A compartment is a portion of the space within a

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

defined vertically between decks and horizontally between bulkheads. It is analogous to a room within a building, and may provide watertight subdivision of the ship's hull important in retaining

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

if the hull is damaged. Subdivision of a ship's hull into watertight compartments is called compartmentation.

History

Bulkheads were known to the ancient Greeks, who employed bulkheads in triremes to support the back of rams. By the Athenian trireme era (500 BC), the hull was strengthened by enclosing the bow behind the ram, forming a bulkhead compartment. Instead of using bulkheads to protect ships against ram attacks, Greeks preferred to reinforce the hull with extra timber along the waterline, making larger ships almost resistant to ramming by smaller ones. Similar to how ships of the Age of Sail allocated more timber to strengthen the hull, so that enemy ships had to be close for cannon fire to be damaging. Bulkhead watertight compartments were originally invented by the Chinese. These compartments strengthened the junks and slowed

flooding A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant concern in agriculture, civi ...

in case of holing during the Han and Song dynasties. The wide application of Chinese watertight compartments soon spread to the Europeans through the Indian and Arab merchants. As wood began to be replaced by iron in European ships in the 18th century, new structures, like bulkheads, started to become prevalent. The economics of early unsinkable passenger ships was scrutinized in an 1882

Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...

article.

Watertight subdivision

Watertight subdivision limits loss of buoyancy and freeboard in the event of damage, and may protect vital machinery from flooding. Most ships have some

pump A pump is a device that moves fluids (liquids or gases), or sometimes Slurry, slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy. Mechanical pumps serve in a wide range of application ...

ing capacity to remove accumulated water from the

bilge The bilge of a ship or boat is the part of the hull that would rest on the ground if the vessel were unsupported by water. The "turn of the bilge" is the transition from the bottom of a hull to the sides of a hull. Internally, the bilges (us ...

s, but a steel ship with no watertight subdivision will sink if water accumulates faster than pumps can remove it. Standards of watertight subdivision assume no dewatering capability, although pumps kept in working order may provide an additional measure of safety in the event of minor leaks. The most common watertight subdivision is accomplished with transverse bulkheads dividing the elongated hull into a number of watertight floodable lengths. Early watertight subdivision tested with hoses sometimes failed to withstand the

hydrostatic pressure Hydrostatics is the branch of fluid mechanics that studies fluids at hydrostatic equilibrium and "the pressure in a fluid or exerted by a fluid on an immersed body". The word "hydrostatics" is sometimes used to refer specifically to water and o ...

of an adjoining flooded compartment. Effective watertight subdivision requires these transverse bulkheads to be both watertight and structurally sound.Manning, pp.146-148 A ship will sink if the transverse bulkheads are so far apart that flooding a single compartment would consume all the ship's reserve buoyancy. Aside from the possible protection of machinery, or areas most susceptible to damage, such a ship would be no better than a ship without watertight subdivision, and is called a one-compartment ship. A ship capable of remaining afloat when any single watertight compartment is flooded is called a two-compartment ship, but damage destroying the tightness of a transverse bulkhead may cause flooding of two compartments and loss of the ship. A ship able to remain afloat with any two compartments flooded is called a three-compartment ship, and will withstand damage to one transverse bulkhead. After the ''Titanic'' sinking, safety standards recommended spacing transverse bulkheads so no single point of damage would either submerge the end of the upper bulkhead deck or reduce bulkhead deck freeboard to less than . Wartime experience with

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such ...

damage indicated the typical damage diameter of defined a practical minimum distance for transverse bulkhead spacing.

Doors

Three types of doors are commonly used between compartments. A closed watertight door is structurally capable of withstanding the same pressures as the watertight bulkheads they penetrate, although such doors require frequent maintenance to maintain effective seals, and must, of course, be kept closed to effectively contain flooding. A closed weathertight door can seal out spray and periodic minor flow over weather decks, but may leak during immersion. These outward opening doors are useful at weather deck entrances to compartments above the

main deck The main deck of a ship is the uppermost complete deck extending from bow to stern. A steel ship's hull may be considered a structural beam with the main deck forming the upper flange of a box girder and the keel forming the lower strength mem ...

. Joiner doors are similar to doors used in conventional buildings ashore. They afford privacy and temperature control for compartments formed by non-structural bulkheads within the ship's hull.

Nomenclature

Compartments are identified by the deck forming the floor of that compartment. Different types of ships have different deck naming conventions. Passenger ships often use letters of the alphabet sequentially down from A deck (the highest) above B deck, and B deck above C deck, and so forth. Another popular naming convention is numbering the

1, the deck below it 2 (or the second deck), and the deck below that the third deck, and so forth. Decks above the main deck may be named, like the

bridge deck A deck is the surface of a bridge. A structural element of its superstructure A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildin ...

poop deck In naval architecture, a poop deck is a deck that forms the roof of a cabin built in the rear, or " aft", part of the superstructure of a ship. The name originates from the French word for stern, , from Latin . Thus the poop deck is technic ...

, or they may be numbered upwards from the main deck with a zero prefix that is pronounced "oh": 01 above the main deck, 02 deck above 01, and so forth. The

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

(USN) has used the latter convention in a compartment numbering system since 1949. The USN system identifies each compartment by a four-part code separated by hyphens. The first part of the code represents a numbered deck, the second part of the code is a hull support

frame A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (con ...

numbered sequentially from the bow, the third part of the code is a number representing compartment position with respect to the ship's centerline, and the fourth part of the code is alphabetic representing the use of that compartment. The centerline position code is zero for a compartment on the ship's centerline, odd numbers for compartments entirely to

starboard Port and starboard are Glossary of nautical terms (M-Z), nautical terms for watercraft and spacecraft, referring respectively to the left and right sides of the vessel, when aboard and facing the Bow (watercraft), bow (front). Vessels with bil ...

of the centerline, and even numbers for compartments entirely to

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Hamburg, Manch ...

. For compartments sharing the same deck and forward frame, the first two parts of the code are identical, and the third part of the code is numbered outward from the centerline. For example, four main-deck compartments at frame 90 would be 1-90-1-L inboard and 1-90-3-L outboard on the starboard side of the ship and 1-90-2-L inboard and 1-90-4-L outboard on the port side. The fourth part of the code is: * A for store rooms (or AA for cargo holds) * C for crewed communication or control centers * E for crewed engineering machinery spaces * F for oil storage tanks (or FF for oil cargo tanks) * G for

gasoline Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...

-storage tanks (or GG for gasoline cargo tanks) * J for JP-5 storage tanks (or JJ for JP-5 cargo tanks) * K for chemical-storage spaces * L for living spaces, including

sleeping Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain Sensory nervous system, sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with th ...

, dining, washrooms, sick bay, and passageways * M for ammunition

magazines A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally fin ...

* Q for miscellaneous spaces not otherwise coded, including laundry,

galley A galley is a type of ship optimised for propulsion by oars. Galleys were historically used for naval warfare, warfare, Maritime transport, trade, and piracy mostly in the seas surrounding Europe. It developed in the Mediterranean world during ...

, pantries, wiring trunks, uncrewed engineering, electrical and electronic spaces, shops, and offices * T for vertical-access trunks (escape trunks) * V for void (empty) spaces * W for water-storage tanks

References

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Notes