WORKING AT HEIGHTS - Wind Energy Network

RISK MANAGEMENTTo quantify ornot to quantify?that is thequestion...Practical examples of Quantitative Risk AssessmentsIn the last issue Risktec introducedQuantitative Risk Assessments(QRA). Here they continue their seriesof articles on risk management byasking; Is there a role for QRA’s in theWind Energy Industry?Back to basics...If we jump back to our second article onRisk Management (June/July 2011), wedefined risk as being the product of thelikelihood of an unwanted event occurring(release of a hazard) and the severity ofthe resulting consequences;The results of a QRA are numericalestimates for risk exposure that cancover the full range of consequenceeffects being considered (e.g. harm tothe environment, plant/asset damage,programme delays, cost overruns, etc.)but are most commonly used in a healthRisk of fatality as aresult of a wind turbineblade failure/throwLikelihood of bladefailure per yearxProbability of a bladelanding at a specificlocationOccupancy rateat specificlocationxProbability of afatality from directimpact of bladeRisk = Likelihood x ConsequenceImage courtesy of Infinergy LtdProbability of loss ofcontainment from bladeimpact [tank integrity] leadingto release of gasxGas concentration at aspecific location[gas dispersion]xProbability of ignitionof releasexOccupancy rateat specificlocationxProbability of afatality from resultingfire/explosionFigure 1: Considerations for QRA of riskfrom Turbine Blade ‘Throw’ on adjacentmajor hazard facilityRisk = Likelihood x ConsequenceWhilst QRAs come in a vast array ofshapes and sizes, performed using aplethora of tools and techniques, in verysimple terms it is a systematic techniquewhereby appropriate numerical values areapplied to ‘likelihood’ and ‘consequence’allowing the associated risk to beexpressed in numerical terms.and safety context to quantify risk topeople and society in general, for exampleby expressing risk as the frequency offatality per annum.68www.windenergynetwork.co.uk