Composite repair system

Key words fiber-reinforced polymer composites, pipes, risers, bonded joints, composite repair systems. 

Armor Plate (Texas, US) is another pipe repair system that uses multipurpose fiberglass/epoxy wraps and different curing agents (see Fig. 18.11). The difference between Armor Plate and StrongBack composite repair systems (discussed below) is that Armor Plate uses chemicals instead of water as the catalyst agent. 

As stated earlier, the purpose of a composite repair system is to reinforce the damage caused as a result of corrosion or mechanically related forces causing... 

The use of fiber-reinforced composite materials for pipeline repairs was developed during work at Southwest Research Institute and Battelle in the late 1980s (Fawley, 1994 Stephens and Kilinski, 1994). There are two basic types of composite repair systems preformed (composite sleeves) and wet lay-up (composite wraps). The first commercially available system was Clock Spring , which consists of an E-glass/polyester resin-based composite material preformed into a multilayer coil that is installed using an adhesive (Figure 4.4). 

ASME PCC-2 Article 4.1, Non-metaUic Composite Repair System for Pipehnes and Pipework High Risk Applications, 2006. 

Alexander, C., 2007. Development of Composite Repair System for Reinforcing Offshore Riser (Ph.D. thesis), Texas A M University. 

Alexander, C., April—May 2012. Design of an optimized composite repair system for offshore risers using integrated analysis and testing techniques. In Offshore Technology Conference. http //dx.doi.org/10.4043/23164-MS. 

Francini, R.B., Kiefner, J.F., 2006. Evaluation of the Aquawrap composite Repair System. Report Prepared for Air Logistics Corporation, Report No. 06—41, April. 

Rehberg, T., Schad, M., Green, M., 2010. Non-metallic Composite Repair Systems for Pipes and Pipelines. Pipe Technology 3R International. Special Edition. 

Alexander, C., Cercone, L., Lockwood, J., 2008. Development of a carhon-fibre composite repair system for offshore risers. In The 27th International Conference on Offshore Mechanics and Arctic Engineering, OMAE2008. The American Society of Mechanical Engineering, Estord, Portugal. 

Frassine, R., 1997. Long-term performance of a polymer composite repair system for gas pipelines. Advances in Polymer Technology 16 (1), 33—43. 

Fold-and-form liners This is a flexible and unbonded composite repair system which is usually made up of thermoplastic pipe folded into a U or C shape, and after being rolled inside the pipe, expanded with pressure and heat. This type of repair system can be either bonded or unbonded, and the process is typically limited to liners less than 450 mm in diameter. 

The unbonded composite repair system can be either rigid or flexible. A rigid composite pipe is installed and cured inside the corroded steel pipe, using the damaged pipe as a form or mould, but is not bonded to the pipe. In this system, the internal composite finer acts as the pipe, with no or minimal contribution from the original pipe. There is no load transfer between the internal composite pipe and the external steel pipe. Therefore, the composite pipe must be capable of carrying the full internal pressure load as well as bending and other external loads. 

Analytical methods are important for internal composite repair systems to ensure that damaged pipelines are properly analysed to evaluate the system against performance measures. Existing methods specifically focus on external repairs of pipelines with internal repairs still unexamined, even though the concept could potentially be applied to internal repairs. Therefore, the concepts and approaches that could be adopted for analysing unbonded and bonded repairs are considered below. 

To overcome the limitations in the Lame theory when applying to orthotropic composite repair systems, a new modified version of Lame s equations (MVLE) was developed by the authors to undertake the analysis of infinitely long orthotropic cyhnders subjected to internal and/or external pressure. The hoop and radial stresses at any point in the wall cross section of an orthotropic cylinder at radius r are given by the following equations ... 

The modified Lame s coefficients and the corresponding MVLE for common available orthotropic material cylinders were studied, and it was concluded that, for currently available orthotropic materials, the values of a and jS are not equal to each other. For isotropic materials, a and jS are equal to 0 and —2, and Eqns (13.7) and (13.8) convert to Isotropic Lame s form as Eqns (13.3) and (13.4). Internal composite repair systems can be split into two cylinders using contact pressure, as depicted in Figure 13.7. Then the system can be analysed by considering strain compatibility at the composite—steel interface and appropriate boundary conditions. 

---