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Although each maintenance task performed on an item of equipment may enhance its reliability, neither preventive nor overhaul maintenance can return the equipment to good‐as‐new condition. Applying the concept of maintenance improvement factors to both types of maintenance, mathematical models are developed that are used to generate preventive and overhaul maintenance schedules. Examples are provided to demonstrate the sensitivity of the schedules to model parameters.

Output from the Irish Dairy Industry has grown rapidly since the abolition of quotas in 2015, with processors investing heavily in capacity expansion to deal with the extra milk volumes. Further capacity gains may be achieved by extending the processing season into the winter, a key enabler for which being the reduction of duration of the winter maintenance overhaul period. This paper aims to investigate if Lean Six Sigma tools and techniques can be used to enhance operational maintenance performance, thereby releasing additional processing capacity.

Combining the Six-Sigma Define, Measure, Analyse, Improve, Control (DMAIC) methodology and the structured approach of Turnaround Maintenance (TAM) widely used in process industries creates a novel hybrid model that promises substantial improvement in maintenance overhaul execution. This paper presents a case study applying the DMAIC/TAM model to Ireland’s largest dairy processing site to optimise the annual maintenance shutdown. The objective was to deliver a 30% reduction in the duration of the overhaul, enabling an extension of the processing season.

Application of the DMAIC/TAM hybrid resulted in process enhancements, employee engagement and a clear roadmap for the operations team. Project goals were delivered, and original objectives exceeded, resulting in €8.9m additional value to the business and a reduction of 36% in the duration of the overhaul.

The results demonstrate that the model provides a structure that promotes systematic working and a continuous improvement focus that can have substantial benefits for wider industry. Opportunities for further model refinement were identified and will enhance performance in subsequent overhauls.

To the best of the authors’ knowledge, this is the first time that the structure and tools of DMAIC and TAM have been combined into a hybrid methodology and applied in an Irish industrial setting.

The purpose of this paper is to present the development results of the overhaul melioration plan for the following aircraft types: MiG‐21Bis, G‐4 Galeb and SA‐341 helicopter. This research has been conducted based on available knowledge and extensive experience gained by performing general maintenance of the Air Force of Serbia aircraft.

A general analysis was performed by processing data collected while performing maintenance and repair procedures. The magnitude of data is based on detecting the delays and errors that occurred while going through the operational and inter‐operational stages of aircraft overhaul. On the basis of the obtained research results, a proposal for the aircraft overhaul optimization is offered.

The proposed overhaul improvement plan points out the priority steps to be taken in order to optimize the most critical features that jeopardize the quality of the aircraft overhaul process relating to organization, technology and design. Moreover, existing technical logistics have been used for providing actions to achieve the objective in focus: the all‐encompassing optimization of the above selected aircraft overhaul.

The method of the overhaul optimization has so far been applicable to the aircraft of the Army of Serbia. However, the particular methodology can be proved potentially useful and highly germane when applying to other aircraft types.

A plan to optimize the overhaul is based on a one‐year monitoring process of the aforementioned aircraft. It enables significant savings in performing overhauls within the financial realm as well as time‐wise.

Industries generally require good maintenance, repair and overhaul (MRO) facilities. Maintenance activities at MRO cover the normal scheduled check-ups known as scheduled preventive maintenance (SPM) whereas an overhaul reviews and rejuvenates the complete system at a scheduled time. The literature is reasonably stocked with reliability modelling of repairable systems considering both the corrective maintenance (CM) and SPM as imperfect. However, in all these situations the overhaul is modelled as perfect repair. Thus, the purpose of this research paper is to develop a mathematical model for the estimation of reliability parameters considering the complete MRO as imperfect.

The paper proposes arithmetic reduction of age (Kijima I) based virtual age model to estimate reliability parameters by considering the complete MRO as imperfect and provides the likelihood and log-likelihood functions for parameter estimation of the proposed model and also presents the various extensions of the proposed model.

For analysis, two real-time data sets of two components, i.e. turbostarter and plunger pump are considered. The analysis mainly focuses on intensity function and availability of components. The availability analysis of the components directly affects the cost analysis. It is very important to analyze the realistic trend of availability, and the comparative analysis shows that the assumption of perfect overhaul overestimates and minimal overhaul underestimates the performance of the components whereas assumption of imperfect overhaul portraits more sensible deteriorating and availability trend of the components.

The proposed methodology in this paper is a novice and not available in the literature.

Addresses a deterministic maintenance‐scheduling problem for a group of non‐identical machines. The problem is formulated as a mixed integer non‐linear program which is approached heuristically. In the model formulation, it is assumed that a major overhaul brings the machine back to its new condition, whereas a minor overhaul restores it to a specified operating condition. An iterative solution procedure is developed to obtain a near‐optimal cyclic overhaul schedule. Presents a worked example to illustrate the proposed solution method.

Degradation of repairable components may not be similar after each maintenance activity; thus, the classic (traditional-time based) maintenance policies, which consider preventive maintenance (PM), age-based maintenance and overhauls to be done at fixed time interval, may fail to monitor the exact condition of the component. Thus, a progressive maintenance policy (PMP) may be more appropriate for the industries that deal with large, complex and critical repairable systems (RS) such as aerospace industries, nuclear power plants, etc.

