Modelling the quality of maintenance of a protection system: a case study on isolation valves used in water distribution systems
A.R. Alberti, C.A.V. Cavalcante, P.A. Scarf and A.L.O. Silva
https://doi.org/10.19124/ima.2018.001.03
Abstract
A hybrid inspection and replacement policy for a protection system is described by a mathematical model that incorporates a set of maintenance quality aspects. A three-state component failure model is assumed, with a defective state preceding failure. The quality of maintenance intervention is modelled by supposing that inspection may induce a defect and is subject to errors in the defective state judgement (false positives and false negatives). The quality of replacement is modelled by supposing that a component arises from a heterogeneous population, composed of weak and strong items. This paper presents a case study on isolation valves used in water distribution systems, that motivated the development of the model. We evaluate the impact of these quality aspects upon cost and production losses. A detailing of the context is presented, highlighting important aspects of the analysis, which should be observed when other studies are carried out in different contexts. We present the results in order to evaluate the impact of the quality aspects regarded, verify conditions that justify investment in higher quality maintenance, and obtain guidance on which aspects should be prioritized in the investment. Defect induction is found to be a key determinant of the cost-optimal policy.