Composite overwrap repairs

Design Pipe-grout gap Grout-sieeve Radiai crack Radial crack 

Numerical study of annular flaws/defects affecting the integrity of grouted composite sleeve repairs on pipehnes. Journal of Reinforced Plastics and Composites 33 (6), 556-565. 

Rehabilitation of Kpelines Using Fiber-reinforced Polymer (HfP) Composites 

Two separate primers, one for use OOW and the other IW, have been developed for the ProAssure Wrap Extreme system. The OOW primer is recommended to be applied at a thickness of 1150 g/m, while the IW primer at an approximate thickness of 3600 g/m. The in-plane mechanical properties of ProAssure Wrap Extreme are summarized in Table 12.2. 

Two chemical types generally used for pipeline repair arc epoxy and polyurethane (PU) resins. PUs have the advantage of curing at ambient temperatures via water activation, but the downside is that they are also easily hydrolysed in water and they have relatively low Tg values. In contrast, epoxy resins are more moisture stable and can be formulated to provide high Tg and environmental stability using aromatic amino compounds (Klein, 1991 Varma and Gupta, 2000). However, most thermosetting systems can only be applied on dry surfaces and are adversely affected by surface moisture and contaminants. Hence, ProAssure Wrap Extreme is a modified proprietary formulation that enhances adhesion in water environments. 

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Conventionally, most steel pipelines were repaired by removing the corroded section and replacing it with a new pipe or by reinforcing the defected section with an external steel sleeve (Mohitpour et al., 2003). Recently, fibre-reinforced polymer (FRP) composite overwrap repair systems have been introduced and overwhelmingly accepted as an alternative repair system for pipelines. 

In 2006, the first revision of two international codes, one by the International Organization for Standardization (ISO), ISO/TS-24817 (ISO, 2006) and the other the ASME PCC-2 (ASME, 2006), were published to assist engineers in designing a reliable composite overwrap repair. The former is recognised as a general code that covers pipes with different materials from steel to FRP while the latter is specifically focused on steel pipes. 

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). 

Saeed, N., Ronagh, H., Virk, A., Ashraf, M., 2012. Investigating the effects of pipe live pressure on the design of composite overwrap repairs. In The Australasian Stmctural Engineering Conference (ASEC 2012). Perth. 

Composite overwrap repairs can provide both strengthening and leak reinforcements to the pipe. Specially formulated resins are required for underwater applications where there are limitations with adhesion and curing. These repairs can be applied in situ without hot work, to partially or completely restore the pressure capacity of a corroded or mptured pipe, with the added corrosion protection benefit. Composite overwraps are primarily suited to onshore or offshore shallow water applications, due to the reliance on personnel to manually apply the composite onto the defect area. In addition, the overwraps require stringent surface preparation to ensure optimum adhesion and effectiveness of the repair, which is not always practical under field conditions. 

Duell, J.M., Wilson, J.M., Kessler, M.R., 2008. Analysis of carbon composite overwrap pipeline repair system. International Journal of Pressure Vessels and Piping 85, 782—788. 

The behaviour of pipes repaired with composite overwraps has been studied by many researchers in order to understand the effects of different parameters such as material properties and loading conditions. 

Freire et al. (2007) carried out an extensive experimental study to investigate the effectiveness of FRP overwrap repair on externally and internally damaged pipelines. They concluded that the use of composite overwrap could restore the burshng pressure resistance of both types of repaired pipes to the level of undamaged pipes. 

FRP overwrap repair systems can be considered as a lifetime repair for the cases where they can retard the growth of external corrosion by isolating the external defect from the corrosive environment. During the past decade it has been proven that FRP is a viable repair system and can be performed adequately under different environmental conditions in industrial projects (Duell et al., 2008). The behaviour of pipes repaired with composite overwraps has been studied by many researchers in order to understand the effects of different parameters (Alexander et al., 2008 Alexander and... 

Unlike the case of a composite clamp which is manufactured under shop-floor conditions that allow close control of the curing process, overwrap repairs are applied and cured in the field. Hence, it is not always practical to replicate laboratory cure conditions and the surface preparation of the substrate that have been used to determine the properties and performance of the overwrap repair system. To this end, a good understanding of the cure behaviour of the overwrap composite material and the composite—substrate interface properties is essential to ensure that repairs are properly applied and the acceptable performance is achieved in the field. 

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...

After preparing of the pipe surface and applying the putty, the composite laminate is applied circumferentially along the cleaned area from one side to another side. The number of required layers is determined by designer based on a proper design method. All of the design methods are explained in previous sections. The typical section of a pipe repaired by overwrap system is shown in Figure 10.2. 

The use of composites in the repair of pipelines is not new, with composite over-wrap repairs having been used effectively previously (Alexander and Ochoa, 2010 Shamsuddoha et al., 2012 Djukic et al., 2014a Leong et al., 2011 Gibson et al., 2011). The overwrap method involves wrapping the damaged pipe with concentric... 

Leong, A.Yi., Leong, K.H., Tan, Y.C., Liew, P.F.M., Wood, C.D., Tian, W., Kozielski, K.A., 2011. Overwrap composite repairs for offshore risers at topside and splash zone. In 18th International Conference on Composite Materials, Korea. 

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