Practical Hazardous Areas

Transcription

1 Practical Hazardous Areas

2 THIS BOOK WAS DEVELOPED BY IDC TECHNOLOGIES WHO ARE WE? IDC Technologies is internationally acknowledged as the premier provider of practical, technical training for engineers and technicians. We specialize in the fields of electrical systems, industrial data communications, telecommunications, automation and control, mechanical engineering, chemical and civil engineering, and are continually adding to our portfolio of over 60 different workshops. Our instructors are highly respected in their fields of expertise and in the last ten years have trained over 200,000 engineers, scientists and technicians. With offices conveniently located worldwide, IDC Technologies has an enthusiastic team of professional engineers, technicians and support staff who are committed to providing the highest level of training and consultancy. TECHNICAL WORKSHOPS TRAINING THAT WORKS We deliver engineering and technology training that will maximize your business goals. In today s competitive environment, you require training that will help you and your organization to achieve its goals and produce a large return on investment. With our training that works objective you and your organization will: Get job-related skills that you need to achieve your business goals Improve the operation and design of your equipment and plant Improve your troubleshooting abilities Sharpen your competitive edge Boost morale and retain valuable staff Save time and money EXPERT INSTRUCTORS We search the world for good quality instructors who have three outstanding attributes: 1. Expert knowledge and experience of the course topic 2. Superb training abilities to ensure the know-how is transferred effectively and quickly to you in a practical, hands-on way 3. Listening skills they listen carefully to the needs of the participants and want to ensure that you benefit from the experience. Each and every instructor is evaluated by the delegates and we assess the presentation after every class to ensure that the instructor stays on track in presenting outstanding courses. HANDS-ON APPROACH TO TRAINING All IDC Technologies workshops include practical, hands-on sessions where the delegates are given the opportunity to apply in practice the theory they have learnt. REFERENCE MATERIALS A fully illustrated workshop book with hundreds of pages of tables, charts, figures and handy hints, plus considerable reference material is provided FREE of charge to each delegate. ACCREDITATION AND CONTINUING EDUCATION Satisfactory completion of all IDC workshops satisfies the requirements of the International Association for Continuing Education and Training for the award of 1.4 Continuing Education Units. IDC workshops also satisfy criteria for Continuing Professional Development according to the requirements of the Institution of Electrical Engineers and Institution of Measurement and Control in the UK, Institution of Engineers in Australia, Institution of Engineers New Zealand, and others.

3 CERTIFICATE OF ATTENDANCE Each delegate receives a Certificate of Attendance documenting their experience. 100% MONEY BACK GUARANTEE IDC Technologies engineers have put considerable time and experience into ensuring that you gain maximum value from each workshop. If by lunchtime on the first day you decide that the workshop is not appropriate for your requirements, please let us know so that we can arrange a 100% refund of your fee. ONSITE WORKSHOPS All IDC Technologies Training Workshops are available on an on-site basis, presented at the venue of your choice, saving delegates travel time and expenses, thus providing your company with even greater savings. OFFICE LOCATIONS AUSTRALIA CANADA INDIA IRELAND MALAYSIA NEW ZEALAND POLAND SINGAPORE SOUTH AFRICA UNITED KINGDOM UNITED STATES idc@idc-online.com Visit our website for FREE Pocket Guides IDC Technologies produce a set of 6 Pocket Guides used by thousands of engineers and technicians worldwide. Vol. 1 ELECTRONICS Vol. 4 INSTRUMENTATION Vol. 2 ELECTRICAL Vol. 5 FORMULAE & CONVERSIONS Vol. 3 COMMUNICATIONS Vol. 6 INDUSTRIAL AUTOMATION To download a FREE copy of these internationally best selling pocket guides go to: On-Site Training SAVE MORE THAN 50% OFF the per person cost CUSTOMISE the training to YOUR WORKPLACE! Have the training delivered WHEN AND WHERE you need it! All IDC Technologies Training Workshops are available on an on-site basis, presented at the venue of your choice, saving delegates travel time and expenses, thus providing your company with even greater savings. For more information or a FREE detailed proposal contact Kevin Baker by ing: training@idc-online.com

