Glossary A-B-C

A

AUXILIARY HOIST: A supplemental hoisting. unit, usually designed to handle lighter loads at a higher speed than the main hoist.

AUXILIARY GIRDER (OUTRIGGER): A girder arranged parallel to the main girder for supporting the platform motor base, operator's cab control panels, etc., to reduce the torsional forces such load would otherwise impose on the main girder.

B

BEAMS: Horizontal structural elements.

BEARING LIFE EXPECTANCY: The L-10 life of an antifriction bearing is the minimum expected life, in hours, of 90% of a group of bearings which are operating at a given speed and loading. The average expected life of the bearings is approximately five times the L-10 life.

BOX SECTION: The rectangular cross section of girders, trucks or other members enclosed on four sides.

BRAKE: A device for retarding or stopping motion by friction or power means.

BRIDGE: That part of an overhead crane consisting of girder(s), trucks, walkway, and drive mechanism which carries the trolley and travels in a direction parallel to the runway.

BRIDGE CONDUCTORS: The electrical conductors located along the bridge structure of a crane to provide power to the trolley.

BUMPERS (BUFFER): An energy absorbing device for reducing impact when a moving crane or trolley reaches the end of its permitted travel; or when two moving cranes or trolleys come into contact.

C

CAB-OPERATED CRANE: A crane controlled by an operator in a cab located on the bridge or trolley.

CAMBER: The slight upward vertical curve given to girders to compensate partially for deflection due to hook load and weight of the crane.

CAPACITY: The maximum rated load (in tons) which a crane is designed to carry.

CHAIN CONTAINER: A bucket or container used to keep the free end of the chain away from the load.

CHAIN HOIST: A lifting device characterized by a chain driven through a pocket sheave to raise and lower a load. Recommend using a chain container.

CRANE CLASSIFICATIONS: Service classes for rating duty cycle capabilities of overhead cranes.

CLASS A: Standby or infrequent service.

CLASS B: Light service.

CLASS C: Moderate service.

CLASS D: Heavy service.

CLASS E: Severe service.

CLASS F: Continuous Severe service

CLEARANCE: Minimum distance from the extremity of a crane to the nearest obstruction.

CMAA: Crane Manufacturers Association of America (formerly EOCI - Electric Overhead Crane Institute).

COLLECTORS: Contacting devices for collecting current from the runway or bridge conductors. The mainline collectors are mounted on the bridge to transmit current from the runway conductors, and the trolley collectors are mounted on the trolley to transmit

current from the bridge conductors.

COLUMNS: Vertical structural elements normally in compression which support the runway beams.

CONTACTOR, MAGNETIC: An electro-magnetic device for repeatedly establishing and interrupting an electric power circuit.

CONTROLLER: A device for regulating in a predetermined way the power delivered to a motor or other equipment.

COVER PLATE: The top and bottom plate of a box girder.

CROSS SHAFT: The shaft extending across the bridge, used to transmit torque from motor to bridge drive wheels.