RISK MANAGEMENT


TO QUANTIFY OR NOT TO QUANTIFY? THAT IS THE QUESTION...


PRACTICAL EXAMPLES OF QUANTITATIVE RISK ASSESSMENTS In the last issue Risktec introduced


BACK TO BASICS...


Quantitative Risk Assessments (QRA). Here they continue their series of articles on risk management by asking; Is there a role for QRA’s in the Wind Energy Industry?


If we jump back to our second article on Risk Management (June/July 2011), we defined risk as being the product of the likelihood of an unwanted event occurring (release of a hazard) and the severity of the resulting consequences;


The results of a QRA are numerical estimates for risk exposure that can cover the full range of consequence effects being considered (e.g. harm to the environment, plant/asset damage, programme delays, cost overruns, etc.) but are most commonly used in a health


Risk of fatality as a


result of a wind turbine blade failure/throw


Likelihood of blade failure per year


x


Probability of a blade landing at a specific location


Occupancy rate at specific location


x


Probability of a fatality from direct impact of blade


Risk=xConsequence Likelihood


Probability of loss of containment from blade


Image courtesy of Infinergy Ltd


impact [tank integrity] leading to release of gas


Figure 1: Considerations for QRA of risk from Turbine Blade ‘Throw’ on adjacent major hazard facility


x


Gas concentration at a specific location [gas dispersion]


x


Probability of ignition of release


x Risk = Likelihood x Consequence


Whilst QRAs come in a vast array of shapes and sizes, performed using a plethora of tools and techniques, in very simple terms it is a systematic technique whereby appropriate numerical values are applied to ‘likelihood’ and ‘consequence’ allowing the associated risk to be expressed in numerical terms.


Occupancy rate at specific location


x Probability of a


fatality from resulting fire/explosion


and safety context to quantify risk to people and society in general, for example by expressing risk as the frequency of fatality per annum.


68


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