Composite Wrap Research Articles

Modelling the performance of a corroded pipe section repaired with three-parts epoxy grout and with three-parts epoxy grout plus nanofiller

Steel pipelines have been used for the transportation of oil and gas for more than a century. With exposure to the harsh condition of the environment, steel pipelines are subjected to corrosion that deteriorates their function through metal loss. To remedy this, several repair techniques have been developed to extend their service life, particularly, techniques that do not interrupt the flow of the oil and gas. There are three main components in a Fibre-reinforced Polymer (FRP) composite repair which are (1) FRP composite wrap, (2) infill material, and (3) interlayer adhesive. Past research had looked at enhancing the infill material, which is usually an epoxy grout, with the aim to reduce or remove the number of FRP composite wrap layers. One of the ways to enhance the infill material is to add Graphene Nanoplatelets (GNPs) to the epoxy grout. This was proven by carrying out different mechanical tests on a neat three-part epoxy (Infill A) and a three-part epoxy with 0.1% GNPs added by weight (Infill B). With the mechanical properties obtained for both infill materials, the pipe sections were then modelled with a finite element software to determine the repair performance without the use of FRP composite wrap. The difference of failure pressures between the pipe repaired using Infill A and Infill B over the unrepaired pipe were 2.7% and 4.2% respectively. The failure of the repair was due to the debonding of the infill materials from the pipe section. However, this research has provided significant information in understanding the properties of the infill materials as well as the numerical modelling on a repaired pipe section.

Optimization of the geometrical parameters of bonded composite wrap for repairing cracked pipelines

In this study the finite element method is used to analyze the performances of bonded composite wrap repair of cracked steel pipelines. Parametric analysis was performed in order to highlight the effects of the geometrical properties on the repair efficiency. The experimental design method is used to explore the effects of wrap dimensions (length, angle and thickness) in order to optimize the repair process. We showed in using the MOODE.5 software the most dominant geometrical parameters on stress intensity factor at the crack front which to determine the most important parameters on the repair efficiency. This optimization can help the composite wrap designers to improve the repair performance and rehabilitation.

EFFECT OF PUTTY PROPERTIES IN REPAIRING CORRODED PIPELINE: A FINITE ELEMENT ANALYSIS

Underground pipelines are the most preferable way to transport oil and gas over a long distance. These steel pipelines often suffered from several deteriorations including corrosion. Corrosion causes the outer lining of a pipeline to thin and subsequently reducing pipeline strength. In order to prevent this loss of strength, repair is required. Composite wrap repair is a technique that can be used to repair damage pipeline. Composite wrap repair consist of Fibre Reinforced Polymer (FRP) composite wrap and putty as infill material to restore the strength of a damaged steel pipe. Recently, there is tendency in reducing the usage of composite wrapping layer due to several reasons. Ultimately, it is hoped that one day the repair can be done without composite wrapping. Thus, the purpose of this research is to explore the potential of using putty alone as a repair material in repairing corroded pipeline without composite wrap via finite element analysis. Difference geometrical defects that simulating external corrosion were investigated to study the influence of defect sizes towards the burst pressure of corroded pipeline. Two infill materials which both have difference mechanical properties are used in this research to investigate their influence towards the performance of the repaired pipes. Finite element analysis has been conducted to determine the behaviour of the defected pipeline with a patch of the infill covered the defected area. The analysis was conducted for three defect sizes: 100mm x 100mm, 75mm x 150mm, and 25mm x 150mm for both putties. It was found that the narrow defect of the pipeline causing the pipe to burst at lower pressure as compared to defect that have the same dimension area for both of the infill material. This may due to high stress concentration at small area of the defect. Furthermore, it was also revealed that infill with higher ultimate tensile strength able to withstand higher pressure. The finding of the research shows that by using appropriate infill, there are potential to increase the burst pressure by about 5%. The findings of this research can serve as stepping stone to study the feasibility of repairing damaged pipeline using putty alone.

