1. Rotating cranes

2. Topping cranes

3. Nonrotating cranes

4. Nontopping cranes

Rotating Cranes.-In general, rotating cranes may be topping or nontopping. Topping, rotating cranes are characterized by a topping boom attached to a king post or pedestal that resists the overturning forces created by the boom and attached load (fig. 18-5). Nontopping, rotating cranes have a boom rigidly attached to a rotating column or base (fig. 18-6).

The topping, rotating crane (fig. 18-5) is the most common type of hull-mounted crane used by the Navy. This type of crane has a boom attached to a rotating structure by a boom hinge, which allows for raising and lowering (resulting in inward and out-ward movement of the load). The rotating structure, which supports the boom and contains the machinery and hoisting systems, is attached to a base structure (king post or pedestal) about which the structure rotates. The base structure may be fixed or may travel on wheels mounted on rails. When the base structure is elevated to a height above the deck to permit passage of objects or personnel on the deck under the crane, the crane is also a portal type.

Nonrotating Cranes.-Nonrotating cranes are characterized by a bridge and trolley arrangement. Hoisting equipment is located on the trolley that, in turn, is transported on movable bridge girders and wheel trucks. Figure 18-7 illustrates a nonrotating, raised runway, overhead traveling crane. The crane is mounted on a pair of elevated parallel rails, adapted to raise or lower a load and to carry it horizontally, parallel, or at right angles to the rails. This crane consists of one or more trolleys operating on the top or bottom of a bridge. The bridge consists of one or more girders or trusses mounted on trucks operating on elevated rails. The operational area is limited to the space between the bridge rails.

Figure 18-7.-Overhead traveling crane.

Another version of a nonrotating crane is the traveling support gantry crane (fig. 18-8). This crane is similar to an overhead traveling crane, except that the bridge for carrying the trolley(s) is rigidly supported on two or more gantry legs. This assembly moves on fixed rails. You can find additional detailed information concerning the major types of Navy cranes in Naval Ships Technical Manual, Chapter 589, Cranes.

OPERATION AND MAINTENANCE.- Your ship should have qualified personnel assigned to supervise and carry out required maintenance of specific cranes. Qualified person-nel must complete formal training in regard to the safety devices and the load-bearing and load-controlling components of the cranes used on your ship. Some maintenance situations may require the use of personnel who are not formally qualified as maintenance technicians. The personnel who are routinely involved in crane maintenance, however, must be qualified technicians.

Before beginning any adjustments, repairs, or inspections on a crane, maintenance personnel must take the following precautions:

1. Stow the crane to be repaired where it will cause the least interference with other cranes and operations.

2. Place the boom in the stowed position for work on the topping.

3. Place all controls in the OFF position.,

4. De-energize the power supplies; place the power supply breaker in the OFF position and tag out.

5. Perform maintenance on energized elec-trical equipment only when specifically authorized to do so by the commanding officer.

6. After completing adjustments and or repairs, do not restore the crane to service until all guards have been reinstalled, sys-tems untagged, safety devices reactivated, maintenance equipment removed, and required testing completed.

7. Unless otherwise authorized by the crane officer on a case basis for unusual repairs, only qualified personnel should perform maintenance on cranes.

All qualified personnel must accomplish PMS requirements according to the instructions listed on applicable MRCs. For additional information on the operation and maintenance of cranes, consult Naval Ships Technical Manual, Chapter 589, Cranes.