4 IDC TECHNOLOGIES Worldwide Offices AUSTRALIA Telephone: Facsimile: West Coast Office 1031 Wellington Street, West Perth, WA 6005 PO Box 1093, West Perth, WA 6872 East Coast Office PO Box 1750, North Sydney, NSW 2059 CANADA Toll Free Telephone: Toll Free Facsimile: Suite 402, 814 Richards Street, Vancouver, NC V6B 3A7 INDIA Telephone : th Street, Kumaran Colony, Vadapalani, Chennai IRELAND Telephone : Facsimile: Caoran, Baile na habhann, Co. Galway MALAYSIA Telephone: Facsimile: Jalan Kota Raja E27/E, Hicom Town Center Seksyen 27, Shah Alam, Selangor NEW ZEALAND Telephone: Facsimile: Parkview Towers, 28 Davies Avenue, Manukau City PO Box , Manukau City POLAND Telephone: Facsimile: ul. Krakowska 50, Balice, Krakow SINGAPORE Telephone: Facsimile: Eu Tong Sen Street, #04-11 Pearl s Centre, Singapore SOUTH AFRICA Telephone: or Facsimile: Pretorius Street, President Park, Midrand PO Box 389, Halfway House 1685 UNITED KINGDOM Telephone: Facsimile: Suite 18, Fitzroy House, Lynwood Drive, Worcester Park, Surrey KT4 7AT UNITED STATES Toll Free Telephone: Toll Free Facsimile: B Hazelhurst Dr. # 6175, Houston, TX 77043, USA Website: idc@idc-online.com

5 Presents Practical Hazardous Areas for Engineers & Technicians Revision 7 Website: idc@idc-online.com

6 IDC Technologies Pty Ltd PO Box 1093, West Perth, Western Australia 6872 Offices in Australia, New Zealand, Singapore, United Kingdom, Ireland, Malaysia, Poland, United States of America, Canada, South Africa and India Copyright IDC Technologies All rights reserved. First published 2010 ISBN: All rights to this publication, associated software and workshop are reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. All enquiries should be made to the publisher at the address above. Disclaimer Whilst all reasonable care has been taken to ensure that the descriptions, opinions, programs, listings, software and diagrams are accurate and workable, IDC Technologies do not accept any legal responsibility or liability to any person, organization or other entity for any direct loss, consequential loss or damage, however caused, that may be suffered as a result of the use of this publication or the associated workshop and software. In case of any uncertainty, we recommend that you contact IDC Technologies for clarification or assistance. Trademarks All logos and trademarks belong to, and are copyrighted to, their companies respectively. Acknowledgements IDC Technologies expresses its sincere thanks to all those engineers and technicians on our training workshops who freely made available their expertise in preparing this manual.

7 Contents Preface 1 Introduction Introduction Definitions Investigation after accidents and disasters History Equipment certification Conclusion 10 2 Flammability Characteristics, Ignition Sources and the Use of Electricity Flammability Flammability information (gasses and vapours) Dusts Theory into practice General sources of ignition Use of electricity and its sources of ignition Electrical protection (as opposed to explosion protection) Toxicity hazard Conclusions 25 3 Area Classification General Overview of the principles of safety Definitions The process of assessment Normal and abnormal operation Classification into zones Area classification process Openings Ventilation HAC calculation Area classification of dust hazards Responsibility and personnel involved Documentation Policy and guidelines for implementation General information Area classification standards HAC examples Dusts Classification in North America Conclusions 59 4 Explosion Protection Philosophy and Equipment Classification Systems General Classification concepts Introduction to equipment certification 62

8 4.4 Temperature classification Equipment grouping Types of explosion protection Overview of explosion protection theory Brief comparison of types of protection Mixed techniques Dust explosion protection methods Selection of the type of explosion protection Conclusion 80 5 Protection Concepts: Type of Protection; d Name Standards Definition Principle of operation Types of flamepath joint and uses Explosion pressure Certification Cabling requirements for Ex d Design and type-testing Installation and conditions of use Regional variations in Ex d implementation Illustrations of mechanical construction Summary Protection Concept e Name Standards Definitions Principles of design for increased safety Component certification Internal requirements of Ex e Ex e enclosures Rotating electrical machines Cable and glanding requirements Periodic inspection requirements Marking Applications Summary Protection Concept n Name Standards Definitions Principles of design Construction Additional means of protection Applications Installation Inspection Live working 128

