S. M. S. M. K. Samarakoon

Maintenance Integrity: Managing Flange Inspections on Aging Offshore Production Facilities

The flange inspection associated with piping on offshore production facilities is a time-consuming activity as the flanges should physically be opened in order to perform close visual inspections. In order to sustain maintenance integrity, a number of inspections are allocated for a subsystem based on factors such as: condition of the medium flowing in the line, risk perception of the pipeline system, and the date of installation. Inspection teams recommend inspections based on the data, experience, and exposure to offshore production facilities, as well as the intuition and intentions of those individuals involved with inspection planning and with carrying out implementation during the preventive maintenance shutdowns. However, there is a tendency for the operating company representatives to raise queries with the contractor company representatives about the number of flanges to be opened during the preventive maintenance shutdown as flange inspection consumes a considerable portion of time and resources. Hence, it is vital to interpret sensibly the importance of recommending close visual inspections for flanges if the maintenance integrity is to be sustained. This study focuses on analyzing the historical data limited to flanges on flowlines over the last fifteen years. The final results provide a snapshot of the present status of the flanges of the production facility.Copyright

Strengthening, modification and repair techniques’ prioritization for structural integrity control of ageing offshore structures

Structural integrity control is vital for existing ageing as well as newly built offshore and onshore structures. Structural integrity control becomes highly sensitive to interventions under a potential loss of structural integrity when it comes to offshore oil and gas production and process facilities. This is mainly due to the inherent constraints present in carrying out engineering work in the offshore atmosphere. It has been further exacerbated by the ageing offshore structures and the necessity of carrying out life extension toward the end of their design service lives. Local and international regulations demand the implementation of appropriate strengthening, modification and repair plans when significant changes in the structural integrity are revealed. In this context, strengthening, modification and repair techniques such as welding, member removal/reduction of loading, mechanical clamping and grouted repairs play a vital role. This manuscript presents an approach for prioritizing the strengthening, modification and repair techniques using a multi-criteria analysis approach. An analytic hierarchy process has been selected for the analysis via an illustrative case. It also provides a comprehensive overview of currently existing; strengthening, modification and repair techniques and their comparative pros and cons.

Structural Integrity Control of Ageing Offshore Structures: Repairing and Strengthening With Grouted Connections

Structural integrity control (SIC) is an increasingly important element of offshore structures. Not only is it used in newly built and existing offshore structures (e.g. oil and gas (O&G) production & process facilities (P&PFs), wind turbine installations, etc.), but SIC is also essential for ageing offshore platforms which are subjected to an extension of their design service life. In these cases, SIC programs must be performed to assess the platforms. If any significant changes in structural integrity (SI) are discovered, then it is essential to implement an appropriate strengthening, modification and/or repair (SMR) plan. Currently, welded and grouted repairs are mostly used for SMR. Although a welded repair may typically restore a structure to its initial condition, if the damage is due to fatigue loading and welded repairs have been carried out, then historical evidence reveals that there is a high potential for the damage to reappear over time. On the other hand, mechanical connections are significantly heavier than grouted connections. Consequently, grouted repairs are widely used to provide additional strength, for instance, to handle situations such as preventing propagation of a dent or buckle, sleeved repairs, leg strengthening, clamped repair for load transfer, leak sealing and plugging, etc. This manuscript examines current developments in grouted connections and their comparative pros and cons in relation to welded or mechanical connections. It also provides recommendations for future research requirements to further develop SMR with grouted connections.Copyright

On the Necessity of Technology Qualification in the Offshore Wind Energy Industry

Wind farm technology can be considered as one of the best available techniques to deliver renewable energy. Similarly, the number of wind farms has been growing rapidly owing to their contribution to sustainable development. Recently also, there has been a growing awareness of the need to develop a plentiful number of wind farms offshore rather than onshore. This is due to the consideration that the offshore wind farms are more beneficial than onshore with respect to their exposure to higher wind speeds while covering extensive areas. Less turbulence offshore also allows the turbines to harvest the available energy more effectively than onshore and to reduce the fatigue on turbines. Furthermore, most of the offshore wind farms are located in remote areas, which helps to avoid noise effects and the visual burden (shadows) on society. However, the malfunctioning of the turbines in offshore wind farms after a few months or years from their commissioning is a one of the challenging issue. The outcome of the failures leads to large financial losses owing to cost-intensive repairs and weather-related delays. Therefore, identification of potential failures at the early stages of development through a technology qualification procedure will help to minimize the loss of financial resources by increasing the reliability of the systems and the availability of wind power. Basically, appraisal of risk and reliability aspects is playing a key role in this qualification process in order to confirm that the system will perform as intended. This study identifies some recent historical failures in offshore wind farms causing significant financial losses. Further, it discusses the reasons of the failures and the possibility to overcome future obstacles in developing offshore wind farms using a technology qualification procedure. Finally, this paper discusses whether the existing technology qualification procedure can be directly applied for offshore wind farms, and what important modifications are necessary.Copyright

Corrosion propagation phase and bond strength degradation of reinforced concrete structures: state of the art

Corrosion causes damage to reinforcing steel in concrete structures and governs the service life of the structures. Currently, researchers are paying attention to modelling the behaviour of the bond between the concrete and steel interface of corroded reinforcement. The main objective of this paper is to study the recent research relevant to the bond behaviour at the interface between corroded ribbed bars and concrete and to identify the future research focus. Initially, the paper presents the mechanisms of corrosion damage of reinforced concrete by discussing corrosive agents, causes and effects. Then mechanisms of corrosion prorogation, mechanical properties of corroded reinforcing steel and effects of corrosion on bond degradation of reinforced concrete are discussed in details. Thereafter, recent experimental researches on bond degradation between reinforcement and concrete are reviewed. Previous studies have proposed formulae, which depend on cover, reinforcing bar diameter, concrete strength and corrosion level, to predict the ultimate bond strength. Effect of other parameters (i.e. type of the bars, bar spacing, crack size, aggregate size, type of loading, stress state and etc.) on bond strength have not been properly studied in literature. Bond strength against biaxial bending or combined load action has not been investigated. Finally, the paper concludes with the significance of testing naturally corroded test specimens, compared to the artificially corroded specimens, as well as discussing loading situations.

