Overhead Crane Definitions
ANSI/ASME B30.2: Safety standard for overhead and gantry cranes, top running bridge, single or multiple girder, top running trolley hoist.
ANSI/ASME B30.11: Safety standard for monorails and underhung cranes.
ANSI/ASME B30.17: Safety standard for overhead and gantry cranes, top running bridge, single girder, underhung hoist.
ASCE Rail: Rail that top running overhead bridge cranes typically run on. Common rail sizes are 30#, 40#, 60#, 80#, or 85#.
Abnormal operating conditions: Environmental conditions that are unfavorable, harmful, or detrimental to or for the operation of a crane, such as excessively high or low ambient temperatures, exposure to adverse weather, corrosive fumes, dust-laden or moisture-laden atmospheres, and hazardous locations. (ASME B30.2-2005)
Ambient temperature: The temperature of the atmosphere surrounding the hoist. (ASME B30.2-2005)
Auxiliary hoist: A supplemental hoisting unit, usually designed to handle lighter loads at a higher speed than the main hoist. (ASME B30.2-2005)
Axle, fixed: A shaft which is fixed in the end truck and about which the wheel revolves (CMAA 70, CMAA 74)
Axle, rotating: A shaft which is fixed in the wheel and which rotates on bearings fixed in the end truck (CMAA 70, CMAA 74)
B-10 bearing life: The B-10 bearing life of an anti-friction bearing is the minimum expected life, in hours, of 90% of a group of bearings which are operated at a given speed and loading. (ANSI MH 27.1-1981) Also referred to as L-10 bearing life.
Box Section: The rectangular cross section of girders, trucks or other members enclosed on four sides. (CMAA 70, CMAA 74)
Brake: A device, other than the motor, used for retarding or stopping motion by friction or power means. (ASME B30.2-2005)
Brake, mechanical load: an automatic type of friction brake used for controlling loads in a lowering direction. This unidirectional device requires torque from the motor to lower a load but does not impose any additional load on the motor when lifting a load. (ASME B30.2-2005)
Braking, plugging, (reverse plugging): a method of controlling speed by reversing the motor line voltage polarity or phase sequence to develop torque in the direction opposite the rotation of the motor. (ASME B30.2-2005)
Branch Circuit: The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s). (CMAA 70-7, CMAA 74-7)
Bridge: That part of an overhead crane consisting of girders, trucks, end ties, walkway and drive mechanism which carries the trolley and travels in a direction parallel to the runway. (CMAA 70-7, CMAA 74-7)
Bridge Conductors: The electrical conductors located along the bridge structure of a crane to provide power to the trolley. (CMAA 70-7, CMAA 74-7)
Brinell Hardness Number (BHN): the hardness of a metal or alloy measured by hydraulically pressing a hard ball under a standard load into the specimen.
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. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Cab-Operated Crane: A crane controlled by an operator in a cab located on the bridge or trolley. (CMAA 70-7, CMAA 74-7)
Camber: The slight upward vertical curve given to girders to compensate partially for deflection due to hook load and weight of the crane. (CMAA 70-7, CMAA 74-7)
Capacity: The maximum rated load (in tons) which a crane is designed to handle. (CMAA 70-7, CMAA 74-7)
Clearance: Minimum distance from the extremity of a crane to the nearest obstruction. (CMAA 70-7, CMAA 74-7)
CMAA: Crane manufacturers Association of America, Inc. (formerly EOCI - Electric Overhead Crane Institute). (CMAA 70-7, CMAA 74-7)
Caution: Indicates a potentially hazardous situation, which, if not avoided, may result in a minor or moderate injury. It may also be used to alert against unsafe practices. (CMAA Crane Operator's Manual)
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 collector are mounted on the trolley to transmit current from the bridge conductors. (CMAA 70-7, CMAA 74-7)
Contactor, Magnetic: An electro-magnetic device for opening and closing an electric power circuit. (CMAA 70-7, CMAA 74-7)
Controller: A device for regulating in a predetermined way the power delivered to the motor or other equipment. (CMAA 70-7, CMAA 74-7)
