Practical Hazardous Areas

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Presents

Practical Hazardous Areas

for Engineers & Technicians

Revision 7

Website: www.idc-online.com E-mail: idc@idc-online.com

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 2010. All rights reserved. First published 2010

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Contents Preface 1 Introduction 1

1.1 Introduction 1 1.2 Definitions 2 1.3 Investigation after accidents and disasters 4 1.4 History 6 1.5 Equipment certification 9 1.6 Conclusion 10

2 Flammability Characteristics, Ignition Sources and the Use of Electricity 11 2.1 Flammability 11 2.2 Flammability information (gasses and vapours) 16 2.3 Dusts 17 2.4 Theory into practice 20 2.5 General sources of ignition 20 2.6 Use of electricity and its sources of ignition 21 2.7 Electrical protection (as opposed to explosion protection) 24 2.8 Toxicity hazard 25 2.9 Conclusions 25

3 Area Classification 27 3.1 General 27 3.2 Overview of the principles of safety 28 3.3 Definitions 28 3.4 The process of assessment 29 3.5 Normal and abnormal operation 32 3.6 Classification into zones 33 3.7 Area classification process 35 3.8 Openings 37 3.9 Ventilation 40 3.10 HAC calculation 42 3.11 Area classification of dust hazards 49 3.12 Responsibility and personnel involved 50 3.13 Documentation 50 3.14 Policy and guidelines for implementation 52 3.15 General information 53 3.16 Area classification standards 54 3.17 HAC examples 55 3.18 Dusts 57 3.19 Classification in North America 59 3.20 Conclusions 59

4 Explosion Protection Philosophy and Equipment Classification Systems 61 4.1 General 61 4.2 Classification concepts 62 4.3 Introduction to equipment certification 62

4.4 Temperature classification 63 4.5 Equipment grouping 65 4.6 Types of explosion protection 69 4.7 Overview of explosion protection theory 71 4.8 Brief comparison of types of protection 71 4.9 Mixed techniques 77 4.10 Dust explosion protection methods 78 4.11 Selection of the type of explosion protection 78 4.12 Conclusion 80

5 Protection Concepts: Type of Protection; ‘d’ 81 5.1 Name 81 5.2 Standards 81 5.3 Definition 82 5.4 Principle of operation 82 5.5 Types of flamepath joint and uses 85 5.6 Explosion pressure 89 5.7 Certification 90 5.8 Cabling requirements for Ex d 91 5.9 Design and type-testing 97 5.10 Installation and conditions of use 97 5.11 Regional variations in Ex d implementation 99 5.12 Illustrations of mechanical construction 100 5.13 Summary 102

6 Protection Concept ‘e’ 103 6.1 Name 103 6.2 Standards 103 6.3 Definitions 104 6.4 Principles of design for increased safety 104 6.5 Component certification 106 6.6 Internal requirements of Ex e 107 6.7 Ex e enclosures 108 6.8 Rotating electrical machines 109 6.9 Cable and glanding requirements 111 6.10 Periodic inspection requirements 113 6.11 Marking 114 6.12 Applications 114 6.13 Summary 115

7 Protection Concept ‘n’ 117 7.1 Name 117 7.2 Standards 117 7.3 Definitions 119 7.4 Principles of design 120 7.5 Construction 121 7.6 Additional means of protection 122 7.7 Applications 126 7.8 Installation 127 7.9 Inspection 128 7.10 Live working 128

8 Protection Concept ‘i’ Principles 129 8.1 Name 129 8.2 Standards 129 8.3 Definition 130 8.4 Origins of intrinsic safety 130 8.5 Principles 130 8.6 Electrical theory 132 8.7 Implementation of IS 138 8.8 The shunt diode safety barrier 142 8.9 Associated apparatus 153 8.10 Electrical apparatus in the hazardous area 155 8.11 Enclosures 162 8.12 Temperature 162 8.13 The Ex i systems concept 163 8.14 An Ex i ‘system’ 163 8.15 Assessment of safety 164 8.16 Simple apparatus 165 8.17 Safety parameters 165 8.18 Temperature classification of systems 166 8.19 Systems concepts in other standards 166 8.20 Conclusion 167

9 Protection Concept Ex p 169 9.1 Name 169 9.2 Standards 169 9.3 Principle of operation 171 9.4 Purging 173 9.5 Pressurisation 175 9.6 Variations 176 9.7 Application notes 178 9.8 Certification and documentation 180 9.9 Pressure / Flow failure 180 9.10 Ex p protection type px, py and pz 182 9.11 Conclusion 183

