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Hazardous area classifications (SANS10108) - EE …

January 2005 - Vector - Page 38 INSTALLATIONS& CONTRACTINGArea classification (in South Africa betterknown as the classification of hazardouslocations) plays a pivotal role in explosionprevention the technology of preventingexplosions due to flammable gases,vapours, mists, dusts and fibres in surfaceindustry and mines. area classification canbe defined in several ways, for examplezpart of major Hazardous installationrisk analysis;za quantification of the probability thatan explosive atmosphere will occur, orzdetermining the appropriate zones andzone geometries associated withsources of release (see Fig. 1), as wellas the properties of the explosiveatmosphere including gas group andtemperature class that can occur inthese concept of area classification hasremained the same over the years, but theapplication has grown in detail requiringthe classifier to be in command of a certainknowledge and skills base.

January 2005 - Vector - Page 40 protection may be involved and will introduce an MIE to the scene. MIEs are sometimes their own worst enemies. Having been exposed to SANS

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Transcription of Hazardous area classifications (SANS10108) - EE …

1 January 2005 - Vector - Page 38 INSTALLATIONS& CONTRACTINGArea classification (in South Africa betterknown as the classification of hazardouslocations) plays a pivotal role in explosionprevention the technology of preventingexplosions due to flammable gases,vapours, mists, dusts and fibres in surfaceindustry and mines. area classification canbe defined in several ways, for examplezpart of major Hazardous installationrisk analysis;za quantification of the probability thatan explosive atmosphere will occur, orzdetermining the appropriate zones andzone geometries associated withsources of release (see Fig. 1), as wellas the properties of the explosiveatmosphere including gas group andtemperature class that can occur inthese concept of area classification hasremained the same over the years, but theapplication has grown in detail requiringthe classifier to be in command of a certainknowledge and skills base.

2 Areaclassification is no longer a part-time activityfor an engineer - it has become a team-based job facilitated by an expert. Thisbrings with it certain disadvantages, but alsoleads to safer plants in Hazardous locationsand to cost locationscommonly found in industryHazardous locations occur in allunderground coal mines. In industry, it isestimated that more than 50% of goodsand materials produced in this country aremanufactured in facilities with hazardouslocations. If the knock-on effect is included,it becomes clear that the manufacturingindustry in a country such as South Africawill grind to a halt were it not for explosionprevention and in particular for areaclassification as one of its main review of typically found hazardouslocations is given are various industries in which thepresence of flammable gases, vapours anddusts in certain places at certain times isinevitable and where the area classificationmust be determined.

3 These includezchemical and petrochemical;zfood and beverage;zpharmaceutical;zpaints and frequently involved in area classification studies as the so-called expert, theauthor wishes to share, from personal experience, some principles that can beapplied by owners and managers in their quest to make their plants safer places ofwork. In addition, the aim is to create greater awareness among plant owners, theirinsurers and safety facilitators, their electrical and instrumentation contractors, andsafety inspectorates of regulatory and other area classifications ( sans10108 )by Dr. Johannes G Auret, ExproblabsFig. 1: Typical area classification of a surface plant whereexplosive vapours are 2005 - Vector - Page 39 MinesAlthough coal mines are traditionally theprime focus for explosion prevention dueto the flammability of coal and of methanedust carried by the coal, hard rock minessuch as gold and platinum mines in SouthAfrica have reported the presence offlammable gases (hydrocarbons andhydrogen)

4 On a regular basis in recentyears, accompanied by a series ofdestructive explosions that has led to thestrict application of explosion risk analysisand explosion prevention in this processingplants associated with minesThese plants are categorised separatelybecause of their legal status as beingcontrolled by the Mine Health and SafetyAct and cover a wide range ofpetrochemical and minerals processingplants, including refineries and of the improved modern-day reagentsused in platinum concentrators are unstableand decompose into flammable products,as a result of which explosion preventionhas been introduced in reagent-handlingplants. Recent incidents in concentratorshave shown clearly that, although safety andexplosion prevention procedures have beendeveloped, these must be improved coal mining, surface crushing plants, coalstorage silos, coal beneficiation plants andbulk handling and loading facilities cancontain Hazardous areas due to theformation of coal dust clouds and thick legal compulsionArea classification is a legally enforcedactivity as shown 4(1)EIR 4(1)EIR 4(1)EIR 4(1)EIR 4(1)

5 No person shall install or permitor require the installation of an electricalinstallation, other than in accordance witha safety standard incorporated into theseregulations under section 36 of the Act,provided that items of an electricalinstallation not covered by such safetystandard and the conductors between thepoint of supply and the point of control shallbe installed in accordance with the by-lawsor regulations of the supplier 8(1)EMR 8(1)EMR 8(1)EMR 8(1)EMR 8(1) No person may useelectrical machinery in locations where thereis danger of fire or explosion owing to thepresence, occurrence or development ofexplosive or flammable articles, or whereexplosive articles are manufactured,handled or stored, unless such electricalmachinery, with regard to its constructionrelating to the classification of the hazardouslocations in which it is to be used, meets therequirements of a safety standardincorporated for this purpose in theseregulations under Section 36 of the manager shall identifyand define any Hazardous area referred toin regulation 1(11A)(ii) in or on a mine or ata works and record it on a plan or in aregister provided for that a decentclassification (the Do s andDon ts)We know that legally the plant or mine ownercarries the can for area classification .