Counter-torque: A method of control by which the motor is reversed to develop power to the opposite direction. (CMAA 70-7, CMAA 74-7)
Cover Plate: The top or bottom plate of a box girder. (CMAA 70-7, CMAA 74-7)
Crane: a machine for lifting and lowering a load and moving it horizontally, with the hoisting mechanism being an integral part of the machine. (ASME B30.2-2005)
Crane classifications, Class A: standby or infrequent service (CMAA 70-7, CMAA 74-7)
Crane classifications, Class B: light service (CMAA 70-7, CMAA 74-7)
Crane classifications, Class C: moderate service (CMAA 70-7, CMAA 74-7)
Crane classifications, Class D: heavy service (CMAA 70-7, CMAA 74-7)
Crane classifications, Class E: severe service (CMAA 70-7, CMAA 74-7)
Crane classifications, Class F: continuous severe service (CMAA 70-7, CMAA 74-7)
Crane, automatic: A crane which, when activated, operates through a preset cycle or cycles. (ASME B30.2-2005)
Crane, cab operated: A crane whose movements are controlled by an operator through the use of controllers located in a cab this is attached to the crane. (ASME B30.2-2005)
Crane, cantilever gantry: a gantry or semi-gantry crane in which the bridge girders or trusses extend transversely beyond the crane runway on one or both sides. (ASME B30.2-2005)
Crane, floor operated: a crane whose movements are controlled by an operator through the use of controllers contained in the pendant station suspended from the crane. (ASME B30.2-2005)
Crane, gantry: A crane similar to an overhead crane except that the bridge for carrying the trolley or trolleys is rigidly supported on one or more legs running on fixed rails or other runway. (ASME B30.2-2005)
Crane, molten-material-handling: an overhead crane used for transporting or pouring molten material. (ASME B30.2-2005)
Crane, manually operated: a crane whose hoist mechanism is driven by pulling an endless chain, or whose travel mechanism is driven in the same manner or by manually moving the load or hook. (ASME B30.2-2005)
Crane, outdoor: an overhead or gantry crane that operates outdoors and for which provisions are not available for storage in an area that provides protection to the crane from weather conditions. An indoor crane that may operate outdoors on a periodic basis is not classified as an outdoor crane. (ASME B30.2-2005)
Crane, overhead: a crane with a single or multiple girder movable bridge carrying a movable or fixed hoisting mechanism and traveling on an overhead fixed runway structure. (ASME B30.2-2005)
Crane, polar: an overhead or gantry crane that travels on a circular runway. (ASME B30.2-2005)
Crane, power-operated: a crane whose mechanism is driven by electric, pneumatic, hydraulic, or internal combustion means. (ASME B30.2-2005)
Crane, pulpit-operated: A crane whose movements are controlled by an operator through the use of controllers located in the control room or a fixed or moveable cab or platform that is independent of the crane. (ASME B30.2-2005)
Crane, remote operated: A crane whose movements are controlled by an operator through the use of controllers contained in a portable operating station not attached to the crane. (ASME B30.2-2005)
Crane, semi-gantry: A gantry with one end of the bridge rigidly supported on one or more legs that run on a fixed rail or runway, the other end of the bridge being supported by an end truck running on an elevated rail or runway. (ASME B30.2-2005)
Crane, standby: a crane not in regulate service that is used occasionally or intermittently as required. (ASME B30.2-2005)
Crane, service heavy: Service that involves operating at 85 to 100% of rated load or in excess of 10 lift cycles/hr as a regular specified procedure. (ASME B30.2-2005)
Crane, service normal: service that involves operating at less than 85% of rated load and not more than 10 lift cycles/hr except for isolated instances. (ASME B30.2-2005)
Crane, service severe: service that involves normal or heavy service with abnormal operating conditions. (ASME B30.2-2005)
Crane Kit: Main components of a crane sold as a kit typically including hoist, end trucks, controls, and festooning for final assembly by crane distributor or end user.
