A Systems Approach Towards Reliability-Centred Maintenance (RCM) of Wind Turbines

AbstractWind turbines are a proven source of clean energy with wind power energy harvesting technologies supplying about 3% of global electricity consumption. However there is an increasing demand on maintenance and operational improvements since turbines have been plagued with downtime problems of major components e.g. gearboxes and generators, especially with offshore turbines which are difficult to access. Reliability Centric Maintenance (RCM) is a way of capturing the potential causes of downtime and poor performance by preventing failures and having a proactive approach to operations and maintenance (O&M). However, for a large fleet of turbines, adopting the RCM approach becomes difficult due to the complexities that arise as a result of the interactions between individual elements that make up the system in the product lifecycle. This paper discusses how a systems thinking approach can be used to identify the relevant aspects and possible interactions between the RCM approach and wind turbine gearboxes and also how the gaps that exist within the system can be closed so as to add value to business. The outcome of the paper is a proposal for applying a systems approach to wind turbine gearbox operation and maintenance, optimising the asset value adding contribution at minimal total cost to the operator

Modelling the impact of the environment on offshore wind turbine failure rates

For offshore wind turbines to become an economical energy generation option it is vital that the impact of the offshore environment on reliability is understood. This paper aims to model the impact of the wind speed and the external humidity and temperature. This is achieved using reliability data comprising of two modern, large scale wind farm sites consisting of approximately 380 wind turbine years of data. Weather data comes from a nearby weather station and an onsite met mast. A model is developed, using the reliability data, which calculates weather dependant failure rates and downtimes which are used to populate a Markov Chain. Monte Carlo simulation is then exercised to simulate the lifetime of a large scale wind farm which is subjected to controlled weather conditions. The model then calculates wind farm availability and component seasonal failure rates. Results show that offshore, the wind speed will have the biggest impact on component reliability, increasing the wind turbine failure rate by approximately 61%. The components affected most by this are the control system and the drive train. The higher offshore wind speeds appear to cause a higher proportion of major failures than experienced onshore. Research from this paper will be of interest to operators and wind turbine manufacturers who are interested in maintenance costs and logistics

Availability Improvement Methodology in Thermal Power Plant

Availability of a complex system of thermal power plant is strongly influenced by maintenance program and component reliability. Various maintenance techniques, likes RCM (reliability-centred maintenance), RBM (risk based maintenance) and CBM (condition-based maintenance), have been applied to improve the availability. Implementation of RCM, RBM, CBM alone or combined RCM and RBM or RCM and CBM is a maintenance technique used in thermal power plants. This study develops an new maintenance methodology integrating RCM, RBM and CBM to increase the availability of thermal plants. The method generates MPI (Priority Maintenance Index) and FDT (Failure Defense Task). MPI is used to determine the priority of components in maintenance program. FDT consists of the tasks of monitoring and assessment of conditions other than maintenance tasks. Both MPI and FDT obtained from development of functional tree, failure mode effects analysis, fault-tree analysis, and risk analysis (risk assessment and risk evaluation) were then used to develop and implement a plan and schedule maintenance, monitoring and assessment of the condition and ultimately perform availability analysis. The results of this study indicate that the reliability, risks and conditions-based maintenance methods, in an integrated manner can increase the availability of thermal power plant

Asset management strategies for power electronic converters in transmission networks: Application to HVdc and FACTS devices

The urgency for an increased capacity boost bounded by enhanced reliability and sustainability through operating cost reduction has become the major objective of electric utilities worldwide. Power electronics have contributed to this goal for decades by providing additional flexibility and controllability to the power systems. Among power electronic based assets, high-voltage dc (HVdc) transmission systems and flexible ac transmission systems (FACTS) controllers have played a substantial role on sustainable grid infrastructure. Recent advancements in power semiconductor devices, in particular in voltage source converter based technology, have facilitated the widespread application of HVdc systems and FACTS devices in transmission networks. Converters with larger power ratings and higher number of switches have been increasingly deployed for bulk power transfer and large scale renewable integration—increasing the need of managing power converter assets optimally and in an efficient way. To this end, this paper reviews the state-of-the-art of asset management strategies in the power industry and indicates the research challenges associated with the management of high power converter assets. Emphasis is made on the following aspects: condition monitoring, maintenance policies, and ageing and failure mechanisms. Within this context, the use of a physics-of-failure based assessment for the life-cycle management of power converter assets is introduced and discussed

An investigation into the improvement of maintenance quality in a production plant through the use of reliability management

