CompEx-Atex course Manual 1210.pdf
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(2) 6th Edition, March 2010. Introduction.
(3) National Training and Certification of Personnel for Work on Electrical Apparatus for Use in Potentially Hazardous Atmospheres This package has been compiled with information gathered from current standards and the authors will not be held responsible for any inaccuracies found therein. Acknowledgements: The production of this document would not have been possible without the much appreciated assistance from the following authorities and, therefore, the authors of the document wish to thank and gratefully acknowledge all those who provided material and advice for the production of the package, particularly the following: The British Standards Institute James Scott Ltd, Aberdeen, Scotland Weidmuller (Klippon Products) Ltd, Sheerness, Kent Hawke Cable Glands Ltd, Ashton-under-Lyne, Lancashire Hecagon Technology Ltd, Aylesbury, Buckinghamshire Measurement Technology Ltd, Luton, Bedfordshire Brook Hansen, Huddersfield, West Yorkshire The Design and Presentation Team of Aberdeen College, including all staff at the Altens Centre. The BASEEFA Crown mark shown in this document is the property of the Health and Safety Executive and should not be interpreted to convey certification. The marks have been reproduced with the kind permission of the EECS (HSE).. Copyright of Document: No part of this document may be reproduced, stored in a retrieval system or transmitted in any form by any means. i.e. electronic, electrostatic, magnetic media, mechanical, photocopying, recording or otherwise without the permission in writing of the appointed representative of Aberdeen College.. Ex Facility March 2010. © 2.
(4) Introduction About the ‘Ex’ Facility Ex training courses have been run in Aberdeen College since 1990 and have developed to the level of sophistication we have today. In its present form the CompEx course has been in operation since August 1994 and has been designed and constructed specifically for the National Training of personnel who work with electrical installations and plant in hazardous and/or potentially explosive environments. The facility includes both classroom and simulated work areas, these being designed to give as realistic site conditions as is possible to achieve. The practical work candidates are required to carry out will take place in these simulated areas and this is intended to make the candidates feel they are working under site conditions. Approximately half of the week will be spent in the classroom where the ‘job knowledge’ elements of the course will be delivered by means of presentations incorporating lectures, demonstrations, and photographic slides of good and bad practice on apparatus. The remaining time will be spent on Competence Validation Testing in the simulated hazardous areas. The tests are nationally set for Ex training.. The Outcome The objective of the training is to introduce the candidate to operating procedures and techniques and to give candidates and their employer’s confidence that the candidates are competent to work on electrical apparatus in hazardous or potentially explosive environments. The competence laid down nationally by industry and through this will help make your industry a safer one.. About the Programme The need for training in these areas of work is self evident in that the safe operation of electrical equipment in hazardous areas is paramount. It is extremely important for all personnel who operate in these conditions to be competent in the correct techniques and operational procedures. This can best be achieved by means of training by skilled staff in an environment as close to the ‘real thing’ as possible. In addition to this, the job knowledge developed through the course must be put into operation in the actual working situation so that the levels of expertise are increased through experience.. The Design of the Programme The program is dived into two halves, namely: a. Job Knowledge b. Competence Validation Testing (CVT) The ‘job knowledge’ component takes place during the first half of the week and provides the information and experience you need to tackle the CVT’S. Ex Facility March 2010. © 3.
(5) Selection, Installation, and Maintenance of Electrical Apparatus for use in Hazardous Locations.. Units: 1). General principles (a) (b) (c) (d) (e). Nature of flammable materials gas grouping basic principles of area classification temperature codes ingress protection. 2). Standards, Certification and Marking. 3). Flameproof Ex d. 4). Increased Safety Ex e. 5). Type ‘n’ protection. 6). Pressurisation Ex p. 7). Intrinsic Safety Ex i. 8). Other methods of protection, Ex o, Ex q, Ex m & Ex s. 9). Combined (Hybrid) methods of protection. 10). Wiring Systems. 11). Inspection & Maintenance to BS EN60079-17. 12). Sources of ignition. 13). Induction to Competence Validation Testing. 14). Permit to Work System and Safe Isolation. Appendix 1. Data for flammable materials for use with electrical equipment, ref BS5345: Part 1: General recommendations.. Appendix 2. Self assessment project and apparatus label reading.. Ex Facility March 2010. © 4.
(6) Course outline The training scheme The training scheme is arranged to prepare candidates for the assessment programme which comprises four discreet Competence Validation Tests (CVT’s) offered as complimentary pairs. The four CVT’s are as follows: EX01 Preparation & Installation of Ex d, Ex e, Ex n and Ex p Systems EX02 Inspection & Maintenance of Ex d, Ex e, Ex n and Ex p Systems EX03 Preparation & Installation of Ex i Systems EX04 Inspection & Maintenance of Ex i Systems. Job knowledge The classroom (job knowledge) part of the training scheme consists of 12 Units which apply to the four CVT’s as illustrated below.. Unit 1: General principles. Unit 2: Standards, Certification and Marking EX01 & EX02 EX03 & EX04. Unit 3: Flameproof Ex d. Unit 4: Increased Safety Ex e EX01 & EX02. Unit 5: Type ‘n’ protection EX01 & EX02. Unit 6: Pressurisation Ex p EX01 & EX02 (Written Assessment). Unit 7: Intrinsic Safety Ex i. Unit 8: Other methods of protection (Written Assessment). Unit 9: Combined (Hybrid) protection methods EX01 & EX02. Unit 11: Inspection & Maintenance to BS EN60079-17 EX01 & EX02 EX03 & EX04. Unit 12: Sources of ignition. EX01 & EX02 EX03 & EX04. EX03 & EX04 Unit 10: Wiring Systems. EX01 & EX02 EX03 & EX04 Unit 13: Induction to Competence Validation Testing EX01 & EX02 EX03 & EX04. EX01 & EX02. EX01 & EX02 EX03 & EX04. Unit 14: Permit to Work and Safe Isolation EX01 & EX02 EX03 & EX04. Ex Facility March 2010. © 5.
(7) The CVT’s are a series of practical tests which you will undertake within the simulated work areas during the second half of the programme. On successful completion of these tests you will be awarded a Certificate of Core Competence which will indicate the areas the awarding body, Joint Training Ltd. (JTL), has deemed you are competent. During the final half-day of the programme you are required to sit written assessments in the form of multi-choice papers which are related to the practical CVT assessments. The staff who are involved in monitoring the various assessments are present only as observers and not to prompt or offer technical assistance. Their observations of your work is recorded on Nationally written checklists which are processed outwith the Centre and your results cannot be determined until this process is complete.. Manual Units and applicable CVT’s Unit 1:. General Principles. EX01, EX02, EX03 & EX04. Unit 2 :. Standards, Certification & Marking. EX01, EX02, EX03 & EX04. Unit 3:. Flameproof Ex d. EX01 & EX02. Unit 4:. Increased Safety Ex e. EX01 & EX02. Unit 5:. Type ‘n’ Protection. EX01 & EX02. Unit 6:. Pressurisation Ex p. EX01 & EX02. Unit 7:. Intrinsic Safety E x i. EX03 & EX04. Unit 8:. Other methods of Protection. Unit 9:. Combined (Hybrid) Protection Methods. EX01 & EX02. Unit 10:. Wiring Systems. EX01, EX02, EX03 & EX04. Unit 11:. Inspection & Maintenance to BS EN60079-17. EX01, EX02, EX03 & EX04. Unit 12:. Sources of Ignition. EX01, EX02. EX03 & Ex04. Unit 13:. Induction to Competence Validation Testing. EX01, EX02. EX03 & Ex04. Unit 14:. Permit to Work. EX01, EX02. EX03 & Ex04. (Written Assessment). (Written Assessment). Course programme The following course programme is for illustration purposes only, particularly for the CVT assessments, and can change according to candidate numbers attending the course. A programme for the CVT assessments will be compiled during the week.. Ex Facility March 2010. © 6.