9 8 Protection Concept i Principles Name Standards Definition Origins of intrinsic safety Principles Electrical theory Implementation of IS The shunt diode safety barrier Associated apparatus Electrical apparatus in the hazardous area Enclosures Temperature The Ex i systems concept An Ex i system Assessment of safety Simple apparatus Safety parameters Temperature classification of systems Systems concepts in other standards Conclusion Protection Concept Ex p Name Standards Principle of operation Purging Pressurisation Variations Application notes Certification and documentation Pressure / Flow failure Ex p protection type px, py and pz Conclusion Other types of Ex Protection and their use in Combination General Ex o Ex q Ex m Ex s Multiple-certification Selection of certification method Equipment certified for dust Conclusion Earthing and Bonding Earthing Personnel safety Hazardous area considerations Earthing and bonding Static electricity 203

10 11.6 Clean and dirty earthing Electrical interference Earthing terminology Connection of earthing systems Power supply systems Portable equipment using batteries Earthing arrangement standard solutions Earth loops Computer earthing Surge protection systems Summary Installations Introduction to installations Selection and installation in general IEC : 2007 contents Other relevant installation standards and codes Verification dossier General requirements of the standard Selection of electrical equipment Dusts Electrical supply systems Commissioning Installed arrangements Summary Inspection and Maintenance Introduction Standards Scope of IEC Definitions Layout of the standard Types of protection Insulation testing Maintenance Testing Unauthorised modification Earthing integrity verification Need for inspection and maintenance IEC inspection tables Safe Working Practices Introduction Risk assessment General rules Danger signals of electrical malfunctioning Recording of incidents and observations Maintenance and safe practices Training of personnel Electrical fire and shock Summary 277

11 15 Fault Finding and Testing Fault finding Fault finding routine Electrical testing in hazardous area Earth testing in a hazardous area Repairs Competency assessment Summary Standards, Certification, Marking, ATEX and DSEAR Introduction Harmonisation of standards A brief history of certification and approval Introduction to ATEX Product directive Bird s eye view of ATEX product directive Summary of marking The workers directive Dangerous substances and explosive atmospheres regulations Summary Conclusion 320 Appendix A 321 Appendix B 329 Appendix C 331 Appendix D 335 Appendix E 339

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13 Preface This book provides delegates with an understanding of the hazards involved in using electrical equipment in potentially explosive atmospheres. It is based on the harmonised IEC79 Series of International Standards that have now replaced the older national Standards and are directly applicable to most countries in the world (including North America). Explosion-Protected installations can be expensive to design, install and operate. The wider approaches described in these standards can significantly reduce costs whilst maintaining plant safety. The book explains the associated terminology and its correct use. It covers from Area Classification through to the selection of explosion protected electrical apparatus, describing how protection is achieved and maintained in line with these international requirements. Standards require that engineering staff and their management are trained effectively and safely in Hazardous Areas and this book is designed to help fulfill that need. This book is aimed at anyone involved in design, specification, installation, commissioning, maintenance, inspection or documentation of industrial instrumentation, control and electrical systems. This includes: Tradespersons working in potentially explosive areas Electrical and Instrument Tradespersons Instrumentation and Control Engineers Electrical Engineers Instrumentation Technicians Design Engineers Managers with responsibility for hazardous areas We would hope that you will gain the following from this book: A good understanding of terminology used with Hazardous Areas An understanding of the hazards of using Electrical equipment in the presence of flammable gases, vapours and dusts. A basic knowledge of Explosion Protection to IEC Standards The ability to do a simple hazardous area classification Details of the types of apparatus that can be used in a given hazardous area How to design and install safe working systems in hazardous areas An understanding of the safety and operational aspects of hazardous areas Knowledge of the system limitations in using hazardous areas protection A brief review of the key areas of the national codes of practice You will need a basic understanding of instrumentation and electrical theory for the book to be of greatest benefit. No previous knowledge of hazardous area installation is required.

