system -- including area classification, gas grouping, temperature codes, protection methods and markings.

These U.S. national deviations were primarily necessary to assure compliance with the NECŪ, because the IEC installation requirements allow markings, wiring methods and grounding constructions that do not comply with the NECŪ. In addition to deviations in the NECŪ, deviations that assure compliance with U.S. fire and electric shock hazard equipment requirements are necessary. This is because the IEC equipment requirements only address the risk of explosion associated with Zone equipment, and do not address such issues as insulation properties, electrical spacings, and overload and endurance capabilities for all equipment.

HOW THE DIVISION AND ZONE SYSTEMS DIFFER

While the U.S. Division and Zone area classification systems are independent, their apparent differences actually reflect an overall similarity in the way hazardous locations are addressed throughout the world. Under both the Division and Zone systems, electrical equipment for use in explosive gas atmospheres is identified based on designations that address:

1. The likelihood that the explosive gas atmosphere is present when the equipment is operating (see the Division and Zone designations in Table 1;
2. The ignition-related properties of the explosive gas atmosphere (see the Gas Group designations in Table 2;
3. The maximum surface temperature of the equipment under normal operating conditions (see the Temperature Code designations in Table 3; and
4. The protection method(s) used by the equipment to prevent ignition of the surrounding atmosphere (see the Protection Method designations in Table 4.

Note:Table 5 provides an example of how these designations are incorporated into typical equipment markings.

The differences between the Gas Groups and the Temperature Codes for Division and Zones in Tables 2 and 3, respectively, are basically organizational (for example, grouping the same gases into four Gas Groups for Divisions versus three Gas Groups for Zones). However, while the differences in the Division and Zone designations in Table 1 may also appear to be merely organizational, the difference of two Divisions versus three Zones is what truly makes the Division and Zone systems independent.

While the Division system relies on a single designation -- Division 1 -- to define a location where ignitable concentrations of flammable gases, vapors or liquids can exist, either all of the time or some of the time, under normal operating conditions, the Zone system relies on two designations, Zone 0 and Zone 1. A Zone 0 location is defined as a location where ignitable concentrations of flammable gases, vapors or liquids can exist all of the time (or for long periods of time), while a Zone 1 location is defined as a location where ignitable concentrations of flammable gases, vapors or liquids can exist only some of the time. In other words, a Zone 0 area represents the most hazardous portion of a Division 1 area, and a Zone 1 area represents the less hazardous portion. Division 2 and Zone 2 represent basically the same level of hazard.

Therefore, with Zone 0 representing the equivalent worst-case hazard to Division 1, and Zone 2 representing the equivalent worst-case hazard to Division 2, the methods of equipment protection allowed in Zone 0 and Zone 2 areas are very similar to the ones allowed in Division 1 and Division 2 areas. However, since a Zone 1 area has no worst-case equivalency to an area under the Division system, new international methods of protection for U.S. equipment that have not been available before are now possible (see Table 4).

Regarding the protection methods allowed under the new U.S. Zone system, the NECŪ does not yet identify specific methods for Zones. In lieu of specifying requirements for suitable methods of equipment protection for use in Zones, Article 505 of the 1996 NECŪ requires all equipment for use in Zones to be "listed" as defined in the NECŪ -- thus relying on third-party testing and certification organizations such as UL to determine suitability. In response to requests from industry, UL developed requirements for this determination.

DEVELOPING U.S. ZONE REQUIREMENTS

The two-stage method UL used to develop requirements for zone protection methods was initiated by UL distributing bulletins proposing requirements based on Exceptions to Section 505-20 (b) and (c) of Article 505. These bulletins proposed that products complying with UL's Class I, Division 1 or 2 requirements could additionally or alternatively be marked for the corresponding Class I, Zone 0, 1 or 2 location. In the second stage, UL issued a bulletin in October 1995 announcing UL's intent to adopt the Zone requirements outlined in the IEC 79 series of standards -- as modified by the necessary U.S. national deviations regarding the NECŪ installation issues and the equipment fire and shock hazard issues discussed earlier. This announcement was based on guidance provided by the National Fire Protection Association (NFPA) Standards Council regarding the technical merit of the Zone concept and the benefits of international harmonization, in concert with input from UL, industry and others.

