Breaking of mooring lines whilst mooring m.v. Edisongracht between ...

The vessel was turned around, under pilot’s advise in the channel near the mooring buoys (seeposition 2 in figure 3). The two tugs, on standby, assisted as found necessary.Figure 3: The performed manoeuvres (source: shipping company)3.4 Setting out the mooring linesThe vessel was positioned between the mooring buoys with the assistance of the tugs. Similar tothe two previous times, both the fore and stern would be secured to the mooring buoys, with thebow of the vessel facing the northern direction. In order to bridge the distance to the mooringbuoy, which was approximately 90 metres, the fixed starboard mooring line on the winch drum wasextended with another mooring line with a minimum breaking load (MBL 7 ) of 36.3 tons (see figure4) through a steel shackle with a Safe Working Load (SWL 8 ) of 20 tons. Synthetic mooring lineswith a maximum strain of 18% were used on board the vessel.Figure 4: Example of a comparable mooring line extension as used during the mooring manoeuvreAround 8:50 a.m., the extended starboard mooring line was released through the centre lead ofthe forecastle and brought to and secured to the mooring buoy by boatmen*, using a motorboat. Asecond mooring line that had been extended in the same way as the starboard mooring line andoriginated from the fixed port winch was also released by the centre lead and secured by theboatmen to the mooring buoy. In the meantime, the pilot directed the tug from port to starboard inorder to prevent the vessel from being drifted away by the current, aiming to keep the vessel at its7SWL = Safe Working Load: the maximum allowed load for lifting tools such as shackles and cranes.8MBL = Minimum Breaking Load: the minimum load a mooring line should be able to withstand withoutbreaking For a mooring line the MBL is generally determined through a combination of designercalculation and testing (trial and error). The SWL is subsequently determined by applying a safety factoron an MBL.- 9 -