Conducting HAZOPs in continuous chemical processes: Part II. A new model for estimating HAZOP time and a standardized approach for examining nodes

The HAZOP organization phase entails two main tasks to ensure the success of the study, especially when reviewing complex continuous chemical processes (e.g., petroleum-refining processes). The first task deals with selecting the nodes, as we discussed in Part I of this paper. It addresses that task by proposing and justifying tools for and criteria on how to break a process into manageable sections that could be reviewed independently (i.e., nodes selection). Part II describes the development of a time-estimation model for planning HAZOP sessions. Its practical value was confirmed with field work and data analyses of five HAZOPs. Furthermore, we focus on optimizing the time spent in examining selected nodes. This papers also introduces a Deviations Structural Hierarchy (DSH) for treating deviations. Finally, considering the Nodes Selection Methodology (NSM) defined in paper I, the HAZOP time-estimation model (HTEM), and the Deviations Structural Hierarchy (DSH), we present the key tools, criteria, and guidelines for leading HAZOPs for highly complex processes.

► A time-estimation model for planning HAZOP sessions is presented in this paper.
► The paper also introduces a Deviations Structural Hierarchy (DHS) for treating deviations.
► Keytools, criteria and guidelines for leading HAZOPS in complex continuous chemical processes are presented.
► The new procedure presented in this paper, reinforces the HAZOP structure and ensures reviewing the key factors that could entail hazardous scenarios.