Abstract: Extensive research has been conducted on plant reliability maintenance. However, getting the maintenance system in place remains the core of maintenance improvement. The purpose of this research dissertation is to investigate the impact reliability management has within production industries and its role in improving the quality of maintenance. This study will assist management to reflect on the costeffectiveness and influence that the maintenance management system has within the organisation. The study will also contribute to existing knowledge in plant reliability maintenance. It is, therefore, significant for an organisation to establish good management practices and set maintenance as an integral part of their overall plant strategy. The approach that was followed by this research is a mixed method – a combination of quantitative and qualitative. Data collection was carried out through a literature review, observations, a questionnaire, a survey, interviews and from company documentation. An employee questionnaire was prepared and distributed to 25 participants to conduct gap analysis and evaluate the maintenance practices within the observed company. A benchmark study was also performed using an online survey, based on 85 responses from employees in other processing plant industries within South Africa. The empirical study conducted with Company A’s employees (mainly from the maintenance and operation departments) identified possible blunders, which transpired during the reliability management system implementation phase. Based on this sample the results obtained indicated that maintenance is done unnecessarily on the plant on average. The study also found issues regarding maintenance financial planning ineffectiveness, unavailability of spares and lack of skillsets to perform jobs. The online survey revealed that organisations do make use of Computerised Maintenance Management System (CMMS) to facilitate their maintenance. CMMS also has a positive impact on the overall maintenance processes and productivity. The study identified the importance of planning and scheduling shutdowns in advance, as a significant part of the maintenance annual budget and cost reduction. ..M.Phil. (Engineering Management

The contribution of planned maintenance on plant performance at Richards Bay Transnet port terminal.

Master’s degree. University of KwaZulu-Natal, Durban.This study aimed to evaluate the effectiveness of maintenance management function at Transnet Richards Bay Plant (TRP), located in Richards Bay, KwaZulu Natal. The highly automated manufacturing machinery, reliable production machines and stringent health and safety legislation have hoisted the significance of the maintenance function within the manufacturing plants into the higher trajectory. Research data was solicited by conducting a survey of TRP employees who were directly and indirectly impacted by the maintenance function. A sample of 95 employees, from all hierarchical levels at TRP, participated and responded to the questionnaire. Statistical analysis using descriptive and inferential statistics were conducted. The empirical research done in this study supplemented the theory of maintenance management pertaining to the strategic role of the maintenance function within manufacturing plants. The findings of this study revealed that, the maintenance function at TRP is perceived to be an important business management function which contributes positively towards the company’s overall objectives and profitability. The study also revealed that, perceived shortcomings of the maintenance function make TRP’s maintenance function ineffective. The study also revealed TRP is a closed system manufacturing firm with a cost centre view towards the maintenance management function. The study also confirmed the positive support towards the implementation of Total Productive Maintenance (TPM) as the panacea for improvement of maintenance effectiveness. The study recommends that TPM is a maintenance strategy which must be implemented in order to improve maintenance effectiveness and manufacturing operational performance, at TRP. The recommendations with regards to the study findings and the means to ensure expeditious execution to improve the effectiveness of the maintenance function were developed and stated

An integrated model for asset reliability, risk and production efficiency management in subsea oil and gas operations

PhD ThesisThe global demand for energy has been predicted to rise by 56% between 2010 and 2040 due to industrialization and population growth. This continuous rise in energy demand has consequently prompted oil and gas firms to shift activities from onshore oil fields to tougher terrains such as shallow, deep, ultra-deep and arctic fields. Operations in these domains often require deployment of unconventional subsea assets and technology. Subsea assets when installed offshore are super-bombarded by marine elements and human factors which increase the risk of failure. Whilst many risk standards, asset integrity and reliability analysis models have been suggested by many previous researchers, there is a gap on the capability of predictive reliability models to simultaneously address the impact of corrosion inducing elements such as temperature, pressure, pH corrosion on material wear-out and failure. There is also a gap in the methodology for evaluation of capital expenditure, human factor risk elements and use of historical data to evaluate risk. This thesis aims to contribute original knowledge to help improve production assurance by developing an integrated model which addresses pump-pipe capital expenditure, asset risk and reliability in subsea systems. The key contributions of this research is the development of a practical model which links four sub-models on reliability analysis, asset capital cost, event risk severity analysis and subsea risk management implementation. Firstly, an accelerated reliability analysis model was developed by incorporating a corrosion covariate stress on Weibull model of OREDA data. This was applied on a subsea compression system to predict failure times. A second methodology was developed by enhancing Hubbert oil production forecast model, and using nodal analysis for asset capital cost analysis of a pump-pipe system and optimal selection of best option based on physical parameters such as pipeline diameter, power needs, pressure drop and velocity of fluid. Thirdly, a risk evaluation method based on the mathematical determinant of historical event magnitude, frequency and influencing factors was developed for estimating the severity of risk in a system. Finally, a survey is conducted on subsea engineers and the results along with the previous models were developed into an integrated assurance model for ensuring asset reliability and risk management in subsea operations. A guide is provided for subsea asset management with due consideration to both technical and operational perspectives. The operational requirements of a subsea system can be measured, analysed and improved using the mix of mathematical, computational, stochastic and logical frameworks recommended in this work