(8) Programme: Electrical Apparatus in Potentially Hazardous Areas 5 – Day Programme Presenter 8:30. 12:30. 13:00. 17:00. Monday. Tuesday. Course registration and induction. Unit 2: Standards: certification & marking. Unit 1: General Principles. Unit 4: Increased Safety Ex e. Unit 10: Wiring systems & Demonstration of compound filled gland and diaphragm seal gland assembly. Unit 5: Type ‘n’ Protection. Break Unit 3: Flameproof Ex d. Break Unit 8: Other methods of protection. Unit 10: Practical exercise: Assembly of compound filled and diaphragm seal type glands.. Wednesday Unit 7: Intrinsic Safety E x i. Friday. EX01 CVT Inspection & Maintenance of d, e & n apparatus. EX02 CVT Preparation & Installation of d, e & n apparatus. EX03 CVT Inspection & Maintenance of d, e & n apparatus. EX04 CVT Preparation & Installation of d, e & n apparatus. Candidates 7-12. Candidates 1-6. Candidates 7-12. Candidates 1-6. Unit 6: Pressurisation Ex p. Unit 9: Combined (Hybrid) methods of protection Unit 11: Inspection & Maintenance. Break EX01 CVT Preparation & Installation of d, e & n apparatus. EX02 CVT Inspection & Maintenance of d, e & n apparatus. Break EX03 CVT Preparation & Installation of d, e & n apparatus. EX04 CVT Inspection & Maintenance of d, e & n apparatus. Candidates 1-6. Candidates 712. Candidates 1-6. Candidates 7-12. Unit 13: Introduction to CVT’s Unit 14: Work permit. Ex Facility November 2008. Thursday. 7. Break Job Knowledge assessment EX01, EX02, EX03 & EX04 Multi-choice examination.
(9) Unit 1: General Principles.
(10) Objectives: On completion of this unit, ‘General Principles’, you should know: a. The nature of flammable materials with regard to ‘explosive limits’ (LEL/UEL), ‘flashpoint’, ‘ignition’ temperature’, the effect of ‘oxygen enrichment’ and ‘relative density’. b. The basic principles of area classification. c. The Grouping of gases according to ‘minimum ignition energy’ (MIE) and ‘maximum experimental safe gap’ (MESG). d. Appropriate T-ratings for apparatus relative to the ignition temperature of a given flammable material. e. The levels of ‘ingress protection’.. ©. March 2010. 2.
(11) General Principles Nature of Flammable Materials Fire Triangle The fire triangle represents the three elements which must be present before combustion can take place. Each point of the triangle represents one of the essential elements which are: 1. Fuel:. This can be in the form of a gas, vapour, mist or dust. 2. Oxygen:. Plentiful supply since there is approximately 21% by volume in air.. 3. Source of Ignition:. This can be an arc, spark, naked flame or hot surface.. Gas or vapour. Source of ignition. Oxygen ( 21% in air ). Combustion will take place if all three elements, in one form or another, are present, the gas/air mixture is within certain limits and the source of ignition has sufficient energy. The removal of one element is sufficient to prevent combustion, as is the isolation or separation of the source of ignition from the gas/air mixture. These are two techniques used in explosion protected equipment. Other protection techniques allow the three elements to coexist and either ensures that the energy of the source of ignition is maintained below specific values, or allows an explosion to take place and contains it within a robust enclosure. These techniques are addressed in the various sections of this manual.. ©. March 2010. 3.
(12) Flammable (Explosive) Limits Combustion will only occur if the flammable mixture comprising fuel, in the form of a gas or vapour, and air are within certain limits. These limits are the ‘lower explosive limit’ (LEL), and the ‘upper explosive limit’ (UEL), and between these limits is known as the flammable range. An every day example of this is the carburettor of a petrol engine, which must be tuned to a particular point between these limits in order that the engine may function efficiently.. Lower Explosive Limit:. When the percentage of gas, by volume, is below this limit the mixture is too weak to burn, i.e. insufficient fuel and/or too much air.. Upper Explosive Limit:. When the percentage of gas, by volume, is above this limit the mixture is too rich to burn, i.e. insufficient air and/or too much fuel.. The flammable limits of some materials are given below.. Material. LEL % by Volume. UEL % by Volume. Propane. 1.7. 10.9. Methane. 4.4. 17. Ethylene. 2.3. 36. Hydrogen. 4. 77. Acetylene. 2.3. 100. Diethyl Ether. 1.7. 36. Kerosene. 0.7. 5. Carbon Disulphide. 0.6. 60. ©. March 2010. 4.
(13) Flammable (Explosive) Limits (continued) Different gases or vapours have different flammable limits and the greater the difference between the LEL and the UEL, known as the flammable range, the more dangerous the material. An explosive (flammable) atmosphere, therefore, only exists between these limits. Operational safety with flammable mixtures above the UEL is possible, but is not a practical proposition. It is more practical to operate below the LEL.. Sources of Ignition Sources of ignition are many and varied and include: a. Electrical arc/sparks b. Frictional sparks c. Hot surfaces d. Welding activities e. Cigarettes f.. Static discharges. g. Batteries h. Exhausts of combustion engines i.. Thermite action. j.. Sodium exposed to water. k. Pyrophoric reaction l.. Chemical reactions. m. Lightning strikes. The source of ignition as far as this text is concerned is primarily electrical equipment.. ©. March 2010. 5.
(14) Flashpoint By definition flashpoint is: ‘the lowest temperature at which sufficient vapour is given off a liquid, to form a flammable mixture with air that can be ignited by an arc, spark or naked flame’. Typical values are given below.. Material. Flashpoint °C. Propane. -104. Ethylene. -120*. Hydrogen. -256*. Acetylene. -82*. Diethyl Ether. -45. Kerosene. 38 -95*. Carbon Disulphide. * Values obtained form a source other than PD IEC60079-20. The flashpoint of a material gives an indication of how readily that material will ignite in normal ambient temperatures. Reference to the tables of flammable materials from PD IEC60079-20 (see Appendix 1) reveals that different materials have different flashpoints, which vary from well below to well above 0°C. Materials with high flashpoints should not be overlooked as a potential hazard since exposure to hot surfaces can allow a flammable mixture to form locally. Furthermore, if a flammable material is discharged under pressure from a jet, its flashpoint may be reduced.. Amount of vapour released dependent on temperature. ©. March 2010. 6.
(15) Flashpoint (continued). Kerosene: Flashpoint 38°C. At 38°C “Ignition”. At 37°C Insufficient vapour given off. At 0°C Negligible vapour given off. ©. March 2010. 7.
(16) Ignition Temperature Ignition temperature is defined as: ‘the minimum temperature at which a flammable material will spontaneously ignite’. Ignition temperature, formerly known as auto-ignition temperature, is an important parameter since many industrial processes generate heat. Careful selection of electrical equipment will ensure that the surface temperature produced by the equipment, indicated by the T-rating, will not exceed the ignition temperature of the flammable atmosphere which may be present around the equipment. Typical values of ignition temperature are:. Material. Ignition Temperature °C. Propane. 470. Methane. 537. Ethylene. 425. Hydrogen. 560. Acetylene. 305. Diethyl Ether. 160. Kerosene. 210 95. Carbon Disulphide. ©. March 2010. 8.
(17) Oxygen Enrichment The normal oxygen content in the atmosphere is around 20.95%, and if a given location has a value which exceeds this it is deemed to be oxygen enriched. Typical examples of where oxygen enrichment may occur are gas manufacturing plants, hospital operating theatres, and where oxy-acetylene equipment is used. Oxygen enrichment has three distinct disadvantages. First of all, it can lower the ignition temperature of flammable materials as shown in the table below.. Material. Air. Increased Oxygen. Ignition Temperature °C. Ignition Temperature °C. Hydrogen sulphide. 260. 220. Acetylene. 305. 296. Ethane. 512. 506. * All values obtained from a source other than PD IEC60079-20. Secondly, oxygen enrichment significantly raises the upper explosive limit (UEL) of the majority of gases and vapours, thereby widening their flammable range. This is illustrated in the following table.. Material. Air. Increased Oxygen. LEL %. UEL %. LEL %. UEL %. Methane. 5. 15. 5.2. 79. Propane. 2.2. 9.5. 2.3. 55. 4. 75. 4.7. 94. Hydrogen. * All values obtained from a source other than PD IEC60079-20. Thirdly, oxygen enrichment of a flammable atmosphere can allow it to be ignited with much lower values of electrical energy. Explosion protected equipment will have been tested in normal atmospheric conditions and, therefore, the safety of such equipment in an oxygen enriched atmosphere cannot be assured because of the modified nature of the flammable mixture.. ©. March 2010. 9.
