Browsing by Author "Strutt, J. E."
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Item Open Access Analysis of sweet corrosion profiles(Cranfield University, 1990-05) Esfahani, A.; Strutt, J. E.The sweet corrosion profiles of X-52 carbon steel in 0.l% NaCl at 30, 40, 50 and 60°C were analysed. The corrosion tests lasted for a period of one month. They were performed using a flow loop under a total gas pressure of 1 atm. containing carbon dioxide (99.95% & 100 vpm O2). The corrosion profiles were obtained by scanning the corroded surfaces with a stylus. The results were analysed and compared with linear polarisation resistance (LPR) data. lt has been found that the (LPR) data at 40°C, i the absence of significant pitting, progressively underestimated the actual metal loss values. It has been proposed that the above discrepancy is due to the occurrence of small scale localised corrosion. The above effect was found to be exaggerated at 60°C, where extensive pitting occurred. Attempts to find a correlation between the (LPR) measurements and the actual metal loss distributions were unsuccessful. Furthermore, although sudden increase of the instantaneous corrosion rates for passive samples appeared to signal the onset of localised attack, i the absence of prior knowledge of the relative spread of the localised corrosion, it was not possible to quantify the observed errors. The range of the metal loss distributions was found to increase with time. This was most notíceable at 60°C. The progress of localised corrosion therefore, appears to have extended the distributions towards the extreme values. It has been proposed that, in the absence of severe pitting, the sweet corrosion profiles can be approximated by the Weibull statistical function. For pitted samples, where the localised attack resulted i metal loss on different scales, the upper 10% of the values were also found to be approximated by the Weibull function. The Weibull function was used for predicting the progress of the metal loss values with time. The analysis of the top 10% values, for pitted surfaces at 60°C, however, suggested the occurrence of an accelerating rate of attack. The original model was therefore improved to provide a time dependent sweet corrosion model. It has been estimated that the corrosion rate at 60°C increases with time at intervals of approximately 8 days. The effect of methanol on the sweet corrosion of X-52 carbon steel in 1% NaCl was also studied under stagnant conditions at 4, 40 and 60°C. The partial pressure of carbon dioxide was maintained at 0.3 bar. lt has been found that the corrosion rate decreases with increasing methanol concentration. The data was used to develop a predictive model within the range of 10 to 60% vol. methanol.Item Open Access Assessment of Emergency Management Performance and Capability(Cranfield University, 2003-09-04) Jones, Brian J.; Strutt, J. E.Hazardous industries in the UK and Europe are under pressure to increase the transparency and accountability of the ways in which they manage their hazards and the risks they pose to the population and environment. The literature has indicated that the field would benefit from a risk-based, continuous improvement approach to emergency management in hazardous industry. The aim of this research was to construct a framework to enable assessment of the emergency management performance and capability within UK hazardous industry operators. Continuous improvement models from other fields were examined, and an established model called the Capability Maturity Model was selected to form the basis of the framework. A three-stage data collection methodology was designed to gain an overview of an organisation's emergency management capability. This methodology involved reviewing a sample of emergency plans related to UK hazardous industrial sites and observing eight emergency exercises at major hazard industrial sites. The third stage was to record the learning capability of the organisation by observing their feedback processes and interviewing members of staff were necessary. Analysis of the resulting data enabled the construction of a set of eight key processes that define an emergency management system. Using the five- level structure of the Capability Maturity Model along with the principals of continuous improvement, an emergency management assessment framework was constructed. The assessment framework was successfully tested in a large Local Authority, using its emergency plan, a major exercise and a follow-up interview to collect the relevant information. The assessment provided clear details of current capability and maturity of the emergency management system, giving structured guidance on weaknesses in specific process areas and more generally in particular stages of the emergency management system. This ultimately enabled the Local Authority to focus its improvement efforts, increasing their efficiency in learning and effectiveness in preparedness and response.Item Open Access Benchmarking risk management practice within the water utility sector(Cranfield University, 2006-12) MacGillivray, Brian H.; Pollard, Simon; Strutt, J. E.Explicit approaches to risk analysis within the water utility sector, traditionally applied to occupational health and safety and public health protection, are now seeing broader application in contexts including corporate level decision making, asset management, watershed protection and network reliability. Our research suggested that neither the development of novel risk analysis techniques nor the refinement of existing ones was of paramount importance in improving the capabilities of water utilities to manage risk. It was thought that a more fruitful approach would be to focus on the implementation of risk management rather than the techniques employed per se. Thus, we developed a prescriptive capability maturity model for benchmarking the maturity of implementation of water utility risk management practice, and applied it to the sector via case study and benchmarking survey. We observed risk management practices ranging from the application of hazard