EFFECT OF PUTTY PROPERTIES IN REPAIRING CORRODED PIPELINE: A FINITE ELEMENT ANALYSIS

Underground pipelines are the most preferable way to transport oil and gas over a long distance. These steel pipelines often suffered from several deteriorations including corrosion. Corrosion causes the outer lining of a pipeline to thin and subsequently reducing pipeline strength. In order to prevent this loss of strength, repair is required. Composite wrap repair is a technique that can be used to repair damage pipeline. Composite wrap repair consist of Fibre Reinforced Polymer (FRP) composite wrap and putty as infill material to restore the strength of a damaged steel pipe. Recently, there is tendency in reducing the usage of composite wrapping layer due to several reasons. Ultimately, it is hoped that one day the repair can be done without composite wrapping. Thus, the purpose of this research is to explore the potential of using putty alone as a repair material in repairing corroded pipeline without composite wrap via finite element analysis. Difference geometrical defects that simulating external corrosion were investigated to study the influence of defect sizes towards the burst pressure of corroded pipeline. Two infill materials which both have difference mechanical properties are used in this research to investigate their influence towards the performance of the repaired pipes. Finite element analysis has been conducted to determine the behaviour of the defected pipeline with a patch of the infill covered the defected area. The analysis was conducted for three defect sizes: 100mm x 100mm, 75mm x 150mm, and 25mm x 150mm for both putties. It was found that the narrow defect of the pipeline causing the pipe to burst at lower pressure as compared to defect that have the same dimension area for both of the infill material. This may due to high stress concentration at small area of the defect. Furthermore, it was also revealed that infill with higher ultimate tensile strength able to withstand higher pressure. The finding of the research shows that by using appropriate infill, there are potential to increase the burst pressure by about 5%. The findings of this research can serve as stepping stone to study the feasibility of repairing damaged pipeline using putty alone.

Testing of composite repairs according to ISO and ASME standards and beyond

MAINTAINING PIPELINES IS A top priority for every operator to ensure safety, efficiency and sustainability. Composite wrap repairs are an alternative repair method which is less expensive and less time-consuming, but which enables an extension in lifetime of up to 20 years. It is particularly suitable for live repairs to avoid unplanned shutdowns. Although it has been used in the field for more than two decades and is described in the standards ISO 24817 and ASME PCC-2, the technology is still not always applied, or even considered as a solution in situations where it would be of advantage. Based on its expertise in adhesive technology, Henkel Loctite has developed a composite repair system, which meets the standards ISO 24817 and ASME PCC-2. Furthermore, in order to increase the level of confidence, the Loctite composite-repair system for pipes underwent several years of certification processes defined and fully audited by independent inspection authorities, namely DNV GL, Lloyd’s Register, and TUEV Rheinland. Henkel operates with its standard repair system up to 80°C and with a newly developed high-temperature system up to 130°C. Both these systems have been approved and certified according to the standards. In addition to the testing programme required by ISO and ASME, a range of further experimental investigations, exceeding the requirements of the repair standards, has been carried out to show the performance and robustness achievable by composite repairs. Important topics covered include tests on cyclic pressure loads, the fatigue strength of the composite, and permeation resistance vs gaseous hydrocarbons. Furthermore, a FE model has been developed that specifically enables the design of repair cases, which are not usually described in detail by the repair standards, like the repair of dents. The combination of these methods clarifies further details and improves our understanding of composite repair reliability.

Repair of through thickness corrosion/leaking defects in corroded pipelines using Fiber Reinforced Polymer overwrap

The present study is concerned with the repair of through thickness corrosion or leaking defects in metallic pipelines using a commercially available metallic seal and glass/epoxy composite. Pipe specimens are made with three different types of most commonly occurring through thickness corrosion/leaking defects. The metallic seal is applied over the through thickness corrosion/leaking defect and it is reinforced with glass/epoxy composite overwrap. The main objective of the metallic seal is to arrest the leak at live pressure. After reinforcing the metallic seal with glass/epoxy composite overwrap, the repaired composite wrap is able to sustain high pressures. Burst test is performed for different configurations of metallic seal and optimum configuration of metallic seal is determined. The optimum configurations of metallic seal for three different types of through thickness corrosion/leaking defects are further reinforced with glass/epoxy composite wrap and experimental failure pressure is determined by performing the burst test. An analytical model as per ISO 24817 has been developed to validate experimental results.