(18) Density If a flammable material is released, it is important to know whether the material will rise or fall in the atmosphere. The different flammable materials are compared with air and allocated a number to denote their relative density with air. Since air is the reference, its relative density is 1 so that for a material twice as heavy as air, its relative density will be 2. Therefore, materials with a relative density less than unity will rise in the atmosphere, and those greater than unity will fall in the atmosphere. Materials which rise in the atmosphere can collect in roof spaces, and those which fall, such as butane or propane, can drift along at ground level and possibly into a non-hazardous location, or may collect in locations lower than ground level without ever dispersing. Such locations should be well ventilated in order to avoid ignition due to a stray spark or a discarded cigarette. Knowledge of where a flammable material will collect ensures that gas detectors when fitted will be located at the correct level and ventilation is directed accordingly.. Material. <1. Air Propane Methane Ethylene Hydrogen Acetylene Diethyl Ether Kerosene Carbon Disulphide. Relative vapour density 1 1.56 0.55 0.97 0.07 0.9 2.55 4.5* 2.64. * Value obtained from a source other than PD IEC60079-20. >1. ©. March 2010. 10.
(19) Area Classification An hazardous area is defined as: ‘An area in which an explosive gas atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of apparatus.’ A non-hazardous area is defined as: ‘An area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of apparatus.’. Zones Zoning is a means of representing the frequency of the occurrence and duration of an explosive gas atmosphere based on the identification and consideration of each and every source of release in the given areas of an installation. Zoning will have a bearing on, and simplify the selection of, the type of explosion protected equipment which may be used. Hazardous areas are, therefore, divided into three Zones which represent this risk in terms of the probability, frequency and duration of a release. The three Zones, as defined in BS EN60079-10-1: Electrical apparatus for explosive gas atmospheres, Part 10. Classification of hazardous areas, are as follows:. Zone 0. -. An area in which an explosive gas atmosphere is present continuously or for long periods or frequently.. Zone 1. -. An area in which an explosive gas atmosphere is likely to occur in normal operation occasionally.. Zone 2. -. An area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only.. Although not specified in IEC 60079-10-1, but quoted in API RP 505**, the duration of a gas release, or a number of gas releases, on an annual basis (one year comprises circa 8760 hours), for the different Zones is as follows.. Zone 2. -. 0 – 10 hours. Zone 1. -. 10 – 1000 hours. Zone 0. -. over 1000 hours. ** The above document, API RP 505, is published by the American Petroleum Institute and entitled “Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2.. ©. March 2010. 11.
(20) Area Classification (continued) Zone representation for ‘Area Classification Diagrams’ In accordance with BS EN60079-10, the illustrations below are the preferred method for representing the various zones in an hazardous area.. ©. March 2010. 12.
(21) Area Classification (continued). Fixed Roof Storage Tank. Zone 0 c. Zone 1 a. b Zone 2. Sump: Zone 1 Distances: ‘a’ 3m from vent opening ‘b’ 3m above the roof ‘c’ 3m horizontally from the side of the tank. ©. March 2010. 13.
(22) Area Classification (continued). Sources of Release. Welded pipe joint: ( Non-hazardous ). Flanged joint: ( Zone 2). Pump gland: ( Zone 2 or Zone 1 depending on the quality of the seal ). Space above liquid in a closed tank: ( Zone 0). ©. March 2010. 14.
(23) Gas / Apparatus Grouping In the IEC system, the group allocation for surface and underground (mining) industries are separate. Group I is reserved for the mining industry, and Group II which is subdivided into IIC, IIB and IIA for surface industries. The representative gases for the sub-groups are shown in the table below. Two methods have been used to ‘group’ these flammable materials according to the degree of risk they represent when ignited. One method involved determining the minimum ignition energy which would ignite the representative gases. The values obtained are relevant to Intrinsically Safe apparatus. In the table below it can be seen that for Group II, hydrogen and acetylene are the most easily ignited and propane the least easily ignited. The other method involved tests using, for example, a special flameproof enclosure in the form of an 8 litre sphere which was situated inside a gas-tight enclosure. Both halves of the sphere had 25mm flanges and a mechanism enabled the gap dimension between the flanges to be varied. During tests, the area inside and outside the sphere were occupied with a gas in its most explosive concentration in air and, by means of a spark-plug the gas inside the sphere was ignited. The maximum dimension between the flanges, which prevented ignition of the gas/air mixture, is known as the ‘maximum experimental safe gap’ (MESG), and the values for the representative gases are shown in the table below. The more dangerous a gas, the tighter the gap at the flanges has to be. It is important to note that the MESG values are not used for the design of Flameproof apparatus, only the maximum working gaps. The table also shows that these flammable materials fall into the same order for both tests, i.e. in a relative context, hydrogen and acetylene present the most risk and propane the least risk in terms of ‘minimum ignition energy’ and ‘MESG’.. Gas Group. Representative Gas. MESG (mm). Maximum Working Gap (mm). Minimum Ignition Energy (μJ). 1.14. 0.5. 260. 0.91. 0.4. 160. 0.2. 95. 0.1. 20. IIA. Methane (Firedamp) Propane. IIB. Ethylene. 0.65. Hydrogen. 0.28. Acetylene. 0.37. I. IIC. Note: Apparatus other than flameproof or intrinsic safety, which has no sub-division letter (A, B or C) after the group II mark, may be used in all hazards.. Apparatus marked IIxxxxx:. xxxxx represents the chemical formula or name of a flammable material, and apparatus marked in this way may only be used in that hazard.. ©. March 2010. 15.
(24) Gas / Apparatus Grouping (continued) The sub-group marking is one of the important considerations during the selection process of explosion protected apparatus. For example, apparatus marked IIA can only be used in IIA hazards such as propane, it cannot be used in IIB or IIC hazards. Apparatus marked IIB can be used in IIB and IIA hazards but not IIC hazards. Apparatus marked IIC can be used in all hazards.. Apparatus for determination of M.E.S.G. ©. March 2010. 16.
(25) Gas / Apparatus Grouping (continued) Comparison of BS 229 and IEC BS 229 is an old British Standard, which has now been withdrawn, but electrical apparatus was still manufactured to this standard up until several years ago. Apparatus manufactured to BS 229 has sub-group markings which are different to those of the IEC system and the comparison is shown in the table below. The introduction of the ATEX Directives after 30 June 2003 has caused manufacturers to discontinue the production of apparatus to this standard, but apparatus already in use will be unaffected.. BS 229. Representative Gas. IEC. 1. Methane. I. 2. Propane. IIA. 3a. Ethylene. 3b. Coal Gas. 4. Hydrogen & Acetylene. IIB. IIC. ©. March 2010. 17.
(26) Temperature Classification Approved electrical equipment must be selected with due regard to the ignition temperature of the flammable gas or vapour which may be present in the hazardous location. Apparatus will usually be marked with one of the temperature classes shown in the table below. The temperature class indicates the maximum temperature the surfaces of an enclosure, which are exposed to a flammable gas, must not exceed during normal or specified fault conditions.. Temperature Classes. T - Class. Maximum Surface Temperature. T1. 450°C. T2. 300°C. T3. 200°C. T4. 135°C. T5. 100°C. T6. 85°C. In the table below, it will be observed that for each material, the T-rating temperature is below the ignition temperature of the flammable material. Moreover, the T-rating temperatures are based on a maximum ambient rating of 40°C as far as the UK is concerned. For example, apparatus classified T5, based on a 40°C ambient rating, will have a maximum permitted temperature rise of 60°C. In order to avoid infringement of the apparatus certification, the ambient rating must be compatible with environmental ambient temperatures, and the temperature rise not exceeded. This is demonstrated on page 20. A further consideration is apparatus for use in hotter climates, typically found in Middle and Far Eastern countries, which will usually require ambient ratings greater than 40°C. Apparatus for use in colder (arctic) climates will require a much lower limit to the ambient temperature range which may be as low as -50°C.. Ignition Temperature. T-Rating. Methane. 537°C. T1 (450°C). Ethylene. 425°C. T2 (300°C). Cyclohexane. 259°C. T3 (200°C). Diethyl Ether. 160°C. T4 (135°C). Material. T5 (100°C) Carbon Disulphide. 95°C. T6 (85°C). ©. March 2010. 18.
(27) -2. -2. Temperature Classification (continued). ©. March 2010. 19.
