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Reference Number NIA_NGGD0094
Title Composite Repairs to Complex Shapes
Status Completed
Energy Categories Fossil Fuels: Oil Gas and Coal(Oil and Gas, Refining, transport and storage of oil and gas) 100%;
Research Types Applied Research and Development 100%
Science and Technology Fields PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials) 50%;
ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering) 50%;
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Project Contact
No email address given
Cadent Gas
Award Type Network Innovation Allowance
Funding Source Ofgem
Start Date 01 March 2017
End Date 01 November 2018
Duration 20 months
Total Grant Value £999,999
Industrial Sectors Technical Consultancy
Region London
Programme Network Innovation Allowance
Investigators Principal Investigator Project Contact , Cadent Gas (99.996%)
  Other Investigator Project Contact , Wales and West Utilities (0.001%)
Project Contact , National Grid Gas Transmission (0.001%)
Project Contact , Northern Gas Networks (0.001%)
Project Contact , SGN (0.001%)
Web Site
Objectives The objectives of the scope of work proposed are;Development of a guidance document detailing the design and installation requirements for the repair of part-wall, blunt, metal loss defects associated with complex geometry componentsVerification of the suitability of the composite repair system through full scale testing supported by analytical and numerical analysis, as appropriateAssessment of environmental variables on the integrity of the composite repair. The success criteria for the work proposed will be;Verification and implementation of new technology enabling repairs of part through-wall, blunt, metal loss defects associated with complex shaped geometries at a reduced cost and reduced downtime compared with conventional techniques/methods. A consistent approach to the repair of part through-wall, blunt, metal loss defects for the UK gas transmission and distribution system. Verification of the ISO recommendations and industry practice guidance for the design and installation of composite systems, and development of a comprehensive guidance document governing the design and installation of composite systems.
Abstract Since the early 1980’s, National Grid and the Gas Networks have been repairing pipeline damage using a full encapsulation epoxy filled steel shell. The quality of repair using the steel shell is not in question; the reliability of the UK gas transmission and distribution system is testimony to this. However, given the advances in composite technology over recent years, and the outstanding results of the IFI43 research program, there is interest in the potential use of this system for the repair of other complex shaped piping components, both as an emergency repair system and as a permanent long term repair solution. Application of the composite repair systems to complex shaped components such as bends and Tees is an immature area of research; although some guidance is given in the standards, it is acknowledged that further research is required. The main objective of the proposed scope of work is to verify the suitability of the design equations in ISO 24817 by testing and evaluation, to ensure that the repaired piping component has sufficient reinforcement to mitigate a failure due to static internal pressure and pressure cycling, without impacting on the stiffness and/or flexibility of the piping system. Consideration is given to part through-wall, blunt, metal loss defects such as corrosion, and gouges that are ground to a smooth profile prior to application of a repair. The ISO standard considers long term as 20 years; this is reflected in the design equations when calculating the repair thickness for pipeline components. On achieving the 20 years design life, the ISO standard recommends that the composite repair is either replaced, or an analysis be undertaken towards revalidation of the system. It is not the intention of the work proposed to extend the design life beyond 20 years. The repair thickness for the different piping components is calculated using the standard equation for a straight pipe section, multiplied by a repair thickness increase factor which is dependent on the piping component; 1. 2 for a bend, 2 for a tee and 1. 1 for a reducer. Verification of the long term suitability of the repair system will be via full-scale test, supported by analytical and numerical studies, as required. Based on the performance of the Furmanite and T D Williams On composite systems that were tested in IFI43, further testing of these manufacturer’s products is recommended. However, the testing proposed herein will only be undertaken on the Furmanite product, to verify its suitability for the gas transmission and distribution system and to obtain base-line performance data. If a new candidate product comes to market, National Grid and the Networks will be able to specify what testing the manufacturer will be required to undertake in order to demonstrate the suitability of their system; the results of those limited tests will be compared against the Furmanite bench-mark test results. For the purposes of this proposal, installation of the repair system will be undertaken by trained Furmanite Engineers. In a composite material, the fibre is the primary load carrying element of the system. The composite material is only strong and stiff in the direction of the fibres; their behaviour is said to be anisotropic (in contrast, steel is an isotropic material, with uniform properties in all directions). To achieve desired properties in different directions, fibre orientation is key; for example, the Furmanite system (FurmaCarbon) used for the bend tests in IFI43 was a bi-directional fabric, fibres orientated in the 0° and 90° directions to give good strength and stiffness in the hoop and axial directions. Compared with steel, composite systems exhibit very complex failure mechanisms under static and fatigue loading. Although both the Furmanite (and T D Williams On) composite system preformed will under static loading conditions (IFI43), its performance when subjected to repeated load cycles (fatigue) may be significantly different to that of the pipeline. Fatigue of composite systems causes extensive damage (matrix cracking, delamination, fibre breakage and interfacial debonding) through the thickness of the repair, leading to failure from general degradation of the material, instead of a predominant single crack that would initiate and propagate in steel. As a result, for application to complex shape geometries, prediction of the fatigue performance is complex. However, pipelines have a design fatigue life; for example, the fatigue life of a pipeline subjected to a high level pressure test in accordance with the requirements of IGEM/TD/1 will not be less than 15,000 cycles of a hoop stress range of 125N/mm . If the pipeline has been subjected to a lower level test pressure, the fatigue design life may be less; National Grid’s specification, T/SP/TR/19 provides a detailed method and screening charts for predicting the fatigue life of a pipeline, depending on its maximum operating pressure (MOP) and hydrotest pressure. Hence, it is not necessary to be able to predict the fatigue performance of the repair system; rather, the repair system must not fail prior to expiry of the fatigue design life of the pipeline. On that basis, the fatigue performance of the repaired piping component will be assessed against the fatigue design life of a pipeline subjected to a high level pressure test, 15,000 cycles of 125N/mm hoop stress range. For consistency with the design philosophy of the epoxy shell, the target number of stress cycles for the fatigue tests will incorporate a factor of safety of 10 on life; i. e. , the target number of cycles will be 150,000. While the mechanical properties of composite repairs for pipelines will be the focus of this programme of work, the performance of the entire metal-composite system also needs to be considered with regard to corrosion of the substrate, water intrusion at the composite-metal interface, cathodic disbondment behaviour and adhesion loss etc. , and aspects of this have been covered in the proposed Stage 3. An overview of each Stage, and Task within each stage, is given below.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above
Publications (none)
Final Report (none)
Added to Database 09/08/18