Structural behaviour of square RC columns confined with CFRP wraps

Loading capacity and strains of square reinforced concrete (RC) columns, strengthened with external carbon fiber reinforced polymer (CFRP) sheets, were tested and evaluated. The experimental parameters include: number of wrap layers, concrete strength and the slenderness of the columns (L/a). All test specimens were loaded to failure in axial compression. Compressive stress, axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate strength, stiffness, and ductility of the specimens.Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility. The effects of test parameters are evidenced and compared.

Structural behaviour of square RC columns confined with CFRP wraps

Loading capacity and strains of square reinforced concrete (RC) columns, strengthened with external carbon fiber reinforced polymer (CFRP) sheets, were tested and evaluated. The experimental parameters include: number of wrap layers, concrete strength and the slenderness of the columns (L/a). All test specimens were loaded to failure in axial compression. Compressive stress, axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate strength, stiffness, and ductility of the specimens.Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility. The effects of test parameters are evidenced and compared.

Effective Dispersion of Carbon Nanotube in Epoxy Grout for Structural Rehabilitation

The industry nowadays is incorporating the composite repair system for repairing pipelines rather than the conventional steel repair. The mechanism of this repair method usually consists of three components which are the composite wrapping, infill material and the adhesive. However, there has been very little research on the function of the infill in the repair mechanism. This work is concerning the enhancement of the performance or the strength properties of the infill material in pipeline repair by reinforcing the putty with carbon nanotubes (CNT). The enhancement of the performance of the infill has been carried out by dispersing the CNT into epoxy resin with a three roll mill. In the mechanical properties testing, it is found that the CNT is an effective material to improve the tensile strength of the epoxy grout. However, the CNT-modified samples in the compressive property test show a contrast to the tensile test. All the CNT-modified samples exhibit a lower compressive strength than the control sample and the milled down sample. In conclusion, CNT shows the potential to be a very good material to enhance the mechanical properties of epoxy grout, however, with this specific brand of epoxy grout that contains steel filler in the resin, the CNT only improve the tensile properties but the compressive properties of the epoxy grout has been compromised as compared to the control sample.

Tensile Properties of Epoxy Grout Incorporating Graphene Nanoplatelets for Pipeline Repair

In oil and gas industry, fibre-reinforced polymer (FRP) composite are widely used to repair pipeline subjected to external metal loss. This repair technique can be done by incorporating epoxy grout as infill material to smoothen the defect on pipeline surface and later wrapped with a composite wrap to restore the strength of the pipe. This paper attempts to investigate the behaviour of an epoxy grout with 0.5wt% graphene nanoplatelets (GnPs) under tensile loading according to the ASTM D638. GnPs were dispersed through the sonication method followed by calendering process to ensure an optimum enhancement in the properties of polymer matrix can be achieved. The results show positive improvement in terms of strength and Young's modulus of tested grout with the inclusion of GnPs. It shows that the presence of low concentration of GnPs as an additive has a significant reinforcement effect by improving tensile properties of epoxy grout up to 14% as compared to control sample.

Nanofillers Reinforced Polymer Composites Wrap to Repair Corroded Steel Pipe Lines

This paper presents the analysis of repair of pipelines using nanofiller dispersed composites. Steel pipe with part wall loss as per ISO 24817 is repaired using glass/epoxy composites with and without nanoclay reinforcement and burst test is performed in order to assess the performance and effectiveness of nanocomposites-based repair system. A simple methodology is developed to find out the failure pressure of pipelines and is compared with the experimental and ISO 24817 repair code results. The thickness of the composite wrap is predicted analytically for 1–5% nanofiller dispersion in the epoxy for 30–80% of pipe wall loss and live pressure of pipe. The results are analyzed to find effectiveness of clay dispersion and effect of live pressure for 30–80% of pipe wall loss. It is observed that the dispersion of nanofiller improves the bursting resistance of composite wrapping over outer surface of pipe.

Use of advanced composite materials in strengthening axially loaded reinforced concrete columns

The present study deals with the analysis of experimental results, regarding of load carrying capacity and strains, obtained from tests on reinforced concrete (RC) columns, strengthened with external carbon fibre reinforced polymer (CFRP) sheets. The experimental parameters include: number of wrap layers, slenderness of the columns (L/a or L/D) and section geometry (circular or square). A total of 48 specimens were subjected to axial compression. All test specimens were loaded to failure. Compressive stress, both axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate stress, stiffness, and ductility. First, the effects of test parameters are analysed and compared. Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility.

