A COMPARISON OF THE HAZARD AND OPERABILITY (HAZOP) STUDY WITH MAJOR HAZARD ANALYSIS (MHA): A MORE EFFICIENT AND EFFECTIVE PROCESS HAZARD ANALYSIS (PHA) METHOD by Paul Baybutt and Remigio Agraz-Boeneker

The Hazard and Operability (HAZOP) study is the most commonly used process hazard analysis (PHA) method in the process industries. While the HAZOP method provides a more thorough and complete treatment than other classical PHA methods, HAZOP studies tend to be tedious and time-consuming which can compromise the quality of the work performed. Major Hazard Analysis (MHA) was developed in an attempt to overcome these disadvantages of the HAZOP method. The HAZOP method requires PHA teams to consider a variety of deviations from design intent and brainstorm causes of the deviations. Unfortunately, it is difficult for PHA teams to select only those aspects of design intent that will result in the identification of issues within the scope and objectives of the PHA. Consequently, effort is often expended in HAZOP studies on issues that turn out to be unimportant. MHA starts with the direct identification of pertinent initiating events for hazard scenarios. PHA teams using MHA find it a more sensible and understandable approach. In addition, they are more willing to participate in the study since immediate dividends are evident from their work. This paper presents comparisons of the results of PHAs performed using both MHA and HAZOP. Generally, MHA studies can be performed in substantially less time and identify more hazard scenarios than HAZOP studies. While MHA was developed to address the types of hazards that arise from the release of toxic, reactive, flammable and explosive materials from processes, it has been extended to look at other hazards such as overpressurization and entrapment by moving equipment. In this form, it is called Direct Hazard Analysis (DHA) and is used in combination with the Hazard Identification (HAZID) method. Such applications are also described in this paper.