Complete information is needed for comprehensive risk assessment and management of pipelines. However. obtaining information using quantitative risk assessment (QRA) (probabilistic model) is not readily possible. Thus, in this research. using probabilistic and indexing models, an algorithm is developed, which overcomes most of the limitations of the models, and is an appropriate technique for the comprehensive risk assessment and management of pipelines. For this reason, 60 feed and product pipelines of the Mahshahr Petrochemical complexes were evaluated and chlorine pipeline was selected based on high-hazard distances for risk analysis Furthermore, the relative risk indices were also determined in all parts of the pipeline. The failure rate of the pipeline was assessed oil the basis of different failure causes Heavy Gas Dispersion Model developed by ALOHA software was used for the consequence analysis of chlorine gas in different concentrations. Subsequently, the results of the relative risk assessment indices were used as an adjusting factor to correct the pipeline failure rate and to develop an algorithm for the comprehensive risk assessment technique. Finally, sensitivity analysis of the algorithm was carried out The present algorithm enables the identification of most of the pipeline failure causes. Application of historical incident data is not only important in risk management and emergency response plans. but is also helpful in evaluating the risk by using acceptable risk criterion, such as "as low as reasonably practicable" (ALARP). (C) 2009 Elsevier Ltd. All rights reserved