Dorbyl's contract on the Polaris saw us working closely with teams from Rolls Royce to undertake the warranty survey on four retractable thrusters as well as complete some other minor modifications and renewals.

The Polaris was a "challenging" project to secure as, a drydock with a substantial depth was needed to accommodate the barge. Cape Town was one of only three other potential destinations as it features a 13,7m (hwost) draft at the mouth of the dock. The strongest competition came from shipyards in Brazil and Portugal.

To accommodate the removal of the thrusters, which were situated underneath the barge, about 140 fabricated concrete docking blocks were specially designed to dock the barge at a height of 4m. The four Azimutal thrusters, each weighing 45 tons, were skidded out on special plates under the auspices of the Rolls Royce team and removed to Dorbyl Marine's workshops to perform the complete overhaul. This included the strip-down, inspection and survey of all components as well as re-machining and the re-build of the units with new bearings and steel.

Committed to the drydock for a period of 55 days, the Polaris also underwent a 20 year survey that included extensive steelwork (290 tons), blasting and painting.

All the tanks, voids, ballast water tanks, fresh water tanks and fuel tanks were hydra-blasted, cleaned and tested before the Classification Society Surveyor and Stolt Offshore Services QA personnel inspected them.

The scope of the internal steelwork repairs to the ballast water tanks more than doubled the required steel to 120 tons. New manholes were fitted to the majority of the tanks and considerable amounts of piping had to be renewed in the ballast tanks. They were subjected to air tests after the steel repairs.

External steelwork structures consisted of the pre-fabrication of a new rescue launch structure; modifications to the J-lay structure; extensions to the bridge-deck; port and starboard repairs as well as modifications to the crane boom jib end and other minor steelworks.

Extensive piping and valve repairs were carried out as part of the scope of work. Sea intake valves were overhauled and replaced.

Dorbyl also undertook work on the ventilation system including the removal and overhaul of the fans. Electrical work included the renewal of cable trays as well as cables for the Remotely Operated Vehicle (ROV). The crane boom spotlights were overhauled and new lights installed in the living quarters which were also refurbished.

Upgrades to safety equipment included the installation of a new foam gun platform and monitor as well as a new CO2 fire-fighting system. Additional fire-fighting lines were fitted to the rotating crane machinery space.

The Clyde crane underwent a painting programme using Jotun paint who have offered the owners a five-year paint warranty.

All the side shell wooden protection fenders were removed and completely renewed with steel top cappings. The decks, which are protected with a double layer of timber, had to be removed and replaced with new timber supplied by the owners.

Mechanical work consisted of the removal of the Besemer winch drums including the overhaul and replacement of all bearings. The mooring fairleaders were removed for complete overhaul and the sheave bearings were replaced. An extensive overhaul of the two aft stinger hitch pins and associated jacking systems was also undertaken. The active heave compensator was decommissioned and removed from the crane boom.