QUANTIFYING THE TOLERABILITY OF POTENTIAL IGNITION SOURCES FROM UNCERTIFIED MECHANICAL EQUIPMENT INSTALLED IN HAZARDOUS AREAS

摘要

The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) place a requirement on the operators of equipment located in hazardous areas to ensure that equipment cannot produce an ignition source. Certified electrical equipment has been widely available for a number of years but certified mechanical equipment has only been produced for the last 10 years. The DSEAR ACOP states, 'Equipment/protective systems at the workplace can continue to be used provided that the assessment indicates it is safe to do so.' Guidance on how to carry out this assessment can be taken from BS 13463-1:2009 [2], 'Non-electrical equipment for potentially explosive atmospheres — Part 1: Basic method and requirements'.This standard states that the tolerability of the potential ignition source is proportional to the hazardous zone where the machine is installed. What the standard does not do, is fully define what is meant by a rare failure or an expected failure with respect to existing equipment.ABB has developed a methodology that defines the tolerability of these failure rates and then determines the suitability of equipment using a semi quantified risk assessment. This process uses failure data and potential mitigating measures to either justify the continued use of the equipment or specify extra safeguards that need to be implemented in order to assure the continued use of the machines.This paper discusses the practical experience gained in carrying out studies using this methodology and gives real worked examples from a study carried out at SRM Ltd., Sunderland Ocean Terminal site.