The Chemical plants, particularly those manufacturing urea are amongst the most complex plants in the chemical process industry. The severe operating conditions affect the safety of equipment, personnel involved and the environment. Different occurred accidents such as Port Neal Nitrogen Fertilizer (Dec 1994), Toulouse Fertilizer complex (Sept 2001) and Coffeyville Fertilizer Plant (Oct 2010) stresses to conduct hazard studies in fertilizer plants. Urea manufacturing process is described for understanding before conducting HAZOP studies. PHA is discussed including its basics, requirements,...