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  • 1.
    Dandotiya, Rajiv
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Decision support models for the maintenance and design of mill liners2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mining companies use heavy-duty equipment that work round the clock in highly abrasive environments. Autogenous (AG) mills used in the mining industry and in ore dressing plants are examples of major bottlenecks in the context of downtime and exert an influence on production economics. The rubber liners inside the mill are critical components for mill shell protection and ore grinding. The replacement and inspection of mill liners are major factors regarding mill stoppages and lead to production losses. The wear readings of mill liners are critical when making replacement decisions, and periodic inspections need to be carried out to obtain wear readings. Wear measurement devices are important in terms of measurement accuracy. The appropriate selection of wear measurement devices can lead to a significant reduction in the overall costs, including the device costs and the production loss costs incurred during inspections of the wear of mill liners. An approach has been developed for selection of the optimum wear measurement method, considering the industry specifications. Based on an analysis performed in a case study, a cost-effective wear measurement method has been suggested, taking the industry requirements into consideration. The wear of mill liners affects the production performance of the mining mill. Hence, the replacement decision for mill liners affects not only the lining cost and the production loss cost, but also the mill revenue due to variation in the metal output. Therefore, the production performance has to be considered when developing decision models for making maintenance replacement policies for mill liners. Variation in the ore properties also affects the liner wear and ore value. Both these parameters have an effect on the cost and revenue parameters. Therefore, consideration of the ore properties in the life cycle profit (LCP) formulation will provide more effective maintenance decisions. A maintenance decision support model has been developed to meet the specific requirements of process, purchase and maintenance departments. The lifetime of different parts (components) of mill liners also varies due to the wear of the parts, for technical reasons concerning the grinding process and the different wear zones inside the mill. The mill needs to stop on a number of occasions for the replacement of parts of mill liners. These stoppages are also one of the major causes of mill downtime and corresponding production losses, which can be minimized by a cost-effective maintenance schedule for the optimum grouping of mill liners for combined replacement. The maintenance schedule depends on the lifetime of the mill liners. The life cycle cost (LCC) can be reduced further through optimum improvement of the lifetime of different parts of the mill liners. A decision support model has been developed to determine the optimum grouping of parts of mill liners for replacement and the optimum improvement in the lifetime of parts of mill liners. The proposed LCC model is also useful for the design departments of liner manufacturers for optimizing the material and dimensions of mill liners, in order to achieve a proposed improved lifetime. A significant improvement in the annual profit was observed when the maintenance policies suggested in the thesis replaced the existing maintenance policies. The research presented in this thesis has used a systematic evaluation approach and pair-wise comparison methods for selection of the optimum wear measurement method for mill liners. Time sampling, correlation studies and simulation methods have been used for LCP optimization, in order to determine the optimum replacement interval for major replacements of mill liners. An approach based on an exhaustive enumeration search has been used for LCC optimization for determining the optimum grouping and the optimum improvement in the lifetime of parts of mill liners. The usefulness of LCC and LCP analyses for mill liners in mining companies is illustrated in the thesis and decision models for effective maintenance planning are demonstrated. The results of the present research are promising for the possibility of making a significant reduction in production losses and the LCC after optimizing the maintenance activities and the lifetime of the mill liners studied in this specific case study. The results of the present thesis are related to specific industrial requirements, and are expected to enhance the capability of making cost-effective replacement decisions. Keywords: Mining industry; Maintenance decisions; Mill liners; Life Cycle Cost (LCC); Life Cycle Profit (LCP); Mill liner design; Economic model; Production Economics; Optimization; Replacement decision; Wear measurement device; Combined replacement; Life improvement

  • 2.
    Dandotiya, Rajiv
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Mathematical model for optimum replacement interval of grinding mill liners2009Conference paper (Refereed)
    Abstract [en]

    This paper presents an approach to decide a cost effective replacement intervals for the liners of a grinding mill used in ore processing plants. The replacement model is based on the detailed analysis of mill performance characteristics, mill failure statistics and maintenance of mill liner. The model formulation for optimum replacement and mill efficiency includes the cost and revenue drivers for the mill. The developed decision model incorporates maintenance cost and monetary gain by doing analysis of production performance of the mill.The developed mathematical model uses the various types of process data i.e. power consumption, mill load, feed flow, metal recovery etc. which is analyzed to establish correlation with life cycle of mill liners. Due to lack of process data for some particular ore types, various techniques such as smoothing, interpolation, simulation and distribution analysis are used to generate the data for the periods for which data is not available. The paper also discusses practical problems encountered while modeling of the real data using classical approach for replacement decisions. The main objective of this paper is to develop a decision support model for taking a cost effective optimum replacement interval for mill liners. A case study was carried out on real data obtained from an ore dressing plant to validate the model.

  • 3.
    Dandotiya, Rajiv
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Banerjee, Rabindra Nath
    Indian Institute of Technology, Kharagpur.
    Ghodrati, Behzad
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Optimal pricing and terminal location for a rail-truck intermodal service: a case study2011In: International Journal of Logistics, ISSN 1367-5567, E-ISSN 1469-848X, Vol. 14, no 5, p. 335-359Article in journal (Refereed)
    Abstract [en]

    To be competitive with other modes of transport, the railway needs to be cost-effective. In order to become more competitive in the logistics industry, Indian Railways has taken new initiative to improve their operations in recent years. A rail-truck intermodal transportation service for Indian Railways is described in this paper. The main focus of the present research is to optimize the freight rate and terminal location together, in order to minimize the total shipping cost of truckers while ensuring the targeted profit of the railway. A model has been developed for the determination of the optimal freight rate and the corresponding intermodal terminal location. The key regulators of this model are the price sensitivity of the trucker and profit guarantee for railways. A case study was developed on the Delhi - Mumbai freight corridor. An analysis was performed to gain insight into the trade-offs among shipment cost and terminal locations.

  • 4.
    Dandotiya, Rajiv
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Berglund, Filip
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Increased production systems effectiveness through condition monitoring and prognostics2011Conference paper (Other academic)
  • 5. Dandotiya, Rajiv
    et al.
    Fuqing, Yuan
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Optimal maintenance decision for line reparable units (LRU) for an aircraft system: a conceptual approach2008In: Quarterly Journal of the Operational Research Society of India (OPSEARCH), ISSN 0030-3887, E-ISSN 0975-0320, Vol. 45, no 3, p. 291-302Article in journal (Refereed)
    Abstract [en]

    Maintenance decisions concerning repair of the Line Replaceable Unit (LRU) of an aircraft fleet need to be considered carefully while deciding the phasing out of the fleet. This is important for achieving higher degree of cost effectiveness and fleet availability at desired level. Discard rate and phasing out period for an aircraft fleet are the critical parameters for determining optimum time to stop the maintenance of LRU. The economic value of remaining useful life of an aircraft fleet should be taken into consideration by salvaging the LRU at the end of the phasing out. The paper suggests a methodology to arrive the time that will minimize the total life cycle cost and provide us economic basis to withdraw the maintenance resources. A mathematical model has been developed for the discard rate of aircrafts based on failure rate, mission life and remaining useful life of the aircrafts in the fleet. This will assist in fulfilling the managing demand of LRU while phasing out of the aircraft fleet.

  • 6.
    Dandotiya, Rajiv
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Economic model for maintenance decision: a case study for mill liners2012In: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 18, no 1, p. 79-97Article in journal (Refereed)
    Abstract [en]

    Purpose – Wear life of mill liners is an important parameter concerning maintenance decision for mill liners. Variations in process parameters such as different ore properties due to the use of multiple ore types influences the wear life of mill liners whereas random order of processing, processing time and monetary value of different ore types leads to variation in mill profitability. The purpose of the present paper is to develop an economic decision model considering the variations in process parameters and maintenance parameters for making more cost effective maintenance decisions. Methodology/approach – Correlation studies, experimental results and experience of industry experts are used for wear life modeling whereas simulation is used for maximizing mill profit to develop economic decision model. The weighting approach and simulation have been considered to emphasize the contribution of parameters such as ore value and processing time of a specific ore type to a final result. Findings – This study resulted in developing an economic decision support model for mill liner replacement considering the influence of the variation in the process parameters and its affect on maintenance decisions. This study identified the various important process and maintenance parameters and described the influence of variations in the process parameters on decisions model. The results obtained from the model show that an optimum maintenance policy can only not reduce the maintenance cost, but also affect the process performance, which leads to significant improvement in the savings of the ore dressing mill. Originality and Value – The developed model considers the economic influence of ore properties, variation in process parameters and proposed an approach for considering these parameters in decision making which enhance its value in terms of increased mill profit. Practical implications – The proposed economic decision model is practically feasible and can be implemented within the ore dressing mill industries. Using the model, the cost effective maintenance decision can increase the profit of the organization significantly. Paper type – Case study Keywords: Economic model; Replacement decision; Mill liners; Ore properties; Optimization; Process parameters

  • 7.
    Dandotiya, Rajiv
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lundberg, Jan
    Parida, Aditya
    Nordström, Jakob
    LTU.
    A systematic evaluation of devices for measuring abrasive wear of mill liners2009In: 22nd International Congress on Condition Monitoring and Diagnostic Engineering Management: COMADEM 2009 ; June 9 - 11, 2009, San Sebastian, Spain, Miramar Palace / [ed] Aitor Arnaiz, Eibar: Fundaci n Tekniker , 2009, p. 419-427Conference paper (Refereed)
    Abstract [en]

    Inspection of the liner wear in the mill of an ore dressing plant is one of the critical parameters in the context of mill downtime and production performance. The total downtime cost during measurement can be reduced by a significant fraction by using appropriate measurement devices. Due to the different quality dimensions of a measuring device, e.g. the cost, accuracy, reliability and accessibility, it is necessary to select an appropriate device based on the specific needs of the industry. Customer satisfaction is perhaps the most important performance measure for the service quality of the device, and therefore this paper provides an approach to define the customer satisfaction with reference to the mentioned quality dimensions. The main aim of this paper is to determine a unified measure or quality index for the service quality of the measurement device across all the dimensions. Each quality index will then correspond to the total predicted usability of the particular measurement method based on the industry needs. Furthermore, this study also discusses the advantages and disadvantages of existing measurement methods and proposes an indirect measurement method to reduce the downtime during inspection.

  • 8.
    Dandotiya, Rajiv
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Wijaya, Andi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Evaluation of abrasive wear measurement devices of mill liners2011In: International Journal of COMADEM, ISSN 1363-7681, Vol. 14, no 2, p. 3-17Article in journal (Refereed)
    Abstract [en]

    Measurement of the liner wear in the mill of an ore dressing plant is one of the critical parameters in the context of mill downtime and production performance. The total downtime cost during measurement can be reduced by a significant fraction by using appropriate measurement devices. Due to the different quality attributes of a measuring device, e.g. the cost, accuracy, reliability and accessibility, it is necessary to select an appropriate device based on the specific needs of the industry. The main aim of this study is to determine a unified measure or quality index for the service quality of the measurement device across selected attributes. Each quality index will then correspond to the total predicted usability of the particular measurement method based on the industry needs. Furthermore, this study includes test of selected measurement methods and discusses the advantages and disadvantages for the same. It also proposes a new concept of an indirect measurement method to reduce the downtime during inspection.

  • 9. Kumar, Saurabh
    et al.
    Dandotiya, Rajiv
    Kumar, Rajesh
    Aker Kvaerner, Stavanger.
    Kumar, Uday
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Inspection frequency optimization model for degrading flowlines on an offshore platform2008In: International Journal of Reliability, Quality and Safety Engineering (IJRQSE), ISSN 0218-5393, Vol. 15, no 2, p. 167-180Article in journal (Refereed)
    Abstract [en]

    Many offshore oil and gas installations in the North Sea are approaching the end of their designed lifetimes. Technological improvements and higher oil prices have developed favorable conditions for more oil recovery from these existing installations. However, in most cases, an extended oil production period does not justify investment in new installations. Therefore cost-effective maintenance of the existing platform infrastructure is becoming very important. In this paper, an inspection frequency optimization model has been developed which can be used effectively by the inspection and maintenance personnel in the industry to estimate the number of inspections/optimum preventive maintenance time required for a degrading component at any age or interval in its lifecycle at a minimum total maintenance cost. The model can help in planning inspections and maintenance intervals for different components of the platform infrastructure. The model has been validated by a case study performed on flowlines installed on the top side of an offshore oil and gas platform in the North Sea. Reliability analysis has been carried out to arrive at the best inspection frequency for the flowline segments under study

  • 10.
    Larsson, Michael
    et al.
    Luleå tekniska universitet.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Dandotiya, Rajiv
    Development of a decision optimization model for aircraft workshop capacity2010In: Proceedings of the 1st international workshop and congress on eMaintenance, Luleå tekniska universitet, 2010, p. 121-126Conference paper (Refereed)
    Abstract [en]

    This paper presents an approach to determine the optimal aircraft overhaul capacity in the workshops for an aircraft fleet. The aircraft fleet contains one aircraft type with different models of that type. A mathematical model has been constructed to calculate the lowest cost alternative.The mathematical model uses various types of data to calculate the optimal workshop overhaul capacity like costs, times, numbers of workers, aircrafts used flight time etc. the paper presents one case study carried out representing a future coming need. Parts of the sensitivity analysis are given to show the models behaviour. The objective of this paper is to introduce a model that can be used as a decision helping tool for the decision makers when determine the future needed aircraft overhaul capacity in the workshops. The model can be a part of the emaintenance platform.

  • 11.
    Nordström, Jakob
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Parida, Aditya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Dandotiya, Rajiv
    Lundberg, Jan
    Crack detection methods and ranking for mining mill machinery2009In: 22nd International Congress on Condition Monitoring and Diagnostic Engineering Management: COMADEM 2009 ; June 9 - 11, 2009, San Sebastian, Spain, Miramar Palace / [ed] Aitor Arnaiz, Eibar: Fundaci n Tekniker , 2009, p. 313-321Conference paper (Refereed)
    Abstract [en]

    The mining industry is severely exposed to various effects of the dynamic global business scenario today. The main issue for the mining industry is to maximize the availability of its machinery. Fatigue cracking in rotating mill machines is one of many critical factors in the context of function, safety, reliability and increased maintenance cost due to related unpredictable mill failures. There are several reasons for the appearance of cracks in mills. Several detection methods and technologies are available today, which are crack specific, depending on size and location. It is essential to select an appropriate crack detection method to fulfil the needs of the industries and the operational conditions, because each method has its own particular advantages and disadvantages. The main aim of this paper is to highlight the scopes and limitations of these methods. In this paper also the Analytical Hierarchical Process (AHP) is applied to determine the rank or unified measure for the selected crack detection methods. The aim of this analysis is to assist maintenance personnel in selecting the appropriate crack detection device.

  • 12.
    Parida, Aditya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Nordström, Jakob
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lundberg, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Dandotiya, Rajiv
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Crack detection methods for mining mill machinery2010In: Asset Management & Maintenance Journal, ISSN 1835-789X, Vol. 23, no 2, p. 44-49Article in journal (Refereed)
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