The practical aspects involved in the decision making process for selecting and implementing a repair strategy for the rehabilitation of an aging onshore pipeline are discussed. As part of the selection of the appropriate technology an overview of the different repair methods for in-service pipelines is introduced.
Different factors such as type of defect, operating conditions, field implementation, costs, etc for the different techniques are reviewed for the selection of the appropriate technique in relation to the severity of the defects found in conjunction with the operational requirements of the line in question at any one point in time.
Methods utilised include Direct Deposition Welding to Live Lines, Bolted Clamps, Epoxy Resin Sleeve, Welded Sleeve, and composite repair materials. For the different repair technologies the associated surface preparation and final coating/wrapping is also discussed.
The approach discussed in the paper for the development of the rehabilitation strategy is applied to a number of the UK Ministry of Defence pipelines. These lines were originally manufactured for the British War effort in the 1940’s and were generally relayed with welded joints and coal tar enamel wrapping by the 1970’s. For some of these lines the original coating methods and the passage of time have allowed the ingress of water at the interface of flood coating and the Hot/Cold applied tapes used.
The key elements discussed in the paper are then applied to a case study to evaluate the immediate and future integrity condition of the line and for developing a strategy to rehabilitate the pipeline ensuring the future safe and reliable operation in relation to the MAOP.