Improving the efficiency of technology qualification in the industrial sector

Technology qualification processes enable the user to confirm the function of the newly introduced technology as intended for particular operational limits within a specified confidence interval. Technology qualification procedures describe the technology readiness level and then outline how to plan the processes leading towards the resulting technology qualification through tests or analytical programmes. The analysis and testing represent the major costs of a qualification process and are also time-consuming compared with other steps in a process. Further, if a wrong selection is made for the analysis and testing method, then the result can be wastage of resources leading to outcome with no value. Hence, it is necessary to identify the methodology for making a selection of the most appropriate method considering various constraints. This manuscript provides a suggestion of how a multi-criteria decision making tool [analytical hierarchy processes (AHP)] can be utilised to improve the efficiency of a process.

Retaining the Sustainability of Oil and Gas Operations: Qualifying the Best Available Techniques

By nature, oil and gas operations are sensitive to Health, Safety and Environment (HSE) requirements. Within the Norwegian Continental Self (NCS), it is mandatory to implement the Best Available Techniques (BAT) guidelines as required in the European Union’s Integrated Pollution Prevention and Control (IPPC) directive. The directive provides guidelines for selecting BAT in industrial activities while protecting the environment as a whole. One of the major challenges for an oil and gas operator is to satisfy the guidelines while confirming fitness for purpose with respect to the different technologies applied. Hence, the concept of technique qualification is paramount to reveal opportunities to improve system design, to minimize schedule risk and to reduce cost risks during operations by reducing uncertainties and increasing reliability. In this paper, we are concerned with the process of selecting a technique for supplying power from shore to an offshore unit. This paper discusses how we can give priorities to HSE concerns, while also satisfying financial objectives, in the context of implementing the BAT guidelines. The analysis aims to qualify the technique as a whole, considering the capability of satisfying the underlying objective of controlling environmental pollution.Copyright

Use of Technology Qualification in Offshore Oil and Gas Operations: An FMECA Analysis for Mitigating Potential Failures

The implementation of new technology introduces uncertainties. Due to the consequence of failures, these uncertainties generate risks for the technology developers, manufacturers, vendors, operators and end-users. In this context, the application of proven technology in a new environment is also considered as new technology. In essence, a system as a whole is considered to be new technology when it has been assembled in a novel way consisting of individual components built using proven technology. The concerns in deploying new technology are significant in offshore oil and gas (O&G) operations, as they involve hazardous procedures. Moreover, technology is considered new when applied to offshore O&G operations due to the variability of technical challenges from field to field and the complexity of systems with limited space and experience in a harsh and sensitive environment. When new technology is integrated into a large system, it is necessary to evaluate the effect on the total system’s reliability in order to increase the level of confidence via a technology qualification procedure. Hence, it is vital to interpret how the risks are managed by the provision of evidence to reduce uncertainties. This manuscript presents an illustrative case of failure mode, effect and criticality analysis (FMECA) in qualifying new technology when it is implemented in an unfamiliar environment.Copyright

Use of engineering robust design approach to improve the surface quality of pre-cast concrete elements: An experimental approach

Pre-cast concrete components are commonly used for columns, beams, floors, walls and other structural elements in buildings. In general, several quality control assessments must be performed during the production of pre-cast concrete elements. Further, the quality of any cast product depends on material selection, equipment used and workmanship. The quality of surface finish is one feature which gives an immediate visual impact. In order to minimize life cycle costing for the structure, it is vital to have durable material and formed surfaces with few surface detects (i.e. honeycombing, air void surfaces, etc.). Surfaces of acceptable quality and accuracy are difficult to achieve and depend on functional and aesthetic requirements. However, the end user of pre-cast elements expects a high quality surface finish with minimum defects. It is a great challenge to reduce the occurrence of such surface defects during the production of the elements. This manuscript identifies factors affecting the surface finish of pre-cast elements. It also describes the possibility of using an engineering robust design approach to improve the surface finish of pre-cast elements and explains the experimentation approach.

In-service inspection of offshore concrete structures: Application of an expert system

In-service inspection plays a significant role in maintaining the structural integrity of offshore structures. The in-service inspection covers in-situ inspections, evaluation of inspection results, condition assessment of the structure and planning for future inspections. The planning of in-service inspection is a complex process due to the presence of uncertainties; in particular the uncertainties present in the inspection results. In addition, the vagueness and the importance of expert knowledge necessitate having a methodology to integrate in a coherent manner. This manuscript suggests a fuzzy expert system to address the aforementioned. This enables optimizing the number of inspection points to be focused on, whilst identifying the potential risk areas needing priority in future inspections with minimal effort and higher efficiency. This manuscript also discusses the use of available inspection methods of offshore concrete structures subject to deterioration and the use of inspection evaluation results to develop an expert system for future inspections.