(28) Ingress Protection Enclosures of electrical equipment are classified according to their ability to resist the ingress of solid objects and water by means of a system of numbers known as the ‘International Protection (IP) Code’. This code, which is not always marked on apparatus, consists of the letters IP followed by two numbers, e.g. IP56. The first number, in the range 0-6, indicates the degree of protection against solid objects, and the higher the number the smaller the solid object that is prevented from entering the enclosure. Zero (0) indicates no protection and 6 indicate the apparatus is dust-tight. The second number, ranging from 0-8, identifies the level of protection against water entering the enclosure, i.e. 0 indicates than no protection is afforded, and 8 that the apparatus can withstand continuous immersion in water at a specified pressure. An abridged version of the full table is shown below.. Solid Objects First Numeral. Level of Protection. Water Second Numeral. Level of Protection. 0. No protection. 0. No protection. 1. Protection against objects greater than 50 mm. 1. Protection against drops of water falling vertically. 2. Protection against objects greater than 12 mm. 2. Protection against drops of water when tilted up to 15°. 3. Protection against objects greater than 2.5 mm. 3. Protection against sprayed water up to 60°. 4. Protection against objects greater than 1.0 mm. 4. Protection against splashed water from any direction. 5. Dust-protected. 5. Protection against jets of water from any direction. 6. Dust-tight. 6. Protection against heavy seas - deck watertight. 7. 8. Protection against immersion in water 1m in depth and for a specified time Protection against indefinite immersion in water at a specified depth. ©. March 2010. 20.
(29) Unit 2: Standards, Certification and Marking.
(30) Objectives: On completion of this unit, ‘Standards, Certification and Marking’, you should know: a. Current British, European and International Standards and also relevant older British Standards and Codes of Practice. b. The certification process for explosion protected apparatus. c. The methods of marking explosion protected apparatus. d. The basic requirements of the ATEX Directives. e. The correlation between the ATEX categories and Equipment Protection Levels (EPL’s). ©. March 2010. 2.
(31) Standards, Certification and Marking Introduction There are many industries involved in the process of hazardous materials, and these include chemical plants, oil refineries, gas terminals and offshore installations. These industries rely heavily on electrical energy to power, for example, lighting, heating and rotating electrical machines. The safe use of electrical energy in the hazardous locations of these industries can only be achieved if tried and tested methods of explosion protection are implemented and to this end, the organisations involved in the writing of standards, testing and certification of equipment have a very important role to play. Since the early 1920’s, many standards have evolved as a result of careful research, often prompted by incidents such as the Senghennydd colliery disaster in 1913 in which 439 miners lost their lives. The cause at that time was not fully understood but after investigation, was thought to have been due to an electrical spark igniting methane (firedamp) present in the atmosphere. Other disasters include Abbeystead Water Pumping Station in which 16 people lost their lives, once again due to the electrical ignition of methane gas, Flixborough where an explosion killed 28 people due to ignition of a massive release of cyclohexane, and more recently Piper Alpha in the North Sea in which 167 men lost their lives. Construction of equipment to relevant standards coupled with testing by an independent certification body will ensure that the equipment is suitable for its intended purpose. Explosion protected equipment may be constructed in accordance with relevant standards, but the integrity of such equipment will only be preserved if it is selected, installed and maintained in accordance with the manufacturers recommendations. Guidance in this respect has been provided for many years by the UK Code of Practice BS 5345, but this document has been superseded by a new series of five separate standards based on the IEC 60079 series of International standards. These five documents apply to explosion protected equipment/systems in all countries in the EU and cover, (1) selection and installation of equipment, (2) classification of hazardous areas, (3) inspection and maintenance, (4) repair of explosion protected equipment, and (5) data for flammable gases provided by an IEC document (See lower table on page 13). The BS EN60079 standards are identical to the IEC60079 standards. Although BS 5345 has been withdrawn, it nevertheless remains a source of information for older installations, but applies to the UK only with regard to the EU. In the United Kingdom, manufacturing and testing standards are published by an organisation known as the British Standards Institute (BSI). With regard to the European Community, the organisation which publishes harmonised standards for its member nations is the European Committee for Electrotechnical Standardisation (CENELEC) and, with global harmonisation of standards the ultimate aim, the International Electrotechnical Commission (IEC) publishes standards for this purpose. Historically, equipment designs are evaluated and prototypes tested by independent organisations, one of which was formerly known as ‘British Approvals Service for Electrical Equipment in Flammable Atmospheres (BASEEFA), but was later known as ‘Electrical Equipment Certification Service (EECS)’. The acronym BASEEFA, which has been closely associated with explosion protected equipment for many years, was retained by EECS for certification marking purposes. EECS, which was part of the Health and Safety Executive (HSE), also published standards for special applications. EECS, however, closed. ©. March 2010. 3.
(32) for business in September 2002, but encouraged by several major customers, former staff established an independent organisation known as Baseefa (2001) Ltd, and became simply Baseefa Ltd. two-years later. Having traded since March 2002, Baseefa Ltd. became an EU Notified Body (NB) in June 2002 and was allocated the NB Number 1180. With the introduction of the ATEX Directives, which become mandatory after 30 June 2003, a procedure for the evaluation of equipment for compliance with the ATEX directives was implemented. This procedure involves a series of modules, listed on page 5, covering the design, quality control and production phases for equipment, which are audited by a Notified Body. A Notified Body is an independent organisation that has been assessed and accredited by a national body (United Kingdom Accreditation Service, UKAS, in the UK) as having the expertise to operate as a Notified Body in accordance with the directives with regard to conformity assessment of products. A Notified Body has been notified to the European Commission by its member state Notified Bodies have their own unique NB number, which will be marked on the certification labels of ATEX compliant apparatus. Other Notified Bodies in the UK include SIRA Certification Service, NB Number 0518, and ITS Testing and Certification Ltd., NB Number 0359 and many others throughout the EU. Notified bodies may require the services of other organisations for testing product prototypes.. ATEX Directives On the 12 June 1989 a Framework Directive 89/391/EEC was adopted by the European Commission the objective being to establish a basis for improving the safety of employees in the workplace. Supplementary directives namely, 94/9/EC, introduced under Article 100a of the Treaty of Rome and now known as ATEX 95, and 99/92/EC, now ATEX 137, address equipment use and safety in hazardous areas. ATEX 95 is the product directive and ATEX 137 is the workplace directive. Both these directives, unlike previous directives, establish a New Approach in that they are mandatory by law rather than advisory. ATEX 95, the product directive, mandatory from 01 July 2003, requires all new equipment, which includes not only electrical equipment but also mechanical (non-electrical) equipment, e.g. pumps, gearboxes etc, and protective systems for use in potentially explosive atmospheres, placed on the market of the European Community for the first time to be manufactured in compliance with the directive. Equipment from out-with the EU, whether new or second hand, imported into the European Community and placed on the market for the first time must also be in compliance with the directive. ATEX 95 applies to the design requirements of equipment and hence concerns mainly the manufacturer and supplier but availability of spare parts and items held in stock would be of concern to equipment users. Therefore, in order to comply with ATEX 95, products must satisfy the Essential Health & Safety Requirements (EHSR’s) specified in the annexes of the Directives, with regard to the inherent risks associated with the product for the protection of the public. This is usually achieved by compliance with relevant harmonised standards, and although it is possible to achieve compliance by means other than the harmonised standards, difficulty would arise installing, inspecting and repairing such equipment to the BS EN60079 standards 14, 17 & 19. Subject to a successful Conformity Assessment, the product can display the CE mark which indicates compliance with the ATEX Directive. ATEX 137, the user directive, became fully mandatory from 01 July 2006 and places responsibilities on employers to provide a safe working environment for employees.. ©. March 2010. 4.
(33) CE Conformity Assessment Modules The Conformity Assessment involves a series of Basic Modules which are listed in the table below and their application in the subsequent simplified flow chart.. A. Internal control of production. Covers internal design and production control. Does not require the involvement of a notified body.. B. EC type-examination. Covers the design phase, the EC type-examination being issued by a notified body. Has to be followed by a module for assessment during the production phase.. C. Conformity to type. Covers the production phase after module B. This module confirms conformity of the product with that described in the EC examination certificate as issued during module B.. D. Production quality assurance. Covers the production phase following module B. Production quality assurance is based on the standard EN ISO 9002 and the involvement of a notified body who has responsibility for the approval and control of the quality system regarding production, end product inspection and testing implemented by the manufacturer.. E. Product quality assurance. Covers the production phase following module B. Production quality assurance is based on the standard EN ISO 9003 and the involvement of a notified body who has responsibility for the approval and control of the quality system regarding end product inspection and testing implemented by the manufacturer.. F. Product verification. Covers the production phase following module B. The EC type examination carried out by the notified body, to ensure conformity to type in module B, is followed by the issue of a certificate of conformity.. G. Unit verification. Covers the design and production phases. A certificate of conformity is issued after examination of every product by the notified body.. H. Full quality assurance. Covers the design and production phases. Quality assurance is based on the standard EN ISO 9003 and the involvement of a notified body who has responsibility for the approval and control of the quality system for design, manufacture, final product inspection and testing implemented by the manufacturer.. ©. March 2010. 5.
