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ISSN : 1598-7248 (Print)
ISSN : 2234-6473 (Online)
Industrial Engineering & Management Systems Vol.18 No.2 pp.222-233
DOI : https://doi.org/10.7232/iems.2019.18.2.222

An Efficient Maintenance Plan Using Proposed Framework of RCM Made Simple Approach

Eman K. Abd Elhalim*, Ragab K. Abdel-Magied, Islam H. Afefy, Mohamed F. Aly
Industrial Engineering Department, Faculty of Engineering, Misr University for Science and Technology (MUST), Egypt
Mechanical Engineering Department, Faculty of Engineering, Beni-Suef University, Egypt
Industrial Engineering Department, Faculty of Engineering, Fayoum University, Egypt
Corresponding Author, E-mail: emankhtab2005@gmail.com
November 5, 2018 February 7, 2019 May 15, 2019

ABSTRACT


Reliability Centered Maintenance (RCM) is an effective maintenance strategy and a powerful tool for industrial system enhancement. In this paper, a Framework of RCM is proposed. RCM Made Simple approach is adopted instead of classical RCM to overcome its complexity. A comprehensive analysis is carried out using the proposed Framework which generates a maintenance plane for industrial systems. This analysis is applied on a real case study. The results revealed which component could be critical, potentially critical, commitment, or run to failure. Moreover, it presented the function of each component, failure modes, failure effects and its consequence on the system, failure causes, PM task required, PM frequency for each task, and how to prevent each failure cause. The Framework that proposed in this paper could be adopted as a simple approach to enhance the Reliability, Availability, and Maintainability (RAM) of the industrial systems.



초록


    1. INTRODUCTION

    Maintenance is very important in industry because it keeps the performance of the machines in an acceptable level after failure occurrence. RCM is one of the modern maintenance strategies used to preserve the system functions, extend the lifetime of the machine, eliminate the unnecessary maintenance tasks, and reduce the total maintenance cost (Velmurugan and Dhingra, 2015;Yssaad et al., 2014). RCM strategy had been applied in several industries e.g. electric power industry (Moon et al., (2006), Thermal Power Plant (An air compressor unit) (Narnaware et al., 2014), a steam-process plant (Afefy, 2010), maritime operations (Mokashi et al., 2002), safety considerations in steel plant (Deshpande and Modak, 2002), wind turbines (Fischer et al., 2011) Satisfied results have been obtained due to its application.

    RCM strategy includes different approaches e.g. Classical, Streamlined and RCM Made Simple. The RCM classical needs a lot of accurate data and resources, high training for the personal, more time and cost to apply the analysis (Carretero et al., 2003). Another approach of RCM which is called Streamlined Reliability Centered Maintenance (SRCM) has been investigated by Lifei et al. (2010). In which the failure mode effect analysis (FMEA) concepts are used to apply the analysis. This type of RCM doesn’t need high details and an intensive resource as in classical RCM.

    In recent years, some modifications have been added to RCM classical to overcome its complexity. Tang et al. (2017) presented a Framework to identify the most maintenance significant items (MSI) and apply the Failure Mode and Effects Analysis (FMEA) in the analysis. They adopted their Framework on a case study from the oil and gas industry and proved the applicability of the Framework for identifying MSI. Dini and Starr (2012) presented a maintenance plan using RCM made simple approach which is applied on an Electric Vehicles Power Train (EVPT). In which the COFA tool is used instead of FMEA to simplify the implementation of the RCM.

    Gas Turbine (GT) is considered a curtail equipment in the industry and it must be always in good operating conditions whereas; any failure occurs to its components, will lead to system shutdown. Several studies had been carried out to investigate the failures that occur for the GT during the operating time. Meher-Homji and Gabriles (1998) presented a comprehensive study of the blade failures of the Gas Turbine illustrating the causes of these failures and how to avoid its occurrence. Meher-Homji et al. (1998) studied the deterioration mechanisms of the compressor in the Gas Turbine. The failure analysis of the main components of the GT was presented through different studies (Biswas et al., 2014;Farrahi et al., 2011;Mokaberi et al., 2015).

    Evidently, RCM classical has more complexity during its application, in spite of using in unique or new systems. Also, it could be used in cases when the consequence of failure led to catastrophic risk to safety, health, or environment. In addition, the streamlined RCM doesn’t analyze all the failure modes of the system and it depends on the knowledge and experience of the analysts. In contrast, the application of RCM Made Simple based on the component level could overcome these problems; this is the motivation of this work.