Progressive Failure Analysis of Pipeline Repaired by Composite Wrapping

Composite overwrap systems have been widely used to repair damaged pipelines. Its effectiveness has been proven by many researches and engineering applications. However, the research on progressive failure mode of the repaired structure has not been reported. In the present paper, finite element method with Hashin failure criteria is developed to realize the progressive failure analysis. The predicted burst pressure is in good agreement with the burst experiment. Different from widely-reported failure progress in Composite Overwrapped Pressure Vessels (COPV), the progressive failure analysis for the defected pipeline overwrapped by composite reveals very different failure stages: stable failure propagation and rapid failure propagation. The identification of critical pressure between these two stages is valuable in composite reparation design for the defected pipeline.

Behaviour of FRP Confined Concrete Cylinders: Experimental Investigation and Strength Model

The present paper is devoted to investigate the behaviour of FRP confined concrete cylinders subjected under axial compressive loading. A total of 54 FRP confined concrete cylinders with 2 types of FRP composite wrap, Carbone fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP), were tested under monotonic axial compression. The effects of several parameters such as unconfined concrete strength, type of FRP composite and number of FRP layers are investigated. Three different concrete mixes were examined, with a compressive strengths average of 26, 40 and 60MPa. The effective circumferential FRP failure strain and the effect of the effective lateral confining pressure were investigated. Peak axial compressive strength and corresponding strain of unconfined and FRP confined concrete cylinders were compared. The obtained results show that the CFRP reinforced cylinders provide a significant increase in ultimate compression stress compared to the GFRP reinforced ones. A new model is presented to predict the compressive axial strength and corresponding strain of FRP confined columns.

Application of Composite Wraps for Strengthening of Buried Steel Pipelines Crossing Active Faults

In the paper, the efficiency of strengthening of a buried steel pipeline with a composite wrap subjected to an active faults action is analyzed. A three-dimensional numerical model of the pipeline is developed. The pipeline is considered as an elastoplastic steel shell, while the composite wrap is represented as an orthotropic elastic shell. The model takes into account the elastoplastic behavior of soil, contact interaction between the soil and the pipe, large inelastic strains, distortion of the pipeline cross section, and local buckling formation. A normal-slip fault kinematics with large fault offsets is considered in numerical modeling. The effect of the wrap thickness, length, and position relative to the fault plane is analyzed.

Analysis of Repaired Cracks With Bonded Composite Wrap in Pipes Under Bending

Composite materials have been used to structurally repair piping and other facilities for many years. However, the original use of composite materials was for repairing corroded pipelines where the intent was to restore strength to the damaged section of the pipeline. In addition to repairing corrosion, composite materials have successfully been used to repair dents, wrinkle bends, induction bends, and pipe fittings including elbows and tees as well as repair of offshore risers. In this study, the behavior of circumferential through cracks in repaired pipe with bonded composite wrap subjected to bending moment is investigated using three-dimensional finite-element analysis. The stress intensity factor (SIF) is utilized as a fracture criterion. The effects of the mechanical and geometrical properties of the adhesive on the variation of the SIF at the crack front were also analyzed. The obtained results show that the presence of the bonded composite repair significantly reduces the SIF, which can improve the residual lifespan of the pipe. Meanwhile, the SIF is also reduced as the elastic and the geometrical wrap properties are improved, particularly when the Young's modulus of the adhesive and the wrap thickness are increased.