and operability studies, to the use of scenario planning in guiding organisational restructuring programmes. We observed methods for their institutionalisation, including the use of initiation criteria for applying risk analysis techniques; the adoption of formalised procedures to guide their application; and auditing and peer reviews to ensure procedural compliance and provide quality assurance. We then built upon this research to develop a descriptive1 capability maturity model of utility risk analysis and risk based decision making practice, and described its case study application. The contribution to knowledge of this stage of the research was three-fold, we: synthesized empirical observations with behavioral and normative theories to codify the processes of risk analysis and risk based decision making; placed these processes within a maturity framework which distinguishes their relative maturity of implementation from ad hoc to adaptive; and provided a comparative analysis of risk analysis and risk based decision making practices, and their maturity of implementation, across a range of utility functions. The research provides utility managers, technical staff, project managers and chief finance officers with a practical and systematic understanding of how to implement and improve risk management, and offers preliminary guidance to regulators concerning how improved water utility governance can be made real.Item Open Access Benchmarking risk management within the international water utility sector. Part I: Design of a capability maturity methodology.(Taylor & Francis, 2007-01-31T00:00:00Z) MacGillivray, Brian H.; Sharp, J. V.; Strutt, J. E.; Hamilton, Paul D.; Pollard, Simon J. T.Risk management in the water utility sector is becoming increasingly explicit. However, due to the novelty and complexity of the discipline, utilities are encountering difficulties in defining and institutionalising their risk management processes. In response, the authors have developed a sector specific capability maturity methodology for benchmarking and improving risk management. The research, conducted in consultation with water utility practitioners, has distilled risk management into a coherent, process-based framework. We identified eleven risk management processes, and eight key attributes with characterise the extent to which these processes are defined, controlled and institutionalised. Implementation of the model should enable utilities to more effectively employ their portfolio of risk analysis techniques for optimal, credible and defensible decision making.Item Open Access Benchmarking risk management within the international water utility sector. Part II: A survey of eight water utilities.(Taylor & Francis, 2007-01-31T00:00:00Z) MacGillivray, Brian H.; Sharp, J. V.; Strutt, J. E.; Hamilton, Paul D.; Pollard, Simon J. T.Risk management in the water utility sector is fast becoming explicit. Here, we describe application of a capability model to benchmark the risk management maturity of eight water utilities from the UK, Australia and the USA. Our analysis codifies risk management practice and offers practical guidance as to how utilities may more effectively employ their portfolio of risk analysis techniques for optimal, credible, and defensible decision making. For risk analysis, observed good practices include the use of initiation criteria for applying risk assessment techniques; the adoption of formalised procedures to guide their application; and auditing and peer reviews to ensure procedural compliance and provide quality assurance. Additionally, we have identified common weaknesses likely to be representative of the sector as a whole, in particular a need for improved risk knowledge management and education and training in the discipline.Item Open Access Development of a generic methodology for probabilistically predicting the reliability of offshore mechanical components at the design stage(Cranfield University, 2000-10) Warburton, D; Strutt, J. E.The continuously developing requirements of the offshore oil and gas Operators are placing more stringent demands on the designers to produce optimised solutions, with reduced development schedules, and application of new technologies for extreme environmental and operational conditions. The compounding uncertainty of service conditions and in the design capabilities is causing the designer to over-design, conduct extensive pre-service testing and introduce design redundancy. As such, designers have been forced to turn to reliability techniques in order to quantify the life of their designs. This has extended as far as needing to integrate reliability concepts, tools and methodologies into the design process. In recent times, the industry has attempted to apply conventional reliability tools within the design process, in terms of failure identification and reliability quantification. However, the use of historical reliability data has shown to be a particular downfall. As such, there has been a drive to predict the reliability of mechanical components based on their underlying degradation and failure processes and mechanisms. Consequently, this research is initially concerned with the development of a methodology, including an assessment of existing methods, that could be used to more readily understand the underlying failure characteristics of a mechanical component in terms of material, geometrical, environmental and operational characteristics. A particular underlying mechanism has been chosen and mathematical models were developed that simulate its physical behaviour and its degradation characteristics. Additionally, due to the potential uncertainty in the models and limited understanding of the characteristics of the underlying mechanism, the model was simulated within a probabilistic framework, fundamentally by application of the stress strength interference modelling approach. Finally, the model and its parameters were assessed to determine how uncertain governing parameters could appear to lead to variations in the reliability of the actuator.Item Open Access Erosion - corrosion