Impact of Maintenance on Machine Reliability: A Review

. This review investigates the impact of maintenance methods on machine reliability, focusing on their relationship with overall performance, durability


Introduction
The science of reliability has many potential applications in communication and medicine due to global development, particularly in science and technology, and the use of sophisticated and complex systems [1][2][3].
There is also interest in the frequency of failures and the causes of the unexpected failures that devices experience, which can raise costs, reduce output, and result in significant losses in human and material resources [4][5][6].Reliability is the probability of a system performing a particular job for a specific period under the working conditions for which it is designed.It can be evaluated to determine the type and size of production and improve it through engineering designs based on design for maintainability [7][8][9][10].Maintenance has great impact and importance when considering machine tools and their reliability, [11] equipment that is smart and networking-based is a product of the most recent industrial revolution.Understanding the full worth of these equipment and other company assets has become more crucial using technology solutions like the Internet of Things, cloud computing, cyberphysical systems, and big data analytics, [11][12][13] strategic asset management can decrease or even eliminate some of the administrative, technical, and methodological issues it encounters [14].Optimizing maintenance tasks is essential in every industrial setting, including manufacturing, chemical plants, process engineering (e.g., nuclear plants), operations of field equipment (e.g., construction, mining equipment, and others) [14].However, a reliability centred maintenance (RCM) methodology improves the availability of machines and equipment in the various industry [14].Failure mode and effect analysis (FMEA) is used to analyse failures and preventive measures are proposed to reduce downtime and improve availability [14 -15].Maintaining a production or logistic system in such a state that it can perform its output is the core maintenance goal, age replacement policy is used to estimate replacement intervals and costs [16].Traditionally, maintenance schedules have either been reactive or preventive, which frequently leads to costly unanticipated machine malfunctions or wasteful maintenance that causes substantial downtime and lost productivity [17].Although, preventive maintenance entails doing routine maintenance operations with the goal of extending the life, reactive maintenance concentrates on performing maintenance only after a machine or component has failed [18].

Importance of Maintaining Machine Reliability
According to [19], maintaining machine reliability is crucial for minimizing downtime and production losses, enhancing operational efficiency, ensuring workplace safety, and extending equipment lifespan.Regular maintenance activities, such as cleaning, lubrication, and calibration, contribute to smooth operations and consistent performance [20].It also helps prevent major breakdowns and reduce emergency repairs, ultimately improving the bottom line [21].However, reliable machines lead to consistent product quality and on-time delivery, satisfying customer expectations [22].Regular maintenance also helps companies comply with regulatory standards, avoiding legal and financial consequences [23], improve predictability and planning, allowing businesses to better plan production schedules, allocate resources, and manage inventory [24].Neglecting machine reliability maintenance increases the risk of catastrophic failures, which can have severe consequences such as extensive damage, loss of production, and potential harm to personnel [25].Regular maintenance helps identify and address potential issues before they escalate into major problems [26].Another advantage of maintaining machine reliability is providing a competitive advantage in the marketplace [27].Companies with reliable machines can offer consistent product quality, shorter lead times, and better customer service, setting them apart from competitors and attracting more customers.

Factors Affecting Machine Reliability Maintenance
The reliability of a machine is significantly influenced by various factors, including usage intensity, environmental conditions, maintenance practices, skill and training, component quality and reliability, proactive vs. reactive maintenance, age and usage history, documentation and record-keeping, availability of spare parts, and continuous improvement and feedback [28].Usage intensity is a significant factor, as machines that are used heavily or continuously are more prone to wear and tear, requiring more frequent maintenance [29].Although, environmental conditions, such as temperature, humidity, dust, vibrations, and corrosive substances, can accelerate the degradation of machine components [30], necessitating regular maintenance to ensure optimal performance.Maintenance practices, such as adherence to manufacturer-recommended schedules, inspections, lubrication, cleaning, and component replacement, significantly improve reliability [31].Nevertheless, skill and training are crucial for maintaining personnel competence, as adequate training and knowledge of the equipment are essential for identifying potential issues, performing tasks correctly, and addressing emerging problems promptly [32 -33].Component quality and reliability are also crucial, with high-quality components and regular inspections and replacements enhancing overall machine reliability.Reliability verification and validation must be used in the creation of new machinery and components.Methods like Accelerate Life Test (ALT), High Accelerate Life Test (HALT), and Reliability Growth Analysis (RGA) can forecast component reliability for electronic and electrical components and also track the growth in reliability during design-phase improvement actions [34].Age and usage history are important factors to consider, as older machines may require more frequent maintenance due to wear and aging of components [35].Additionally, machines subjected to harsh operating conditions or inadequate maintenance history may exhibit reduced reliability [36 -37].Accurate documentation of maintenance activities, repairs, and component replacements is essential for effective reliability maintenance, tracking machine history, identifying recurring issues, and ensuring timely maintenance tasks [38].Genuine spare parts are essential for maintaining reliability, and continuous improvement and feedback can provide valuable insights for improving reliability and maintenance practices [39].