14 2 Practical hazardous areas

15 1 Introduction This manual accompanies the Hazardous Areas training course presented by IDC Technologies. In this first Chapter we begin by examining the legacy of learning from previous accidents. We present an overview of the background and history of Explosion Protection. Learning objectives To learn from previous disasters To realise the risk posed by electrical equipment in hazardous areas To understand the need for the development of Standards 1.1 Introduction Any threat to life, property and investment is said to constitute a hazard. In modern manufacturing industries there are many types of hazard. These are encountered in various ways. Each hazard poses a different level of threat. Where materials that can be ignited are used as part of any industrial process, they are referred to as flammable materials and precautions must be taken to prevent the inadvertent occurrence of explosion and fire. In the design of a plant, the flammable material which may be in the form of a gas, vapour, mist or dust, can be confined, transported, processed or possibly released under different circumstances. In each situation, if it can form a potentially explosive atmosphere (PEA) by mixing with air then the simultaneous presence of sources of ignition must be eliminated or adequately controlled. The design of an industrial plant or facility and the equipment and procedures used must render the plant as safe as is reasonably practicable. The combination of scientific research, technological development and practical experience are the three key considerations in human endeavour to minimise risk. Risk Assessment is the process by which this learning is applied to the concept of safety to achieve what is judged to be at an acceptable level. This course will study current thinking and practise on the protection of industrial plants to train delegates on the technical and organisational measures required for safety purposes. It focuses on the use of explosion protected equipment operating in hazardous areas. It is suitable for personnel involved in the following activities on industrial plant and equipment:- Process Design Selection

16 2 Practical hazardous areas Installation Operation Inspection Maintenance Repair and overhaul and Troubleshooting 1.2 Definitions It is important to define and understand some of the key terms used in this subject: Fire and explosion FIRE (Combustion) is the process of a flammable material undergoing a rapid oxidation reaction that results in the production of heat (and, generally, visible light). EXPLOSION is the violent and sudden expansion of gases produced by rapid combustion. It is a strong force, producing noise and supersonic shock waves that can cause extensive mechanical damage by the uncontrolled release of energy. Examples are: - boiler explosion combustion of a gas/air mixture detonation of explosives Hazard Hazards are of two types, either Natural or Manmade. Natural Hazards, such as blizzards, flash floods, earthquakes, heat waves, hurricanes, tornadoes, volcanic eruption etc, cannot be prevented. Countermeasures can only be taken to minimise the consequences. Manmade Hazards, such as the potential occurrence of explosion and fire in industrial situations, are that which this course seeks to address Hazardous area A HAZARDOUS AREA in the context of this subject is:- An area in which a flammable gas or vapour may be present in sufficient quantity to form a potentially explosive atmosphere One is reminded that this may be only one of many areas on an industrial site which might be prone to an accident or the onset of a potentially dangerous situation in a defined region, owing to the presence of other predominant risks. The hazard about which this subject is concerned is for when a fuel in the form of a gas, vapour mist or dust is present in atmospheric air and a source of ignition caused by the presence of electrical equipment occurs simultaneously Hazard An explosion occurs when there is a convergence of three basic ingredients as depicted in the classic Fire Triangle analogy (see Figure 1.1):- Fuel, any combustible material Air with 21% Oxygen Ignition source Where electricity is in use, it is known that heat and sparking at sufficient levels can provide an adequate source of ignition.

