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• Comprehensive scientometric and systematic reviews of corrosion protection methods for metallic pipelines are detailed. • 122 research articles are used to divide, classify, and discuss external and internal corrosion protection methods. • The functions, limitations, and requirements of corrosion protection methods are reported and discussed. • The purpose of this review is to assist researchers in filling research gaps and focusing on future directions. Metallic pipelines carrying water and/or oil/gas are exposed to deterioration, leaks/bursts, and failures due to corrosion. A suitable corrosion protection technique can prevent corrosion of these metallic pipelines, particularly in hostile environments, and corrosive soils. It can also reduce pipe deterioration, leaks/breaks, and failure, prolong service life, and improve the transportation process. Based on prior studies, this comprehensive review is regarded as an early attempt to cover both external and internal corrosion protection techniques for metallic pipelines in depth. The external corrosion protection techniques are classified into passive, active and hybrid corrosion protection techniques. The passive techniques include coatings, linings, barriers, material design, electrical isolation, inhibitors, and multi-passive techniques. Whereas active corrosion protection techniques include sacrificial anode and impressed current cathodic protections. Active and passive techniques are frequently combined to provide a more comprehensive corrosion protection system against newly discovered corrosion causes or coating degradations. On the other hand, internal corrosion protection techniques include internal coatings/linings/barriers, corrosion allowance, inhibitors/chemical treatments, dehydration, pigging, pipe material selection and flow control. The functions, merits, demerits, limitations/shortcomings, and requirements of corrosion protection techniques, as well as the various considerations that control their use have been covered and discussed. This comprehensive review will assist researchers, practitioners, and the industrial sector in prioritizing their policies in order not only to select the appropriate external and internal corrosion protection technique but also to fill current research gaps and focus on the future directions. [ABSTRACT FROM AUTHOR]

• An improved directional simulation is developed using meta -heuristic algorithms. • Harris Hawks Optimization is integrated to determine the sensitivity vector. • Efficiency of reliability analysis is conducted against several reliability methods. • Results indicate a strong adaptation for solving highly nonlinear functions. • The proposed method estimate the reliability index with low computational cost. In this paper, a new framework for accurate reliability analysis is proposed based on improving the directional simulation by using metaheuristic algorithms. Usually for highly nonlinear and complex performance functions, finding the unit vector direction requires very high calculations or impossible practically. Hence, the novel improved version incorporates the Harris Hawks Optimization algorithm, where the unit vector of direction is formulated as a constrained optimization problem and estimated using metaheuristic algorithms. Given that metaheuristic algorithms have been introduced to solve unconstrained problems, the penalty function method is used to convert the constrained problem into an unconstrained problem. The applicability of the proposed framework is firstly tested on five highly nonlinear benchmark functions and then applied to solve four high-dimensional engineering problems. The performance of six simulations-based reliability analysis methods and the first-order reliability method were compared with the proposed method. Besides the feasibility of other metaheuristic algorithms were investigated. The results show high-performance abilities of the improved version of the directional simulation for solving highly nonlinear engineering problems. [ABSTRACT FROM AUTHOR]

• Novel predictive models are developed for FRP- confined concrete. • Support Vector Regression is combined with meta -heuristic optimization algorithms. • The proposed hybrid models are compared with the existed design relations of the ultimate strain and strain capacities. • The proposed hybrid models showed superior abilities in terms of accuracy and agreement. Fibre Reinforced Polymer (FRP) composites can provide efficient enhancements in terms of strength and deformability for concrete structures, in which accurate predictions of FRP confined concrete ultimate conditions is highly essential to maintain safety levels, further structural analysis and members design. In this paper, three novel hybrid intelligence models were proposed based on the hybridization of Support Vector Regression (SVR) model with three bio-inspired optimization algorithms as genetic algorithm (GA), particle swarm optimization (PSO) and Whale optimization algorithm (WOA) for predicting the ultimate conditions of FRP-confined concrete. Moreover, 15 existing empirical relations for the prediction of the ultimate strength and strain of FRP-confined concrete have been comprehensively reviewed. The performances of the empirical models and the proposed hybrid models as SVR-GA, SVR-PSO and SVR-WOA are evaluated and compared based on a large database, including 780 circular FRP-confined concrete specimens, which are collected from the open-source published experiments. By comparing the predicted results based on several statistical indicators, the proposed hybrid SVR-models are generally outperforming the existing empirical relations in terms of accuracy and agreement with the experimental database. SVR-WOA provides superior performances than SVR-PSO, SVR-GA and all existed empirical models. The root mean square error is improved using SVR-WOA by 0.9%, 14.9 % and 37% for the ultimate strain capacity, and 2.7%, 4.6% and 17.3% for the ultimate strength compared to SVR-PSO, SVR-GA and the best empirical relation, respectively. [ABSTRACT FROM AUTHOR]