(34) CE Conformity Assessment Modules (continued) The illustration below shows how the modules listed on the previous page may be implemented to obtain the CE marking for apparatus.. Design phase. Production phase Module A Module C Module D. Manufacturer. Module B Module E Module F Module G. Module H. ATEX 95 The ATEX Directive 94/9/EC ( ATEX 95 ) was adopted by the EC to enable free trade of products between member states through alignment of technical and legal requirements and concerns the design of explosion protected equipment. The directive applies not only to electrical equipment but also to mechanical equipment and protective systems used in the presence of potentially explosive atmospheres containing gases/vapours or combustible dusts. Equipment is defined as any item which is inherently ignition capable or is potentially ignition capable and requiring the inclusion of special design and installation techniques to prevent ignition of any surrounding flammable atmosphere which may be present. The ‘equipment’ may also be interfaces located in the non-hazardous area which are part of an explosion protection system. Protective systems include quenching systems, flame arrestors, fastacting shut-off valves and pressure relief panels installed to limit damage due to an explosion or prevent the spread of explosions.. ©. March 2010. 6.
(35) ATEX 137 The ATEX Directive 99/92/EC ( ATEX 137 ), commonly known as the ‘use’ directive, is implemented in the UK via the Dangerous Substances and Explosives Atmosphere Regulations 2002 (DSEARs). Employers are obliged to implement the following minimum requirements in the workplace with regard to DSEARs. a. Carry out a risk assessment where dangerous substances are or may be present. b. Eliminate or reduce risk as far as is reasonably practicable. c. Classify locations in the workplace where explosive atmospheres may be present into hazardous or non-hazardous areas. d. Have in place procedures/facilities to deal with accidents, incidents and emergencies involving dangerous substances in the workplace. e. Provide appropriate information and training of employees for their safety regarding precautions to be taken when dangerous substances are present in the workplace, written instruction for tasks undertaken by employees and operation of a permit-towork system. f.. Clearly identify the contents of containers and pipes.. g. Co-ordinate operations where two or more employees share a workplace in which a dangerous substance may be present. h. Posting of warning signs for locations where explosive atmospheres may occur. i.. Selection of equipment in accordance with ATEX 95 and establishment of a maintenance programme.. Marking of Hazardous Areas Article 7 in the Directive ATEX 137 states: ‘Where necessary, places where explosive atmospheres may occur in such quantities as to endanger the health and safety of workers shall be marked with signs at their points of entry in accordance with Annex III.’ Annex III of the directive specifies the exact requirements for the sign but generally it is required to be triangular with a yellow background, black border and marked ‘Ex’.. Ex ©. March 2010. 7.
(36) European Notified Bodies The illustration below shows some of the Notified Bodies along with their unique Notified Body (NB) number. There are around sixty Notified bodies in the EU at the time of writing.. Finland: VTT Industrial Systems (0537). Sweden: SP-Swedish National Testing (402). Norway: NEMKO AS (0470) DNV AS (0575). Denmark: UL Int DEMKO A/S (0539). UK:. Baseefa. (1180). SIRA. (0518). BSI Product Services (0086). Germany: PTB (0102). ITS Testing & Cert. Ltd (0359) Lloyd’s Reg Ver Ltd. (0038). Netherlands: KEMA (0344). Belgium: ISSeP (0539). France: LCIE (0081) INERIS (0080). Spain: LOM (0163). Italy: CESI (0722). ©. March 2010. 8.
(37) Comparison of IEC, European (CENELEC) and British Standards Prior to the closer ties between the UK and Europe, electrical equipment, such as flameproof or increased safety etc., was manufactured in accordance with the British Standard BS 4683 (see table in page 11). Equipment built and certified to this standard was entitled to display the mark Ex on its label, which indicated that the apparatus was explosion protected. This term should not be confused with term explosion-proof as they are entirely different. In addition to the ‘Ex’ mark, the label was also marked with a ‘crown’ symbol, which is the distinctive mark for the UK test house BASEEFA, later to become known as EECS. Other examples of marks are shown on page 14 of this Unit. Because of the differences in standards, e.g. equipment manufactured in the UK could not be used in the other European countries and vice-versa, and hence, equipment made to BS 4683 could only be used in the UK, or in other countries outside Europe. Co-operation between the standards writing bodies in the UK and Europe resulted in the development of ‘Harmonised’ standards, also known as ‘Euronorms’, for which the English version was published as BS 5501 and comprised nine separate parts as shown in the third column of the table on page 10. The Euronorm equivalents, written in French or German, are shown on the first column. Column four shows the second generation of the UK version of the harmonised standards which replaced BS5501. However, with the trend towards global harmonisation of standards continuing to make progress, a new series of standards have been gradually introduced having numbers based on the International Standard numbers (second column), i.e. BS EN60079, as shown in column five of the following table.. ©. March 2010. 9.
(38) Comparison of IEC, European (CENELEC) and British Standards CENELEC Euronorm (EN) Number. International Standards. British Standard (BS) Number. Revised Standard (BS EN) Number. Latest Revised Standard (BS EN) Number. Type of Protection. EN 50 014. IEC 60079-0. BS 5501: Pt. 1. BS EN50 014. BS EN60079-0. General Requirements. EN 50 015. IEC 60079-6. BS 5501: Pt. 2. BS EN50 015. BS EN60079-6. Oil Immersion ‘o’. EN 50 016. IEC 60079-2. BS 5501: Pt. 3. BS EN50 016. BS EN60079-2. Pressurised Apparatus ‘p’. EN 50 017. IEC 60079-5. BS 5501: Pt. 4. BS EN50 017. BS EN60079-5. Power Filling ‘q’. EN 50 018. IEC 60079-1. BS 5501: Pt. 5. BS EN50 018. BS EN60079-1. Flameproof Enclosure ‘d’. EN 50 019. IEC 60079-7. BS 5501: Pt. 6. BS EN50 019. BS EN60079-7. Increased Safety ’e’. EN 50 020. IEC 60079-11. BS 5501: Pt. 7. BS EN50 020. BS EN60079-11. Intrinsic Safety ‘i’. EN 50 028. IEC 60079-18. BS 5501: Pt. 8. BS EN50 028. BS EN60079-18. Encapsulation ‘m’. EN 50 039. IEC 60079-25. BS 5501: Pt. 9. BS EN50 039. BS EN60079-25. Intrinsic Safety Systems ‘i’. EN 50 021. IEC 60079-15. BS EN50 021. BS EN60079-15. Type of Protection ‘n’. IEC 60079-26. BS EN60079-26. Equipment with Equipment Protection Level Ga. IEC 60079-27. BS EN60079-27. Fieldbus intrinsically safe concept (FISCO). IEC 60079-29-2. BS EN60079-29-2. Gas detector selection, installation, use and maintenance. IEC 60079-30-1. BS EN60079-30-1. Electrical resistance trace heating – General & testing requirements. IEC 60079-30-2. BS EN60079-30-2. Electrical resistance trace heating – Application guide. ©. March 2010. 10.
(39) Other (older) British Standards The standards listed below are those which preceded the harmonised European standards listed in the previous table. These standards, with the exception of BS 889, were not entirely obsolete, and older designs of equipment were still manufactured to these standards and available on the market prior to 30 June 2003, the date after which implementation of the ATEX Directives became mandatory. Apparatus manufactured to these standards, where still in use, must be maintained in accordance with these standards. It is, therefore, important that reference to the correct standard is made before maintenance is carried out on such apparatus.. BS 229. Flameproof enclosure of electrical apparatus. BS 889. Flameproof electric fittings. BS 1259. Intrinsically safe electric apparatus and circuits for use in explosive atmospheres. BS 4683: Part 1. Classification of maximum surface temperature. BS 4683: Part 2. The construction and testing of flameproof enclosures of electrical apparatus. BS 4683: Part 3. Type of protection ‘N’. BS 4683: Part 4. Type of protection ‘e’. BS 6941. Type of Protection ‘N’. BS 5000: Part 15. Machines with type of protections ‘e’. BS 5000: Part 16. Type ‘N’ electric motors. March 2010. 11.