10 Other types of Ex Protection and their use in Combination 185 10.1 General 185 10.2 Ex o 185 10.3 Ex q 187 10.4 Ex m 188 10.5 Ex s 190 10.6 Multiple-certification 192 10.7 Selection of certification method 194 10.8 Equipment certified for dust 194 10.9 Conclusion 195

11 Earthing and Bonding 197 11.1 Earthing 197 11.2 Personnel safety 198 11.3 Hazardous area considerations 199 11.4 Earthing and bonding 200 11.5 Static electricity 203

11.6 Clean and dirty earthing 206 11.7 Electrical interference 207 11.8 Earthing terminology 209 11.9 Connection of earthing systems 212 11.10 Power supply systems 214 11.11 Portable equipment using batteries 216 11.12 Earthing arrangement standard solutions 216 11.13 Earth loops 219 11.14 Computer earthing 220 11.15 Surge protection systems 223 11.16 Summary 225

12 Installations 227 12.1 Introduction to installations 227 12.2 Selection and installation in general 228 12.3 IEC 60079-14: 2007 contents 230 12.4 Other relevant installation standards and codes 230 12.5 Verification dossier 231 12.6 General requirements of the standard 231 12.7 Selection of electrical equipment 234 12.8 Dusts 237 12.9 Electrical supply systems 240 12.10 Commissioning 244 12.11 Installed arrangements 244 12.12 Summary 245

13 Inspection and Maintenance 247 13.1 Introduction 247 13.2 Standards 247 13.3 Scope of IEC 60079-17 249 13.4 Definitions 249 13.5 Layout of the standard 250 13.6 Types of protection 253 13.7 Insulation testing 254 13.8 Maintenance 255 13.9 Testing 256 13.10 Unauthorised modification 256 13.11 Earthing integrity verification 256 13.12 Need for inspection and maintenance 257 13.13 IEC inspection tables 263

14 Safe Working Practices 269 14.1 Introduction 269 14.2 Risk assessment 270 14.3 General rules 270 14.4 Danger signals of electrical malfunctioning 271 14.5 Recording of incidents and observations 272 14.6 Maintenance and safe practices 272 14.7 Training of personnel 275 14.8 Electrical fire and shock 275 14.9 Summary 277

15 Fault Finding and Testing 279 15.1 Fault finding 279 15.2 Fault finding routine 279 15.3 Electrical testing in hazardous area 281 15.4 Earth testing in a hazardous area 284 15.5 Repairs 285 15.6 Competency assessment 287 15.7 Summary 287

16 Standards, Certification, Marking, ATEX and DSEAR 289 16.1 Introduction 289 16.2 Harmonisation of standards 290 16.3 A brief history of certification and approval 291 16.4 Introduction to ATEX 294 16.5 Product directive 295 16.6 Bird’s eye view of ATEX product directive 310 16.7 Summary of marking 316 16.8 The workers directive 317 16.9 Dangerous substances and explosive atmospheres

regulations 319 16.10 Summary 320 16.11 Conclusion 320

Appendix A 321 Appendix B 329 Appendix C 331 Appendix D 335 Appendix E 339

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.

2 Practical hazardous areas

2

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

2 Practical hazardous areas 2

• 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:-

1.2.1 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

1.2.2 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.

1.2.3 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.

1.2.4 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.

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.

Figure 1.1 The explosion triangle

1.2.5 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

!

Fire

Source of Ignition

Heat or Sparks

O 2 Fuel: Gas Vapour Mist Dust

Air (21% Oxygen)

4 Practical hazardous areas 4

• 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 1st 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 14th 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.

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.

1.3.1 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

1.3.2 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.

6 Practical hazardous areas 6

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 25th 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 9th January 1816. This invention must have saved innumerable lives over the years.

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’.

Oil Reservoir

Flame behind glass cylinder

Combustible gas enters and ignites. Burning gas cannot pass back through gauze

Gauze barrier: air enters to support flame burning.

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.

1.4.1 ‘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.

1.4.2 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 1928. 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.

8 Practical hazardous areas 8

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.

1.4.3 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 1948. 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 1894. 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 1974. 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 1906. 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.

1.4.4 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

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 79-10. 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-à-vis, the suitability and integrity of quality and design and lessens the work of manufacturer in getting each piece approved all over the globe.

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

PTB Ex PTB Germany BASEEFA UK (Pre-2003)

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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.