17 Introduction 3 Wherever combustible or flammable materials are stored, handled or processed there is an increased likelihood of leakage or availability of the fuel and so it is necessary to be able to predict the circumstances of presence of the elements of the fire triangle. This is a form of Risk Assessment. Proper application is necessary to manage the hazard safely. In practical terms, with the abundance of air around a process plant, adequate control must be exerted over the other two elements to reduce risk of explosion to acceptable levels. Air (21% Oxygen) O 2! Fuel: Gas Vapour Mist Dust Fire Source of Ignition Heat or Sparks Figure 1.1 The explosion triangle Risk assessment The process of Risk Assessment applied to Hazardous Areas is to define its nature and presence in a given location. Electricity is essential to industry but its use can generate heat or sparks that can ignite a potentially flammable atmosphere. Once defined, equipment and procedures suitable for use in such a hazard can be selected and operated safely. Examination of the issues and acceptable solutions are discussed in this course. The use of electrical equipment protection measures are well established but risk from non-electrical sources are now being included into Standards to be discussed. Risk assessment must cover all sources of ignition. After the occurrence of accidents and disasters, the human quest for safety forces thorough investigation by diligent scientific means to reveal likely or actual causes. Root Cause Analysis ensures that the set of conditions that has occurred to cause the disaster, are adequately understood. Appropriate precautions can then be taken to ensure that they cannot occur under the same circumstances again. In this way risk is managed and reduced. The investigation must also take into account the actions of humans in relation to the circumstances of the accident. Causes of accidents have been shown to be by:- Improper installation and selection Lack of proper maintenance Improper use

18 4 Practical hazardous areas Carelessness or oversight Ignoring warning signs of failure Inadequate training and supervision Such foreseeable and avoidable human errors must therefore be the subject of scrutiny and prevention. 1.3 Investigation after accidents and disasters Industrial accidents involving explosion and fire will always be the subject of investigation. Lessons can be learned and so prevention knowledge and techniques can be further developed and improved. Cumulative knowledge now helps to fertilise the thinking processes and the approach taken on an international footing. The Piper Alpha oil platform disaster occurred on 1 st June 1988 in the North Sea off the coast of Scotland and is shown in Figure 1.2. The subsequent investigation uncovered how and why it happened exposing many bad practices owing to poor management. The report was responsible for initiating a dramatic change in the oil and petrochemical industries attitude to the management of safety. Figure 1.2 The explosion triangle This is one of many risks that the Owner of any industrial process on commercial premises must consider. The Owner, often referred to as the Duty-holder in Law, must ensure that risks are adequately understood and therefore adequate precautions are in place to ensure safety to life, property and investment. The term Loss Prevention is a modern title applied to any body within an organisation responsible for overseeing the wider implementation of safety. The loss could be to any one or more of the three critical values of life, property and investment. Accidents in the mining industry are still common with other recent deaths in China and other Far Eastern countries. Closer to home in the UK, the Senghenydd disaster, in South Wales on 14 th October 1913, killed 439 miners. Investigation into this disaster and the subsequent research taught the mining industry a great lesson that was passed on internationally.

19 Introduction 5 This has led to extensive research and detailed studies to assimilate knowledge in order to prevent explosions and fires in all types of industrial, commercial and domestic circumstances. Hazardous environment found in various industries. Globally, expertise is now shared to educate and prevent accidents. This is culminated in the International Standards to which industries work to maintain safety. The technology is currently based on the identification of the risk of an explosive atmosphere being present in a particular place. This is coupled with the identification of the likelihood of electrical equipment within the explosive atmosphere malfunctioning in a way that would cause it to become a source of ignition coincident with the presence of that explosive atmosphere. The objectives are not just to identify these coincidences but to utilise the information so obtained to influence the design of particular process plants and similar operational situations. This will help to minimize the risk of an explosion due to electrical installations. In this approach, the areas normally prone to have an explosive atmosphere due to the requirement of varies processes involved, are identified. Similarly, the areas where its likelihood is low but identifiable are marked up. It is needless to say that this is not an end in itself but should be deployed as a part of Overall Safety Strategy for the plant Emergence of standards The ability of electricity to cause ignition and trigger explosions has been understood since the turn of the twentieth century. Measures to control and minimise the risks have become part of the engineering discipline of design and to meet legislation for safety ever since. Initially, countries developed their own regional practices independently of each other. The types of industry which were developed in that region depended on the natural resources available and hence the development of local expertise to deal with the hazards. In those early days the rules or practices were created by different organisations often depending on the system of Law in the country. These have evolved into Standards which will be introduced and discussed in this manual. Local Standards such as British Standards have merged into Regional Standards such as from Europe and then have become International Standards. This is discussed in detail in the Chapter on Standards. Examples are:- UK: BS5501 North America: NFPA70 NEC Article 500 Europe: CENELEC EN50 Series Global: International Electrotechnical Commission: IEC 79 Series Methodology The Standards impose a methodology that looks not only at technical issues but management and control issues. Under the European ATEX Directives, discussed in detail later and adopted by many institutes, the route to safe analysis is based on:- First step : identification of the risk of an explosive atmosphere being present in a particular area Second step : eliminating the use of electrical equipment in such areas Third step : if installation becomes essential: identify the likelihood of electrical equipment malfunctioning Thus precautions can be taken to assess and prevent ignition occurring in such areas in the most logical and effective way. An overall plant safety strategy must be developed of which Area Classification, the outcome of the risk assessment, must be part to ensure safety. Thus Explosion Protection techniques can be applied where equipment must function in the possible presence of a hazard.

