Reliability Analysis of Two Unit Standby Model with Controlled and Uncontrolled Failure of Unit and Replacement Facility Available in the System

Planning a highly reliable and efficient system has always been a primary interest for reliability engineers by devising the powerful design strategy and employing effective repair and replacement policy. Keeping in view this, the basic aim of this paper is to analyze the reliability of a system which comprised of two units A and B in which unit A is functional and B is held standby. Unit A after failure may be controlled or uncontrolled. The failed unit undergoes for repair in the controlled unit. If the repair of a unit is not controlled then it is replaced by a new one. Upon the breakdown of operational unit A, unit B come becomes active instantaneously. Unit B after failure is repaired by regular repairmen. System failure takes place when both the units quit serving. The unit serves as good as a fresh after preventive repair and replacement policy. The regenerative point technique has been used to obtain the expression for several reliability measures. Finally, the graphical behavior of MTSF and profit of the present model has been observed for arbitrary values of parameters and costs.

Optimal Maintenance Policy for Second-Hand Equipments under Uncertainty

This chapter addresses a maintenance optimization problem for re-manufactured equipments that will be reintroduced into the market as second-hand equipments. The main difference of this work and the previous literature on the maintenance optimization of second-hand equipments is the influence of the uncertainties due to the indirect obsolescence concept. The uncertainty is herein about the spare parts availability to perform some maintenance actions on equipment due to technology vanishing. The maintenance policy involves in fact a minimal repair at failure and a preventive repair after some operating period. To deal with this shortcoming, the life cycle of technology or spare parts availability is defined and modeled as a random variable whose lifetimes distribution is well known and Weibull distributed. Accordingly, an optimal maintenance policy is discussed and derived for such equipment in order to overcome the uncertainty on reparation action. Moreover, experiments are then conducted and different life cycle of technologies are evaluated according to their obsolescence processes (accidental or progressive vanishing) on the optimal operating condition.

Semi-Markov model for the Kaplan preventive repair system for water turbines with periodic inspection of the technical condition

The paper presents a semi-Markow model of a preventive repair system by age, implemented in hydroelectric power plants with Kaplan turbines. In the case of the analyzed technical objects, the profit per time unit is considered as the criterion of the quality of functioning. On the basis of the adopted assumptions, for the developed mathematical model, formulas describing the criterion function were determined and the conditions for the existence of the extreme (maximum) of this function were formulated. The proposed method makes it possible to determine the optimal time for preventive repair of the considered technical objects. The theoretical considerations presented in the work are illustrated by a computational example developed on the basis of data obtained from the actual operating system of Kaplan water turbines with a rated power of 120 kW.