The application of CFRP to strengthen buried steel pipelines against subsurface explosion

Multiple explosions in the route of oil and gas transmission pipelines during recent years demonstrate that terrorist attacks and sabotages have unfortunately increased. The present investigation is carried out numerically in order to minimize the amount of damages imposed on steel pipelines under close-in explosions. This research presents a novel concept, using CFRP (Carbon Fiber Reinforced Polymer) to strengthen the wall of steel pipelines against these incidents. For this purpose, a full coupled 3D finite element model developed using a combined Eulerian-Lagrangian method. The simplified Johnson-Cook material model, the JWL equation of state, and the ideal gas equation of state were employed for modeling the pipe material behavior, charge detonation, and air, respectively. Mechanical behavior of the composite wrap was simulated using an anisotropic material model and the damage initiation criteria were based on Hashin's theory. In addition, soil mass behavior was modeled applying a Drucker-Prager strength criterion with piecewise hardening and hydro tensile limit accompanied by Mie-Grüneisen equation of state. Several comparisons carried out between the results from present investigation and those from field and empirical studies and good agreements were observed. The results show that using a proper thickness of CFRP wrap for every particular circumstance can significantly improve the performance of steel pipelines under blast loads. For instance, in the current example, maximum equivalent strains developed in the most of the studied pipelines decreased by over 30% (up to 64%) with the application of 4-mm-thickness CFRP wrap. The present study contributes to protective design of steel pipelines.

Environmental Aspects of Using Metallic Organic Frameworks As Adsorbents in Natural Gas Storage Systems

The use of natural gas (NG) for automotive industry has gained renewed interest due to its growing supplies in the United States, relatively low cost compared to gasoline and diesel fuels and reduced emissions of carbon and particulate per equivalent. Because of its relatively low energy density NG must be stored at high pressure, 3,600 psi service pressure in the United States, in order to achieve an energy density suitable for vehicular use. Compressed NG cylinders are available in four types. Type 1, all metal (steel or aluminum) are the most widely used CNG cylinders in the world. Type 2 cylinders are metal liner reinforced by composite wrap (glass or carbon fiber) around the middle. Metal liner reinforced by composite wrap around the entire tank constitutes Type 3. While Type 4 cylinders are made of plastic gas-tight liner reinforced by composite wrap around the entire tank. Utilization of CNG storage systems in light duty vehicles has limited market penetration because of the cost of the pressure vessel and its occupancy of cargo space. Adsorbents materials are becoming an attractive option to develop low pressure and conformable NG storage system. Adsorbed NG storage relies on physisorption, i.e. weak gas-solid interactions between the fuel and the adsorbent surface. While research into adsorbents has focused on assessing their storage capabilities there is, to our knowledge, no reported data on their compatibility with the storage vessel and components in NG environment. High surface area porous materials such as Activated Carbons and Metal Organic Frameworks (MOF) are considered as the most promising adsorbents. The Cu3(btc)2 MOF, copper benzene-1,3,5-tricarboxylate also known as HKUST-1, has been extensively studied for gas storage. Herein we report its compatibility in NG environment with the pressure vessel, more particularly with the metal liner. We show that not only the stability of the adsorbent but also the integrity of the metallic liner can be drastically affected.

Finite-Element Modeling of a Damaged Pipeline Repaired Using the Wrap of a Composite Material

The nonlinear static problem of FEM modeling of a damaged pipeline repaired by a composite material and subjected to internal pressure is considered. The calculation is carried out using plasticity theory for the pipeline material and considering the polymeric filler and the composite wrap. The level of stresses in various zones of the structure is analyzed. The most widespread alloy used for oil pipelines is selected as pipe material. The contribution of each component of the pipeline-filler-wrap system to the level of stresses is investigated. The effect of the number of composite wrap layers is estimated. The results obtained allow one to decrease the costs needed for producing test specimens.

A Comparison Study of Bonded Composite Repairs of Through-Wall Cracks in Pipes Subjected to Traction, Bending Moment and Internal Pressure

In this study, a finite element analysis of the crack repair with composite wrap of circumferential through cracks in pipes subjected to bending moment is presented. Also, the evaluation of the long-term performance of composite repair systems has been addressed. The stress intensity factor is utilized as a fracture criterion. Finally, an attempt was made to provide industry with an overview of the current state of the art in composite repair technology and how the integrity of pipeline systems is being restored using composite materials. The obtained results show that the presence of the bonded composite repair reduces significantly the stress intensity factor, which can improve the residual fatigue life of the pipe. However, the main disadvantage of the technique of bonded composite repair in pipe is the impossibility to bond double sided composite wrap in order to equilibrate the stress transfer between the internal and external crack tip