No abstract

Natural gas is used as fuel in industries, power plants, commercial installations, and households. In its application, natural gas leaks can be considered as a major hazard because of its flammable and explosive nature. In addition to fuel, heat and oxygen sources, fires and explosions can occur if the concentration of natural gas in the air is between Low Flammable Limit (LFL) and Upper Flammable Limit (UFL). If the release of natural gas is not ignited, it will immediately form a Vapor Cloud Explosion (VCE) that can cause an explosion if it meets ignition point. Therefore, a research on dispersion patterns in a particular area or space is needed to minimize hazards and to develop safety procedures and regulations. This research aims to determine the external parameters that affect the dispersion and explosion caused by natural gas by using FLACS software from PT. Gexcon Indonesia. This software can display overpressure graphs of time and 3D visuals of simulations. The external parameters consist of vent size (5.4 m2 and 2.7 m2), wind direction, lighter position (center and back), day and night condition, and the presence of a obstacle (with and without obstacle). From the research results by the simulations, it is obtained that the highest overpressure value when there is an obstacle with a vent size of 2.7 m2; wind direction from the north; night condition, and back ignition point is 0.503 bars at 40, 835 s which can cause most buildings to collapse and the death rate to increase.

Construction of new highways, buildings, airport runways and other facilities is often planned at locations where aboveground pipelines are present. Relocating such lines can be extremely expensive in terms of shutdown time and new pipeline materials. Lowering this existing pipeline can have big cost benefits. The line can be lowered while remaining in service with no lost production and the cost of such lowering an existing pipeline section is relatively cheap. In this paper, the calculation method with both analytically and numerically are discussed and explained in a 28 in pipeline lowering process while keep the pipeline is safe and still in-service.