Failure scenarios in water supply system by means of fault tree analysis

Failure analysis need include the entire water supply system (WSS), from source to tap. Such events can cause interruptions in the supply of water or secondary water pollution in the water-pipe network. These pollution events may occur for many reasons such as: unfavorable hydraulic conditions of the network operation (low-speed flow), combined with older pipelines or chemical instability of water. In the paper the failure scenarios analysis framework was reviewed, in order to determine likelihood of occurrence of top undesirable event (threat to water consumers) Fault Tree Analysis was used. The paper contains the methodology of the analysis and two examples of application—analysis of the whole and part of created fault tree. The analysis includes two main situations: lack of water and contaminated water delivered to consumer. The objective of the paper is to discuss the role of failure analysis for decision making process and preventive strategies. of these factors are failure events causing unreliability of the entire or part of WSS, which in consequence may lead to a loss of water consumer’s safety that should be considered in two aspects (Tchorzewska-Cieslak & Boryczko 2010): threats resulting from the lack of water or interruption in the supply of water, threats resulting from the possibility of consuming contaminated water (which may cause the loss of life or health of consumers) (Porto 2004). The main aim of this paper is to present a method for the analysis of failure scenarios in WSS using Fault Tree Analysis (FTA). The paper contains the characteristics of failure events in WSS and an example of the analysis of failure scenarios using FTA, in order to determine the likelihood of the occurrence of the top undesirable event (threat to consumers safety as a result of lack of water or restriction in water supply or consuming water with quality that is contrary to the current standard). For the purposes of this paper, operational reliability of the WSS is defined as the ability to supply a constant flow of water for various groups of consumers, with a specific quality and specific pressure, according to consumer’s demands, in specific operational conditions, at any or at a specific time. The objective of this paper is to present the failure scenarios analysis for the design and operation of water resources engineering projects.

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