modelling of materials used in petroleum production(Cranfield University, 1994-09) Hamzah, Razali Bin; Strutt, J. E.; Stephenson, David J.Experimental erosion/corrosion modelling was performed on C-Mn steels and corrosion resistant alloys commonly used in petroleum production. A graded commercial sand of 50-30b pm size range, similar to sands produced from typical oil/gas fields was used to simulate the erosive medium. The experimental conditions such as the sand flux, particle velocity, pressure and temperature, were chosen based on typical field operating conditions for corrosion, erosion and erosion-corrosion tests imposed on the materials. The corrosion environment was created by feeding in CO2 gas with atomised water into the test chamber. A centrifugal erosion rig (45) with necessary modifications to suit wet and dry test conditions was used in the experiments. The rig was capable of generating over 150 m/s particle velocity and could operate at high temperatures to generate consistent results. Results show that (a) there was a soft thin layer of corrosion products formed on the C-Mn specimens even at 20°C which can easily be removed by the impacting particles , (b) the scale growth rate kinetics were found to be parabolic and vary between 8x10-3 pun'/h to 50x10-3 iim2/h depending on the material and temperature, (c) the process of metal recession consists of the removal and regrowth of soft corrosion scale at low flux and low velocity, and erosion of substrate at high flux and high velocity, (d) the erosion-corrosion rates were found to vary between 2- 30 times over the pure erosion rates under the same conditions, depending on the sand flux, particle velocity and temperature. An existing computer simulation model (46) was used to simulate the conditions observed from the experiments. Some improvements were incorporated into the programme and the final model is capable of predicting the erosion and erosion-corrosion rates applicable to petroleum production.Item Open Access Evaluation of a task performance resource constraint model to assess the impact of offshore emergency management on risk reduction(Cranfield University, 2000-05) Lyons, Melinda; Strutt, J. E.In this age of safety awareness, technological emergencies still happen, occasionally with catastrophic results. Often human intervention is the only way of averting disaster. Ensuring that the chosen emergency managers are competent requires a combination of training and assessmentH. owever, assessmenct urrently relies on expert judgement of behaviour as opposed to its impact on outcome, therefore it would be difficult to incorporate such data into formal Quantitative Risk Assessments (QRA). Although there is, as yet, no suitable alternative to expert judgement, there is a need for methods of quantifying the impact of emergency management on risk reduction in accident and incidents. The Task Performance Resource Constraint (TPRC) model is capable of representing the critical factors. It calculates probability of task success with respect to time based on uncertainties associated with the task and resource variables. The results can then be used to assess the management performance based on the physical outcome in the emergency, thereby providing a measure of the impact of emergency management on risk with a high degree of objectivity. Data obtained from training exercises for offshore and onshore emergency management were measured and successfully used with the TPRC model. The resulting probability of success functions also demonstrated a high level of external validity when used with improvements in emergency management or design changes or real data from the Piper Alpha disaster. It also appeared to have more external validity than other HRQ/QRA techniques as it uses physical data that are a greater influence on outcome than psychological changes - though this could be because the current HRA/QRA techniques view human unreliability as probability of error rather than probability of failure. The simulation data were also used to build up distributions of timings for simple emergency management tasks. Using additional theoretical data, this demonstrated the model's potential for assessing the probability of successf or novel situations and future designs.Item Open Access Modelling of multiple failure mechanisms for system reliability prediction(Cranfield University, 2002-01) Place, C. S.; Strutt, J. E.; Irving, Phil E.Helicopters are highly dependent on their transmission systems, which provide the vital links from the engines to the rotor and ancillary systems. Components are highly loaded and must be manufactured to a high degree of accuracy; the lack of redundancy implies that this is a `series-chain' system. Existing techniques for calculating expected life are based upon historical data from different gearbox and helicopter types, thus limiting the confidence of the results. Design techniques may be conservative in some areas, whilst neglecting to consider different load patterns, usage, maintenance and environmental factors. This work describes the development of probabilistic models that represent damage accumulated by fatigue, wear and corrosion of the key components with an Intermediate gearbox (IGB). The parameters of these models represent geometrical, load and material data at the design stage, and produce an output in terms of failure probability against operating hours. This allows the influential parameters to be identified before building a prototype helicopter gearbox. The results from these models are then used to predict the upper and lower bounds of system reliability. This enables the combination of diverse failure mechanisms to be viewed to determine the relevant significance of each failure mechanisms. The effectiveness of the gearbox monitoring systems has been incorporated in the computer model by considering the probability of detection (POD) of each failure mechanism. The work to develop models found that there is a large body of work available to describe damage accumulation due to fatigue, but far less in regard to wear and corrosion. Fatigue