Maintaining Reliability-Centric Systems
RCM is a set of structured processes that determine the equipment maintenance strategies needed for any physical asset to ensure that it continues to perform its intended function(s) under current operating conditions [40].The goal of RCM is to identify the critical components in any process and then design a customized preventive/predictive maintenance strategy based on this information [41].Another strategy is the root-cause failure analysis (RCFA), which is based on previous failures.Beyond the component stage, RCFA should lead to corrective actions at the system's deficiency or latent root stage [42].

Classifying Equipment for maintenance
All equipment must first be categorized in order to choose the proper maintenance method for the situation.There are four components of RCM program which are:

Reactive Maintenance
Reactive maintenance, also known as "breakdown maintenance" or "run-to-failure maintenance," is a maintenance approach where repairs are performed on a machine or equipment only after it has already experienced a failure or malfunction.In this approach, maintenance activities are not scheduled in advance, and the focus is primarily on restoring the machine to its normal operating condition as quickly as possible [44].However, some essential characteristics of reactive maintenance are unplanned repairs in response to failures, which increases downtime, raises repair costs, creates unpredictability, and shortens the lifespan of the equipment [45].However, the disadvantages of this approach include unpredictable and fluctuating production capacity, higher levels of out-of-tolerance and scrap output, and increased overall maintenance costs to repair catastrophic failures [46][47].

Preventive Maintenance
Preventative maintenance involves implementing safeguards and measures to prevent accidents and equipment breakdowns [48].It involves routine inspections, cleaning and lubricating equipment, and maintaining company facilities [49].This approach lowers accident risk and allows employees to focus on enhancing current systems rather than fixing broken ones.By implementing specific procedures, companies can focus on enhancing their operations and reducing potential hazards [50].Therefore, any type of maintenance that is not reactive (i.e., a response to a problem, malfunctioning equipment, technology, etc.) is preventive.There are a number of steps involved in developing a preventive maintenance program.Figure 2

Types of Preventive Maintenance
Preventive maintenance can be very robust and vary with different approach with which you chose to engage it.Below are few types of preventive maintenance:

i. Time-Based Maintenance
Making a maintenance schedule that complies with manufacturer recommendations for inspecting and cleaning equipment can be useful for keeping you on track.The most crucial pieces of equipment for your company should be checked frequently to ensure the best operations, even if you don't follow these suggestions.When developing a time-based preventive maintenance plan, consider the essential resources, machinery, tools, and technology for your company's success.Regularly examine these factors to ensure company success and avoid potential shutdowns due to unavoidable problems [50].

ii. Usage-Based Maintenance
Prescriptive maintenance utilizes advanced analytics, machine learning, and artificial intelligence to generate and act on maintenance predictions, enhancing system operations and producing work orders.It follows up on its own to oversee the entire process, similar to predictive maintenance [50].

iii. Condition-Based Maintenance
According to the management philosophy known as condition-based maintenance (CBM), decisions regarding equipment repair or replacement are made based on the equipment's present or potential future conditions [52].It is referred to as a maintenance program that consists of three main steps: data collection, data processing, and maintenance decision-making.It is defined as a maintenance program that suggests maintenance solutions based on data obtained from condition monitoring  [53].CBM is a more advanced form of preventative maintenance in which alarms are triggered automatically before a failure happens.Alarms that are automatically triggered are set off before any failure is detected.To fulfil the application requirements of CBM, complicated multi-variable methods and algorithms are used [54].