    In this work, RCM Made Simple approach concepts are adopted in the proposed Framework of RCM. In which a comprehensive analysis is carried out. A maintenance plane for industrial systems is deduced and applied on a real case study from previous work done by the authors (Aly et al., 2018), in which the RAM of the considered system has been analyzed and its results revealed that the subsystem Turbine (T3) was a critical due to its lower reliability. The T3 subsystem is considered the system under consideration. This proposed Framework is considered a useful tool to enhance the RAM of the industrial systems

    2. RCM STRATEGY

    The RCM strategy can be applied and implemented to preserve the system functions, in which the components are classifying due to its criticality to apply the suitable maintenance type that maintains the assets reliability. In addition, RCM could be applied in a different manner based on the system or component level, in which different tools e.g. Failure Mode Effect Analysis (FMEA) or Consequence of Failure Analysis (COFA) could be used. Three approaches of RCM strategy; named Classical RCM, Streamlined RCM (SRCM), and RCM Made Simple could be applied in industry. The selection from these approaches is usually based on the Consequences of failure, a likelihood of failure and failure mode, the availability of the necessary resources, availability of the historical data, criticality, and Risk, …, etc. these three approaches could briefly be explained as presented in Table 1 (Bloom, 2006).

    Evidentially, the application of the RCM Made Simple approach has been verified empirically, from which the implications reveal that the complexity of classical RCM can be overcome (Nabhan, 2010;Fouché, 2015), Moreover, it adopts component level rather than the system level (Bloom, 2006), in addition, it saves time and cost as well as its concepts are easy to be understood, applied and modified (Dini and Starr, 2012). These are the motivations to adopt this approach in the present work.

    3. RCM MADE SIMPLE

    RCM Made Simple introduces new concepts as the potential critical component to address hidden failures component, Canon Law to address run to failure components, economic component to determine the economic consequences, and the concept of the consequence of failure. These concepts are applied through three phases which are presented as shown in Figure 1.

    3.1 Phase I of RCM Made Simple

    Phase.1 is considered as the root of the analysis that determines which equipment is important for the plant’s operations, safety or reliability criteria of the asset. To complete phase.1 four steps are required as presented in Figure 2. In step.1 an accurate and specific “reliability criteria” to measure the success of the asset reliability is performed, these criteria describe all the failures consequences and all unwanted actions that have to be prevented so, it considered as a performance standard for the asset. In step 2, all components are labeled with ID for sake of elimination time consuming, duplication as well as it used as a reference for each component.

    In step three, all components of the system are classified according to its criticality. An integrated logic tree is presented in Figure 3. It is adopted for the system components classification, in which all failure modes go through four filters (e.g. COFA logic Tree, Potentially Critical Guideline, Commitment, and Economically Significant Guideline) to specify asset component type as shown in Table 2. The component which passes all filters is classified as Run to Failure component. In step four, the COFA is applied. It should be noted that the COFA introduces the same concepts of FMEA but in component level. In addition, it gives an accurate, specific, and precise format. COFA identifies the consequence of failure which results from an unwanted impact on one or more of the ARC at the system or plant level. As shown in Figure 3 COFA worksheet includes the component ID, component functions, …, etc. Finally, the component with a failure mode that results in an unwanted consequence is classified as either critical, potentially critical, commitment, economic or run to failure. After completing the COFA worksheet Phase.1 become completed

    3.2 Phase II of RCM Made Simple

    The role of Phase II is to specify the required PM type for the components that identified in phase I and apply the PM worksheet as presented in Figure 4. The PM task selection is conducted through the PM Logic Tree, as shown in Figure 5 to specify the PM type which is required for each failure cause that identified in the COFA worksheet. Different types of PM tasks can be applied; Condition Directed (CD), Time Directed (TD), and Failure Finding (FF). A CD type applies predictive maintenance technology or performing external tests. TD includes overhauls, spare parts replacement, internal inspections, .... etc.

    The FF task is efficient for the potentially critical component only and not applicable to the critical, commitment, and economic component because the failure consequence has already taken place. The selected tasks must be efficient and applicable to prevent the unwanted consequence or any additional failure that may occur.

    The PM Worksheet integrates the results form RCM COFA Worksheet and PM Logic Tree. Figure 4 shows the elements of the PM Worksheet. The first five elements come from COFA worksheet, where the description and identification of failure cause for each dominant failure mode, the specified PM and its frequency, and design change decision are added to this worksheet.

    3.3 Phase III of RCM Made Simple

    In this phase, the application of the resulted maintenance plan from the last phases is implemented in practice to measure the effectiveness of the RCM plan.

    4. PROPOSED MAINTENANCE PLAN

    4.1 System Description

    In this paper, the considered system that used for RCM plan application is described in details by Authors (Aly et al., 2018) which is considered as part one of this study. In that part, the analysis of the considered system revealed that T3, as the sub-system, has the lower reliability 59%. The number of failures which occurred for T3 during the year 2015 was 6 failures. Moreover, it could be seen from the historical data presented in Table 3 that the downtime of that turbine is high. For this, it is considered the most critical item and needs more attention to enhance the system performance.

    In this paper, the sub-system T3 in part one is used as a considered system for RCM plan application. The function of the Gas Turbines is converting the gaseous energy to the mechanical energy which comes from the rotating shaft to generate an electric power with an output of 3.8 MW. The model of T3 is TB5000 and its sub-systems illustrated in Figure 6 and explained in Table 4.

    4.2 RCM Made Simple Application

    In this section, the steps of the first two phases of RCM Made Simple approach, explained in section 3, are applied to obtain maintenance plane of the system under consideration.

