This incident information refer to to heavy corrosion/pitting and subsequent cracking that was discovered in the side shell plating and frames of an old bulk carrier at sea, in ballast condition. The damage was found in way of the pipes connecting the hopper tanks and the top side tanks in cargo hold no. 4.
During a loaded voyage of a bulk carrier it was discovered that water had entered into the double bottom tank No.4, amidships. After inspection it was found that the water was coming through the ship’s side via the access trunk from the top wing tank and then to the double bottom ballast tank. The ingress water was estimated to be approximately 300 cubic meters per hour. Fortunately, the leak was limited to the double bottom ballast tank and the ballast pumps were able to keep the tank empty until the crack could be dealt with.
During a Class survey of a tanker, several cracks were found in the deck structure in the midship area, at the connection between the deck longitudinals and the deck openings (access and Butterworth hatches).
During survey several fatigue cracks were found in way of the elliptic curved corner of the opening in way of cargo hatch ways on the main deck. A shedder plate had been welded to the main deck in way of the hatch opening corner. This is believed to be the most probable cause of the crack in the deck plate.
The ship was banned in Italy in 2002. The banning was lifted in December 2007 and the vessel was on a voyage to Port of Szczecin in Poland. After lifting the ship from banning, she was due for a Mandatory Expanded Inspection (MEI). The Mandatory Expanded PSC PMoU Inspection was carried out on 19 December 2007 on partly discharged ship in Szczecin – Poland by two of our PSC Officers. After the inspection the ship was detained having among other 27 deficiencies identified.
This incident refers to cracks identified in a vessel’s propeller hub. When carrying out hull renewal survey in drydock, two open cracks were found during the visual inspection of the propeller hub. The propeller was a 4 bladed mono-block fixed pitch manganese aluminium bronze propeller fitted with cone and key and with diameter: 5205 mm.
Cracks in deck plating in way of deck penetrations of oil tankers has been an increasing problem and is typical on vessels with high strength steel in deck and most typically found on Buoy loading Oil Tankers trading in the North Sea. The damaged areas (as shown in this post) were limited to cracks in the upper deck plating in way of the pipe penetrations resulting in small leaks, but could easily have resulted in more serious damage to the deck structure and the safety of the ship if left unattended over time.
The semi-submersible “flotel” (floating hotel) Alexander L. Kielland capsized on 27 March 1980 while bridge connected to the steel jacket Ekofisk Edda platform. The flotel lost one of its five legs in severe gale force winds, but not an extreme storm. The accident started with one of the bracings failing due to fatigue, thereby causing a succession of failures of all bracings attached to this leg. It was discovered during the investigation that the weld of an instrument connection on the bracing had contained cracks, which had probably been in existence since the rig was built. The cracks had developed over time, and the remaining steel was less than 50%.
During survey of cargo centre tanks, cracks were found in some of the deck longitudinals in a amidships. The cracks had penetrated through the flange, into the web of the deck longitudinal, and further into the deck plating at one location. The most probable cause of the cracking was fatigue due to longitudinal hull girder stresses combined with unfavourable location of welding in a knuckle.
A welding structure in order to have the required reliability, during her lifetime, it should have satisfactory quality. This means that it should:
Welding quality is a relative term and this means that it is not necessary a construction to have better quality from what is needed according to the requirements. When the requirements are strict, that has as consequence the cost of production to be extremely high. On the other hand when the requirements are loose, that has as consequence the cost of maintenance to be high and the forecasting lifetime to be reduced.
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Officer of the Watch 