6 Howdoes he achieve this in practice?Role of ownerIt is fine if the owner wants to carry out hisown area classification , as long as theavailability of in-house competence can bedemonstrated, if necessary in a court of , once a plant is commissioned,explosion prevention is often left in the careof maintenance staff that have an imperfectunderstanding of the , on the other hand, is evenless well informed and is not able toconstructively support these maintenanceefforts. The result is that bad practicesabound and that the statutory requirementsare seldom complied with, including situation will improve once a nationallyrecognized technical qualification thatprovides explosion prevention as aspecialized subject has been established,but due to its multi-faceted nature and thecomplexity of the most current standards tobe applied, the use of external expertise isoften the appropriate , this does not mean for onemoment that the owner can abandonresponsibility for participation in theclassification process!

7 The classificationbelongs to the owner, not a third party thatcomes in and disappears again in the of Hazardous locations shouldonly be undertaken by well experienced,multidisciplinary teams. By definition, theowner knows best about the inner workingsof his plant, and finer details such asmaintenance approach and effectiveness,cleaning methods, use of sampling points,and permit-to-work procedures, to namebut a few, lies with a new plant a typical classification teamcould be made up as follows:zMain engineering constructioncompany: project manager, process,electrical/instrumentation, mechanical,pipingzSubcontractorszClient/ end user/plant owner: projectmanager, process, electrical/instrumentation, safety a review of an existing plant with an in-house upgrade, the engineering companyinvolvement will of course fall specialistsIt is a fact of life, resented by many membersof the profession, that electrical engineersand electricians are often entrusted with -or shall we say forced to take responsibilityfor - area situation stems from the fact that whena new plant is designed by an engineeringteam, the electrical engineer is normallyfamiliar with the fact that explosion protectedapparatus has to be used in hazardouslocations.

8 He or she then starts asking someprobing questions and, if persistent enoughas project engineers normally are, will in90% of cases land up with the job to sortout the classification . The recent advent ofconsultants with the time and interest tospecialize in the field has saved the life ofmany frustrated electrical engineers on theverge of mental of small and medium-sized plantsoften rely on an electrical contractor for theelectrical work. Of course, if the installationinvolves flammable materials, a goodelectrician (and fortunately there are many)that knows his installation standardSANS 10142-1 will recognize that explosiontcAnoitalugeR)wolebees(elbacilp pAdradnatsrofelbisnopsersiohWnoitacifiss alcdnahtlaeHlanoitapuccOtcAytefaS)3991fo 58tcA()1(4 RIE)1(8 RME80101 SNAS tnemeganamtnalPtcAytefaSdnahtlaeHeniM)69 91fo92tcA()1( ()snoitacolsuodrazahsnoitalugeRyrenihcaM lacirtcelE=RMEsnoitalugeRnoitallatsnIlac irtcelE=RIEnoitalugeR=RJanuary 2005 - Vector - Page 40protection may be involved and willintroduce an MIE to the are sometimes their own worstenemies.

9 Having been exposed to sans10108 , the national standard that providesthe basis for area classification , an MIEoften assumes the role of expert in mattersof area classification as well, and oftencarries out the little task single-handedly!Unfortunately he does not realize that he isexposing himself to severe legalconsequences if a mistake is made. Inaddition, the position of being judge andjury at the same time (he will also normallyspecify the apparatus that must bepurchased as a result of his classification )causes major anti-trust issues and theproject ends up as a tug-of-war betweenthe MIE who is belatedly trying to ensure asafe plant at the expense of a nice profitmargin and the owner who has lost somefaith in the MIE and is trying to cut classification team approach is a self-regulating one as external expertise can bebrought in; the interests of all parties areconsidered; proper records are generatedand it is legally defendable as thereasonable-man the technical basefor classifications , but are theyuser-friendly?

10 This subject is included because the varietyof standards and different interpretationsof these standards has caused many plantowners to consider area classification as ablack art or a technical rules for classificationstandards for area classification have beenavailable for many years. Some of the bestwork has always been forthcoming fromthe chemical and especially petrochemicalindustries, initially from large individualcompanies ( the then ICI) and later fromnational technical organizations andeventually national, regional andinternational standards writing the scientific foundation for zone sizesand geometries in particular was somewhatinstinctive and based on practicalexperience, but current standards are prettysolidly based on facts and of the old approachOne is the 180m distance from the workingface allocated for compulsory hazardouslocations in an underground coal the main reason lies in the typicalmaximum length of power cables, thisfigure allowed switchgear to be placed justoutside of the Hazardous location.


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