A progressive maintenance policy is developed, in which hard life, PM scheduled time and overhaul period of the system are revised after each service activity by adjusting PM interval and mean residual life (MRL) such that the risk of failure is not increased.

A comparative study is then carried out between the classic PM policy and developed PMP, and the improvement in availability, mean time between failures and reduction in maintenance cost is registered.

The proposed PMP takes care of the equipment degradation more efficiently than any other existing maintenance policies and is also flexible in its application as the policy can be continuously amended as per the failure profile of the equipment. Similar maintenance policies assuming lifetime distributions are available in the literature, but to ascertain that the proposed PMP is more suitable and applicable to the industries, this paper uses Kijima-based imperfect maintenance models. The proposed PMP is demonstrated through a real-time data set example.

DEVELOPMENT of the Kansas City base of Transcontinental and Western Air has been proceeding since 1946, in which year the wartime Army‐operated modification centre in the city for B‐25 bombers and Constellations was leased from the Reconstruction Finance Corporation and converted to peacetime use at a cost of $1,000,000. The hangars, shop and office buildings enclose a combined area of 427,000 square feet and are surrounded by more than 1,000,000 square feet of concrete ramp or apron. The hangars are fitted to accommodate at the same time three Constellations and eight Stratocruisers, DC‐4's or DC‐3's. Nearly 2,000 men and women are employed at the base.

The basic organization of maintenance and overhaul is examined, with some notes about the aircraft in use, the Convair 240 and the Douglas DC‐3, DC‐4 and DC‐6, and the reasons for the maintenance on each type being carried out differently. Owing to the operating conditions of Sabena, with both long‐range routes and short‐range networks in Europe and the Congo, organization of maintenance presents special problems. The routine inspections on the DC‐3, Convair and DC‐6 are described separately in order to present a picture of the line maintenance of the Company. The DC‐3 is maintained on a 125/500/1,000 hour cycle, with a special major inspection at 3,000 hours; the Convair has a similar progressive scheme; while the DC‐6 is serviced on an alternating 75/150 hour cycle, plus certain progressive items, to a major inspection at 2,400 hours. Airframe overhaul—carried out on all types despite the progressive maintenance schedule for the Convair—occurs at about 10,000 hours. The power plant (or ‘quick‐change’) work, engine overhaul and accessory maintenance is described, but radio, radar and instrument inspection and repair are not covered.

The modern helicopters are designed with maximum serviceability and long life expectancy to ensure minimum life cycle cost. The purpose of this paper is to present a framework to incorporate the customer requirements on reliability and maintainability (R&M) parameters into the design and development phase of a contemporary helicopter, and to discuss the way to capture operational data to establish and improve the R&M parameters to reduce life cycle cost.

From the analysis, it is established that the reliability and maintainability cost is the major contributor to the life cost. The significant reliability and maintainability parameters which influence R&M cost are identified from analysis. The operational and design data of a contemporary helicopter are collected, compiled and analyzed to establish and improve the reliability and maintainability parameters.

The process depicted in the paper is followed for a contemporary helicopter and substantial amount of life cycle cost reduction is observed with improvement of R&M parameters.

The benefits of this methodology not only reduce life cycle cost but also improve the availability/serviceability through less failure and less time for scheduled maintenance. The methodologies also provide the reliability trends indicating potential area for design improvement.

The proposed approach assists asset managers to reduce the life cycle costs through improvement of R&M parameters.

The purpose of this paper is to investigate into the improvement strategies for lead time reduction of military aircraft major overhaul (enhance the overhaul task from present seven to nine-plus aircrafts as agreed to customer) for ABC Company.

This research has been conducted based on the available knowledge and extensive experience gained while working in the overhaul unit of the case organization for a long period of time. The research employs an integrated approach of multi-criteria decision method (in specific analytic hierarchy process (AHP)), theory of constraint (TOC) and simulation for M/M/1/K queuing environment for investigating the improvement strategies for lead time reduction in major overhaul of military aircraft. This has mainly included: Step 1: analysis of existing activity network using actual overhaul data; Step 2: ranking of constraint activities that most affects the lead time using AHP; Step 3: revised flow activity network using time buffers (TBs) concept of TOC; Step 4: mathematical model formulation for effective utilization of TB using single server finite queuing approach (M/M/1/K queuing environment); Step 5: discrete event simulation representing present overhaul conditions and revised overhaul conditions with different scenarios; and Step 6: sensitivity analysis and interpretation of results. The proposed methodology has been tested on an industrial case study dealing with an aircraft overhaul in India (namely ABC Company).

The proposed overhaul lead-time reduction plan points out the augmentation of resources in order to achieve more than 50 per cent reduction in lead time and waiting time under two scenarios – with overtime and without overtime.

An integrated approach proposed has so far been applicable to the specific aircrafts (Jaguar/Mirage/Kiran) of the ABC Company overhaul division. However, the particular methodology can be proved potentially useful and highly practical when applying to other aircraft types.

The results indicate several problems with the current overhaul strategies that need focused process improvements and a need for capacity augmentation for achieving the enhanced overhaul task of nine+ aircrafts per year with reduced overhaul lead time. The proposed approach also provides the maintenance planners with a platform for decision analysis and support often ignored the capacity augmentation.