Clock Spring has been one of the major successes in the last 20 years in improving the integrity management of pipe systems. The technique has been adopted widely, and applications now include the pipeline, offshore, refinery and chemical industries. Each industry has taken advantage of the ability to complete repairs without disruption to operations.

These advanced composite materials derive their strength from E-glass fibres aligned in a polyester resin matrix. They are manufactured under a recognised quality assurance system. The mechanical performance of the system was extensively tested and refined before its introduction by the independent Gas Research Institute in the USA, to give confidence in the long-term performance of the repairs installed. A 50-year lifespan for the repairs was demonstrated to be realistic, and has been accepted by regulators in the United States for repairs on high pressure gas transmission lines.

Clock Spring has been used to solve a number of problems that are common across pipe applications in all industries. The repair of mechanical damage by third-party interference, and external corrosion are the most common applications on pipelines, with tens of thousands of Clock Spring installations being completed worldwide each year. Internal corrosion and wall thinning can be temporarily repaired to extend the life and allow for a planned replacement. Clock Spring products have also been used to repair leaks on oil and gas pipelines. A recent application saw Heath Pipeline Services successfully complete a leak repair on a gas pipeline operating at 1,750 kPa.

Putting the ‘tee’ in integrity

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One of the limitations of the Clock Spring is that it is difficult to repair geometries other than straight pipe. This shortcoming has now been addressed by the Clock Spring Contour product. Contour is a combination of a high-strength fibreglass fabric and a chemically resistant epoxy resin. The two materials are combined onsite and laid on the substrate before the resin has cured. This enables them to be applied to a wide range of different geometries.

Contour is often termed a ‘wet wrap’, in the sense that the wrap is applied before the resin matrix cures solid. The scope of repairs that can be considered is wider, with the thickness of the Contour repair being determined by an engineering assessment in accordance with current ASME PCC-2 Repair of Pressure Equipment and Piping and ISO TS 24817 Composite Repairs for Pipework – Qualification and Design, Installation, Testing and Inspection guidance. These documents require each application to be considered individually and the repair length and thickness calculated.

Refinery 900NB flare line repaired

Heath Pipeline Services has recently been contracted for pipe repair works on a refinery 900NB flare line. Due to the repair design, number of elbows, tees and pipe supports, it has been agreed, in discussion with refinery engineering group, that the line of more than 100 m be repaired using Clock Spring Contour exclusively. The design and engineering completed by the Clock Spring Company will confirm the materials, thickness and installation based on the pipeline design and operational life.

Contour can maintain pipeline operating conditions, even if a pipe has internal corrosion and this continues to corrode resulting in a leak within the Contour repair. Pipe repairs can be designed as permanent repairs or to extend operating life through to a planned shutdown and replacement. Most repairs using Clock Spring can be completed during normal operating conditions without shutdown or hot work, thus potentially saving many thousands of dollars.

Repairs of corrosion and mechanical damage to pipe can now be undertaken with confidence using Clock Spring products and Heath Pipeline Services. Repair and protection of straights, elbows, tees, nozzles and other components have been completed and can give rise to significant cost savings as expensive shutdowns are avoided.