Investigation of Operational Hazards at Gas Depressurization Station Using HAZOP Method

Hazard and operability studies (HAZOP) are necessary for risk management and safety enhancement at municipal gas depressurization stations. The present study was performed to identify operational hazards at gas depressurization station and propose technical and management solutions for attenuating them. This study was performed in two gas depressurization stations in Isfahan Province, Iran. For this purpose, firstly, HAZOP team was built, and based on the team members’ opinions, five principal nodes were identified across the gas depressurization process: gas inlet, filter inlet, filter, heater, regulator, and odorizer. Operational parameters, design limit, and possible deviations were investigated. Required information for HAZOP worksheets were gathered by referring to textbooks, operational procedures, daily report book, and interviews with engineers and operators working at the stations. Findings: Deviations in pressure, flow intensity, temperature and corrosion at the gas and filter inlet nodes, and also those in gas flow, gas temperature, heater temperature, gas pressure, and corrosion at the heater node were determined. At the regulator node, deviations in gas pressure at upstream and downstream of the regulator, corrosion, regulator pilot, and insensitivity of the pilot to the pressure at downstream were evaluated. Finally, deviations in injection rate of odorant, gas flow, pressure, and velocity, and odor intensity were considered at the odorizer node. In this HAZOP study, causes and effects of deviations in operational parameters at five nodes in gas depressurization station were identified, and preventive and corrective actions were emphasized, such as preventive and timely maintenance, consistent inspection of pipelines, preparing a well-scheduled plan for inspecting the equipment in terms of corrosion, inspection, and design revision.