Behaviour of infilled rehabilitation system with composites for steel pipe

Fibre-reinforced polymer-based composites are found effective and suitable for steel pipe repairs because of their unique advantages such as high strength, lightweight, non-corrosive, and fast and easy to handle. In this study, the behaviour of a new type of composite repair system for steel pipelines underwater, which is the grouted composite sleeve, was investigated. This type of repair system relies on the effective transfer of stresses from the steel pipe to the encircling composite sleeve through the grout infill. Research was therefore necessary in optimising the material and geometric properties of each component of this system in order to have a betterunderstanding on its overall behaviour and its effectiveness in repairing steel pipelines. An experimental study on the mechanical, thermal and shrinkage properties of five epoxy-based grouts commonly used for structural repair was conducted. Three grouts have compressive strength of more than 80 MPa and total shrinkages of only 2.77%, which were deemed applicable for structural repair of steel pipelines. Moreover, the glass transition temperature of these grouts ranges from 50 to 90oC. The inclusion of coarse filler significantly increased the modulus and compressive strength, and reduced the shrinkage, but also reduced the tensile strength. There was considerable reduction in mechanical properties due to hot-wet conditioning at 70oC. This is because of the plasticisation and weakening of the aggregate matrix debonding at a temperature close to the glass transition temperature. The glass fibre – vinyl ester composites considered in this study have strength and modulus suitable for sleeve in the grouted sleeve repair system. The tensile strength, modulus and interlaminar shear strength of this composite was 427 MPa, 25 GPa and 30 MPa, respectively and its glass transition temperature was 110oC. It absorbed only 0.22% of moisture after hot-wet conditioning of 3000 hours. More importantly, there was almost no change in the modulus and it retained sufficient tensile and interlaminar shear strength needed for a composite sleeve repair system even after exposure to moisture and elevated temperature of 80°C. The glass transition temperature decreased to 97°C after conditioning and reached saturation indicating that, the composite was suitable for pipeline repair in continuous service at higher temperature. A finite element analysis using a simplified 2D model was conducted to determine the effect of critical parameters on the behaviour of a grouted composite sleeve repair system. Grout modulus and thickness, and sleeve thickness were considered for the analysis. The results of the analyses indicated that the thinner and higher modulus grouts are more effective to transfer load from the steel to the sleeve than the thicker and lower modulus grouts. Similarly, a thicker sleeve reduced the level of stresses and strains in all the components of the repair. Based on the results of the analysis, it was recommended that a grout thickness of 20 mm with a modulus of at least 5 GPa was appropriate for an effective grouted repair system and for practical application. A full-scale 3D analysis was carried out to determine the effectiveness of the repair system for steel pipelines with a range of localised metal loss. The results of the analyses indicated that the modulus of the infill grout governs the load transfer between the steel and the sleeve, but the tensile strength governs the functionality of the system. The cracking of the grout resulted in a significant increase in the stress level in the steel pipeline and composite sleeve. The repair system using grout with a higher tensile strength provided a higher pipe capacity by utilising the plasticity of the steel, while the grout with a lower tensile strength cracks even before yielding of the yielding at a low applied internal pressure. Moreover, a thicker sleeve provided higher capacity in the repaired pipe, and both the carbon and glass fibre composites were found effective for composite sleeve repair system. Most importantly, it was determined that the considered grouted composite sleeve repair system can effectively reinstate the capacity of the pipelines with a localised defect of up to 70% metal loss. An improved understanding on the behaviour of the grouted composite sleeve repair system for pipeline with metal loss was achieved in this study, providing a base knowledge from which further research could continue. The results obtained provided important information on the optimal material properties of the infill grout and the composite sleeve for an effective repair system and the effect of different operating conditions on the overall behaviour of the repaired steel pipelines. These results are very valuable and will help researchers, engineers and stakeholders to consider the actual application and implementation of this new composite system in repairing steel pipeline

Fibre composites for high pressure pipeline repairs, in-air and subsea: an overview

In 2001 it was reported that in North America alone, corrosion to the Oil & Gas pipeline distribution network cost approximately $2-3.3 billion per annum with 10% of that cost being associated with actual failure of the pipeline. In addition pipelines are also susceptible to erosion and mechanical damage producing further losses in pipe structural integrity. This results in high maintenance costs, possibility of adverse environmental consequences and the costly interruption to product transportation and distribution. The cost and technical challenges of adequately addressing repair are significant and greatly increase for underwater applications particularly with increasing water depth. It therefore induces the need of searching for alternative repair techniques involving new advanced materials for ease of installation and application against adverse environmental effects in the long run. Fibre composite materials provide excellent advantages over conventional metals in engineering practices for many decades. These advantages make fibre composite suitable candidate for effective repair technology. This paper provides a comprehensive review on the recent development and future prospect of using these materials for in-air and underwater pipeline external repairs. Various aspects of technical knowhow; benefits and shortcomings of the repair considerations are also presented

Editorial: COVID-19 and entrepreneurial mindset

[Extract] he entrepreneur’s importance is well-recognized in the economy, especially during critical times. The COVID-19 pandemic is already considered to be one of the biggest socio-economic crises in history. As it is ongoing and bringing many business-related uncertainties, it is very challenging to foresee its impact on the future. However, despite the challenges created, the COVID-19 pandemic also created entrepreneurial opportunities