20 6 Practical hazardous areas 1.4 History The use of electricity in a potentially explosive atmosphere was first encountered in the coal mining industry and it is there where the first precautions were developed and implemented. Even before this the hazard of fire-damp [methane] was recognised. Miners observed that the presence of fire-damp would make the flames of the miners naked-flame lighting sources (oil lamps and candles) burn a different colour. This was also inadvertently the original hydrocarbon gas detector. Unfortunately, this was also the source of ignition causing many deaths. The mining authorities realised that burning off the methane collected in the seams of the mines would deal with the immediate problem at the start of a shift. Young miners were covered in wet sacking and would be induced to crawl down the tunnels with a long lighted taper held up towards the ceiling in the highest points thereby setting light to the gas. In later years, penitents, prisoners for serious crimes, were released to perform this service. This made the mines safe for miners to work. Although this was an effective method, it was somewhat barbaric in nature and fell into disrepute. Subsequently, methane and other noxious gasses were removed by improving ventilation. After a disaster at the Feeling Coal Mine in Northumberland, UK on 25 th May 1815 during which 92 miners died, Sir Humphry Davy (assisted by the young Michael Faraday) invented the Davy Safety Lamp (see Figure 1.3) which was first tested underground in the Hepburn Colliery, Tyne and Wear, on the 9 th January This invention must have saved innumerable lives over the years. Gauze barrier: air enters to support flame burning. Combustible gas enters and ignites. Burning gas cannot pass back through gauze Flame behind glass cylinder Oil Reservoir Figure 1.3 Davy Safety lamp designs Around the late nineteenth century and in the early part of the twentieth century the use of electricity in mining began, using d.c. supplies for lighting and motive power. The early equipment produced sparks and some explosions were caused, igniting methane and coal dust. Before World War II, extensive research work was done in Germany and the UK to prevent this and so came the development of a crude form of flameproof enclosure suitable for sparking equipment. As a result of the Welsh Mining Disaster, mentioned earlier, the ignition capability of control and signalling systems was realised and so the concept of energy limited circuits became understood and was developed. The concept of Flameproofing was to contain an ignition, preventing it from propagating into a hazardous area. Scientists and engineers, however, also knew that if the power and energy levels in circuits were regulated and limited then it could not cause ignition. This subsequently became known as Intrinsic Safety.