Cross Shaft: The shaft extending across the bridge, used to transmit torque from the motor to bridge drive wheels. (CMAA 70-7, CMAA 74-7)
Cushioned Start: An electrical or mechanical method for reducing the rate of acceleration of a travel motion. (CMAA 70-7, CMAA 74-7)
Danger: Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury. (CMAA Crane Operator's Manual)
Dead Loads: The loads on a structure, which remain in a fixed position relative to the structure. On a crane bridge such loads include the girders, footwalk, cross shaft, drive units, panels, etc. (CMAA 70-7, CMAA 74-7)
Deflection: Displacement due to bending or twisting in a vertical or lateral plane, caused by the imposed live and dead loads. (CMAA 70-7, CMAA 74-7)
Diaphragm: A plate or partition between the opposite parts of a member serving a definite purpose in the structural design of the member. (CMAA 70-7, CMAA 74-7)
Drive Girder: The girder on which the bridge drive machinery is mounted. (CMAA 70-7, CMAA 74-7)
Drum: The cylindrical member around which the ropes are wound for lifting or lowering the load. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
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. (CMAA 70-7, CMAA 74-7)
Dynamic Lowering: A method of control by which the hoist motor is so connected in the lowering direction, that when it is overhauled by the load, it acts as generator and forces current either through the resistors or back into the line. (CMAA 70-7, CMAA 74-7)
EOT: Electric overhead traveling crane. See below Electric Overhead Traveling Crane
Eddy-Current Braking: A method on control by which the motor drives through an electrical induction load brake. (CMAA 70-7, CMAA 74-7)
Efficiency of Gearing and Sheaves: The percentage of force transmitted through these components that is not lost to friction. (CMAA 70-7, CMAA 74-7)
Electric Overhead Traveling 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. (CMAA 70-7, CMAA 74-7)
Electrical Braking System: A method of controlling crane motor speed when in an overhauling condition, without the use of friction braking. (CMAA 70-7, CMAA 74-7)
Enclosed conductor(s): A conductor or group of conductors substantially enclosed to prevent accidental contact. (CMAA 70-7, CMAA 74-7)
Enclosure: A housing to contain electrical components, usually specified by a NEMA classification number. (CMAA 70-7, CMAA 74-7)
End approach: The minimum horizontal distance, parallel to the runway, between the outermost extremities of the crane and the centerline of the hook. (CMAA 70-7, CMAA 74-7)
End tie: A structural member other than the end truck which connects the ends of the girders to maintain the squareness of the bridge. (CMAA 70-7, ASME B30.2-2005)
End truck: The unit consisting of the truck frame, wheels, bearings, axles, etc., which supports the bridge girders. (CMAA 70-7, CMAA 74-7)
Equalizer: a device that compensates for unequal length or stretch of a rope. (ASME B30.2-2005)
Exposed: applies to hazardous objects not guarded or isolated, and capable of being contacted inadvertently. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Fail-safe: A provision designed to automatically stop or safely control any motion in which a malfunction occurs. (CMAA 70-7, CMAA 74-7)
Field wiring: The wiring required after erection of the crane. (CMAA 70-7, CMAA 74-7)
Fixed axle: An axle which is fixed in the truck and on which the wheel revolves. (CMAA 70-7, CMAA 74-7)
Floor-Operated Crane: A crane which is pendant controlled by an operator on the floor or an independent platform. (CMAA 70-7, CMAA 74-7)
Footwalk: The walkway with handrail and toe-boards, attached to the bridge or trolley for access purposes. (CMAA 70-7, CMAA 74-7)
Gantry Crane: A crane similar to an overhead crane except that the bridge for carrying the trolley or trolleys is rigidly supported on two or more legs running on fixed rails or other runway. (CMAA 70-7, CMAA 74-7)
Girders: The principal horizontal beams of the crane bridge which supports the trolley and is supported by the end trucks. (CMAA 70-7, CMAA 74-7)
Ground Fault: An accidental conducting connection between the electrical circuit or equipment and the earth or some conducting body that serves in place of the earth. (CMAA 70-7, CMAA 74-7)
Hazardous (classified) locations: locations where fire or explosion hazards may exist. Locations are classified depending on the properties of the flammable vapors, liquids, or gases, or combustible dusts or fibers that may be present and the likelihood that a flammable or combustible concentration or quantity is present (see National Electrical Code, ANSI/NFPA 70).
Class I locations: locations in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.
Class II locations: locations that are hazardous because of the presence of combustible dust.
Class III locations: locations that are hazardous because of the presence of easily ignitable fibers or flyings, but in which such fibers or flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Hoist: A machinery unit that is used for lifting and lowering a load. (CMAA 70-7, CMAA 74-7)
Hoist: A machinery unit that is used for lifting or lowering a freely suspended (unguided) load. (ASME B30.2-2005)
Holding Brake: A brake that automatically prevents motion when power is off. (CMAA 70-7, CMAA 74-7)
Hook Approach: The minimum horizontal distance between the center of the runway rail and the hook. (CMAA 70-7, CMAA 74-7)
Hydraulic Brake: A brake that provides retarding or stopping motion by hydraulic means. (CMAA 70-7, CMAA 74-7)
Idler Sheave: A sheave used to equalize tension in opposite parts of a rope. Because of its slight movement, it is not termed a running sheave. (CMAA 70-7, CMAA 74-7)
Impact Allowance: Additional hook load assumed to result from the dynamic effect of the live load. (CMAA 70-7, CMAA 74-7)
Industrial Duty Crane: Service classification covered by CMAA Specification No. 70, 'Specifications for Electric Overhead Traveling Cranes'. (CMAA 70-7)
Insulation Class: Motor winding insulation rating which indicates its ability to withstand heat and moisture. (CMAA 70-7)
Intelligent Assist Devices (IAD's): computer-controlled tools that enable production workers to lift, move and position payloads quickly, accurately, and safely. Examples are Gorbel G-Force and Gorbel Easy Arm.
