How to identify threats and achieve ALARP on a big scale
THE principle of reducing major accident risks to levels that are as low as reasonably practicable (ALARP) is now typically embedded in the risk acceptability criteria specified for the engineering, construction and operation of installations presenting major accident hazards.
The principle, although essential in promoting safety improvements, introduces scoping and execution uncertainties with potential impacts on costs and schedule of major capital projects. Applying ALARP successfully is closely linked to the stages of the engineering lifecycle and the associated contracting strategy, and to fundamental factors of perception, leadership, ownership and communication. We’ll examine these links here to identify possible threats and management measures to deliver installations presenting major accident risks that can be demonstrated as ALARP.
The principle of ALARP applies to risks that are, first and foremost, assessed to fall within tolerable limits. This concept is illustrated in Figure 1 where tolerability limits are typically defined in terms of individual risk per annum (IRPA). Risk tolerability and the distinction between risks that fall within the ALARP region and risks that are tolerable are well documented1 and therefore not the subject of this article, though we note that that risk levels lying within the ALARP region are still occasionally misinterpreted as representing acceptable risk levels or risk levels that are ALARP. Risk estimates within the ALARP region of any risk tolerability framework should only be deemed as acceptable or tolerable once it is demonstrated that all reasonably practicable risk reduction measures have been implemented.
In an engineering context, the following tenets are applied to ensure that the HSE risks associated with the operations of a hazardous installation are ultimately ALARP: