Mohammad Asjad

A life cycle cost based approach of O&M support for mechanical systems

Performance of mechanical systems over their life cycle is the main concern of users. Original equipment manufacturers (OEMs) of such systems are made to deliver customized products with documented support to meet the objective. The product support is of various kinds, one of these is operation and maintenance (O&M) support. Cost incurred for each support action adds to the system life cycle cost (LCC) and therefore, a trade-off between O&M support, operational objectives and design characteristics is required to optimize the LCC. In this paper, important issues are identified for O&M support of mechanical systems and steps are proposed. Mathematical models are developed to assess the support objectives i.e. LCC and operational availability of the system. The LCC takes into accounts the acquisition cost and discounted sum of support activity cost, which consist of operating cost, inspection, corrective, preventive, overhaul and logistic cost. The proposed methodology has been implemented on a real life problem, in which the OEM provides O&M support to their compressors, installed at compressed natural gas workstation in national capital region, India. The results shows that a vital saving can be made in system’s LCC, when the support has been optimized in context to preventive maintenance, viz: age based at system level, while group maintenance based on optimum replacement interval and components’ scale parameter of their failure distribution. The sensitivity analysis validated the robustness of the solution methodology and the obtained results. This work will be helpful to OEMs, customers, academician, researchers, industrialists, and other concerned persons, in understanding the importance, severity and benefits obtained by the application and implementation of the O&M support.

A conceptual framework for analysing, improving and optimising supportability of mechanical systems

Supportability for a user is the ability of the support provider to execute all the required activities for upkeep of the system in the most effective, efficient and timely manner throughout the system’s operating life. From the support provider’s perspective, design, maintenance services and logistics along with appropriate contract help in delivering the required support in a profitable manner. However, from the user’s point of view, apart from uninterrupted availability of the product, the life cycle cost (LCC) associated with the product is of immense importance. Hence, a tradeoff between the supportability and the corresponding LCC is to be achieved. Although a vast amount of literature is available on the subject, yet an integrated approach that considers all parameters affecting supportability and LCC in obtaining an optimal solution needs to be developed. This paper presents a framework for analysing supportability along with a proposed methodology that can help in arriving at the optimal solution.

Supportability issues of mechanical systems for their useful life

Purpose – Original equipment manufacturers (OEMs) start providing support to their products, that helped them in beating the competition across the worldwide. The unavailability of spares and crews may also prolong the downtime of equipment, thereby affecting the systems’ performance. The spares and crews have as much effect on the systems’ performance as the design characteristics (i.e. reliability and maintainability). Thus, the OEMs required to extent the support to their products through maintenance, spares, crews, etc., so as to gain the customer satisfaction. Design/methodology/approach – The mathematical model for spares, crews and support quality has been presented in this research work. The problem has been identified from the literature perspective for mechanical systems. Findings – The model has been implemented on a real-life problem, in which the OEMs provide support to their make installed at compressed natural gas workstation in National Capital Region, India. Originality/value – The resear...

Parametric optimisation of the organic Rankine cycle for power generation from low-grade waste heat

This research work deals with the optimisation of controllable parameters of the organic Rankine cycle (ORC) run by waste heat. Performance measures have been evaluated for different waste heat temperatures, condenser temperatures, refrigerants and mass flow rate. The design of experiment was performed on the L9 orthogonal array of Taguchis method. Three performance measures such as thermal efficiency, exergy destruction rate and the work output were used for the assessment and optimisation of the cycle. An optimum combination of parameters obtained by Taguchis method is compared with analytical results. The comparison suggests that the variance of results is within the desired level of confidence. Individual effect of parameters on the performance of ORC is also estimated using analysis of variance. Turbine inlet temperature has large effects on efficiency and work output. Mass flow rate of the refrigerant has the largest effect on the exergy destruction rate.

Optimal support strategy for mechanical systems under contract realm

Purpose – Original equipment manufacturers (OEMs) start providing support to products that helped them in sustaining their business worldwide. The customers are entering into contracts with the OEM, to get the required level of performance but at minimum possible cost. It required the work distribution between OEM/service provider and the client, and may formalize through contract. The contract structure depends upon the number of player involved (customer, OEM and third party) and the support activity. The different contract alternatives can be formulated and the best one may be selected on the basis of minimum Life cycle cost. The paper aims to discuss these issues. Design/methodology/approach – In this work, mathematical models are developed; which are implemented on a real life problem. The developed models are optimized in context to preventive maintenance schedule. Findings – In this research, important issues are listed; research steps and mathematical models are presented. The problem has been ide...

Supportability scenario-based contract alternatives for operating life of a mechanical system

Supportability for a user is the ability of the manufacturer to execute all the support activities that are required for the upkeep of the system, in the most effective, efficient and timely manner throughout the operating life of the product, whenever and wherever needed. In this work, the various issues of supportability of mechanical systems have been studied. The case study is conducted on a compressor manufacturer (Burckhardt), which provides support to their end products that are installed at compressed natural gas stations in National Capital Region (NCR). Both the Burckhardt and its customer have aggressive plans of expanding their operations to new locations in future. As a first step, it is necessary to have a mechanism to generate and evaluate various contract alternatives (CAs) with an objective of minimising the costs incurred to various players in the contract and at the same time, ensuring the minimum service level performance of the system. The methodology presented in this paper will be helpful to Burckhardt and/or any original equipment manufacturer in general, for selecting supportability-based CAs. This study will also be helpful to researchers, engineers, maintenance professionals and other persons concerned, to understand the issues involved in supportability-based CAs.

Analysis of maintenance cost for an asset using the genetic algorithm

Nowadays, almost every firm focuses to beat the global competition across the worldwide. In order to deal with such situation, companies are undertaking efforts to improve the productivity of their products but at the minimum possible cost. Asset management is one of the ways to enhance the productivity under cost constraint which may also be seen as the management strategy for different the phases of asset life cycle. Operations and maintenance is one of the important phases of asset life cycle that can be focussed to improve the productivity. This phase may extend the equipment life, improves availability and retains them in healthy positions. But at the same time, frequent maintenance actions may increase the maintenance cost thereby increase the life cycle cost of a product. The maintenance cost only includes the preventive and corrective maintenance cost and which may in-turn depend upon the scheduled maintenance interval. Thus, a trade-off between maintenance actions and operational objectives (i.e. availability, etc.) is required to minimize the maintenance cost. In this paper, the genetic algorithm is applied to optimize the maintenance cost for higher performance (i.e. availability). A case study is taken into consideration for implementing the GA to optimize the objective function. The three different cases are presented, in the first case, subassemblies are repaired during maintenance action(s); in the second case subassemblies are repaired in preventive maintenance action and while replaced in corrective maintenance action; in the last case, the subassemblies are replaced in both kind of maintenance. In order to check the robustness of the solution, the sensitivity analysis is also performs and that validates the strength of the solution methodology.

Grey relational analysis coupled with principal component analysis for optimization of the cyclic parameters of a solar-driven organic Rankine cycle

Purpose The purpose of this paper is to investigate the effect of four controllable parameters (fuel mixture, evaporation bubble point temperature, expander inlet temperature and condensation dew point temperature) of a solar-driven organic Rankine cycle (ORC) on the first-law efficiency, the exergetic efficiency, the exergy destruction and the volume flow ratio (expander outlet/expander inlet). Design/methodology/approach Nine experiments as per Taguchi’s standard L9 orthogonal array were performed on the solar-driven ORC. Subsequently, multi-response optimization was performed using grey relational and principal component analyses. Findings The results revealed that the grey relational analysis along with the principal component analysis is a simple as well as effective method for solving the multi-response optimization problem and it provides the optimal combination of the solar-driven ORC parameters. Further, the analysis of variance was also employed to identify the most significant parameter based on the percentage of contribution of each cyclic parameter. Confirmation tests were performed to check the validity of the results which revealed good agreement between predicted and experimental values of the response variables at optimum combination of the input parameters. The optimal combination of process parameters is the set with A3 (the best fuel mixture in the context of optimal performance is 0.9 percent butane and 0.1 percent pentane by weight), B2 (evaporation bubble point temperature=358 K), C1 (condensation dew point temperature=300 K) and D3 (expander inlet temperature=370 K). Research limitations/implications In this research, the Taguchi-based grey relational analysis coupled with the principal components analysis has been successfully carried out, whereas for any optimized solution, it is required to have a real-time scenario that may be taken into consideration by the application of different soft computing techniques like genetic algorithm, simulated annealing, etc. The results generated are purely based on theoretical modeling, and, for further research, experimental analyses are required to consolidate the generated results. Originality/value This piece of research work will be helpful to users of solar energy, academicians, researchers and other concerned persons, in understanding the importance, severity and benefits obtained by the application, implementation and optimization of the cyclic parameters of the solar-driven ORC.

Supportability perspectives: current practices and potential area for future research

Supportability is meant to enhance efficiency and effectiveness of the system through support elements, including design and logistics at the lowest possible cost. Elements of the support are installation, documentation, training, maintenance, etc., which play an important role in proper functioning of the system. The paper outlines two research issues, which identify the dimensions of supportability and approaches for addressing the supportability, and based on this, the literature review is carried out. The paper classified the literature, identified the gaps, and suggested potential directions for future research, on the basis of which a vital area of research has been proposed. It is hoped that this work will help designers, practicing engineers and researchers involved in the area, to carry out further research.

A conceptual framework for capturing supportability attributes of a mechanical system

Supportability is an essential element in the successful marketing of mechanical systems which depends upon a products design and can be evaluated in term of support requirements throughout their operational life. In this paper, a conceptual framework pertaining to capture and evaluate the supportability attributes for a mechanical system has been presented. A case study for a reciprocating compressor, as a mechanical system, has been presented, to identify its supportability attributes. This work will be helpful to original equipment manufacturers (OEMs), customers, academician, researchers, industrialists, or any other person concerned, in understanding the importance, severity and benefits obtained by the application and implementation of the supportability at the design stage.