21 Introduction 7 Originally these crude types of protection were developed specifically for the mining industry to be safe in methane and coal dust, but it was realised that the same approach could be used for the developing surface industry Surface industries and area classification It became apparent over time that, whereas in mines only coal dust and methane gas presented the hazardous conditions, on the surface a myriad of situations depending upon the type of industry and processes used. To ensure that appropriate precautions were taken, a risk assessment technique evolved to classify each Hazardous Area. This led to the process of area classification, that of defining where the hazard might be present, and equipment classification. This was to identify the risks associated with each type of explosive atmosphere and to choose equipment that was known to be safe in those areas UK and Europe In the United Kingdom the first legislation covering the use of electrical equipment in explosive atmospheres came into being through The Electricity (Factories Act) Special Regulations 1908 and 1944, Regulation 27, which states that All conductors and apparatus exposed to the weather, wet, corrosion, inflammable surroundings or explosive atmosphere, or used in any process or for any special purpose other than for lighting or power, shall be so constructed or protected, and such special precautions shall be taken as may be necessary adequately to prevent danger in view of such exposure or use. Even Regulation 6 of Electricity at Work Regulation 1989 is in the same spirit of placing the responsibility of achieving the objective on the owner of industry without specifying the methods to be adopted. In the UK, it was legal to use uncertified equipment in hazardous areas provided that it could be shown to be safe. Thus, as long as owner maintains adequate records of plant safety this clause gets satisfied. This is in variance to the one being followed in USA and Germany and other parts of Europe, where specifics are also formulated. Both approaches have withstood the test of time and there is not much evidence of putting one method over the other. In the UK much work has been done in the area of electrical installation safety in hazardous atmosphere by the Safety in Mines Research Establishment, the Electrical Research Association [now ERA Technology Ltd.], the Fire Protection Association, Institution of Fire Engineers, Loss Prevention Council and The Institute of Petroleum. With the advent of automobiles and airplanes in the early 1920s, fuel refining began and increased in capacity very quickly. Volatile vapours from oil by-products and electrical sparks and heat did not mix safely! Fires and explosions were common in the industry. So the first hazardous area classification was invented about this time but it is thought that the Imperial Chemical Industries (ICI) Company had started to evolve the notion of Divisions. Division 1 described areas being normally hazardous. In the wake of the mining disaster in South Wales, investigation into the cause and then further research pioneered by Newcastle University began the understanding of how Explosion Protection could be harnessed. Thus, a new industry with the goal of protecting electrical equipment in hazardous areas was born. Flameproof enclosures and simple intrinsically safe circuits were now being used, the first Standard for FLP (BS229) equipment being issued in Oil immersion followed and, together, these were the first types of protection developed. World War II brought many changes in Europe and North America. Metal shortages in Europe prompted more plastic use in electrical equipment, and the first construction standards for explosion-protected electrical equipment appeared in Germany.

22 8 Practical hazardous areas At about the same time, North American industries determined that hazardous area classifications needed to be expanded. A Division 2 was needed to describe locations that were not normally hazardous to allow use of less expensive equipment and less restrictive wiring methods The USA In the United States of America the NFPA (National Fire Protection Association) was formed in 1896 with the aim to reduce the burden of fire on quality of life by advocating scientifically based consensus codes and standards. It also carries out research and education for fire and related safety issues. The Association was incorporated in 1930 under laws of the Commonwealth of Massachusetts. The Electrical section was added in The National Electricity Code (NEC) under NFPA 70 defines rules and regulations regarding use of electrical equipment. The sections 500 through to 517 deal with installation, testing, operation and maintenance of electrical equipment in hazardous area. In addition, various government laboratories, university laboratories, private and industrial laboratories do research and education in USA. One of the most prominent is the Underwriters Laboratories Inc. This was founded in It was originally conceived to serve the insurance industry as an arbitrator for safe practice but is now a not-for-profit corporation having as its sole objective the promotion of public safety through the conduct of scientific investigation, study, experiments, and tests, to determine the revelation of various materials, devices, products, equipment, constructions, methods, and systems to hazards appurtenant thereto or to the use thereof affecting life and property and to ascertain, define, and publish standards, classifications, and specifications for materials, devices, products, equipment, constructions, methods, and systems affecting such hazards, and other information tending to reduce or prevent bodily injury, loss of life, and property damage from such hazards. The role of Federal Government was minimal in Fire protection prior to However, in 1974 Congress passed the Federal Fire Prevention and Control Act. Under this act 12 Executive Branch departments and 10 independent agencies are supposed to administer the various provisions of the Act. The NFPA enjoys a co-operative relationship with these agencies. A number of agencies rely upon NFPA Standards and participate in the NFPA standards-making process. In 1970, the Congress established the Occupational Safety and Health Administration (OSHA) within Department of Labour to oversee development and implementation of mandatory occupational safety and health standards rules and regulations applicable at the workplace. The Mine Safety and Health Administration was established in 1977 with a functional scope similar to that of OSHA, but with a focus on mining industry. In order to understand how the electrical code is evolving and what guides this evolution we need to look back in history and their development till date. In the early 1900s, when contractors were busy electrifying industrial buildings, electrical wires were run through existing gas pipes, resulting in today's conduit system of wiring. This formed the basis of wiring in North America and the codes and standards were made to suit the safety requirement pertinent to these practices. While this was being done on the American continent, the International Electro technical Commission (IEC) was founded in Switzerland in The IEC is supposed to be the United Nations of the electrical industry. Its ultimate goal is to unify worldwide electrical codes and standards. Few IEC practices were incorporated into the NEC or CEC mainly because North America operated on different voltages and frequencies than most of the rest of the world Advent of hazardous area in surface industries In the 1960s, the European community was founded to establish free trade through Europe. To reach this goal, technical standards needed to be harmonized. As a result, the European Community

