Overwrap method

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... 

However, fibreboard has been criticised because of loose fibres. Baler bags received favourable publicity a few years ago but found rather limited use against the more competitive shrink wrapping systems. Shrink wraps as sleeves or overwraps may be used around complete pallet loads or small unit quantities. In the case of wrapped pallet loads the bottles may be separated with layer pads. On smaller quantities, bottles may be trayed or left without additional support (i.e. direct shrink wrap). Again the pallet may have a full shrink wrap to give added security and protection, and this is now the preferred method of packing. 

Certain preservative systems can be lost from certain plastic packs by sorption and solubility in the plastic and, if they are also volatile, by evaporation from the external surface which is in contact with the atmosphere. Reports, particularly as references in textbooks, often suggested that phenol could not be used as a preservative in lowdensity packs. Subsequent work, many years later, established that the solubility of phenol in polyethylene was relatively low and that sufficient phenol for adequate preservative efficacy could be retained by a number of methods, i.e. coating LDPE internally or externally, or enclosing the pack in an additional barrier overwrap (e.g. paper/foil/PE or similar foil-bearing barriers). 

Film Processing Methods For use on form-fill-seal and overwrap equipment as well as thermoforming equipment. 

Properties Overwrap film Chub packaging film A Chub packaging filmB Unit packaging film A Unit packaging filmB High barrier packaging film Test methods... 

Method validation report of HPLG limit test for potential leachables from foil laminate overwrap, Analytical Test Report, Dey L.P., Napa CA., USA. 

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). 

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. 

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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