WATERTIGHT DOORS

                                                WATERTIGHT DOORS

We need water-tight doors, to exclude the possibility of one or more of the vessel’s spaces becoming flooded & compromising the water-tight integrity of the vessel.

In order to maintain the efficiency of a watertight bulkhead it is desirable that it remains intact. However in some instances it becomes necessary to provide access between compartments on either side of a watertight bulkhead and watertight doors are fitted for this purpose. A particular example of this in cargo ships is the direct means of access required between the engine room and the shaft tunnel. In passenger ships watertight doors are more frequently found where they allow passengers to pass between

one point of the accommodation and another.

Where a doorway is cut in the lower part of a watertight bulkhead care must be taken to maintain the strength of the bulkhead. The opening is to be framed and reinforced, if the vertical stiffeners are cut in way of the opening. If the stiffener spacing is increased to accommodate the opening, the scantlings of the stiffeners on either side of the opening are increased to give an equivalent strength to that of an unpierced bulkhead. The actual opening is kept as small as possible, the access to the shaft tunnel being about 1000 to 1250 mm high and about 700 mm wide. In passenger accommodation

the openings would be somewhat larger.

Mild steel or cast steel watertight doors fitted below the water line are either of the vertical or horizontal sliding type. A swinging hinged type of door could prove impossible to close in the event of flooding and is not permitted.

Hinged water tight doors may be allowed in passenger ships and in watertight bulkheads above decks which are placed 2.2m or more above the waterline. Similar doors may be fitted in weather decks openings in cargo ships.

Hinged watertight doors are not permitted below the waterline.

These may be similar to the weathertight doors fitted in superstructures,  but are to have gunmetal pins in the hinges.

                                  Hinged Door

                                               

Sliding W/T doors may be hand operated, but in most modern ships they are hydraulically controlled.

Power-operated sliding doors shall be capable of being closed simultaneously from the central operating console at the navigation bridge in not more than 60 s with the ship in the upright position.

•     The means of operation whether by power or by hand of any power operated sliding watertight door shall be capable of closing the door with the ship listed to 15 degrees either  way.

•     Watertight door controls, including hydraulic piping and electric cables, shall be kept as close as practicable to the bulkhead in which the doors are fitted, in order to minimize the likelihood of them being involved in any damage which the ship may sustain.

•     All power-operated sliding watertight doors shall be provided with means of indication which will show at all remote operating positions whether the doors are open or closed.

•     Each power-operated sliding watertight door shall have a vertical or horizontal motion

Sliding Doors

                                                           

                                                            Vertically Operated Sliding Door

•     It shall be provided with an individual hand-operated mechanism. It shall be possible to open and close the door by hand at the door itself from either side, and in addition, close the door from an accessible position above the bulkhead deck with an all round crank motion or some other movement providing the same degree of safety acceptable to the Administration.

•     Direction of rotation or other movement is to be clearly indicated at all operating positions. The time necessary for the complete closure of the door, when operating by hand gear, shall not exceed 90 s with the ship in the upright position

•     Watertight doors for passenger ships are tested to a head of water equivalent to their depth below the bulkhead deck before they are installed in the ship. When in place,these and other watertight doors are hose tested.

•     It shall be provided with controls for opening and closing the door by power from both sides of the door and also for closing the door by power from the central operating console at the navigation bridge; It shall be provided with an audible alarm, distinct from any other alarm in the area, which will sound whenever the door is closed remotely by power and which shall sound for at least 5 s but no more than 10 s before the door begins to move and shall continue sounding until the door is completely closed.

•      In the case of remote hand operation it is sufficient for the audible alarm to sound only when the door is moving.

•     Administration may require the audible alarm to be supplemented by an intermittent visual signal at the door and  shall have an approximately uniform rate of closure under power.

•     The electrical power required for power-operated sliding watertight doors shall be supplied from the emergency switchboard either directly or by a dedicated distribution board situated above the bulkhead deck

Watertight Tunnels :

 Unless the ship’s machinery is right aft, a watertight tunnel will be fitted to enclose the propeller shaft. The tunnel protects the shaft from the cargo.

To allow the passage for personnel water tight doors are fitted,  openings must be cut only were essential and they should be as small as possible. 1.0 - 1.25m high, 0.7m wide being the usual.

Doors should be of mild steel or cast steel, and they may be arranged to close vertically or horizontally.

A sliding w/t door will be fitted at the forward end leading to the engine room. Also, at the aft end, a trunk leading to the bulkhead deck is often fitted since there must be two means of escape from the shaft tunnel.

The thickness of the tunnel plating and stiffener scantlings are determined in similar manner to that for watertight bulkheads.

The tunnel top is lighter if it is rounded rather than flat, but must be of increased thickness under hatchways unless it is sheathed with timber.

                                   

Cargo W/T Doors

Cargo doors are fitted on ships in certain trades to provide access to ’tween deck spaces e.g. direct loading by forklift truck from the quay into the ’tween deck.

Openings are cut in the side shell plating and arrangements must be made to maintain the strength, particularly in a longitudinal direction. The corners of all openings are to be well rounded to avoid stress concentrations.

Following are illustrated :

1)    A cargo port, manually operated by closely spaced dogs or bolts. This arrangement is typical of the type fitted to facilitate the loading of stores etc.

2)    A patent hydraulically operated sliding door shown in the open & close positions. This type is simple and fast to operate and is self closing since the door is forced against perimeter of the opening assisted by the eccentric path of the guide rollers.

3)    A swing door. This type of door may be fitted at the sides of the ship to give access to the ’tween deck or at the stern to give access for vehicles e.g. Ro-Ro ships. In the latter case the ramps will be a separate item of equipment.

                       

Bow Doors & Ramps

When using the bow doors it is necessary for the bow to run into a specially designed fender. Watertight closure at the bow is usually provided by the ramp in its raised position, or a separate door inside the bow door or visor. This bow door or visor has a spray type seal.

                       

 Stern Doors & Ramps

Many roll on/roll off ships only have stern doors & ramps. The arrangements vary depending on the nature of the service being operated.

At the stern the ramp when in raised position usually forms the W/T closure as shown.

The ramps & doors are normally hydraulically operated & cleated in position.