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Crane Definitions

The following is a short list of some crane and hoist terminology. We hope this will help you in reading specifications or comparing equipment.

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.

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 GIRDER/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.

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.

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

CMAA: Crane Manufacturers Association of America.

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.

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

CONTROLER: A device for regulating in a pre-determined 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.

DEAD LOADS: The loads on a structure which remain in a fixed position relative to the structure. On a crane bridge such loads include to the girders, footwalk, cross shaft, drive units, panels, etc.

DEFLECTION: Displacement due to bending or twisting in a vertical or lateral plane, caused by the imposed live and dead loads.

DIAPHRAGM: A plate or partition between opposite parts of a member, serving a definite purpose in the structural design of a member.

DUMMY CAB: An operator's compartment or platform on a pendant or radio controlled crane, having no permanently mounted electrical controls, in which an operator may ride while controlling the crane, from a pendant or remote control station.

ELECTRIC OVERHEAD TRAVELING (E.O.T.) CRANE: An electrically operated machine for lifting, lowering and transporting loads, consisting of a movable bridge carrying a fixed or movable hoisting mechanism and traveling on an overhead runway structure.

ELECTRICAL BRAKING SYSTEM: A method of controlling crane motor speed without the use of friction braking.

ENCLOSED CONDUCTOR(S): A conductor or group of conductors substantially enclosed to prevent accidental contact.

ENCLOSURE: A housing to contain electrical components, usually specified by a NEMA classification number.

END APPROACH: The minimum horizontal distance, parallel to the runway, between the outermost extremities of the crane and the centerline of the hook..

END TRUCK: The unit consisting of truck frame, wheels, bearings, axles, etc., which supports the bridge girder.

FIELD WIRING: The wiring required after the erection of the crane.

FIXED AXLE: An axle which is fixed in the truck and on which the wheel revolves.

FLOOR OPERATED CRANE: A crane which is pendant controlled by an operator on the floor or on an independent platform.

FOOTWALK: The walkway with handrail and toeboards, attached to the bridge for access purposes.

GIRDER: The principle horizontal beam of the crane bridge which supports the trolley and is supported by the end trucks.

HOIST: A machinery unit that is used for lifting and lowering a load.

HOLDING BRAKE: A brake that automatically prevents motion when power is off.The minimum horizontal distance between the center of the runway rail and the hook.

HOOK APPROACH: The minimum horizontal distance between the center of the runway rail and the hook

IMPACT ALLOWANCE: Additional hook load assumed to result from the dynamic effect of the live load.

INTERLOCKING CRANE: A crane equipped with a device to hold alignment between the crane girder and a spur or another crane girder.

INVERTER (VARIALBLE FREQUENCY DRIVE): A method of control by which the fixed line voltage and frequency is changed to a three-phase system with infinitely variable voltage and frequency.

KSI: Kips per square inch - a measurement of stress intensity.

KIP: A unit of force equivalent to 1,000 pounds.

KNEE BRACE: The diagonal structural member joining the building column and roof truss.

LIFT: Maximum safe vertical distance through which the hook, magnet or bucket can move.

LIFTING DEVICES: Buckets, magnets, grabs, and other supplemental devices, the weight of which is to be considered part of the rated load, used for ease in handling certain types of loads.

LIMIT SWITCH: A device designed to cut off the power automatically at or near the limit of travel for the crane motion.

LINE CONTACTOR: A contactor to disconnect power from the supply lines.

LIVE LOAD: A load which moves relative to the structure under consideration.

LOAD CARRYING PART: Any part of the crane in which the induced stress is influenced by the load on the hook.

MAGNETIC CONTROL: A device or system of devices having all basic functions operated by electromagnets.

MAIN LINE CONTACTOR: A magnetic contractor used in the incoming power circuit from the mainline collectors.

MAIN LINE DISCONNECT: A manual switch which breaks the power lines leading from the main line collectors.

MASTER SWITCH: A manually operated device which serves to govern the operation of contactors and auxiliary devices of an electric control.

MATCH MARKING: Identification of non-interchangeable parts for reassembly after shipment.

OPERATORS CAB: The operator's compartment from which movements of the crane are controlled.

OVERLOAD PROTECTION (OVERCURRENT): A device operative on excessive current to cause and maintain the interruption or reduction of current flow to the equipment governed.

PATENTED TRACK: A generic term referring to crane and monorail equipment built in accordance with the MMA specification utilizing a composite track section incorporating a proprietary bottom flange shape.

PENDANT PUSHBUTTON STATION: Means suspended from the crane for operating the controllers from the floor o other level beneath the crane.

PLAIN REVERSING CONTROL: A reversing control which has identical characteristics for both directions of motor rotation.

PROTECTIVE PANEL: An assembly containing overload and undervoltage protection for all crane motions.

RATED LOAD: The maximum load which the crane is designed to handle safely.

RESISTOR RATING: Rating established by NEMA which classifies resistor according to percent of full load current on first point and duty cycles.

ROTATING AXLE: An axle which rotates with the wheel.

RUNWAY: The rails, beams, brackets and framework on which the crane operates.

RUNWAY CONDUCTORS: The main conductors mounted on or parallel to the runway which supply current to the crane.

RUNWAY RAIL: The rail supported by the runway beams on which the bridge travels.

"S" SECTION (S-BEAM/I-BEAM): A standard beam shape as defined by the American Institute of Steel Construction.

SAFETY LUG: A mechanical device fixed securely to the end truck or trolley yoke which will limit the fall of the crane or carrier in case of wheel or axle failure.

SINGLE GIRDER CRANE: An electric overhead traveling crane having one main girder which supports a fixed hoist mounted on an under-running trolley. An auxiliary girder may be provided to reduce the torsional stresses on the main girder.

SPAN: The horizontal distance center-to-center of runway rails or beams.

STATIC CONTROL: A method of switching electrical circuits without the use of contacts.

STEPPED: A type of control system with three or more speed points.

STOP: A device to limit travel of a trolley or crane bridge. This device normally is attached to a fixed structure and typically does not have energy absorbing ability.

STRENGTH, AVERAGE ULTIMATE: The average tensile force per unit of cross sectional area required to rupture the material as determined by test.

STRESS: Load or force per unit area tending to deform the material usually expressed in pound per square inch.

SWEEP: Maximum lateral deviation from straightness of structural member, measured at right angles to the Y-Y axis.

TOP RUNNING CRANE: An electric overhead traveling crane having the end trucks supported on rails attached to the top of the crane runway.

TORQUE, FULL LOAD(MOTOR): The torque produced by a motor at its rated horsepower and speed.

UNDER RUNNING CRANE: An electric overhead traveling crane having the end trucks supported on track attached to the bottom flanges of the beams; or supported on bottom flanges of beams. These beams make up the crane runway.

UNDER VOLTAGE PROTECTION: A device operative on the reduction or failure of voltage to cause and maintain the interruption of power in the main circuit.

VARIABLE FREQUENCY DRIVE: A method of control by which the motor supply voltage and frequency can be adjusted.

VOLTAGE DROP: The loss of voltage in an electric conductor between supply tap and load tap.

W SECTION (W-BEAM): A wide flange beam shape as defined by the American Institute of Steel Construction.

WEB PLATE: The vertical pate connection the upper and lower flanges or cover plates of a girder.

WHEEL BASE: Distance from center to center of outermost wheels.

WHEEL LOAD: The load without impact on any wheel with the trolley and lifted load (rated capacity) positioned on the bridge to give maximum loading.

Here are some links to useful groups and organizations.

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