23 Introduction 9 for Electro technical Standardisation (CENELEC) was established as the Standards writing body for Europe. By this time the German chemical industry had departed from the traditional conduit or pipe wiring system and migrated towards cable as a less expensive alternative. This wiring-method change led to the zone classification system later adopted in 1972 by most European countries in a publication known as IEC This action led to the different methods of classifying hazardous areas as well as protective, wiring, and installation techniques, which form the basis of present IEC classification. 1.5 Equipment certification It would be a very costly and time-consuming affair to test each electrical installation for safety. Standards could not be written for design validation and conformance of plant as it varies dramatically from one application to another. The nature of the flammable chemicals used would be different. Thus, in Europe, a system of certification evolved for the use of electrical equipment to be installed in a hazardous atmosphere of a Plant. This technology primarily consists of The classification of the area of the Plant where the electrical equipment is needed. The classification of the electrical equipment used in that area of the Plant. The classification systems used for both must be the same so that it would be easy to determine if a particular piece of equipment would or would not be safe in a given area. The International Standards and Codes of Practice have been developed from the range of those used in individual countries. Obtaining agreement has not been easy. The benefit to the user is to provide a level of confidence for safe operation of electrical equipment under the specified conditions. These classifications will be explained in some depth in this course, allowing an understanding of the application for given situations. The certification process merely states conformance with the Construction Standard to which equipment has been assessed. It does not imply that the equipment is safe. A few examples of the marking of equipment are illustrated in Figure 1.4. Currently, internationally acceptable markings are used to identify Explosion Protected (Ex) equipment. This leads to uniformity in the industry and gives a confidence level to the user, vis-àvis, the suitability and integrity of quality and design and lessens the work of manufacturer in getting each piece approved all over the globe. PTB PTB Germany Ex BASEEFA UK (Pre-2003) Figure 1.4 Typical certification logos In Europe, under the ATEX Directives that came into force in member states on 1st July 2003, all ignition-capable equipment (Electrical and NON-electrical) that is sold into or used on plants requires assessment and certification to harmonised Standards if used in a Hazardous Area. The Directives, in line with the Standards, expect Plant management to keep records and documentation

24 10 Practical hazardous areas of all aspects of safety related plant and equipment so as to be able to demonstrate safety compliance. The harmonised IEC 79 Series of Standards are recognised as IEC60079 and have been adopted in many countries including the USA who has now incorporated the relevant classification requirements into NEC. In time all countries claiming IEC compliance are expected to follow. 1.6 Conclusion This chapter has introduced a wide range of subject matter which will be discussed in detail in subsequent chapters. The overview and brief history of the development of the Standards given here will help to provide an appreciation of the depth of engineering that has been dedicated to the prevention of accidents. There are many misconceptions on the principles in this subject that can undermine safety unless properly understood. The early separate development of Standards in different countries goes some way to explaining why the industry suffers from terminological inconsistency which has, in part, thought to have exacerbated these misunderstandings. This Manual focuses on the harmonised International Standards as the primary source of information in an attempt to unify the terminology. There remain regional variations in the approach to Hazardous Area and the implementation of Ex equipment. These are mentioned and clarified where it is felt appropriate.