Reliability of valves and section isolation

Section valves are essential for isolating incidents such as pipe bursts. In older networks where incidents occur most, valves have aged and their reliability has decreased. In addition, design rules or guidelines to locate valves in a network to ensure continuity of supply and to minimize effects on customers are generally lacking, as was concluded at an international workshop on valves in 2001.

Within the framework of the joint research programme of the Dutch water companies a methodology has been developed to translate the reliability of individual valves or clusters of valves into the reliability of supply for one or more sections in a network. The reliability of a section is characterised by performance indicators such as Customer Minutes Lost (CML): the average time in a year that a connection is without water due to an incident in the network. The methodology enables water companies to set priorities within their valve maintenance strategy, based on critical performance indicators, costs and maintenance frequency.

The methodology was translated into software and applied to a case study of the Dune Water Company of South Holland. The case study proved that the methodology and the software work well. Specific changes such as (re)location and enhancing the reliability of valves improve the performance and reliability of the network. As it is an emergency provision, investments can be done at ‘natural’ rehabilitation moments.