Hazard Identification and Quantitative Risk Assessment of Petrochemical Storage Terminal

Abstract

Hazard Identification and Quantitative Risk Assessment Techniques are two of the most important techniques used in process industries. Hazard iden- tification uses many data like chemical properties, toxicity etc. and different analysis methods to prevent and mitigate hazards in process industries and stor- age facilities. The approach must be determined based on the process being analyzed. In this report many literatures like Application Guides, research pa- pers and Standards are reviewed and based on that different Hazard Identifi- cation Techniques like HAZOP, FMEA, and FTA are explained with example worksheets. HAZOP Technique was selected to identify the hazards involved in a Petrochemical storage terminal.The most critical identified hazards in HA- ZOP study is taken as scenario for QRA study of Petrochemical Storage Ter- minal. HAZOP was selected because of global acceptance and high reliability. HAZOP Study report and supporting documents are given in appendix. Major consequences in the operations were identified in HAZOP and will be used as scenarios in QRA study. Quantitative Risk assessment is a method for comprehensive under- standing of the risk from a particular process or operation. Basically it is math- ematical modeling tool to quantify the risk involved in any operation. It has two parts one is consequence part and another is risk part. Risk is calculated by multiplying frequency with the consequence. To find consequence, a model for the particular scenario is formed in Phast. As an example to find the con- sequence of leakage from the storage tank of gasoline, a model of storage tank with its details of storage capacity, physical dimension and storage condition are developed. Respectively weather setup as per the meteorological conditions are figured out and developed for the study as a day and night condition. In spe- cific scenarios leak sizes are identified e.g. 10mm leak in gasoline storage tank. Results in terms of radiation, concentration and shock wave due over pressur- ization are given for individuals weather conditions. The study results are for different cases of fire like Jet Fire, Pool Fire, Flash Fire and Fireball etc. For risk calculation the consequence results are taken to the Phast Risk software where it is required to setup the run rows for the study. The distance traveled by different wind velocities in 16 wind direction is calculated and setup with run row to find its effects on risk. In theoretical concept the risk defined as the multiplication of consequence with its frequency. Frequency means the rate of failure of equipment’s, vessels, pipelines, road tankers etc. The failure frequency can be calculated by two different approaches, Event tree Analysis and Fuggi Method. The calculated frequency is combined with the consequence model to identify the overall risk. There are various sources to identify the fail- ure frequency like UK hse guidelines, TNO purple book and OGP guidelines etc. Ignition sources inside or nearby the facility has also one of the factor which is involved in risk calculation. Similarly on site and off site population is the main factor which plays an important role in calculation of individual risk as well as the societal risk (FN curve). Individual risk is the risk to working personnel’s in that area. Societal risk is the risk and number fatalities per year because of the event failure. Risk Assessment method is used as per UK HSE guidelines to assess the results in terms of risk. The plotted graph is divided in three part unacceptable, ALARP (As Low as reasonably practicable) and ac- ceptable region. Based on RA assessment the mitigation measures are given to reduce the r overall risk. The mitigation measures will be in terms of frequency reduction or consequence reduction.