8.4.1 Developing the task inventory

The first stage of criticality analysis is the development of a task inventory. A task inventory is a high level description of the various human activities in the system of interest. Often, the task of inventory is classified in terms of the main engineering areas in the system. For example in a refinery, activities associated with process units such as furnaces, distillation columns and cat crackers, may be the natural way to organise the task inventory. In the railways, tasks might be organised into groups such as train operations, signalling, train maintenance, and trackside activities.

Often there are discrete stages of operation that can be identified such as start-up, routine operation and shutdown. In the marine and aviation environments there are phases of operation such as starting and completing a voyage or flight sector that will have associated human activities. Because of the wide range of systems that HIRAM might be applied to, it is difficult to stipulate rules for organising the task inventory. However, it must be comprehensive to ensure that no significant activity (in terms of risk potential) is omitted.

Initially, the activities will be considered at quite a high level of detail, e.g. carry out maintenance on system X . The criticality screening criteria, discussed below, are then applied at this level to eliminate areas that do not require detailed application of human reliability techniques. If the criteria cannot be applied at this coarse level of detail, it will...