The present status of maintenance strategies and the impact of maintenance on reliability

Abstract

Abstract-In this paper, the most frequently used maintenance strategies are reviewed. Distinction is made between strategies where maintenance consists of replacement by a new (or "good as new") component and where it is represented by a less costly activity resulting in a limited improvement of the component's condition. Methods are also divided into categories where maintenance is performed at fixed intervals and where it is carried out as needed. A further distinction is made between heuristic methods and those based on mathematical models; the models themselves can be deterministic or probabilistic.From a review of present maintenance policies in electric utilities it is concluded that maintenance at fixed intervals is the most frequently used approach, often augmented by additional corrections. Newer "as needed"-type methods, such as reliability-centered maintenance (RCM), are increasingly considered for application in North America, but methods based on mathematical models are hardly ever used or even considered. Yet only mathematical approaches where component deterioration and condition improvement by maintenance are quantitatively linked can determine the effect of maintenance on reliability. Although more complex, probabilistic models have advantages over deterministic ones: they are capable of describing actual processes more realistically, and also facilitate optimization for maximal reliability or minimal costs.

Maintenance Tools applied to Electric Generators to Improve Energy Efficiency and Power Quality of Thermoelectric Power Plants

“…Among the oldest replacement schemes are the "age replacement" [4,5] and "total replacement" [6][7][8] policies. In the first one, a component is replaced at a certain age or when it fails, whichever occurs first.…”

Dynamic neural networks for gas turbine engine degradation prediction, health monitoring and prognosis

“…However, as pointed out by Luo et al [44], critical system failures cannot be determined based on only the time of the system operation. Consequently, in the past ten years, many utilities replace their time-based maintenance activities with efficient policies that are based on the need of the system to fulfill their needs for availability and safety [45].…”

Spinning reserve contribution using unit responsibility criterion incorporating preventive maintenance scheduling

“…The aim of PMS problem can be both economic-driven as well as reliability-driven. Economic driven minimizes total operation expenditures over a scheduling time horizon [3][4][5][6][7]; while reliability driven utilizes several reliability indices such as: expected lack of peak net reserve, expected energy not supplied (EENS), and loss of load probability (LOLP) [8][9][10][11].…”

“…The aim of PMS problem can be both economic-driven as well as reliability-driven. Economic driven minimizes total operation expenditures over a scheduling time horizon [3][4][5][6][7]; while reliability driven utilizes several reliability indices such as: expected lack of peak net reserve, expected energy not supplied (EENS), and loss of load probability (LOLP) [8][9][10][11].This paper emphasizes on minimizing the total operation and maintenance expenditures in order to investigate the economic benefits of PMS. Indeed, PMS problem is contemplated as a large scale, non-convex, and mixed integer combinatorial optimization problem which can be solved via different deterministic [3,12], heuristic [2,4,[13][14][15][16], and hybrid methods [17][18][19][20], in previous decades.…”