COMPARTMENT NUMBERING

Every compartment in a ship (except minor spaces, such as peacoat lockers, linen lockers, and

cleaning gear lockers) is assigned a compartment number. This number is marked on a label plate that is secured to the door or hatch, and on a 12-inch by 15-inch yellow rectangle on the bulkhead. The Navy uses two systems to number compartments: one is for ships built before March 1949, and the other for ships built after March 1949. Both of these systems agree in the following respects:

. All compartments on the port side end in an even number.

. All compartments on the starboard side end in an odd number.

. A zero precedes the deck number for all levels above the main deck; for example, 01, 02, and 03.

Figure 3-4 shows both of the systems used to number decks. The older system uses 100, 200, 300, and so forth, and always 900 for the double bottoms. The new system uses 1, 2, 3, and so forth, and the double bottoms are given whatever number befalls them.

SHIPS BUILT BEFORE MARCH 1949

An example of a compartment number on ships built before March 1949 follows. Use this example when reading the following explanation:

On ships built before March 1949, the first letter of the compartment number is A, B, or C. This letter indicates the section of the ship in which the compartment is located. The A section extends from the bow of the ship aft to the forward transverse bulkhead of the propulsion machinery spaces. The B section comprises all of the spaces between the forward transverse bulkhead of the forward propulsion machinery compartment and the after transverse bulkhead of the after propulsion machinery compartment. The C section extends from the after transverse bulkhead of the propulsion machinery spaces aft to the stern. The three sections of the ship are shown in figure 3-5. The lower half of the diagram shows how compartments are numbered, beginning at the forward end of each section. The even numbers are on the port side, and the odd numbers are on the starboard side.

Following the section letter is a three- or fourdigit number indicating the deck and compartment number. The first number represents the deck number, the next two the compartment. Main deck compartments are indicated by numbers 102, 109, 117, and so forth. Second deck compartments run from 201 through 299. Third deck compartments are numbered in the 300 series. A zero preceding the first number represents a location above the main deck. The double bottoms always form the 900 series on a ship built before March 1949, regardless of the number of decks above the double bottom.

The third part of the compartment number is a letter that designates the contents or primary use of the compartment. The primary purpose of a compartment is indicated by the following letters:

A-Storerooms

B-Battery compartments (gunnery)

C-Ship control and fire control

E-Machinery compartments

F-Fuel compartments

LUB-Lubricating oil storage tanks

GAS-Gasoline compartments

L-Living compartments and passageways

M-Ammunition spaces

T-Trunks

V-Void compartments

W-Water compartments

Figure 3-5.-Pre-1949 divisions of a ship.

SHIPS BUILT AFTER MARCH 1949

The following example is for ships built after March 1949. Use this example when reading the following explanation.

On ships built after March 1949, the compartment number consists of a deck number, a frame number, a number indicating the relationship of the compartment to the ship's centerline, and a letter showing the primary use of the space. Where a compartment extends through two or more decks, the number of the lower deck is used. The frame number indicates the location of the foremost boundary of the compartment. Frames are identified according to their location to the forward perpendicular and aft perpendicular. The forward perpendicular on a ship (fig. 3-6) is formed by drawing an imaginary line straight up from the forward-most point of the designer waterline (DWL). The after perpendicular is formed in the same manner, but from the aft-most point of the DWL.

All frames forward of the forward perpendicular are identified by a capital letter, starting with A. These frames are identified by starting with the first frame forward of the forward perpendicular and working forward.

The frames aft of the aft perpendicular are identified with double capital letters, starting with AA. These frames are identified by starting with the first frame aft of the aft perpendicular and working aft.

The frames between the forward perpendicular and the aft perpendicular are identified by numbers. The forward perpendicular is identified by the number 0 (zero). Each frame aft of the forward perpendicular will carry the next higher consecutive number. The last numbered frame is the aft perpendicular. If the forward boundary of a compartment is located between frames, the frame number farthest forward within the compartment is used.

Compartments located on the ship's centerline carry the number 0. Compartments completely to starboard are given odd numbers, and those to port are given even numbers. Where two or more compartments have the same deck and frame number, they have consecutively higher odd or even numbers, as applicable, numbering from the centerline outboard. In this instance, the first

Figure 3-6.-Frame numbering.

compartment to starboard is 1, the second is 3, and so on. To port of the centerline they are numbered 2, 4, and so forth. When the centerline passes through more than one compartment, each of which has the same frame number, the compartment having the forward bulkhead through which the centerline passes carries the number 0; the others are numbered 01, 02, 03, as applicable (fig. 3-7).

The last part of the compartment number is the letter that identifies the primary usage of the compartment. On dry- and liquid-cargo ships, a double letter is used to designate cargo spaces. The double letter will differentiate them from spaces containing the same commodity for use by the ship. Fuel oil and JP-5 jet fuel are two examples.

Compartment usage in the post-1949 system is shown in table 3-1.

Access closures are numbered in the same manner as compartments, except that the letter designating the compartment's use is omitted (example: 2-175-3).