Composite overwrap repair, application methods

For layered systems, FRP composite is manufacmred and cured in the factory and transferred to the field as a rigid product. Then it is bonded to the defected pipe by means of an adhesive. Repair using this system is limited to straight pipes only. 

Unlike the layered systems, the wet lay-up systems are shaped into a composite onsite and due to their ease of application are more widely used. They typically come in two different types. The first type involves some type of fabric or sheet made of usual fibres (including carbon fibres, glass fibres and aramid fibres), impregnated by in situ application of resin to the materials. The second variations of the wet lay-up systems are cloths preimpregnated in the factory which are activated by heat, water or other catalysts in the field. These kinds of systems are normally protected in sealed bags and cold environments because once the bag is opened, the chemical reaction between the material and moisture in the environment temperature begins and the product wUl start curing. 

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Many composite overwrap repair systems have been introduced to the pipeline industry, their differences being in fibres, adhesive, resin and method of application. Carbon fibre, glass fibre and aramid fibre (Kevlar reinforcement) are the usual fibres used in these composite systems to provide for the required strength and stiffness. In general, two types of composite repair, namely layered system and wet lay-up system, are currently used for pipeline repair (Figure 10.1). 

Figures 12.14—12.17 show applications of the ProAssure products. It can be seen that overwrap repairs can be successfully applied on the platform, in the splash zone as well as in the sea. Obviously the complexity increases as repairs move from dry to wet and subsea environments. This is not only restricted to application of the composite laminate but also to related activities such as removal of existing coatings and surface preparation, as well as additional requirements such as the need for scaffolding, absailers and/or a service barge. A similar scenario applies to the clamp repair solution, which is generally advantageous over the overwrap repair method in cases of deeper...

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