Cruise ships are still built to survive a minimum of two adjacent compartments being flooded. It is important to note that many modern ships can survive with 4–5 compartments filled with water, well exceeding this requirement. Unfortunately it is impossible to build an unsinkable ship, so every ship will have its limit of survivable flooding.
Each watertight compartment is separated from the very bottom of the ship, up to the 'bulkhead' deck. This deck is several meters above the water line, and should remain dry in all of the damage stability tests the ship needs to pass during the design phase. Just below this bulkhead deck is an imaginary 'margin line'.
If damage and flooding is so severe that the water is able to reach this margin line, the ship is considered unsafe and should be evacuated. This is because if water reaches the bulkhead deck, it is able to flow through corridors and staircases to fill adjacent spaces. This is known as sequential flooding, and once it has begun it will accelerate quickly until the ship sinks.
In many cases the watertight compartments need to be easily accessible - most of the ship’s technical spaces are right in the bottom of the ship, and crew members working there need easy access to pass between compartments. To allow this, watertight doors are provided. They are powerful, solid steel doors sitting on heavy rails, and often have a rubber gasket to ensure a good seal. They are left closed while the ship is at sea, but allow crew to pass through to access adjacent spaces. They can also be closed remotely, and this is one of the first actions taken if any damage is suspected.
One thing that has greatly improved, and continues to do so, is the support given to the crew on a ship to properly assess damage, and decide an appropriate response. One part of this is the ship’s stability computer, which is able to calculate the result of damage to any compartment on the ship, or what happens if the ship goes aground. The ship’s Officers are trained in its use, and often there will be one Officer assigned only to this task during an emergency.
To support the Officers, there are 24/7 support services available often from the ship’s own company, and also their insurers such as Lloyd’s. They can take the ship’s data and give their own professional assessment on how to best deal with the situation at hand.
Any flooding incident on a ship can escalate quickly. The crew’s response needs to be fast in order to identify damage and determine its extent. Damage control teams may be assigned to slow or stop the flooding, and pumps can be used to help empty the compartments. If it is too dangerous to send crew into the area, the compartment can be sacrificed provided the damage is survivable. If not, then the ship should be evacuated.
At the end of the day, the Captain relies on information from a huge number of people in order to decide how best to deal with the emergency, and there are more tools at their disposal to make a better informed decision.
|