(40) Standards for Selection, Installation, Inspection and Maintenance As previously stated, the UK Code of Practice BS 5345, which had for many years provided recommendations for the selection, installation and maintenance of explosion protected equipment for use in potentially explosive atmospheres (other than mining applications or explosives processing and manufacture), listed in the upper table below, was superseded by the standards listed in the lower table. BS 5345, however, may be referred to for installations installed in accordance with its requirements. The table below illustrates the component parts of BS 5345.. UK Code of Practice. Type of Protection. BS 5345: Part 1. General Recommendations. BS 5345: Part 2. Classification of Hazardous Areas. BS 5345: Part 3. ‘d’ Flameproof enclosure. BS 5345: Part 4. BS 5345: Part 6. ‘i’ Intrinsically safe apparatus and systems ‘p’ Pressurisation, continuous dilution and pressurised rooms ‘e’ Increased safety. BS 5345: Part 7. ‘N’ (Non - incendive). BS 5345: Part 8. ‘s’ Special protection. BS 5345: Part 9. ‘o’ Oil immersion ‘q’ Powder filling. BS 5345: Part 5. The standards which supersede the Code of Practice BS 5345 are illustrated in the table below. Furthermore, the BS EN standards are identical to the IEC standards shown within brackets in the table below apart from a few informative annexes.. BS EN / IEC Nos. BS EN60079-10: 2009 (IEC 60079-10-1: 2008) BS EN60079-14: 2008 (IEC 60079-14: 2007). Electrical Apparatus for Explosive Gas Atmospheres: Part 10: Classification of hazardous areas Part 14: Electrical installations in hazardous areas (other than mines). BS EN60079-17: 2007 (IEC 60079-17: 2007). Part 17: Inspection and maintenance of electrical installations in hazardous areas (other than mines). BS EN60079-19: 2007 (IEC 60079-19: 2006). Part 19: Repair and overhaul for apparatus used in explosive atmospheres (other than mines or explosives). BS EN60079-20-1: 2010 (IEC 60079-20-1: 2010). Material characteristics for gas and vapour classification – Test methods and data. ©. March 2010. 12.
(41) Certification body symbols. 1). 2). 3). 4). 5). 6). 7). MEx. Equipment marked with this symbol may only be used for underground (mining) applications in the UK.. Equipment marked with this symbol has been constructed to the old British Standard BS229. Symbol formerly used by EECS (BASEEFA) to identify equipment for surface industry use only.. Equipment marked with this symbol, the European Ex mark, indicates that the equipment has been constructed and tested in accordance with the CENELEC/ EURONORM standards. This mark only will be used on ATEX compliant equipment. Symbol formerly used by the German notified body PTB. The most commonly used symbol of the American certification authority Underwriters Laboratories (UL). The mark used by the Canadian Standards Association. ©. March 2010. 13.
(42) Equipment Marking Prior to the introduction of the ATEX Directives on 1 July 2003, equipment for use in hazardous areas were marked as illustrated below. Equipment complying with the ATEX Directives, however, will still be marked in this way but will have additional markings to indicate that the apparatus conforms with the ATEX Directives. The ATEX markings are shown on page 18. Equipment approved/certified as providing a method of protection for use in hazardous locations is required to display the following markings. a. The symbols Ex, and b. The type of protection used, e.g. ‘d’, ‘e’, ‘N’, and c. The gas group, e.g. IIA, IIB or IIC, and d. The T-rating, e.g. T1, T2 etc. e. The ambient rating, e.g. -200C to +400C (normal range for UK but may not be marked on equipment.) Note: For higher ambient ratings the marking may be either Tamb +500C, or -200C < Tamb < +500C Examples: (i) Ex d IIB T3 (ii) EEx d IIC T4 (iii) EEx e II T6 In example (i), equipment marked thus (Ex), as far as Europe was concerned, could only be used in the UK because it had been constructed to the British Standard BS 4683, which was not a harmonised European standard. Equipment constructed to this standard, however, was used in other countries out-with the European Community. Such equipment would also be marked with the EECS certification authority symbol (fig 3) on the previous page. Equipment certified in accordance with the IEC Ex scheme will be marked Ex. See page 20 onwards for details of this scheme. For equipment marked EEx as in example ii. and iii., the additional letter ‘E’ indicates that the equipment has been constructed to a harmonised European standard. Such equipment would be marked with the EECS certification authority symbol (fig 3) as well as the European Community mark (fig 4). Sample labels are shown below, and it should be noted that the construction standard to which the equipment has been manufactured to, i.e. BS 4683: Part 2, BS 5501: Parts 1 & 5 and EN50 014 & EN50 018 are also given on the labels. For BS 4683 equipment, the IEC equivalent standard, i.e. IEC 79-1 in example (a) below, is usually included.. (a). (b). ©. March 2010. 14.
(43) Equipment marking (continued) The certification labels attached to explosion protected equipment will display markings to enable their correct selection for use in hazardous areas. For example, equipment manufactured to the old UK standard BS4683 and the subsequent CENELEC EN500 series of harmonised standards will be marked Ex and EEx respectively. However, with the CENELEC and IEC standards becoming technically identical, i.e. the EN60079 standards are identical to the IEC60079 standards, the marking has reverted to Ex. The illustration below shows the marking on equipment constructed to the harmonised standard BS EN50018.. Equipment manufactured to the latest standards, the BS EN60079 series, will be marked as follows along with the ATEX markings shown on page 17. The main differences are the removal of the letter ‘E’ compared to the illustration above and the introduction of the EPL ‘Gb’. EPL’s are explained on pages 18 to 21.. Ex d IIC T6 Gb. ©. March 2010. 15.
(44) Certification Numbers The certification number illustrated below was used by BASEEFA prior to the introduction of the ATEX directives, but the numbers used by other certification authorities will be different.. Components typically displaying a suffix ‘U’ include Ex e terminals, Ex d stoppers for flamepoof enclosures, and small volume plastic flameproof switches which have exposed terminals.. ATEX compliant equipment will have standardised certification numbers which will include the abbreviation of the notified body’s name followed by the year of certification, the acronym ATEX, the serial number and either of the suffix’s ‘X’ or ‘U’ where applicable, as shown below.. BAS 08 ATEX 1234 X ©. March 2010. 16.
(45) Marking of ATEX Compliant Equipment The ATEX Directive 94/9/EC, now known as ATEX 95, specifies the new approach for the certification of explosion protected equipment. An introduction to the ATEX approach has been considered in pages 4-7 but its wider issues are beyond the scope of this Unit. What is relevant, however, is the influence the directive will have on the marking of explosion protected equipment. This will be the most obvious difference to those involved in the selection, installation and maintenance of explosion protected apparatus. The marking required by ATEX 95 is illustrated below, which is additional to the marking requirements already discussed. Also, the hexagonal symbol below will replace the individual symbols used by the different certification bodies, and the CE mark indicates compliance with the ATEX Directive.. 0000 CE Mark. EU Explosive Atmosphere Symbol. Notified body ID number. The Equipment Categories are defined overleaf. ©. March 2010. 17.
(46) Category (Cat) Definitions The ATEX Categories were introduced to ‘break’ the traditional link between the protection types and zones, i.e. the selection of equipment suitable for the zone. This approach enables, for example, Cat 3 equipment, typically Ex n, to be used in zone 1 if a risk assessment revealed that the consequences of ignition of a flammable atmosphere was low. The Categories below, however, show the traditional link with the zones. Conversely, if the consequences of ignition were greater then a better Category of protection may be required.. Group II. Cat 1:. Very high level of protection Equipment with this category of protection may be used where an explosive atmosphere is present continuously or for long periods, i.e. Zone 0 or Zone 20.. Cat 2:. High level of protection Equipment with this category of protection may be used where an explosive atmosphere is likely to occur in normal operation, i.e. Zone 1 or Zone 21.. Cat 3:. Normal level of protection Equipment with this category of protection may be used where an explosive atmosphere is unlikely to occur or be short duration, i.e. Zone 2 or Zone 22.. Group I. Cat M1:. Very high level of protection Equipment can be operated in the presence of an explosive atmosphere.. Cat M2:. High level of protection Equipment to be de-energised in the presence of an explosive atmosphere.. Note: Zones 20, 21 and 22 are the corresponding zones for combustible dusts.. Equipment protection levels (EPL’s) The introduction of Equipment Protection Levels (EPL’s), which are used internationally, enables a risk assessment approach to be implemented for the selection of explosion protected equipment in hazardous areas. This provides an alternative to the traditional method of selecting equipment to suit the zone, which does not take into consideration the consequences of an explosion. The table below shows the zones where both ATEX Categories and EPL’s may be used from a traditional selection approach. Selection of equipment according to the EPL will in future be according to the EPL’s specified for the zones in area classification diagrams so that where the consequences of an explosion are likely to be greater, a higher EPL will be specified. Alternatively, if the consequences of an explosion are lower, a lesser EPL may be specified. Zone. ATEX Categories. EPL’s. 0. 1. Ga. 1. 2. Gb. 2. 3. Gc. ©. March 2010. 18.
