Keywords

1 Introduction

There are various types of maintenance programs that power plants can use by selecting a right maintenance strategy [1]. Hence the decision of determining the strategy for power plant machinery maintenance is most significant. There is a dearth of development and applicability of an Analytical Hierarchy process (AHP) in selecting maintenance strategy for power plants [2]. In this section the selection of maintenance strategy for power plants has therefore been presented using the analytical hierarchical process. Decisions associated with determining appropriate machine maintenance require the integration of (1) commercial (2) engineering (3) operational (4) safety, health, and environmental (SHE) issues. The important factors identified in maintenance strategies are criticality of machines (CM), Cost (C), availability (A), reliability (R),maintainability (M), maintenance support facility (MSF), SHE, condition monitoring facility, ease of maintenance [3, 4]. A set of questionnaires are designed and a survey was made from the respondents about their opinions. A five-point scale is used for each of the factor/criteria relating to the equipment selection problem (Fig. 1) and the respondents were asked to rate [5, 6].

Fig. 1
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Five scale for questionnaires

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2 Literature Review

A manufacturer’s overall business success will be determined by the following integrated dimensions of performance: fitness of the manufacturer’s products for use and their producibility. History has left the development and management of availability performance with great room for advancement. In this respect, design of the best maintenance strategy will play a great role. Researcher Richard G Lamb has given importance of Availability engineering and management for manufacturing plant performance in the year 1964. The researcher Suleyman Ozekci pointed out that the deterioration and failure process depends on the environment so that the failure rate at any time is a function of the prevailing environmental state. This necessitates the use of the intrinsic age of a device, rather than the real age, in reliability and maintenance problems n view of the fact that choosing of the most suitable maintenance strategy for different equipment is a crucial decision for managers, a large number of studies have been devoted to this field of research. In the literature, Murthy and Asgharizadeh (1999) [7] recommended a methodology based on game theory for selection of maintenance strategy for the companies which outsource the maintenance operations. Almeida and Bohoris (1995) [8] discussed a brief review of different decision theory concepts along with their applicability in the choosing of the most appropriate maintenance strategy. Bevilacqua and Braglia (2000) [9] proposed a multi criteria decision making (MCDM) method based on AHP. In this research sufficient attributes have been considered in the form of a crisp MCDM method. Bertolini and Bevilacqua (2006) [10] selected maintenance strategy for a set of centrifugal pumps used in an Italian oil refinery by using a hybrid method of goal programming and AHP. Al-Najjar and Alsyouf (2003) [11] proposed a combination of fuzzy inference system (FIS) and simple additive weighting (SAW), with considering a few failure causes as attributes, to make the optimum decision about maintenance strategy. Azadivar and Shu (1999) [12] proposed a new method considering 16 different characteristic parameters as criteria for each class of systems in a just-in-time environment. Gaonkar et al. (2008) [13] and Wang et al. (2007) [14] present a fuzzy AHP approach to model the uncertainty in the choosing process of the optimum maintenance strategy.

3 Methodology Used

A five-point scale is used for each of the factor/criteria relating to the equipment selection problem (Fig. 1):

  1. (1)

    Respondents were asked to rate each factor how they liked each using the above scale.

  2. (2)

    Mean value of each factor/criteria is calculated as follow:

  3. (3)

    The mean value of each factor = ∑x i f i /N , where x i number of respondents corresponding to rate associated with a particular factor, f i corresponding value/rate of that particular factor, N—Total no of respondents. The results of survey are given in Fig. 2.

    Fig. 2
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    Survey results of factors

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  4. (4)

    Cut-off value is determined taking the mean of highest (4.8) and the lowest (1.2) mean rating value of all factors considered in survey.

  5. (5)

    Mean rating value of the factors above the cut-off value (Fig. 2) are considered as important criteria or factors for selection of maintenance strategy. The following factors/criteria are found important. CM, COST(C), Availability (A), Reliability (R), Maintainability (M), MSF, SHE.

4 Case Study

4.1 Selection of Maintenance Strategy

For this purpose of selection of appropriate maintenance for power plant machinery in plant five alternative maintenance strategies such as M1, M2, M3, M4, and M5 have been taken [15]. Five maintenance alternatives ( M, i = 1, 2,…, 5) are then evaluated by AHP [16] model in terms of the criteria. Figure 3 presents the systematic procedure to understand the hierarchy for problems. The types of maintenance alternatives are: corrective maintenance, preventive maintenance (PM), total productive maintenance (TPM), reliability centered maintenance (RCM), Terotechnology.

Fig. 3
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AHP model for by availability (relative priority 0.1809)

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5 Results

Table 1 presents the pair wise comparison matrix of Criteria and Fig. 4 presents the importance.

Table 1 Pair wise comparison matrix of criteria
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Fig. 4
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The importance of maintenance criteria

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Table 2 also gives the overall rating of each maintenance. It is seen from Table 2 and Fig. 5 that maintenance alternative M4 (with rating of 0.3588) is the most preferred one considering above seven criteria followed by maintenance M1, M2, M5, M3. That means RCM > Corrective maintenance > PM > Terro technology > TPM. That is, RCM is the best maintenance under the following criteria.

Table 2 Overall rating of maintenance alternatives
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Fig. 5
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Overall rating of maintenance alternative

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6 Concluding Remarks

Categorization of maintenance strategy for selection of appropriate maintenance decision making is very important, AHP is sound surrogate to make it possible to rank maintenance strategy. The AHP model is also unique in determining the machine criticality. Though the suggested methodology is applied to determine the best maintenance strategy and power plant machinery criticality determination for formulation of maintenance decision making, there is nothing unique about the environment and hence this approach can be generalized to any industry or plant. Similarly, we can determine the critical components of the particular machine for the purpose of maintenance decision making. By the exercise carried out in this paper it is found that reliability centered maintenance is the best maintenance strategy.