Published: December 1, 2018

Tank inspections are an important part of the planned maintenance programme on board. Entering a tank involves many personal dangers which are well known for most seafarers and should never be ignored. In addition, there is also a risk of the cargo being damaged, especially when the manhole is left open, and this damage can be very costly.

It may seem obvious and logical that a tank should not be filled when the manhole is open and the consequences of doing this are easily imagined. However, the loss prevention team has recently seen cases where cargo holds have been flooded when the manhole is open, particularly on container ships.

In one case, the covers for two ballast tank manholes had been removed. In order to clean the tanks, it was decided to partly fill them up and then to strip again. After a while both bilge alarms from the adjacent cargo hold sounded. The bilge alarms were ignored for half an hour and then when the hold was checked, the lower tier of containers was found to be flooded.
In another case the bosun removed the cover to a tank he thought was to be stripped. However, the instructions had not been properly communicated and understood by the bosun and in fact the tank was to be filled. The result was that 1.5 meter of water had entered the cargo hold before anyone noticed.

Here are some basic precautions to take:

  • Do not fill a tank if the manhole is open. If there are particular circumstances when this is necessary, then a thorough risk assessment must be carried out and also a watchman must be at the open manhole throughout the process.
  • Make sure that there is effective communication setting out who is responsible for removing and replacing the manhole cover before the work starts.
  • Never ignore a bilge alarm – always check alarms immediately.

One way to keep track of open manholes is by using a white board divided into numbered squares each one with a corresponding numbered magnet. The magnet is then placed on the board on the square corresponding to the removed manhole cover. The magnet is removed when the cover has been refitted. This is a simple but effective system and can be easily introduced into the working systems.


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