Liquid ammonia is the basis of a variety of products, ranging from fertilisers, important intermediate chemical raw material (such as nitric acid and ammonium hydroxide), cosmetics, up to explosives. It is a very toxic product, requiring special care when transported. This paper shall present an automated leak detection system (i. e., without human intervention for shutting pumps down) for a short (approximately 6 kilometres long), 6 inch., liquid ammonia pipeline located at the city of Cubata˜o, state of Sa˜o Paulo, Brazil, within the bounds of a fertiliser producer. The pipeline runs from a Terminal (which is a port) down to a fertiliser complex, where the ammonia is used as raw material to produce ammonium nitrate. There is approximately 3.5 km of buried pipes, as well as 2.5 km of aerial ones. A special set of insulation layers is coating pipeline segments in order to keep ammonia in an undercooled temperature (and showing an undercooled liquid behaviour, as a consequence). The selected leak detection system is based on statistical concepts, using the SPRT (Sequential Probability Ratio Test) sampling technology. The main idea is to establish an automated procedure in which the LDS is capable of sending an alarm signal directly to the SCADA, to shut down pumps, without human intervention. The system architecture is covered, as well as the details on the pipeline hydraulics and ammonia transport properties (especially density and viscosity). Finally, initial field trials data are provided and analysed.

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