Inverter (Variable 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. (CMAA 70-7, CMAA 74-7)
K.S.I.: Kips per square inch, measurement of stress intensity. (CMAA 70-7, CMAA 74-7)
KIP: A unit of force, equivalent to 1000 pounds. (CMAA 70-7, CMAA 74-7)
Knee Brace: The diagonal structural member joining the building column and roof truss. (CMAA 70-7, CMAA 74-7)
Lateral Forces: Horizontal forces perpendicular to the axis of the member being considered. (CMAA 70-7, CMAA 74-7)
Lift: Maximum safe vertical distance through which the hook, magnet, or bucket can move. (CMAA 70-7, CMAA 74-7)
Lift Cycle: Single lifting and lowering motion (with or without load) (CMAA 70-7)
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. (CMAA 70-7, CMAA 74-7)
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 contractor to disconnect power from the supply lines. (CMAA 70-7, CMAA 74-7)
Live Load: A load which moves relative to the structure under consideration. (CMAA 70-7, CMAA 74-7)
Load Block: The assembly of hook, swivel, bearing, sheaves, pins and frame suspended by the hoisting ropes. (CMAA 70-7, CMAA 74-7)
Load Carrying Part: Any part of the crane in which the induced stress is influenced by the load on the hook. (CMAA 70-7, CMAA 74-7)
Load Cycle: One lift cycle with load plus one lift cycle without load. (CMAA 70-7, CMAA 74-7)
Longitudinal Stiffeners: Horizontal members attached to the web of the bridge girder to prevent web buckling. (CMAA 70-7, CMAA 74-7)
Magnetic Control: A means of controlling direction and speed by using magnetic contactors and relays. (CMAA 70-7, CMAA 74-7)
Main Line Contactor: A magnetic contactor used in the incoming power circuit from the main line collectors. (CMAA 70-7, CMAA 74-7)
Main Line Disconnect Switch: A manual switch which breaks the power lines leading from the main line collectors. (CMAA 70-7, CMAA 74-7)
Manual-Magnetic Disconnect Switch: A power disconnecting means consisting of a magnetic contactor that can be operated by remote pushbutton and can be manually operated by a handle on the switch. (CMAA 70-7, CMAA 74-7)
Master Switch: A manually operated device which serves to govern the operation of contactors and auxiliary devices of an electric control. (CMAA 70-7, CMAA 74-7)
Match Marking: Identification of non-interchangeable parts for re-assembly after shipment. (CMAA 70-7, CMAA 74-7)
Mechanical Load Brake: An automatic type of friction brake used for controlling loads in the lowering direction. This unidirectional device requires torque from the motor to lower a load but does not impose additional load on the motor when lifting a load. (CMAA 70-7, CMAA 74-7)
Mean Effective Load: A load used in durability calculations accounting for both maximum and minimum loads. (CMAA 70-7, CMAA 74-7)
Mill Duty Crane: Service classification covered by AISE Standard No. 6, Specification for Electric Overhead Traveling Cranes for Steel Mill Service.
