Keywords

1 Introduction

Maintenance can enhance productivity, quality, health and safety [1]. So, any framework designed to measure maintenance performance should encompass results in different areas [2,3,4,5]. In this scenario, sets of KPIs related to different aspects of maintenance have been developed recently in [6,7,8,9]. As sustainability objectives rise as strategical for organizations [10], companies should know how their maintenance process impact the TBL, as discussed in [11,12,13,14,15,16]. But, with a few exceptions such as [17, 18], sustainability is rarely mentioned in researches about maintenance. This paper contributes to fulfill his gab by highlight the relationship between TBL and the main KPIs mentioned in previous researches and also those used by companies. It discovered the KPIs most suitable to measure the accomplishment of each maintenance objective and which maintenance objective are related to each sustainability dimension.

2 Methodology

As the space for this paper is constrained, we focused in describing the main results instead of providing details about methodology. We highlight that literature review is a part of the methodology, once its results are used as input in the other research steps as it occurs in [19].

2.1 Literature Review

The steps for the literature review were inspired in [20,21,22,23,24]. First of all, it was done a search using the terms “maintenance” and “performance” and “indicators” or “KPI” or “metrics” into Scopus and Web of Science (WOS). The choice of these sources aims to reduce the probability of using “grey science” as mentioned in [25], or even paper published in predatory journals without a qualified peer review process. As the terms used for the query are not specific for the maintenance context, it was necessary to screen the articles removing those not related to industrial maintenance. The full-text of the remaining articles were read, searching for any KPIs used to measure performance of maintenance. A full list of KPIs used on these articles was built and from this step it was possible to perform quantitative analysis on the amount of KPIs used for each maintenance objective and sustainability dimension.

2.2 Exploratory Survey

Aside the literature review, it was explored the perception of maintenance professionals about the TBL. In order to elucidate the main goals and priorities of professional’s companies, maintenance experts answered a survey about their main maintenance objectives, and which KPIs are used for each sustainability dimension. The invitation of maintenance professionals to answer the questionnaire occurred over a professional social network. A link to the questions was shared on several groups regarding maintenance. Sustainability groups were also chosen, because professionals within those groups may contribute with ideas and insights different than those related only to maintenance. The next step was the comparison between the answers from the survey and the results from the literature review. The questions about maintenance objectives and KPIs were open-ended, so it was necessary to refine and sort the answers in order to help the integration with the results from literature review.

2.3 Survey for Mapping Maintenance KPIs Linked to Sustainability

After selecting the main maintenance KPIs and objectives from the previous steps, a second survey was performed. This time the aim was to stablish what KPIs were adequate to measure de accomplishment of each objective, and assess which objectives were related to each sustainability dimension. It was announced on the same groups of the first survey, and an e-mail was sent to the previous respondents.

3 Results

3.1 Literature Review

The queries performed on the Scopus and Web of Science returned a initial list consisting of 1237 articles, as it appears in Fig. 1. After processing filtering steps, it resulted in a set composed by 77 articles for deeper analysis (see Fig. 2). As a result, some prominent topics were found and aggregated into categories. It follows some comments about the main finds in this step.

Fig. 1
figure 1

Number of articles mapped in the scientific bases

Full size image
Fig. 2
figure 2

Articles filtering process

Full size image

  • The large number of papers modifying or creating KPIs, indicates that there is still a lack for the creation or improvement of existing metrics.

  • The Overall Equipment Effectiveness (OEE) is the most mentioned indicator, as it is often modified.

  • A rising topic was the comparison between different maintenance strategies to discover which of maintenance strategies performs better; or, even benchmark, among companies taking KPIs indicators for evaluation.

  • In the case studies, KPIs were most applied to assess the results of actions designed to improve systems performance.

  • The prediction or estimation of indicators were also an important topic within the literature, enabling the use of KPIs as inputs on conditions based maintenance systems.

  • A few papers have explored the tradeoffs between different maintenance KPIs, such as the rate of unexpected failures and the remaining useful life of components.

Some objectives and aspects are repeated on each dimension. It happens because such objectives increase overall maintenance performance, leading to better performance on three dimensions of sustainability. It should lead to a false impression of balance between the three dimensions of sustainability (Fig. 3).

Fig. 3
figure 3

Relationship between maintenance o objectives and sustainability dimensions

Full size image

3.2 Exploratory Survey

The previous section has risen a doubt about the importance attributed by maintenance to sustainability dimensions. In order to elucidate this questioning, a survey was applied to maintenance experts colleting their perceptions about how much maintenance KPIs cover sustainability dimensions. Such survey returned 92 answers, from people spread in 23 countries in Africa, Asia, Europe, Latin America, Middle East and North America.