(47) Equipment protection levels (EPL’s) Equipment Protection Levels (EPL’s) are available for both gases and vapours and also combustible dusts as illustrated in the table below. Equipment marked ‘G’ is for use in flammable gases and vapours, and for use in combustible dusts when marked ‘D’.. Zone. Equipment protection levels ( EPL’s ). 0. Ga. 1. Ga or Gb. 2. Ga, Gb or Gc. 20. Da. 21. Da or Db. 22. Da, Db or Dc. EPL Definitions Group II gases Ga. Equipment for explosive gas atmospheres, having a ‘very high’ level of protection, which is not a source of ignition in normal operation, expected faults, or when subject to rare faults.. Gb. Equipment for explosive gas atmospheres, having a ‘high’ level of protection, which is not a source of ignition in normal operation, or when subject to faults that may be expected, though not necessarily on a regular basis.. Gc. Equipment for explosive gas atmospheres, having an ‘enhanced’ level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences, for example, failure of a lamp.. Group III Dusts Da. Equipment for combustible dust atmospheres, having a ‘very high’ level of protection, which is not a source of ignition in normal operation, or when subject to rare faults.. Db. Equipment for combustible dust atmospheres, having a ‘high’ level of protection, which is not a source of ignition in normal operation, or when subject to faults that may be expected, though not necessarily on a regular basis.. Dc. Equipment for combustible dust atmospheres, having an ‘enhanced’ level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences.. ©. March 2010. 19.
(48) EPL’s assigned to protection types (gases) EPL Ga EPL. Protection type. Marking. Intrinsic Safety. Ex ia. Encapsulation. Ex ma. Ga. EPL Gb EPL. Gb. Protection type. Marking. Flameproof. Ex d. Increased Safety. Ex e. Intrinsic Safety. Ex ib. Encapsulation. Ex m Exmb. Oil immersion. Ex o. Pressurisation. Ex p, Ex px, Ex py. Powder filled. Ex q. Fieldbus Intrinsic Safety Concept (FISCO). **. ** No designated marking code at the time of writing. EPL Gc EPL. Gc. Protection type. Marking. Intrinsic Safety. Ex ic. Encapsulation. Ex mc. Non-sparking. Ex n, Ex nA. Restricted breathing. Ex nR. Energy limitation. Ex nL. Sparking equipment. Ex nC. Pressurisation. Ex pz. Fieldbus (FNICO). non-incendive. Concept. **. ** No designated marking code at the time of writing. ©. March 2010. 20.
(49) EPL’s for combustible dusts. EPL. Da, Db, or Dc. Db or Dc. Protection type. Marking. Intrinsic Safety. Ex iD. Encapsulation. Ex mD. Protection by enclosure. tD. Pressurisation. pD. Equipment marking Since there is now technical alignment of the CENELEC and IEC standards, equipment manufactured in Europe will no longer be marked EEx, and instead will be marked Ex. Where equipment is certified under the IECEx scheme the IECEx Conformity Mark as illustrated below will be displayed on the equipment. For the foreseeable future, however, acceptance in the EU will require the equipment to comply with ATEX and display the marking illustrated on page 18.. Area for code indicating the Licensee Number and the Certification Body. ©. March 2010. 21.
(50) Example of an EC – Type Examination Certificate. ©. March 2010. 22.
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(53) Baseefa Wallchart. ©. March 2010. 25.
(54) UNIT 3 FLAMEPROOF EEx d / Ex d.
(55) OBJECTIVES On completion of this unit, ‘flameproof EEx d / Ex d apparatus, you should know: a. The principle of operation and causes of pressure piling. b. The general constructional requirements including types of joints. c. The installation requirements with regard to thread engagement of cable entries and stopping devices, circuit protection, obstruction of flamepaths and additional weatherproofing methods in accordance with BS EN60079-14. d. The inspection requirements with regard to BS EN60079-17.. ©. March 2010. 2.
(56) Flameproof EEx d / Ex d Flameproof is one of the original methods of explosion protection developed for use in the mining industry. It has a wide range of applications, typically junction boxes, lighting fittings, electric motors etc. The letter ‘d’, which symbolises this type of protection, is from the German word ‘druckfeste’ (kapselung), which roughly translated means ‘pressure tight’ (enclosure).. Flameproof apparatus, when properly installed in the intended location, enables components such as switches, contractors and relays etc. to be safely used in hazardous areas. Flameproof is the only one of the nine different methods of explosion protection in which an explosion is permitted. This explosion, however, must be contained by the robustly constructed flameproof enclosure so that ignition of the surrounding flammable atmosphere cannot occur.. ©. March 2010. 3.
(57) Standards BS EN60079-1: 2007. Flameproof enclosures ‘d’. BS EN50 018: 2000. Flameproof enclosures ‘d’. BS 5501: Part 5: 1977. Flameproof enclosures ‘d’. BS 4683: Part 2: 1971. The construction and testing of flameproof enclosures of electrical apparatus (Ex d). BS 229: 1957. Flameproof enclosures of electrical apparatus. IEC 60079-1: 2007. Electrical Apparatus for explosive gas atmospheres – Part 1: Flameproof enclosures ‘d’. BS EN60079-14: 2008. Electrical Apparatus for explosive gas atmospheres: Part 14 Electrical installations in hazardous areas (other than mines). BS EN60079-17: 2007. Electrical Apparatus for explosive gas atmospheres: Part 17 Inspection and Maintenance of electrical installations in hazardous areas (other than mines). BS 5345: Part 3: 1979 (Withdrawn). Code of Practice for the Selection, Installation and Maintenance of flameproof apparatus. Definition The construction standard BS EN60079-1 defines flameproof as: ‘An enclosure in which the parts which can ignite an explosive atmosphere are placed and which can withstand the pressure developed during an internal explosion of an explosive mixture, and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure’. EPL:. Gb. Zone of Use:. 1&2. Ambient Conditions Flameproof enclosures are normally designed for use in ambient temperatures in the range - 20°C to +40°C unless otherwise marked.. ©. March 2010. 4.
(58) Principle of Operation Flameproof enclosures are not gas tight and a gas or vapour will enter the enclosure where, for example, joints or cable entries exist. Since these enclosures are designed to contain components which are an ignition source, ignition of the gas or vapour may occur, and the resulting explosion pressure can reach a peak value of around 150 p.s.i. The enclosure must, therefore, be strong enough to contain this explosion pressure, and the gaps at the joints and threads of cable entries must be long and narrow to cool the flames/hot gases before they reach and cause ignition of a flammable atmosphere which may exist out with the enclosure. Typical materials used for the construction of flameproof apparatus include cast iron, aluminium alloys, and where corrosion resistance is required, gun metal bronze, phosphor bronze and stainless steel may be used. Plastic materials are also used but the free internal volume must not exceed 10cm3. The latest standard specifies that for flanged joints ‘THERE SHALL BE NO INTENTIONAL GAP AT THE JOINTS’ and infers the same for other joint types. The average roughness Ra of the flamepath surfaces must not exceed 6.3μm.. Flammable MIxture. Arcs, Sparks Hot Surfaces Contactors, Relays etc. Gap. ©. March 2010. 5.
