Pipe repair options

Pipe repair options include (1) external repairs, such as circumferential posttensioning, replacement, external steel or CFRP bands, or encasement of the distressed pipe, or (2) internal repairs, such as installing a steel liner or slip-lining with fiberglass or steel pipes, or lining with hand lay-up CFRP. Selecting the best option depends on access, acceptable duration of construction, impact on operation, the expected cost of repair, and reliability of the repaired pipeline. 

The location of the pipeline is important for repair considerations. A pipe in swampy clay would exclude recoating versus a repair option. On the contrary, prairies are conducive to recoating, with firm footing for the equipment and good accessibility. 

Alternatives other than rehabilitation and replacement such as abandonment of the pipe section with a bypass loop increasing the frequency of ILI enables greater accuracy in determining the point of failure for existing defects. Derating the pipe may extend the life of the pipe provided throughput requirements are met. For the replacement or repair option, it is generally necessary to have a loop system and allow for pressure restrictions or interruptible service to facilitate repairs. 

Another option is the dry-pit design (Fig. 7c). This pump is installed in a dry pit and coimected to a weU via a pipe. Because the dry pit is usually dug out wider than the wet pit, Tenough room is available for pump maintenance, troubleshooting, and repair without pulling the pump to the surface for servicing. 

Field Hydrostatic Testing. Field hydrostatic testing is not an ASME Code requirement. Field testing is optional to test the tightness of piping joints attached to the vessel after installation. Often it is a contractor s policy to design vessels and vessel foundations, with rare exceptions, for a future field hydrotest in the corroded condition. This gives clients the option to test the vessel on its foundation in the future should alterations or repairs warrant such a test. 

A CFRP liner was selected specifically because it could be installed rapidly, allowing the pipe to be put back in service within a very short time window. In this case, the use of CFRP was preplanned so the repair could be completed as an emergency. The planning, notifications, and constmction window for the replacement of the pipe segment made that option infeasible. The CFRP liner utilized to address this longitudinal weakness was designed to specifically provide primary reinforcement in the longitudinal direction. 

The honeycomb-FRP pipe will reduce the pipe diameter by a slight amount over the wet lay-up system. However, considering all the other significant advantages that are detailed below, the honeycomb-FRP pipe can be the preferred option for repair of many pressurized pipes. 

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