|A Guide to Harsh and Hazardous Areas
The technical introduction featured at the front of the Hazardous Area Lighting Product Guide outlines the design and use of equipment protected against the ignition of hazardous atmospheres formed from gases, vapours or dusts. The information given applies specifically to Chalmit® products and can also be used as a general guide.
This guide makes reference to equipment and methods complying with the safety practices being used throughout the world. This material is included both for completeness and because Chalmit® operates throughout the world supplying all lighting requirements in conjunction with group company Killark located in the US . Chalmit® hazardous area products are designed and manufactured in accordance with good engineering practices and to well established construction standards for explosion protected equipment.
The equipment must be selected, installed, maintained and disposed of in accordance with any regulation or legislation appropriate to its use. Reference must be made to the data sheets and the certification applying to each individual product.
The guide also refers to construction standards and application codes. The correct application of protected apparatus is a specialist subject and these notes must be treated as being only informative. In addition to the Chalmit® technical information users must themselves study the relevant codes of practice and construction standards.
Installation, operation and maintenance manuals (IOM) are enclosed with each product and are available on request. These contain information essential to the safe use of the apparatus and must be read and understood by installers and users before putting equipment into service. Much of the information is also available on the Chalmit® web site. Usually this will be for the latest version of a particular range. If detailed information on superseded product is needed Chalmit® should be contacted directly.
International, Regional and National Standards - Ongoing Changes
This revised technical introduction was prepared in 2006 during a period of transition in the history of Ex standardisation. As such this section aims to highlight some of the current initiatives underway to simplify and rationalise product standards on a global scale.
The process of developing product standards which initially began with the invention of equipment for the safe operation of 'gassy mines', led to the standardisation of the 'flameproof' and 'intrinsic safety' concepts for product design. The standardisation of equipment on a national basis is now in its final stage of transition with the final move towards global standardisation under the IECEx scheme.
The early IEC standards were largely based on the national standards of European countries.
The first EU Directive (1976) for product stadardisation prompted the rapid development of Euro-normes [EN] which were numbered in the EN 50014 etc. series. Gradually the IEC 79 series, later re-numbered the 60079- series were updated using the EN's as a basis but with growing international input. These were mostly the gas hazard standards. In the late 1990's it was agreed in CENELEC that all work the could be carried out at IEC level, would be, and the standards voted in parallel as IEC standards and EN's. These standards carry the EN 60079- numbering.
The first edition of te ATEX directive 94/9/EC (1994) introduced further factors. This directive covers gas & dust hazards and both electrical & mechanical equipment. It introduced basic requirements for safety, the 'Essential Health & Safety Requirements [ESHR's]'. Three levels of safety Catagories 1, 2 and 3 were defined as:
Category 1 - 'very safe and considering two possible equipment faults'
Category 2 - 'safe with one fault'
Category 3 - 'safe in normal operation'
Although the performance criteria of the Categories aligned with the expected area of application, the Zones, the designation of equipment protection by zone was removed. The selection of a particular type of explosion protection for a particular Zone was by risk assessment.
The second edition of the ATEX directive issued in July 2005 introduced non-electrical equipment to the concept of 'use' directives.
In order to eliminate this potentially long term anomaly at international levels and to introduct the concept of a declared level of safety, IEC agreed to introduce 'Equipment Protection Levels' (EPL's). These are Ga, Gb and Gc for gas and Da, Db and Dc for dust. These are an alternative and additional specification for equipment made in accordance with the standards.
The key point is that the definitions of product performance are in effect identical to the ATEX Category definitions. In future, rationalisation may see the EPL's incorporated into ATEX.
The basic technical requirements for ATEX and IEC via the IECEx scheme will therefore be identical as EPL's are introduced right across the standard series. The ATEX marking is however different from IEC and must be shown in addition to IEC marking.
Methods of Explosion Protection For Electrical Equipment
This pdf catalogue contains a selection of lighting and ancillary equipment suitable for use in areas where explosive atmospheres may occur.
Explosive atmospheres can be ignited by sparks or hot surfaces arising from the use of electrical power. The hot surfaces can be those of enclosures, components and light sources. Under fault conditions electrical connections may become over-heated and cause arcs or sparks.
Other possible sources of ignition are electrostatic discharges and frictional sparking. In addition, sparks may be the result of the inadvertent discharge of stored energy or from switching contacts.
A number of methods of protecting against ignition have been established and these have been codified in construction standards. These codes enable manufacturers to design apparatus of a uniform type and have it tested by certification authorities for compliance with the standards.