Comparative Safety Assessment of Chlorination Unit in Tehran Treatment Plants with HAZOP & ETBA Techniques

Abstract

Different techniques and tools have been introduced for the analysis of process systems that each has their own capabilities and limitations namely HAZOP and ETBA. One of the process systems which require to be analyzed by these techniques is the chlorination unit of the treatment plants. Due to frequent use of chlorine, an intrinsically hazardous gas, this unit is among the most critical units of a treatment plant. In this study, the safety- related features of the chlorination unit in Tehran treatment plant was investigated employing two methodologies: HAZOP and ETBA and the results from the two techniques were compared. The decision criteria to choose the best methodology was based on six factors (number of identified risks, the cost of eliminating intolerable risks, the number of identified human errors, the identified risk levels, the time and budget required to perform the assessment). Considering the fact that HAZOP and ETBA, each seem to be preferable in accordance with some of these factors, it was difficult to decide on the proffered methodology. In order to determine the best methodology, the AHT (Analytical Hierarchy process) was used. Results from this technique indicated that ETBA is more preferable to serve the purposes of the present study.