Risky Analysis

The current answer to all hazardous area safety problems is that a risk analysis should be compiled by the plant operator, or by some hired ‘expert’. In the particular case where a plant with ‘potentially explosive atmospheres’ is being operated within the European Community then the risk analysis for the complete plant should have been completed by the end of June 2006.

The temptation is to believe that the risk analysis is an easy alternative to using the combined area classification and apparatus selection techniques, which have been used in the past. It has to be appreciated that the current accepted code of practice is based on a pragmatic approach to known problems, and is applicable to electrical equipment in hazardous areas. It provides an adequately safe solution to most situations but does not necessarily stand up to a detailed analysis of risk.

If a risk analysis is attempted then an initial requirement is to define an ‘acceptable’ risk. The ATEX Directive [1992/92/EC] relates only to the ’safety and health of workers’ but it is unlikely that the other consequences of an explosion can be ignored in any reasonable risk analysis. The problem is what is acceptable and to whom has it to be acceptable? The questions of how frequently can someone be killed or injured and/or how much money shall be invested to reduce the frequency of such an occurrence are questions no standards writing committee will ever address. There is also a problem in knowing what is the statistical probability of failure of any of the accepted methods of protection. The only certainty is that the probabilities are not identical, or even very close. Any analysis demonstrates that intrinsic safety is the safer choice, wherever it can be used.

The theoretical possibility of writing a risk analysis without using the conventional approach of area classification [IEC 60079-10] and the choice of equipment in accordance with the code of practice [IEC 60079-14] is not worth pursuing. The use of the conventional approach of area classification and apparatus selection avoids rather than answers the difficult questions but the technique is generally accepted and satisfies most authorities. More importantly it has provided a proven adequate level of safety for many years.

The practical solution to the use of electrical equipment in hazardous areas is to use the existing techniques, and all the use of other forms of risk analysis are for those exceptional circumstances and for the indulgence of those with time on their hands. The risk analysis of hazards created by mechanical equipment is a new and separate subject. This requires much greater expertise, is fraught with unanswered questions and has no history of applicable standards.

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