Watertight Door

 watertight door

Watertight doors are doors which are designed to keep water out. These doors are design to maintain the ships stability should it be involved in a unfortunate accident. Certain rules and regulations adopted by the IMO require ships to be able to survive such a tragic event. For example a ferry carrying passengers needs to be able to withstand a flooding of two of it's compartments.
In order to make sure these rules are followed and still remain practical, ships make use of watertight doors below the waterline. These doors are usually constructed by a specialize enclosure maker, then fitted into the ship. These doors "break" the continuity of a structural bulkhead therefore they reduce the strength of that bulkhead. Because of that, they must be engineered to match the bulkhead's strength and therefore watertight doors can look quite bulky and menacing.
There are numerous types of doors: on deck, some appear to be a heavy safe like doors with numerous latching dogs around it’s perimeter. Pictured left and below are some good examples.
Below the waterline, the door are generally of the sliding type; horizontal or vertical.
Maintenance of the doors should consist of testing it’s full operation, and visual check of operating mechanisms. Hoses and connections checked for chaffing and tightness. Guides should be clear of obstructions and greased. Wear surfaces should be checked to to make sure they are secured and not worn beyond tolerances. The hydraulic ram should be checked for leaks, these can be caused by a damaged cylinder ram. Manual pumps for the door should get a good "once over" checking the fluid level, lever and it's eccentrics for looseness. Check for leaks at the piping joints.
The hydraulic power pack: Checks include things such as hoses, fluid levels, loose wiring. Check piping for leaks. Some power packs have pressure reservoirs so that doors can be actuated with a power failure. These reservoirs store hydraulic energy by compressing nitrogen at high pressure, these can be particularly prone to leakage.
Additionally the controls for the powerpack should be checked. Start and stop buttons, remotes start and stop buttons should be checked for operation with no binding. Horns are annoying and can sometimes be found to be "un-operational". Warning lights, if equipped, should be working. Contact switches should be checked for operation and proper setting.

The above, are pictures of a vertical sliding watertight door. It is to access the shaft tunnel. Below are pictures of a horizontal sliding type.

The pictures above and to the right are of a sliding type door. By clicking on the picture to the right you can clearly see the various points discussed above. The manual operation crank in the foreground and the control buttons, the grey box above the hand crank, are clearly visible. The micro switch is at the top corner of the door's frame. The yellow rotating light can be seen in the upper right of the picture. Incidentally, this picture serves to illustrate the fire pull station as well as the fire extinguisher conveniently located.
Manually operated door: Manually actuated doors will generally have gears and long shafts and chain drives. This is to allow operation from deck level. If these are neglected, they could quickly lead to some difficulties operating the door. Extra care should be taken to maintain these components by cleaning, greasing, and operating them.