(59) Gap Dimensions It is not necessary for a gap to exist at the flamepaths of a flameproof enclosure. The latest standard BS EN60079-1 states there shall be no intentional gap between the surfaces of enclosures with flanged joints. This said, however, a gap will be necessary at the cylindrical joints of rotating machines, i.e. where the rotor shaft exits the end-shield and also where push-button spindles pass through flameproof enclosures to operate the internal switches. Flameproof enclosures with spigot or screwed joints, however, require some clearance to enable covers to be removed relatively easily for installation and maintenance purposes. These clearance/gap dimensions, and also those for rotating machines and push-button stations, must be within the dimensions specified in the tables for gap dimensions in the construction standard for flameproof equipment, e.g. BS EN60079-1. Factors which influence the dimension of the gap are: a. The width of the joint b. The gas group c. The internal volume of the enclosure d. The type of joint. ©. March 2010. 6.
(60) Flamepath Joints The diagrams below illustrate examples of three joint types specified in the British standard BS EN60079-1 for use in flameproof apparatus. In a flanged joint, the machined surface on the cover makes face-to-face contact with the corresponding surface on the base to give a gap dimension normally less than that specified in the tables of gap dimensions in the standard when the cover is properly bolted down. This type of joint will be used at the covers of, for example, junction boxes. Spigot joints will be used at junction box covers and motor enshields. Threaded joints are used for cover joints, cable gland and conduit entries. An adequate flamepath length is normally achieved with a thread engagement of five full threads. In contrast to BS EN50019, the most recent standard, BS EN60079-1 permits the use of flanged joints when a IIC gas such as acetylene is the hazard only if the gap is ≤ 0.04mm, has a length L ≥ 9.5mm and the free internal volume does not exceed 500 cm3.. a) Flanged joint. Interior. b) Spigot joint. Interior. c) Screwed joint. Interior. ©. March 2010. 7.
(61) Flamepath Joints Types (Rotating Machines). (d). cylindrical (shaft gland) joint. (d). labyrinth joint for shafts. ©. March 2010. 8.
(62) Flamepath Joints (other examples) Flamepaths other than those at cover joints are also necessary where, for example, an actuator spindle passes through the wall of an enclosure, or where a cable gland or conduit enters an enclosure. Examples are shown below.. Push-button spindle. Cable (gland) entry. ©. March 2010. 9.
(63) Entry by Cable Gland or Conduit The thread engagement requirements for cable and conduit entries are specified in the standard BS EN60079-1 and apply to the three sub-groups IIA, IIB and IIC. Only threaded entries are permitted for all cable glands or conduits entering flameproof enclosures – clearance entries are not permitted.. Volume ≤ 100 cm3. > 100 cm3. Thread Engagement. Axial Length. Thread Engagement. Axial Length. > 5 Full Threads. > 5mm. > 5 Full Threads. > 8 mm. As already stated the above requirements for thread engagement are specified in the latest standard BS EN60079-1: 2007, but the previous standard BS EN50018: 2000 required at least 6 full threads engagement in order to make sure that 5 full threads were actually engaged. Note: Flameproof equipment manufactured to the old British standard BS229 may have different non-metric thread forms at cable gland entries. This difficulty can be overcome by the use of certified Ex d adaptors which have compatible thread forms to suit both the entry in the enclosure and the cable gland.. ©. March 2010. 10.
(64) Unused Cable or Conduit Entries It is important that unused cable/conduit entries in flameproof enclosures are closed using appropriate stoppers, as specified in the standards, or those supplied by the manufacturer. These must be ‘component certified’ metal stoppers – plastic stoppers are unacceptable – which are fully engaged by 5 full threads. The construction standard specifies suitable types, examples of which are illustrated below.. A Screwdriver slot. Split pin. Special fastener B. Exterior. Interior C. Hexagon recess. D. Hexagon head Shearable neck. Stoppers of the type illustrated by example ‘C’ in the above diagram are available with certification markings on either the plain side or the same side as the hexagon recess. Ideally, stoppers of this type should be fitted with the plain side facing the exterior to make unauthorised removal more difficult, but may be fitted with the hexagon recess facing the exterior. Whichever way round they are fitted the certification markings must be visible for ease of identification during ‘Visual’ inspection programmes. Also the thread engagement requirements must be met. Stoppers of this type are tightened using an Allen Key.. ©. March 2010. 11.
(65) Flamepath Gap Dimensions – BS EN60079-1, Table 1. Maximum gap mm Type of Joint. Flanged, cylindrical or spigot joints. Cylindrical joints for shaft glands of rotating electrical machines with:. Sleeve bearings. Rollingelement bearings. Minimum width of joint L mm. 6 9.5 12.5 25 6 9.5 12.5 25 40 6 9.5 12.5 25 40. For a volume cm3 100 < V ≤ 500. For a volume cm3 V ≤ 100 I 0.30 0.35 0.40 0.50 0.30 0.35 0.40 0.50 0.60 0.45 0.50 0.60 0.75 0.80. IIA 0.30 0.30 0.30 0.40 0.30 0.30 0.35 0.40 0.50 0.45 0.45 0.50 0.60 0.75. IIB 0.20 0.20 0.20 0.20 0.20 0.20 0.25 0.30 0.40 0.30 0.35 0.40 0.45 0.60. I 0.35 0.40 0.50 0.35 0.40 0.50 0.60 0.50 0.60 0.75 0.80. IIA 0.30 0.30 0.40 0.30 0.30 0.40 0.50 0.40 0.45 0.60 0.75. IIB 0.20 0.20 0.20 0.20 0.20 0.25 0.30 0.25 0.30 0.40 0.45. For a volume cm3 500 < v ≤ 2 000 I 0.40 0.50 0.40 0.50 0.60 0.60 0.75 0.80. IIA 0.30 0.40 0.30 0.490 0.50 0.45 0.60 0.75. IIB 0.20 0.20 0.20 0.25 0.30 0.30 0.40 0.45. NOTE: Constructional values rounded according to ISO 31-0 should be taken when determining the maximum gap.. March 2010. 12. For a volume cm3 V > 2 000 I 0.40 0.50 0.40 0.50 0.60 0.60 0.75 0.80. IIA 0.20 0.40 0.20 0.40 0.50 0.30 0.60 0.75. IIB 0.15 0.20 0.20 0.25 0.20 0.30 0.40.
(66) Flamepath Gap Dimensions – BS EN60079-1, Table 2 Maximum gap mm Type of Joint. Flanged joints. Spigot joints (Figure 2a). c ≤ 6mm d ≤ 0.5L L=c+d f ≤ 1mm. Cylindrical joints Spigot joints (Figure 2b) Cylindrical joints for shaft glands of rotating electrical machines with rolling element bearings. Minimum width of joint L mm 5 9.5 15.8 25 12.5 25 40. For a volume cm3 V ≤ 100. For a volume cm3 100 < V ≤ 500. For a volume cm3 500 < v ≤ 2 000. For a volume cm3 V > 2 000. 0.10 0.10 0.10 0.10 0.15 0.18b 0.20c. 0.10 0.10 0.10 0.15 0.18b 0.20c. 0.4 0.4 0.15 0.18b 0.20c. 0.4 0.18b 0.20c. 6 9.5 12.5 25 40 6 9.5 12.5 25 40. 0.10 0.10 0.15 0.l5 0.20 0.15 0.15 0.25 0.25 0.30. 0.10 0.15 0.15 0.20 0.15 0.25 0.25 0.30. 0.15 0.15 0.20 0.25 0.25 0.30. 0.15 0.20 0.25 0.30. a. Flanged joints are permitted for explosive mixtures of acetylene and air only in accordance with 5.2.7. b. Maximum gap of cylindrical part increased to 0.20 mm if f < 0.5 mm. c. Maximum gap of cylindrical part increased to 0.25 mm if f < 0.5 mm. NOTE: The constructional values rounded according to ISO 21 –D should be taken when determining the maximum gap. ©. March 2010. 13.
(67) Pressure Piling. If a flammable mixture us compressed prior to ignition, the resulting explosion will be considerably higher than if the same mixture was ignited at normal atmospheric pressure. Pressure piling can materialise as a result of sub-division of the interior of a flameproof enclosure, which prevents the natural development of an explosion. An explosion at one side of an obstacle pre-compresses the flammable mixture at the other side, resulting in a secondary explosion that can reach an explosion pressure around three times that of the first or normal explosion pressure. Manufacturers, guided by relevant construction standards, must ensure that, in any crosssection within an enclosure, there is adequate free space (typically 20 – 25% of the total cross-section) around any potential obstruction, which may be a large component or a number of components. This will ensure that pressure piling is kept under control.. ©. March 2010. 14.
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