A computer tool to support safe isolation for maintenance

Unsafe maintenance in process plants can cause release of dangerous materials, pipe-work failure and deviations from normal operations, etc (Hale, et al., 1998). It is reported that 30% of accidents are maintenance-related and 50% of them release harmful substances (Wallace and Merritt, 2003). Therefore, it is important that systematic hazard identification is carried out and precaution is taken before maintenance work commences. A computer-aided tool is developed as part of the HAZID system (a knowledge based software system used to identify hazards by emulating conventional HAZOP study) to help the task of identifying hazards related to maintenance work. This tool focuses on safe isolation. It serves two functions. One is to suggest an isolation boundary for maintenance. Given specific equipment items to be maintained, the system will analyze the process and instrumentation diagram (P&ID) to identify the boundary that needs to be closed off for safe maintenance. The other function is to identify the potential hazards related to the isolation tasks. This paper describes in detail how this tool is developed and a case study is used to illustrate how it works.