models are very sensitive to load and material variability, particularly tooth root bending fatigue, for which many loads are considered `non-damaging'. Wear models are mostly affected by changes in material hardness, wear coefficient and slip amplitude; changes in load are less influential on the predicted time to failure. The results for galvanic corrosion are dominated by the corrosion rate and time to initiate. In the system reliability model, reducing gear load appears to be the simplest means to increase life; increases in material strength and reduction in material variability are less achievable without significant improvements in manufacture and/or material technology.Item Open Access Reliability analysis for subsea pipeline cathodic protection systems /(Cranfield University, 1996-10) Trille, Christophe; Strutt, J. E.Subsea pipelines, as the main transportation means for oil and gas produced offshore, are a key element of the production system. Cathodic protection systems (CPS) are used in combination with surface coatings to protect the pipeline from external corrosion. Although cases of pipeline failure due to external corrosion remain rare, such failures can have catastrophic effects in terms of human lives, environment degradation and financial losses. The offshore industry was led to the use of risk analysis techniques subsequent to major disasters, such as Piper Alpha and Alexander Kjelland. These accidents made the development and use of risk analysis techniques of highly significant interest, and reliability analysis is presently becoming a more important management tool in that field for determining reliability of components such as pipelines, subsea valves and offshore structures. This research is based on an analysis of subsea pipeline cathodic protection systems and on a model of the electrochemical potentials at the pipeline surface. This potential model uses finite element modelling techniques, and integrates probabilistic modules for taking into account uncertainties on input parameters. Uncertainties are used to calculate standard deviations on the potential values. Based on the potentials and potential variances obtained, several parameters characteristic of the cathodic protection system reliability, such as probability of failure and time to failure, are calculated. The model developed proved suitable for simulating any pipeline, under any environmental and operational conditions. It was used as a reliability prediction tool, and to assess the effects of some parameters on the cathodic protection system reliability.Item Open Access Reliability modelling of subsea gate valves(Cranfield University, 1993-03) Ouchet, L.; Strutt, J. E.Offshore Installations comprise complex, expensive and potentially hazardous facilities which need to be maintained and operated in a proper and safe manner. Valves are one of the most widely used components on offshore installations and their reliability is important to both to safety and to the minimisation of down time. During discussions with offshore operators and valve manufacturers on the significance of valve failure to safety, it has been found that valve failures are frequent occurrences and not restricted to a few isolated incidents. The problem is wide spread in the petroleum industry. This industry experience can be regarded as unacceptable _ The success of a reliability and risk analysis exercise is ultimately dependent on the availability of historical reliability data. This study conmed the findings of a number of recent surveys which have revealed a dramatic lack of knowledge and understanding of valve mechanical failure mechanisms amongst petroleum related industry. Furthermore it was found that historical reliability data was generally scarce and inadequate for thorough studies. As a result of this situation, it was felt necessary to develop a approach to mechanical valve reliability modelling which was predictive i nature and which would take into account design and operational factors. This research project concentrates on the modelling and prediction of reliability of valves and includes a case study of subsea hydraulically operated gate valves. The modelling process includes procedures for the identification of vulnerable areas in valve design and its relation to the operating and environmental conditions. A number of statistical models have been developed based on stress strength interference concepts. These models enable the probability of failure to be described in terms of the physical characteristics of mechanical valve deterioration for specific failure modes such a internal leakage, fail to close and fail to open. The models require information both on design and on deterioration performance the latter of which is poorly understood. Provided judgement can be utilised to describe the ageing parameters governing failures, the models enable engineers to predict the time dependent reliability of this type of gate valve together with uncertainty at the design stage. I addition to the fundamental modelling work, the implications of reliability management systems have been investigated. The role of condition monitoring and the use of monitoring data for both for anticipation of failure and for updating the predicted reliability has been discussed. The role of failure reporting systems to provide improved understanding of failure mechanisms if valves was considered to be a important element of a reliability management system and vital to the future improvement in valve reliability. No evidence of any systematic failure reporting system was found in the offshore industry.Item Open Access Risk analysis and management in the water utility sector - a review of drivers, tools and techniques(Institute of Chemical Engineers, 2004-03-01T00:00:00Z) Pollard, Simon J. T.; Strutt, J. E.; MacGillivray, Brian H.; Hamilton, Paul D.; Hrudey, Steve E.The provision of wholesome, affordable and safe drinking water that has the trust of customers is the goal of the international water utility sector. Risk management, in terms of protecting the public health from pathogenic and