Bow Impact Damage

During a normal daily inspection serious indents were found in a ship’s bow in way of the Bosun store at port side, affecting shell plating and 12 frames.  The damage was assumed to have occurred during heavy weather conditions, which had caused bow impact pressure, which exceeded the capacity of the bow structure. This could either have happened because the sea state caused higher loads than accounted for in the class rules or the ship may have operated outside the range of “good marine practice”. Damage, has occurred quite frequently on container ships and also on other cargo ships, having comparable speed and high flare angle.

2013.01.04 - Bow Impact Damage Figure 1

Class rules account for a certain bow impact design pressure as basis for approval at newbuilding stage, which should provide sufficient strength in the bow under normal conditions.
However, it also assumes that the handling of the ship is in accordance with “good marine practice”. This may require reduction of speed and changing course in bad weather. Although the rules of all class societies, within IACS in general, provide comparable minimum levels of safety, local variations over the ship may occur, as is the case for the bow impact design pressure.

The ship mentioned in this incident was DNV Classed, but was built to the rules of another IACS class society as far as the bow structure is concerned. Following such damage, this ship and all sister ships were upgraded to DNV latest rules for bow impact design pressure.

In order to avoid damage to the bow area the following may be noted:

  • Any ship may suffer bow impact damage when not competently handled.
  • Large container ships are particularly vulnerable to such damage due to high speed and flare angle. This may be a particular challenge on the large container ship, where the distance from the bridge to the bow may be up to 250-300 m and the bow area is hidden behind the stacks on hatch no.1.
  • Use experienced captains on container ships to share their know how with the younger generation on the bridge watch to improve good marine practice regarding the running of the ship.
  • Collect available information about sea/weather conditions prior to departure. The use of modern weather routing system have proved to be effective in avoiding running into bad weather.
  • Consider using monitoring system on board to improve the surveillance of sea and weather state and the effect on the ship hull.
  • Consider to have the bow impact strength evaluated in order to better know the strength of that area which may be subject to bow impact.
2013.01.04 - Bow Impact Damage Figure 2

High flare angle – one contributing factor to the damage.

Source: DNV

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