The professionals were also asked if their companies where they have worked used indicators related to each sustainability dimension and which KPIs were used. The results demonstrate that 68.5% of the respondents could affirm that economic KPIs were used in their companies, while for the environmental and social dimensions the results were 42% and 30%, respectively.

Table 1 (See Appendix) shows the KPIs mentioned on the survey and those most found out in the literature, both categorized according to the maintenance objectives and dimensions. Despite the differences on objective selection, all the objectives from literature had at least one related KPI mentioned on the survey. But still there are some gaps on the literature and companies’ KPIs. The objectives that would benefit the most for having more KPIs are asset preservation, atmospheric emissions, energy consumption and workforce satisfaction.

Table 1 Main KPIs in literature and companies
Full size table

3.3 Survey for Mapping Maintenance KPIs Linked to Sustainability

A second questionnaire composed by two questions was applied to elucidate the links between sustainability dimensions, maintenance objectives and KPIs. The first question asked the respondents to check if there was a relationship between each objective-dimension pair. Table 2 demonstrates the percentage of positive answers, while Fig. 1 illustrates which objectives were considered significantly related to each sustainability dimension, assuming a level of significance of 5%.

Table 2 Relationship between objectives and dimensions
Full size table

The results in Fig. 1 show that most of the maintenance objectives relates exclusively to the economic dimension. Also, the only objected that have been considered for multiple dimensions were energy consumption, which relates to the economic and environmental dimensions at the same time. Besides, five objectives do not relate to any of the dimensions. Such results evidence that professionals are less prone to link objectives to dimensions. These results were unexpected and show that professionals tend to disregard the relation between objectives and dimensions when the impacts from achieving the objectives are indirect.

The second question of the survey aimed to assess the most adequate KPIs to measure the performance for each objective. After analyzing the answers, it resulted in 25 indicators that need to be taken into account when measuring the sustainability of the maintenance process: 22 of these KPIs are related exclusively to the economic dimension. 2 are related to the environmental dimensions and one is related to both of them. We noticed that there are no indicators for the social dimension. Table 3 presents the indicators and objectives considered for each dimension after the statistical analysis.

Table 3 List of maintenance KPIs linked sustainability
Full size table

In general, the results in Table 2 demonstrate a higher level of prioritization of the economic dimension if compared to the results from the first survey or from the literature review. Part of this difference is due to the choice of objectives related to sustainability dimensions. All the five objectives that were not related to any of sustainability dimensions were part of the social dimension on the initial analyses. Another noteworthy aspect about the objective selection is that most of objectives related to the economic dimension and a second or third dimension were then considered as exclusively regarded as an economic objective, the lack of KPIs related to the image objective has caused the final list of KPIs to ignore the social dimension completely. This scenario highlights the importance of developing indicators related to the image of companies in order to measure its impact on the social dimension.

4 Conclusion

The results from the research demonstrated there is a lack of maintenance KPIs that covers the environmental and social dimensions of sustainability. Also, it was evidenced the unbalance of maintenance KPIs in covering the three dimensions of sustainability, once the KPIs and objectives analyzed mainly cover the economic dimension o sustainability implying in a scarcity of such indicators in covering environmental and social aspects of maintenance operations.

It is also noteworthy that maintenance professionals surveyed often disregarded the indirect impact that some objectives have on multiple sustainability dimensions. For this reason, objectives like health and safety, growth and integration, and compliance were not considered to impact any of the sustainability dimensions. Also, objectives like prevention and predictability and planning were considered related only to the economic dimension. A possible reason for this behavior is that achieving these objectives would lead to indirect impact on sustainability dimensions, rather than direct impact.

This research is into an evident gap: the scarcity of knowledge that link maintenance to sustainability. The results should support managers and researchers, supporting them in reviewing maintenance indicators in order to produce operations more sustainable.

There is a lack of adequate maintenance indicators related to company image, which could imply in reducing organizations reputation. For this reason, it is recommended for future researches the development of KPIs able to measure the impacts of maintenance on companies’ image. It may even be viable for this objective to incorporate others not related to sustainability dimensions, such as workforce satisfaction, responsibility to customers and Growth and integration.

The present work may serve also as a first step towards the practical application of the KPIs, in order to compare the performance of companies’ maintenance systems. Other recommendations for future researches are the allocation of weights to the KPIs in order to identify which of KPIs are more relevant to companies.