chemical hazards has driven and continues to drive developments within the sector. In common with much of industry, the water sector is formalizing and making explicit approaches to risk management and decision-making that have formerly been implicit. Here, we review the risk management frameworks and risk analysis tools and techniques used within the water sector, considering their application at the strategic, programme and operational levels of decision- making. Our analysis extends the application beyond that of public health to issues of financial risk management, reliability and risk-based maintenance and the application of business risk maturity models.Item Open Access Risk management capabilities - Towards 'mindfulness' for the international water utility sector(2006-12-31T00:00:00Z) Pollard, Simon J. T.; Strutt, J. E.; MacGillivray, Brian H.; Sharp, J. V.; Hrudey, Steve E.; Hamilton, Paul D.; Clive Thompson and John GrayPublic health protection must be the primary goal of a drinking water utility; delivered through supplying safe drinking water. For complex multi-utilities, this goal may come under pressure from the need to manage a plethora of business risks. We describe a risk management maturity model for assessing the capacity of utilities to manage business risks and comment on the importance of ‘mindfulness' as a prerequisite for effective risk managemenItem Open Access Risk-based decision-making for the management of structural assets.(Cranfield University, 1999-11) Roberts, Caroline; Strutt, J. E.; Ward, John M.This thesis investigates the benefit of risk-based decision methods in engineering decisions. A thorough literature review identified the major issues and limitations in current methods. Consequently a more comprehensive model was developed to account for the complexities of real life decision-making. The enhancements introduced to the model include identifying and evaluating stakeholder influences, decision objectives, criteria and preferences between criteria and decision outcomes. Monitoring and controlling important parameters during implementation is also included to ensure objectives are met and risks controlled. Tools and techniques were identified to support decision-making within the new model. The research focuses on how available techniques can improve engineering decision-making. The model was applied to four case studies analysing real life, "live" decision problems in bridge management and pipeline management. These confirmed the relevance and importance of the model enhancements. The practicality of the methods, their benefits and limitations were evaluated such that the proposed model was enhanced further. The enhanced model was shown to bring enhanced understanding to all four case studies and made the decisions more rational, thorough and auditable. The fifth case study reviewed how unsupported decisions are currently made within the sponsoring company. This involved a detailed desktop analysis of past projects and interviews with senior engineers and provided further evidence, which emphasised the value of using the decision model. General guidelines were developed based on the case study experiences to help the decision-maker identify the level of analysis required for different types of decision problems. These were defined as applicability matrices. The benefit of using a third party facilitator in each of the case studies was identified in terms of the roles of leader, liaison, disseminator, spokesman and disturbance handler. The balance between these five roles through the stages of the decision process was found to be important to ensure the facilitator does not dominate the decision.Item Open Access Tools and techniques - what we need or what people think we want?(2005-04-06T00:00:00Z) Hamilton, Paul D.; MacGillivray, Brian H.; Bradshaw, R.; Strutt, J. E.; Pollard, Simon J. T.INTRODUCTION: Traditionally, water utilities have carried out risk assessments in a relatively small number of fields, addressing specific safety, health and environmental (SHE) risk concerns. In the last few years, however, the use of risk techniques has been extended as these companies increasingly seek to establish sound risk governance throughout all levels of their business to safeguard the interests of their customers and investors. Many new techniques have been imported from other process industries (offshore, energy supply, nuclear) and other businesses and financial institutions. In many respects, risk management is a practitioner led discipline and as such, its development and implementation within water utilities can vary significantly according to their size, operations, ownership and leadership, as well as the political, economic, legislative and regulatory frameworks in which they operate. As part of the ongoing AwwaRF Project 2939 ‘Risk analysis strategies for more credible and defensible decisions, studies have been undertaken in order to better understand the current level of application of risk analysis within the sector and to identify sector-specific views on key implementation issues. This research has realised the development of a maturity model for assessing capabilities in risk management and has also included a series of structured interviews with utility risk managers and industry spokespeople. Between 13th May, 2004 and 25th January, a total of sixteen interviews were conducted with specialists from five different countries (Australia, Canada, New Zealand, the United Kingdom and the United States). Fifteen work primarily within the water sector; the sixteenth works for an energy company. A full summary of this research and its findings will be published in the AwwaRF Project Report. With regard to the topic of risk analysis tools and techniques in the sector, the following key issues emerged: Does anyone use the risk management frameworks in practice? Are they useful and practical? What are the practical limits of, and people views of quantitative risk analysis techniques? Should we and how do we make consistent the various tools and techniques for risk management across utility companies?