The Control of Major Accidents and Hazards Directive-implications for electrical and control engineers

The Control of Major Accidents and Hazards Directive is the replacement of an existing regulation which came out of the EEC (Seveso Directive) and is known as CIMAH in the UK, the scope of the newer directive is wider and will require to be adopted within industries which have no track record of managing such legislation. The author describes a case study which is a safety report within the existing CZMAH regulations which will be updated to meet the new requirements. The case study is that for an agrochemical active ingredient plant, the utility in question is the power system. In the event of a power system failure the operation of some critical drives will cease which will prevent the circulation of cooling water to the chemical reactors which at certain stages of the process can be exothermic, the failure could lead to over pressurisation of the reactor leading to the release of toxic chemicals into the environment. Options to counter the probability of failure are many and varied from fully installed spare pumps through to emergency shut down systems to take the process through to a safe state. The chosen system was a closed loop cooling water system with a cooling tower and three pumps; of the three pumps one would be operational, one standby and one available for maintenance