Effect of hygrothermal conditioning on the mechanical and thermal properties of epoxy grouts for offshore pipeline rehabilitation

Offshore oil and gas pipelines are susceptible to corrosion and need rehabilitation to keep them operating in-service conditions. Fibre composite filled with epoxy-based grout is emerging as an effective repair and rehabilitation system for offshore pipelines performing underwater. In such applications, the infill grout is often subjected to moisture and elevated temperature along with compressive, tensile and localised stresses at the defect. Current standards and practices for composite repairs suggest detailed investigation of the fibre reinforced sleeve, while the characterisation of the infill material is yet to be conducted for performance evaluation. The present work investigates the mechanical and thermal properties of three epoxy grouts as candidates for infill in a grouted sleeve repair for underwater pipeline. An understanding on the effect of hygrothermal ageing on the grout properties for defining the period of 1000 hours as “long-term” according to ISO/TS 24817, in comparison to their unconditioned state, is also presented. The compressive and tensile strength of the unconditioned grouts ranges from 100–120 MPa, and 19–32 MPa, respectively, which indicates that these grouts are suitable for structural rehabilitation of the pipelines. Moreover, the glass transition temperatures, Tg and Tt of the unconditioned grouts are found to be within the ranges of 50–60 °C, and 80–90 °C, respectively, which are reduced by about 20°C after conditioning

Superplasticizer and Shrinkage Reducing Admixture Dosages for Microfine Cement in Grout Systems

Grouts have numerous applications including crack repair as maintenance in construction industries. Microfine cements are intensively used for high strength mortar and grout products. They are ideal for injection grouting in structural repair. Such grouts should have suitable rheological properties to be injectable, especially those used in repair and rehabilitation. The use of superplasticizers (SP) in these products is thus becoming increasingly crucial to achieve favorable workability and viscosity properties. A difficulty in such grouts is the plastic shrinkage due to finer particles used. It is thus necessary to determine optimum SP and shrinkage reducing admixture (SRA) dosages for a microfine cement based grout. In this study, a saturation dosage was decided from two Polycarboxylate ether (PCE) based SPs in relation to neat cement using slump flow and rheological parameters. A range of grout mixtures was formulated containing micro silica (MS) and fly ash (FA), and tested for suitable rheological and mechanical parameters. Based on the results, a grout mixture with MS and FA was selected to determine optimum SRA content. According to the results, a SP dosage of 3% by weight of neat cement is sufficient to achieve saturation. The grout material including MS and FA can produce comparable properties to neat cement grout. MS is found to improve compressive strength within the range considered, whereas a higher FA content provides favourable rheological properties. Finally, a SRA dosage of 4%, which could reduce the shrinkage by about 43% after 28d days, is determined for the grout system

Effects of flowering behavior and pod maturity synchrony on yield of mungbean [Vigna radiata (L.) Wilczek].

A number of experiments were set up to assess the flower production and flowering pattern in synchrony with pod maturity and seed yield in twelve mungbean genotypes. Synchrony of pod maturity was measured based on percentage of mature pods at first harvest, where; synchrony (>90% mature pods), partial synchrony (80-90% mature pods) and asynchrony (<80% mature pods). Results revealed that genotypes that produced maximal opened flowers within 10-15 days, and ceased flowering within 15-20 days after first flowering (DAF), have synchrony in pod maturity. Additionally, seed yield was strongly correlated with the number of opened flowers and number of produced mature pods. Four genotypes showed synchrony in pod maturity which accompanied with cessation of flower production at 10-15 DAF, but produced lower yields due to fewer opened flowers. In contrast, the remaining genotypes showed partial synchrony or asynchrony in pod maturity due to longer flowering durations, with higher number of opened flowers and seed yield. These results indicate that synchrony in pod maturity and seed yield in mungbean is inversely related

Planning exceptionalism? Political Economy of Climate Resilient Development in Bangladesh

As part of an international project led by Institute of Development Studies to understand change processes required for delivery of climate resilient and low carbon development this case study illustrates how a significant change process of a transnational problem depends on the interplay of actors, their ideas and power relations in a particular political circumstance influenced by international climate governance, initiatives, and actors. This shows the strength and weakness of Bangladesh‟s planning process especially in understanding whether existing power relations, interests and ideology of different actors can explain why some ideas win and some do not. The study findings are not only beneficial for Bangladeshi policy makers, researchers and public but also other climate vulnerable countries pursuing similar planning process.DfI

Integrated effects of marketing stimuli on customer loyalty in Palestine grocery supply-chain: does satisfaction perform mediating role?

Grocery stores are a crucial connection in the food delivery system and a fundamental component of the retail industry. Some grocery stores have worked with regional suppliers to benefit the community and the consumer. Palestinian market is uncommon because clients have connected what they manufacture and sell under particular circumstances. This study is, therefore, an integrated examination of the critical influencing factors on the marketing of food products in Palestine. A survey questionnaire was used. An organised, self-administered survey was used to acquire data, and analysis techniques were outlined using Structural Equation Modelling (SEM). According to the findings, relationship marketing and service quality are the crucial brand strategy factors influencing customers’ decisions to purchase groceries and showing how happy and devoted they are to grocery stores. The Palestinian government has greatly benefited from the results of this study of how consumers perceive essential factors that may be considered when formulating future regulations about food and other grocery items