Predictive Maintenance
Predictive maintenance (PdM) is a more recent preventive maintenance strategy that aims to increase the equipment's life expectancy and ensure sustainable operational management while also enhancing the performance and efficiency of the manufacturing process.This suggests, on the one hand, a decrease in downtime and the number of needless stops, accompanied by a decrease in repair costs, by providing the opportunity for interventions through the prediction of failures [55].
Condition monitoring, which is defined as the continuous monitoring of machines during process conditions to ensure the optimal use of machines, is required for predictive maintenance to exist.Condition monitoring has three components: online, periodic, and remote."Condition Monitoring of Rotating Machines," Istec International, defines online condition monitoring as "the continuous monitoring of machines or production processes, with data collected on critical speeds and changing spindle positions" [56].Periodic Condition Monitoring provides information on how installations' vibration behaviour changes over time.Vibration measurements with a fixed interval are used to create a trend analysis.The trend analysis identifies the source of the changing vibrations and is followed by expert advice on predictive measures [57].Remote Condition Monitoring allows for data analysis from a distance.Remote data reading allows measurements and analyses to be performed without disrupting your organization or requiring unnecessary travel time [57-58].

Proactive Maintenance
Proactive maintenance is a maintenance strategy that aims to identify the root cause of equipment failures so that they can be corrected before they cause further problems and machine breakdowns.Proactive maintenance in the workplace can increase productivity, maximize asset utilization, and contribute to workplace safety [59].Equipment lifespan extension, incorrect usage, poor materials, production, maintenance errors, and lack of technician training contribute to equipment failure.This type of maintenance allows you to extend the life of your assets while also improving their performance.This is possible due to continuous monitoring of the equipment, data collection and analysis, and the ability to perform maintenance efficiently only when it is truly necessary [60].To fully understand how this maintenance strategy works, the 3 examples below will be useful: 1. Machinery lubrication: performed at regular intervals to avoid problems due to friction between the surfaces, avoiding deterioration of the motors; 2. Pipe inspection: to verify the integrity of the pipe distribution system and prevent costly interruptions due to cracks, corrosion and thinning of the ducts; 3. Application of anti-corrosion coatings on metal surfaces: to avoid immediate replacement of machine parts.

Link Between Maintenance and Improved Machine Reliability
Maintenance is critical to increasing machine reliability [63].Organizations can mitigate potential failures, reduce downtime, and optimize machine performance by implementing effective maintenance practices [64].Inspections, lubrication, cleaning, and calibration are examples of routine maintenance activities that help identify and address issues before they become major issues [65].Preventive maintenance, in particular, focuses on proactive measures to prevent failures and ensure that machines run at peak performance [66].Furthermore, predictive maintenance techniques like condition monitoring and data analysis allow organizations to anticipate maintenance needs and address them before they cause unplanned downtime [67].Organizations can boost productivity, cut costs, and achieve operational excellence by establishing a strong link between maintenance and improved machine reliability.A study gap in understanding the impact of maintenance on machine reliability is the exploration of the specific influence of different maintenance strategies on machines across different industries.Existing research on maintenance's importance and its impact on reliability lacks comprehensive studies on industry-specific variations.Understanding how maintenance practices like preventive, predictive, or condition-based maintenance contribute to machine reliability in specific sectors like manufacturing, energy, transportation, or healthcare can provide valuable insights and help tailor maintenance approaches to different sectors' unique requirements and challenges.This understanding can lead to the development of targeted maintenance guidelines and best practices for improved machine reliability.

Conclusion
Ultimately, this review has shed light on the critical role of maintenance in machine reliability.It has the importance of maintenance practices in preventing failures, reducing downtime, and improving machine performance.Organizations can identify and address potential issues before they lead to major failures by implementing proactive maintenance strategies such as preventive maintenance, predictive maintenance, and condition-based maintenance.The review also emphasized the importance of maintenance and operations collaboration, continuous skill development, and embracing technological advancements to improve maintenance effectiveness.However, there are still opportunities for additional research, such as investigating the impact of industry-specific variations in maintenance strategies on machine reliability.Overall, understanding and prioritizing maintenance in a comprehensive and proactive manner is critical to improving machine reliability, lowering costs, and increasing productivity.

Fig. 4 :
Fig. 4: Proactive maintenance examples Source: [62] /doi.org/10.1051/e3sconf/202343001226226 430 Figure 1 below explains the type of maintenance strategy needed for different type of equipment depending on how such equipment is classified in the manufacturing environment.