The use of composite flexible pipelines seems reliable and promising to the oil and gas industry to transport hydrocarbons as it is one of the best alternatives to overcome the major problem of corrosion in conventional carbon steel pipelines. However, throughout the years of operation, composite flexible pipelines can also degrade and tend to experience failures such as cracking, delamination and buckling due to several external or internal factors. It is crucial to periodically inspect and monitor the actual condition of composite pipelines in order to determine their safety and integrity throughout their design life. Therefore, with the scientometric and systematic review method, this paper aims to provide insight and future direction on the reliability and integrity assessment of composite pipelines that may be beneficial to pipeline operators as well as researchers or scholars within this field of expertise. Discussion on the common failure drivers, modes and mechanisms are detailed to better understand the relationship between the failure, reliability and integrity of composite flexible pipelines. A brief discussion about the available inspection and monitoring techniques for composite pipelines is also reported. From this comprehensive review, it is found that available approaches for the structural reliability analysis and integrity assessments of composite flexible pipelines are mainly based on quantitative risk-based inspection (QRBI) to produce a more reliable risk interpretation. Nevertheless, combining multiple inspection techniques and employing machine learning methodologies can aid in improving the real-time damage evaluation and safety performance of composite flexible pipes. • A scientometric review of 184 peer-reviewed articles on composite pipes in the oil and gas industry is being done. • A thorough examination of failure drivers, failure modes, and failure mechanisms is provided. • The evaluation discusses inspection and monitoring methodologies, as well as safety procedures. • Research gab and future directions for dealing with them are also offered. [ABSTRACT FROM AUTHOR]

• A probabilistic framework for the structural integrity and fracture is proposed. • Pipelines of mid- and high-strength steels under corrosion are analysed. • Novel burst pressure models are included in the reliability analysis. • The effect of different models for the strain-hardening exponent is suggested. • The probability analysis for separated- and multi-failure modes is conducted. In order to reduce the economic costs of pipeline construction projects and for offering a good combination of strength and toughness for efficient transportation of large quantities of hydrocarbon products under high pressure, High Strength Steels (HSS) such as API 5L X70 to X120 are used recently in the construction of pipeline systems for the large oil and gas projects. The commonly utilized models for the reliability evaluation of the HSS pipelines may lead to some conservatism regarding the used data. This paper aims to evaluate the system reliability of HSS pipelines with combined corrosion and cracks defects. Therefore, two failure modes as the plastic collapse and fracture are considered. The effect of different correlations under the term of the strain-hardening exponent that depends on the yield to ultimate tensile strength (Y/T) ratio is investigated. The reliability index of HSS pipelines is evaluated separately for each failure mode using the subset simulation technique. Herein, the tensile strength proprieties of the HSS pipelines are taken into consideration, while the applied methodology utilizes novel probabilistic models to predict the burst pressure for the plastic collapse failure mode. The steels toughness is taken as equal to the minimum requirement for both the ductile and the brittle fracture arrest applied in the HSS pipelines. Moreover, the reliability of the system with multiple failure modes is evaluated to show the mutual existence effect of crack and corrosion defects on pipeline safety. [ABSTRACT FROM AUTHOR]

• Integration of inertia and viscous forces with attack angle in dynamic impact pressure modelling is presented. • The significance of Hershel-Bulkley rheological model in CFD simulation is highlighted. • Effect of debris flow regime in impact mechanism is revealed. • The findings provide valuable insights of pipeline design and mitigation strategies in mountainous regions. The interaction of debris flows, and impacted structures is still not well understood due to the complex mechanisms of the flows. Although several methodologies from experimental to numerical have developed so far, a thorough assessment of impact mechanism necessitates multiphase modelling approaches. Therefore, this paper presents a dynamic impact pressure modelling approach of debris flows using experimental and numerical techniques. The experimental investigations involved seven type of debris flows based on solid volume fraction (α s), that being released on an inclined flume, impacting a 2″(52 mm) pipe model. The numerical investigations were performed in Computational Fluid Dynamics (CFD) environment by utilising the Spalart-Allmaras turbulence and Hershel- Bulkley rheological models by considering different inclined angle (β) impact scenarios. The findings revealed that all debris flows produced were in supercritical flows regime and characterized as dilute, medium viscous, and highly viscous flows, based on Froude (Fr) and Reynold (Re) numbers. Drag coefficients ( C D - 90 / C D - 0 ) were behaved non-linearly with respect to Fr and Re. The proposed refined dynamic normal ( p d - 90 ) and axial (p d - 0 ) impact models using different set of Fr , Re and β will offer valuable insight for pipeline operators seeking to comprehend the complex interaction between debris flows and pipelines. [ABSTRACT FROM AUTHOR]