Establishment of a novel predictive reliability assessment strategy for ship machinery

There is no doubt that recent years, maritime industry is moving forward to novel and sophisticated inspection and maintenance practices. Nowadays maintenance is encountered as an operational method, which can be employed both as a profit generating process and a cost reduction budget centre through an enhanced Operation and Maintenance (O&M) strategy. In the first place, a flexible framework to be applicable on complex system level of machinery can be introduced towards ship maintenance scheduling of systems, subsystems and components.;This holistic inspection and maintenance notion should be implemented by integrating different strategies, methodologies, technologies and tools, suitably selected by fulfilling the requirements of the selected ship systems. In this thesis, an innovative maintenance strategy for ship machinery is proposed, namely the Probabilistic Machinery Reliability Assessment (PMRA) strategy focusing towards the reliability and safety enhancement of main systems, subsystems and maintainable units and components.;In this respect, the combination of a data mining method (k-means), the manufacturer safety aspects, the dynamic state modelling (Markov Chains), the probabilistic predictive reliability assessment (Bayesian Belief Networks) and the qualitative decision making (Failure Modes and Effects Analysis) is employed encompassing the benefits of qualitative and quantitative reliability assessment. PMRA has been clearly demonstrated in two case studies applied on offshore platform oil and gas and selected ship machinery.;The results are used to identify the most unreliability systems, subsystems and components, while advising suitable practical inspection and maintenance activities. The proposed PMRA strategy is also tested in a flexible sensitivity analysis scheme.There is no doubt that recent years, maritime industry is moving forward to novel and sophisticated inspection and maintenance practices. Nowadays maintenance is encountered as an operational method, which can be employed both as a profit generating process and a cost reduction budget centre through an enhanced Operation and Maintenance (O&M) strategy. In the first place, a flexible framework to be applicable on complex system level of machinery can be introduced towards ship maintenance scheduling of systems, subsystems and components.;This holistic inspection and maintenance notion should be implemented by integrating different strategies, methodologies, technologies and tools, suitably selected by fulfilling the requirements of the selected ship systems. In this thesis, an innovative maintenance strategy for ship machinery is proposed, namely the Probabilistic Machinery Reliability Assessment (PMRA) strategy focusing towards the reliability and safety enhancement of main systems, subsystems and maintainable units and components.;In this respect, the combination of a data mining method (k-means), the manufacturer safety aspects, the dynamic state modelling (Markov Chains), the probabilistic predictive reliability assessment (Bayesian Belief Networks) and the qualitative decision making (Failure Modes and Effects Analysis) is employed encompassing the benefits of qualitative and quantitative reliability assessment. PMRA has been clearly demonstrated in two case studies applied on offshore platform oil and gas and selected ship machinery.;The results are used to identify the most unreliability systems, subsystems and components, while advising suitable practical inspection and maintenance activities. The proposed PMRA strategy is also tested in a flexible sensitivity analysis scheme

Financing sustainable cities in South Africa

Although directives exist with respect to promoting sustainable development, financial strategies to cater for collective sustainable development, along with an increasing population, need to be formulated relevant to metropolitan and urban areas. This study determined the infrastructure investment basis of a sustainable city to investigate various funding mechanisms resulting in the design of a model for the financing of sustainable cities. For the study, first the various infrastructure investment alternatives were established from the literature, and thirteen themes and their relevant interventions were identified. Tangible and intangible methods of assessment were then identified as ways to calculate the acceptability of an intervention. A case study based on a hypothetical city was developed to determine the infrastructure investment base. Initially, only one intervention of a theme was populated and then confirmed by city development experts. Thereafter, all the themes were populated, and the acceptability of the interventions were determined. This provided an overview of the investment base of a sustainable city. The investment base facilitated deriving applicable tools and instruments to finance it. As a result, possible finance alternatives were derived for each of the identified themes. Although most of the financing of sustainable cities revolved around public sector finance, the private sector also played an important role for the financing of sustainable cities. Based on the investment base for sustainable cities and the resultant financing thereof, a model for the financing of sustainable cities was developed. The model consisted of four components. Firstly, the model included an application of financing tools and instruments relevant to the identified themes of sustainable city development. Secondly, the model included the application of financing tools and instruments with respect to an immediate interventionist focus, a facilitative focus, a gradual intervention and an enabling intervention. Thirdly, the model included financing tools and instrument types in terms of incentive, opportunity, punitive and mandatory interventions. Fourthly, the model included the application of financing tools and instruments with respect to scale in terms of a city-wide application, sector-wide application, urban application or suburban application. In addition, the model included the application of financing tools and instruments and their relation to addressing poverty within the city context. Although the public sector will always remain the key initiator behind infrastructure development, various mechanisms of financing, along with applicable financing partners and the basis of investment, are required to address future sustainable cities. This study may potentially form the basis of that platform