It is rare to see such excessive loss of clearance between the slewing pinion and the pedestal post flange. Great attention is required by crew during loading operations, especially when same are carried out at anchor. It is imperative that all operating conditions are within Makers’ limits and that stevedores are notified to halt operation when same are exceeded – in addition to standard preventive maintenance procedures (rocking tests, greasing, sampling etc).
Repair Process
In this case, slewing rings renewal was required, which involves machining of both pedestal and turret post flanges, to comply with new slewing rings flatness tolerances which may be as low as 0.2mm.
Initially, and once turrets have been removed ashore by use of mobile cranes, laser alignment measurements were taken to verify the flatness of pedestal and turret post flanges. Subsequently the machining of the surfaces was carried out with a special tool provided by local Piraeus contractors, and machining required an average of 2 days to complete per flange, subject to weather conditions prevailing.
In order for the above to be carried out, custom cradles were fabricated in order for the tower posts to be placed horizontally on pier, for easier access of the machining tool.
Repairs were carried out whilst vessel was fastened alongside a repair berth at Piraeus. Our Piraeus Head Office Surveyors continuously attended on site and at workshop, as always providing our proactive advice to H&M Underwriters with regards to progress of repairs and estimated costs.