    4.2.1 Asset Reliability Criteria (ARC)

    The Asset Reliability Criteria for T3 based on the RCM Made simple approach are presented in Figure 7.

    4.2.2 Components Labeling

    The proposed labels of failed components of T3 that need a special attention are shown in Table 5, in addition, the number of failures, downtime, and repair time for each component are also presented.

    4.2.3 RCM Logic Tree

    Figure 8 shows the block diagram of T3 which present the relationship between its subsystems. It is noted that all the subsystems are connected in series which is meaning that failure in any subsystem will lead the T3 to stop working.

    The specified components that described in Table 5 passed through the integrated RCM COFA Logic Tree, the output is as presented in Table 6.

    It should be noted that the resulted classification reveals that the components are critical and potentially critical, by which a severe effect on the system performance will occur and this requires an effective maintenance program to preserve the system functions at the acceptable level. Figure 9

    4.2.4 COFA Worksheet

    All the failure modes of the five components are identified and described in details in the COFA Work-sheet as shown in Table 7. The failure effects and consequences on the system level according to ARC are also identified. The failure consequences are classified into3categories as follows:

    • System shutdown due to safety concerns.

    • System shutdown due to operation.

    • Power reduction.

    4.2.5 PM Task Selection (PM Logic Tree)

    All the specified components that faced failure are passed through the PM logic tree to specify the kind of PM type for each failure cause that required avoiding failure occurrence. Table 8 shows the PM type required for each component, and the tasks required for each cause to avoid the failure. Figure 10

    4.2.6 PM Task Worksheet

    After completing the COFA worksheet and the Logic Tree the PM worksheet is presented to address the failure causes and frequency for each task as presented in Table 9.

    5. VERIFICATION OF PROPOSED PLAN

    This work is a part of the ongoing study, and the deduced plans of this work will be implemented in the practice. It is expected that the results will reveal decreasing in the number of failures and downtime of failed components, the full results of this implementation will appear elsewhere.

    However, the proposed plan could be verified by its application in the context of systems engineering process. Subsequently the practical implications of the proposed approach/framework could be presented with evidences. To verify the proposed plan, the total downtime and repair time for each failure mode is compared, after its application, with the planned maintenance data for each failure modes of industrial Gas turbine obtained from Offshore Reliability Data Handbook (OREDA) (Oreda, 2002). The values of the downtime for each failure mode before and after application of the proposed plan are presented in Table 10. The reduction percent in downtime due to the application of the proposed plan compared with data obtained from OREDA is illustrated in Table 11. It can be read from this table, for example, the proposed plan can reduce the down time by 28% for the solenoid valve, this reduction is within the range of reduction of the planned maintenance from OREDA, which is 11% to 53%.

    Evidently, the successful implementation of the proposed maintenance plan is very useful, particularly in practice, since it reduces the total downtime and the total maintenance cost, reduces the spare parts consumption, enhances the RAM of the considered system as well as it is considered a powerful tool for industrial systems evaluation

    6. CONCLUSION

    This study introduces a proposed maintenance plan through a comprehensive RCM study in a simple way using COFA instead of FMEA to enhance the system performance. The concepts of how to apply RCM Made Simple are illustrated clearly. These concepts are applied to a real case study of the previous work. Subsystem (T3) was found the most critical component, which is considered the main system in this work. A new finding of this work can be concluded as follows:

    • A Framework for RCM in a simple way is proposed and applied on the real case study.

    • A deduced maintenance plan from this application can introduce comprehensive study for each failure at the component level.

    • Also, it could be used to avoid or minimize the system failure through taking the suitable PM action and eliminating the unnecessary tasks consequently enhance and improve the system performance.

    • A comprehensive analysis is carried on the real case study using the proposed Framework.

    This analysis presented the function of each component, failure modes, failure effects, failure consequence, system component classification due to its critically, failure causes, PM task required, PM frequency for each task and how to prevent each failure cause.

    Figure

    IEMS-18-2-222_F1.gif

    The framework of RCM made simple.

    IEMS-18-2-222_F2.gif

    RCM made simple phase 1.

    IEMS-18-2-222_F3.gif

    RCM made simple COFA logic tree.

    IEMS-18-2-222_F4.gif

    RCM made simple phase II.

    IEMS-18-2-222_F5.gif

    PM logic tree.

    IEMS-18-2-222_F6.gif

    Gas turbine subsystems.

    IEMS-18-2-222_F7.gif

    Reliability criteria for T3.

    IEMS-18-2-222_F8.gif

    Block diagram for T3 subsystems.

    IEMS-18-2-222_F9.gif

    Sight glass CC2 failure.

    IEMS-18-2-222_F10.gif

    Cracked flame tube CC1.

    Table

    RCM approaches (Bloom, 2006)

    Component classifications

    The real data for the considered system collected during the year 2015

    Gas Turbine (T3) subsystems description

    The labels of the critical components in T3.

    Component classification due to its criticality

    COFA worksheet

    PM types and tasks for each failure cause.

    PM worksheet

    Downtime before and after application of the proposed plan.

    A comparison of reduction percentage in downtime

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