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4 TECHNICAL INTRODUCTION This technical guide outlines the design and use of eq

4 TECHNICAL INTRODUCTION This technical 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 Lighting products and can also be used as a general guide. The guide refers to equipment and methods complying with 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. Chalmit hazardous area products are designed and manufactured in accordance with the best 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 equipment 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 equipment 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 If detailed information on superseded product is needed Chalmit should be contacted directly. 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 IEC Ex scheme. This may cause some confusion in the short term but leads to international uniformity. The early IEC standards were largely based on the national standards of European countries. The first EU Directive [1976] for product standardisation 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 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 that 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 second ATEX directive [1994], see later section, introduced further factors. The directive covers gas and dust hazards and both electrical and mechanical equipment. It introduced basic requirements for safety, the “Essential Health and Safety Requirements [ESHR's]”. Three levels of safety Categories 1, 2 and 3 were defined effectively 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. In order to eliminate this potentially long term anomaly at international level and to introduce the concept of a declared level of safety, IEC agreed to introduce “Equipment Protection Levels” [EPL's]. These EPL's are Ga, Gb and Gc for gas and Da, Db and Dc for dust. Ma and Mb also exist for mining. 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 IEC Ex scheme (see the section on the IEX Ex scheme) will therefore be identical as EPL's are introduced right across the standards series. The ATEX marking is different from IEC and must be shown in addition to the IEC marking. International, Regional and National Standards - Ongoing Changes IEC Standards & ATEX Rationalisation 5 Sub-Division Index to Technical Introduction A further effect of the introduction of EPL's is to give a definition to the emergence of sub-divisions in some of the protection concepts. The sub-division of 'intrinsic safety' into ia and ib has existed for many years. Now ma, mb also exist, further sub-divisions mc and ic will be introduced as well. Ex p is currently sub-divided into px, py and pz but will be rationalised. Sub-divisions of other concepts may be developed in due course and some existing requirements in the Ex n standard may be re-located. A further imminent change is the addition to the General Requirements IEC 60079-0 of general requirements common to protection against the ignition of combustible dusts. This will enable the dust protection concept standards to be incorporated in the 60079 series. As many equipment enclosures have certification for both gas and dust, this will be of benefit to both manufacturers and users. The current IEC dust standards are the IEC 61241 series. These cover test methods, construction and use. There are also various equipment standard concepts: ● tD, protection by enclosure ● pD pressurisation ● mD encapsulation. As stated, where possible these IEC 61241 standards are being incorporated into the IEC 60079 series. In Europe these standards are becoming Euro Norms (EN's) and supersede the EN 50281 series. These new editions of the IEC standards for gas and dust have been prepared with the full participation of the USA. Products currently being produced may have marking and catalogue information in the EN 50000 series or EN 50281 series. Because of the movement towards IEC, references to EN's are not used in this introduction except where there is no current Euro-norme in the IEC series, in which case the EN numbering in the EN 50014 etc. series will be given in brackets. Euro Norms Standards for Combustible Dusts Lamps and Control Gear Lamp Standardisation Control Gear and Electrical Supplies Emergency Lighting Applications Glossary TABLES Table 1 Methods of Explosion Protection Table 2 Hazardous Areas Classification Table 3 Selection of Protected Apparatus in Hazardous Areas according to EN 60079-14 Table 4 EPL, ATEX Catagory, Design Requirements and Expected Application Table 5 Classification of Maximum Surface Temperatures for Electrical Equipment IEC 60079-0 Table 6 Gas Grouping for Electrical Equipment IEC 60079-0 Table 7 Comparison of Practice A and Practice B for Dust Protected Enclosures Table 8 Comparison of Surface Temperature Classification IEC and NEC Table 9 Comparison of Representative Gases in IEC and NEC Gas Groups Table 10 Definition of Ingress Protection Table 11 Impact Energy Requirements for IEC 60079-0 Group II Equipment Table 12 Impact Energy Requirements IK Code Table 13 Summary of Lamp Characteristics and their Application International, Regional and National Standards - Ongoing Changes Methods of Explosion Protection for Electrical Equipment in Explosive Gas Atmospheres General Requirements IEC 60079-0 Protection against the Ignition of Atmospheres containing Dusts Classification of Hazardous Areas and the use of Protected Equipment The EU ATEX Directives Protection Codes for Chalmit Products Examination Certificates IEC & ATEX Marking of an ATEX Product and the CE Mark Surface Temperature Rating and Gas Grouping Surface Temperature for Ignition Gas Grouping Protection against the Ignition of Explosive Atmospheres formed from Combustible Dust The IEC Ex Scheme International Standards Ingress Protection Resistance to Mechanical Damage Compliance with General Product Standards Operational Temperatures - Tamb 'X' suffix on Certificate Delayed Opening Cabling and Cable Glands PAGE 16 18 18 18 19 19 6 8 8 9 10 11 12 13 13 14 14 15 17 PAGE 4 6 6 7 8 8 9 9 9 10 10 10 11 11 12 12 14 14 15 15 15 15 16 6 This 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. In addition, sparks may be the result of the inadvertent discharge of stored energy or from switching contacts. Other possible sources of ignition are electrostatic discharges and frictional sparking. A number of methods of protecting against ignition have been established and these have been codified in construction standards. These codes enable manufacturers uploads/S4/ hac-guide.pdf