Portable Cable Repair Spread

An energy service provider requested engineering support from MDL for finalising deck equipment specifications onboard their HV cable repair barge. The vessel was to be used for repairing subsea cable bundles at depths of up to 40m, capable of handling 3 different types of cable bundles, including HVDC and fibre optic cables. The spread would also have to unspool individual bundle elements for joining before overboarding.

To identify the most efficient solution to enable these versatile cable handling operations, MDL carried out a feasibility study to specify product handling equipment for the barge, with product being deployed/recovered over the stern of the vessel. The feasibility study first outlined the steps in the cable repair process, before identifying a spread of equipment which would facilitate the operations pertaining to safe on-deck product handling under tension, including recovery, testing, jointing with new cable sections, bundling and overboarding. Cable load calculations specified the technical requirements of the individual systems in the spread, which included tensioners, cable engines, spoolers, drum winches, overboarding cable chutes, rollers and a cable handling quadrant.

The key elements of the spread to ensure efficient and safe operations were the two MDL TTS-2 tensioners, which would be responsible for onboarding the bundled cable ends, controlling the overboarding of the healthy sealed ends, retaining the damaged cable end during cutting operations, holding the cable in place during joining operations and controlling the position of the cable on deck. This secure hold would be ensured with the Failsafe Grip System - an inherent feature in all MDL TTS units. The two outboard tensioners would mostly operate independently of each other, but would also work concurrently when overboarding the final repaired cable. In this case, both units would be set to maintain a constant tension in the line to pay out at the same rate. Specific track pads would be supplied to accommodate the shape of the combined cable bundles. The tensioner layout and pad design would be arranged such that the tensioner would not apply any squeeze to the more delicate fire optic cable. MDL tensioners pivot fully open, allowing completed joints to pass by them as well as allowing the completed cable to pass when it is overboarded using the cable quadrant. The MDL quadrant features rollers to aid smooth cable movement, while bumper frames around the edge keep the product contained in the quadrant. The quadrant would be supplied with a track system to ensure running across the deck in a straight line and equidistant between the outboard tensioners and chutes.