CASUALTY POWER SYSTEMS

The casualty power system is one of the most important shipboard damage control systems. The system is a simple electrical distribution system. It is used to maintain a source of electrical power for the most vital machinery and equipment needed to keep the ship afloat or to get the ship out of a danger area. The casualty power system is intended to provide power during real

emergencies only. It must NOT be used as a means of making temporary routine repairs. A casualty power system consists of the following items:

. Portable cables stowed in racks throughout the ship

. Bulkhead terminals for carrying the circuit through bulkheads without breaking the watertight integrity of the ship . Risers between decks

. Casualty power connections at the source of supply

Figure 7-31 illustrates a casualty power run.

Portable casualty power cables are equipped with metal tags that indicate the length of the cable and the location of the cable stowage rack (fig. 7-32). Portable casualty power cables should be rigged only when required for use or when required for practice in rigging the casualty power system. At all other times, the cables should be stowed in the cable rack indicated on the cable tag.

When casualty power cables are rigged, the connections must always be made from the load

Figure 7-31.-Casualty power run. 7-26

Figure 7-32.-Portable casualty power cable tag.

to the supply to avoid handling energized cables. Portable signs saying DANGER-HIGH VOLTAGE must be posted at each connection and at 10-foot intervals along the length of the cable. The cables must be secured to the overhead, clear of the deck.

Sources of supply for casualty power use are provided at each ship's service and emergency switchboard. These consist of casualty power connection terminals on each switchboard; the terminals are connected to the bus bars through circuit breakers. Some ships also have small dieseldriven generators designated for casualty power use only. These generators are quite small and have very little control equipment.

Casualty power connection terminals are installed in power panels that feed equipment designed to receive casualty power. The casualty power connection terminals on the power panels

may also be used as a source of supply to the casualty power system.

Remember that all terminals on power panels are hot. The normal supply to a panel must be shut off before the casualty power cable is connected to the terminals.

Machinery that can be supplied by the casualty power system includes steering gear, IC switchboards, fire pumps, and vital auxiliaries in firerooms and engine rooms.

An alternating current (a.c.) casualty power system consists of the following equipment and fixtures:

. Racks containing various lengths of portable thermoplastic-covered or neoprene-covered cable. Each cable contains three leads or conductors (fig. 7-33). One lead is colored black, one is white, and one is red. This same color code is used in all three-wire power circuits throughout the electrical installations aboard ship. l On small ships, bulkhead terminals provide for a single horizontal run of portable cable along the main deck, inside the superstructure. On large ships, there are generally terminals for two horizontal runs, one port and one starboard. These runs are located on the second deck. The terminals extend through the bulkhead and project from it on both sides. They do not impair the watertight integrity of the ship. The cable ends are inserted around the outer rim (or curved surface) of the terminal into the holes provided. There are three groups of three holes each. The

Figure 7-33.-Portable casualty power, 450 volts, three-phase cable end. 7-27

face of the terminal also contains three groups of three holes each. The square-shanked insulated wrenches fit into these holes and are used to secure the cable in the terminal. Two of these wrenches are provided in a rack mounted on the bulkhead at each point where they are required. They must be kept in the rack at all times except when they are actually in use.

. Riser terminals are similar to bulkhead terminals. However, they are connected to other riser terminals by permanently installed armored cable to provide vertical runs. These riser terminals carry the casualty power from the generators to the main and the second deck levels.

. Portable switches are sometimes mounted on bulkheads near the cable racks. These are simply ON-OFF switches that are equipped with special holes for use with the portable cables.

The faces of the casualty power terminals of an a.c. system are marked A, B, and C, and the ends of the cables are colored black, white, and red, respectively. When connecting the cables to the terminals, connect the black lead to A, the white lead to B, and the red lead to C.

The color code is not sufficient for making proper connections in the dark or under other adverse conditions. Therefore, it is necessary to provide some means to identify each lead and its proper hole in the terminal by touch. This is accomplished by molded knobs in the A, B, and C portions of the terminals. There are one, two, or three knobs, respectively, in the A, B, and C portions of the terminals. Similarly, a piece of heavy twine is placed on the black lead of the

portable cables, two pieces are placed on the white lead, and three pieces are placed on the red lead. Each of these servings of twine is about one-half of an inch wide. (A new method of phase identification is similar to the old method, except that O rings and heat shrinkable tubing have been substituted for the cotton cord servings, as shown in figure 7-34. ) Each lead and its corresponding position in the terminal can be identified by merely feeling the leads and matching the number of

Figure 7-34.-New method of cable identification.

pieces of twine on each lead with the same number of raised knobs in the proper area of the terminal. In older ships, the casualty power fittings have identifying V-shaped notches in the outer edge of the fittings instead of the knobs.

When connecting a casualty power cable run, remember that you must ALWAYS connect from the load to the source of supply. This is to avoid working with live cables.

SUMMARY

When battle damage occurs, it must be repaired. In most cases, you will make a temporary repair until a permanent repair can be made. Shoring, plugging, and patching are your normal means of making the necessary temporary repairs. When the power source for certain vital equipment is discontinued, you will be required to supply power to the equipment by an alternate means, known as the casualty power system.

Review the information presented to you in this chapter until you are familiar with it. If it is possible, put the information into practical use with training aids such as a section of pipe that may be connected to a ship's fireplug. Do not use expendable materials for training purposes until you have received permission from your work center supervisor or the damage control assistant (DCA).