• Experimental burst capacity are conducted using API 5L X42 pipe specimens. • Numerical modelling based FEM is used for various radial arrangements. • The influence of the radial effect is investigated experimentally and numerically. • Radial interacting rules are developed for several arrangements of defect colonies. Pipelines failures during its service life caused by the impact of multiple corrosion defects are most probable to occur, which may induce severe consequences as compared to single defect acting alone. Interaction rules were developed for multiple defects in the longitudinal and circumferential directions previously, but the knowledge on two or more defects aligned radially is still not well understood. This paper aims at investigating new interacting limits when corrosion defects are acting both on the internal and external wall, separated by a radial spacing, S R. The studies were carried out using burst test experiments as well as numerical modelling using pipe specimens of type API 5L X42. Six colonies of radial interacting corrosion defect arrangements were tested. The paper investigates the effects of the radial interaction by means of radial limit, S R Lim . It was found that increasing the defect depths of internal and external defects would highly reduce the failure pressure, P multiple. Depending on the orientations of the multiple defects acting radially, the failure pressure may be less or more than the case of single defect, P single. Thus, the failure pressure ratio of P multiple /P single should be used as a measure, with any values larger than 0.99 depict no interaction taken place among those multiple defects. From the six colonies, only two colonies showed the significance of radial interactions. The paper then suggests that when radial interaction does not presence, multiple corrosion defects acting radially may then be treated as single defect. [ABSTRACT FROM AUTHOR]

• Experimental burst test is used to study the physical behavior of RTPs subjected to crack defects. • Numerical simulation based finite element analysis is carried out and adjusted using the burst test results. • Two crack orientations as longitudinal and circumferential are investigated. • Von-Mises stress criterion is implemented to compare the performance intact RTP, while Stress Intensity Factor for the cracked RTP. Reinforced Thermoplastic Pipe (RTP) is a composite pipeline that has received considerable attention in the oil and gas applications due to benefits such as high strength and corrosion resistance. Limitations occurred, however, when the performance of this pipe-type towards various defects is still not fully addressed. Thus, this paper attempts to highlight the response of RTP imposed to crack failures using hydrostatic burst test and validated with numerical simulations under various internal pressures. Two defect orientations were studied, namely longitudinal and circumferential, as measured with respect to the pipeline length. The established Von-Mises stress criterion was used to compare the intact RTP performance, while Stress Intensity Factor (SIF) for the cracked RTP. Parametric studies having different crack dimensions were also investigated, with results showing that the longitudinal crack would be giving higher impact as compared to the circumferential one, even at low operating pressure. Observations on the RTP specimen's failure were also shared. Results obtained from this study would be beneficial in giving initial understandings to pipeline operators on the RTP behaviors towards crack failures. [ABSTRACT FROM AUTHOR]

• An experimental program is developed to assess the RTP behavior under lateral load impact. • Dents are fabricated using a quasi-static indentation procedure to burst the RTP specimens. • Relationships between the lateral load, indentation depth and the burst pressure is extracted. Reinforced Thermoplastic Pipe (RTP) is a flexible composite pipe that currently receives fair acceptance in the oil and gas industry, with high potentials to be used as a replacement to the carbon steel (CS) pipes especially in high corrosive environment. As RTP is relatively new products, their designs and qualifications are governed by the industry practice at present in the absence of comprehensive technical design standards. Most literatures to date are mainly dedicated to the intact RTPs, while the response of the pipe towards various defects have not been fully understood. Quite often, the assessments are made by referring to the design standards of the CS pipes, which are not entirely suitable due to the flexible characteristics of the composite pipe itself. Thus, this paper aims at assessing the performance of a 4″ RTP when exposed to lateral loads from external interferences such as the anchor dropped. Herein, the damaged to the RTP pipe was made in the form of a dent indented by a cylindrical conical nose under the quasi-static indentation procedures carried out experimentally. The damaged or dented pipe was later tested for its burst capacity using a burst testing facility specially fabricated for composite pipes. During the experiments, two types of failure modes were observed, namely single unit and ply-by-ply failures. Outcomes obtained from the experiments were used to describe the relationships between three important parameters, namely lateral load, indentation depth and burst pressure using polynomial regression equations. These simplified equations may be adopted directly in pipeline assessments and operations of RTP pipes exposed to dents. Moreover, outcomes from this paper will be beneficial in qualifying further RTP as a new free-corrosion risk transportation system for the oil and gas industry. [ABSTRACT FROM AUTHOR]