India today has a vast network of underground pipelines being used for transportation and distribution of natural gas. Big power plants, fertilizer plants & other industrial enterprises are the main consumers of natural gas as on today. However, with the increase in its popularity, it is now being used in the domestic sector as well as a fuel in the automotive sector in the big metropolitan cities. To take the gas to such end users who are located within the boundaries of a main city, there’s need to build up city gas distribution pipeline networks. Such networks have already been developed in the cities of Delhi, Mumbai, Vadodara, Surat, Agra/Firozabad, Kanpur and many more such networks are being planned in the near future. Looking at the available infrastructure and layout in typical Indian cities, it becomes a difficult task to build up such a city gas distribution networks in the absence of separate corridors for the competing utilities. Depending upon the pressures, flow and economic criteria, these networks can either be constructed using steel pipelines, polyethylene (PE) pipes or a hybrid system of both PE & steel pipelines.
Unlike cross-country pipelines which runs straight for kilometers through open fields, city gas distribution network are more complex in nature. These are laid in densely populated areas and there are a large number of branches in the network catering to the need of users in different localities within a city. Though, these are much smaller in length and size than cross-country pipelines, the network in a city is much more distributed and varied. Increased number of branches means more number of joints, bends, reducers, fittings etc. in the network apart from more number of delivery points for the supply of natural gas. Coupled with all these factors, the pipelines have to pass through the congested areas within the city criss-crossing the various other underground utilities. Due to the various activities by third party/ other agencies within the city area, the risk of damages and accidents is all the more high as compared to cross-country pipelines. All these factors call for greater in-built safety systems in the network and the need of special preparedness to handle any emergency situation.
The paper presents detailed study and explanation of the various hazards and issues related to emergency preparedness to handle an unprecedented situation in City Gas Distribution Networks with the help of a case study prepared on one of incidences in City Gas Distribution Networks in India.