Natural Gas pipelines distribution: analysis of risk, design and maintenance to improve the safety performance Augusto Bianchini*, Filippo Donini*, Alessandro Guzzini*, Marco Pellegrini*, Cesare Saccani* *Department of Industrial Engineering, University of Bologna, Viale Risorgimento 2, 40136 - Bologna – Italy (augusto.bianchini@unibo.it, filippo.donini2@unibo.it, alessandro.guzzini@studio.unibo.it, marco.pellegrini3@unibo.it, cesare.saccani@unibo.it) Abstract: The paper shows an overview of general characteristics, design, maintenance and hazards of natural gas transportation systems. Paper analysis starts from the description of the natural gas distribution systems, which represent the final section of the natural gas transportation. Since accidents on distribution gas system could threatening the urban safety, risk analysis needs to be assessed. For this purpose, the main hazardous consequences that may happen after a failure of the natural gas pipeline are defined. Correct design, installation and maintenance are required to reduce both frequency and impact of these accidents: a brief description of the principal technical requirements is reported. Keywords: Natural Gas pipeline, Risk assessment, Release rate, Natural gas pipeline design. 1.The Natural Gas Distribution System 1.1 Main characteristics and components Natural Gas (NG) transport from wellhead to residential or business as clean and efficient source of energy needs of a complex transportation system that have to be safety and reliable. NG moves through a complex pipeline system, which includes elements like pipes, valves, compression stations, pressure regulation stations, metering stations, pressure vessels, pulsation dampeners and relief valves that vent NG when safety conditions are not assured. Figure 1: NG compression station. There are three major type of NG pipelines ranging in size and inside pressure: gathering systems, transmission systems and distribution systems. Gathering pipelines gather raw NG from production wells; transmission pipeline transport NG to pre-processing plants or storage facilities. Distribution system is the last part of the transportation system and distributes NG to the end- users. Figure 2: NG distribution system. In Italy, Gas distribution system is composed by: 1. A first pressure reducing station (REMI): NG comes from the national transportation system, conducted by XX Summer School "Francesco Turco" - Industrial Systems Engineering 243