Based on support for the first-stage proposal, revisions were adopted in all UL Class I, Division 1 and 2 Standards to allow Class I, Division 1 or 2 equipment to additionally or alternatively be marked Class I, Zone 0, 1 or 2, as appropriate. As a result of support for the second-stage proposal, UL issued a new Standard -- UL 2279, Electrical Equipment For Use In Class I, Zone 0, 1 and 2 Hazardous (Classified) Locations. This Standard, published in July 1996, contains the UL requirements for IEC-based Zone certifications. UL 2279 was approved as an American National Standard by the American National Standards Institute (ANSI) on Aug. 7, 1997.

UL issues Zone Listings in accordance with both the Division-based (UL's first-stage proposal) and the IEC-based (UL's second-stage proposal) Zone requirements. Current IEC-based Zone Listings involve a variety of different protection methods (such as Zone 0 -- intrinsically safe; Zone 1 -- flameproof, increased safety and encapsulation; and Zone 2 -- nonincendive, non-sparking and restricted breathing) for a variety of different equipment (such as Zone 0 gas detectors; Zone 1 junction boxes, industrial control equipment, outlet boxes, panelboards, terminal blocks and heat tracing systems; and Zone 2 fixtures, fittings and industrial control equipment).

OTHER ZONE EFFORTS NATIONAL AND INTERNATIONAL

In addition to clarifying the product certification requirements for U.S. Zones, UL is working to help clarify the requirements for the installation of equipment for use in U.S. Zones. UL actively participates in codes and standards proposals to familiarize manufacturers and the code community with the concepts and applications of the Zone system. For the upcoming 1999 NECŪ, UL's participation on American Petroleum Institute (API) Working Groups furthers UL's ability to assist in the development of proposals to clarify installation requirements for U.S. Zones.

On the international scene, UL represents the United States on Technical Advisory Groups and through serving as the Secretary for IEC Zone subcommittees. Also, UL is currently working with the Council for Harmonization of Electrotechnical Standardization of North America (CANENA) to further harmonize Zone requirements for Canada, Mexico and the United States. This involves meeting with Canadian, Mexican and other U.S. representatives as part of the development of a trinational Zone standard based on ANSI/UL 2279, the CAN/CSA-E79 series of Canadian Zone standards, and the applicable Mexican requirements.

ZONE SYSTEM TRULY GLOBAL

With country after country on every continent embracing this international method of identifying hazardous locations, the Zone system has gone truly global. A manufacturer in one country can now more easily sell products for installation in key marketplaces around the world. Education is an important part of promoting the Zone system. Everyone involved -- manufacturers, installers, jurisdictional authorities, importers and others -- needs to understand the new requirements and the associated markings and installation issues for products for use in Zone-classified hazardous locations. The "Big Boom" can be prevented if everyone understands the requirements.

NOTE: This information was current as of the fall of 1997 and is presented here for archival purposes only. For current information, please see the UL webpage devoted to this subject.

Haz Loc zones -- Education the key

For those who need to know about the Zone system, UL has developed a seminar titled Global Harmonization of Hazardous (Classified) Locations. This seminar was most recently offered in New Orleans, and is scheduled for other cities across the United States in 1998. Also, UL continues to provide one-on-one training seminars tailored to the specific needs of inspectors, users and manufacturers. UL has published several articles discussing the Zone system in its own publications, and the November and December 1995 editions of the industry magazine "EC&M" include articles with helpful information regarding Zones.

Also, UL developed an educational poster that addresses technical issues associated with Class I, Zone 0, 1 and 2 areas in addition to Class I, II and III, Division 1 and 2 areas and has distributed thousands of them all over the world. For your complimentary copy of this poster, call Danica Walker in Northbrook, Ill., at (847) 272-8800, ext. 43731; fax her at +1-847-509-6235; or e-mail walkerd@ul.com.

One of UL's most recent educational efforts took place the week of June 15th, when two UL engineers from Northbrook, Ill., traveled to the city of Villahermosa in Tabasco, Mexico, to conduct a seminar for representatives of the Mexican petroleum industry (PEMEX) and a Mexican federation of electrical and mechanical engineers (FECIME). The seminar covered Articles 500 through 505 and 514 of the NECŪ regarding hazardous locations. Another seminar in Mexico has been requested, and other avenues of education are being considered at this time.

NOTE: This information was current as of the fall of 1997 and is presented here for archival purposes only. For current information, please see the UL webpage devoted to this subject.