THE RISK AS A MEASURE OF SYSTEM SAFETY

Water supply system (WSS) is characterized by its continuous work and requires high reliability level for its operating as well as for its safety System operating is inseparably connected with the possibility that different failures (undesirable events) occur. The most often they have random character and then they can be described by the classical methods used in the reliability engineering including the probabilistic methods but sometimes they are the consequences of the events which can cause the catastrophic situation. Events of this type cause the so called domino effect that is a chain of the undesirable events which very often develops according to some definite scenarios. In many cases the consequences of such events can be very serious for water consumers as well as for water pipe companies. The basic measure describing WSS safety is risk and the elaboration of the model to analyze risk connected with WSS will allow to use the safety barriers properly. The paper presents paradigms of risk analysis in WSS in the aspect of improving safety for water consumers.