Multiple Girder Crane: A crane which has two or more girders for supporting the live load. (CMAA 70-7, CMAA 74-7)
Non-coasting Mechanical Drive: A drive with coasting characteristics such that it will stop the motion within a distance in feet equal to 10 percent of the rated speed in feet per minute when traveling at rated speed with rated load. (CMAA 70-7, CMAA 74-7)
Operator's Cab: The operator's compartment from which movements of the crane are controlled. To be specified by the manufacturer as open, having only sides or a railing around the operator, or enclosed, complete with roof, windows, etc. (CMAA 70-7, CMAA 74-7)
Overload: Any load greater than the rated load. (CMAA 70-7, CMAA 74-7)
Overload Limit Device: Normally only provided when specified. Such a device is an emergency device intended to permit the load to lift a freely suspended load within its rated capacity, but prevents lifting of an overload that would cause permanent damage to a properly maintained hoist, trolley, or crane. (CMAA 70-7, CMAA 74-7)
Overload Protection (Overcurrent): A device operative on excessive current to cause and maintain the interruption or reduction of current flow to the equipment governed. (CMAA 70-7, CMAA 74-7)
Pendant Pushbutton Station: Means suspended from the crane operating the controllers from the floor or other level beneath the crane. (CMAA 70-7, CMAA 74-7)
Pitch Diameter (Rope): Distance through the center of a drum or sheave from center to center of a rope passed about the periphery. (CMAA 70-7, CMAA 74-7)
Plain Reversing Control: a reversing control which has identical characteristics for both directions of motor rotation. (CMAA 70-7, CMAA 74-7)
Plugging: A control function which accomplishes braking by reversing the motor line voltage polarity or phase sequence. (CMAA 70-7, CMAA 74-7)
Protective Panel: An assembly containing overload and undervoltage protection for all crane motions. (CMAA 70-7, CMAA 74-7)
Qualified: A person who, by possession of a recognized degree, certificate of professional standing or who by extensive knowledge, training, and experience, has successfully demonstrated the ability to solve or resolve problems relating to the subject matter and work. (ASME B30.2-2005)
Rated Load: The maximum load which the crane is designed to handle safely as designated by the manufacturer. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Reeving: A system in which a rope travels around drums or sheaves. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Regenerative Braking: A method of controlling speed in which electrical energy generated by the motor is fed back into the power system.
Regulated Speed: A function which tends to maintain constant motor speed for any load for a given speed setting of the controller.
Resistor Rating: Rating established by NEMA which classifies resistors according to percent of full load current on first point and duty cycle.
Running Sheave: A sheave which rotates as the hook is raised or lowered.
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 supplies current to the crane.
Runway Rail: The rail supported by the runway beams on which the bridge travels. (CMAA 70-7, CMAA 74-7)
Sheave: A grooved wheel or pulley used with a rope or chain to change direction and point of application of a pulling force. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Sheave, non-running (equalizer): a sheave used to equalize tension in opposite parts of the rope. Because of its slight movement, it is not termed a running sheave. (ASME B30.2-2005)
Skeleton Cab: Same as dummy cab.
Skewing Forces: Lateral forces on the bridge truck wheels caused by the bridge girders not running perpendicular to the runways. Some normal skewing occurs in all bridges.
Span: The horizontal distance center-to-center of runway rails. (CMAA 70-7, CMAA 74-7, ASME B30.2-2005)
Static Control: A method of switching electrical circuits without the use of contacts. (CMAA 70-7, CMAA 74-7)
Stepless Control: Control which does not have fixed speed points. Infinitely variable control.
Stepped Control: A type of control system with 2 or more fixed speed points. (CMAA 70-7, CMAA 74-7)
Stop: A device to limit travel of a trolley or crane bridge. This device normally is attached to a fixed structure and normally does not have energy absorbing ability. (CMAA 70-7, CMAA 74-7)
Strength, Average Ultimate: The average tensile force per unit of cross sections area required to rupture the material as determined by test. (CMAA 70-7, CMAA 74-7)
Sweep: Maximum lateral deviation from straightness of a structural member, measured at right angles to the Y-Y axis. (CMAA 70-7, CMAA 74-7)
TEFC: Totally enclosed fan cooled. (NEMA, CMAA 70-7, CMAA 74-7)
TENV: Totally enclosed non-ventilated. (NEMA, CMAA 70-7, CMAA 74-7)
Torque, Full Load (Motor): The torque produced by a motor operating at its rated horsepower and speed. (CMAA 70-7, CMAA 74-7)
Torsional Box Girder: Girder in which the trolley rail is located over one web. (CMAA 70-7)
Torsional Forces: Forces which can cause twisting of a member. (CMAA 70-7)
Trolley: The unit carrying the hoisting mechanism which travels on the bridge rails. (CMAA 70-7)
Trolley Frame: The basic structure of the trolley on which are mounted the hoisting and traversing mechanisms. (CMAA 70-7)
True Vertical Lift: There is no hook drift. Hook stays centerline below the drum trough full range of lift. Accomplished with a double reeved hoist or an electric chain hoist.
Two Blocking: Condition under which the load block or load suspended from the hook becomes jammed against the crane structure preventing further winding up of the hoist drum. (CMAA 70-7, CMAA 74-7)
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. (CMAA 70-7, CMAA 74-7)
Variable Frequency: A method of control by which the motor supply voltage and frequency can be adjusted. (CMAA 70-7, CMAA 74-7)
Voltage Drop: The loss of voltage in an electric conductor between supply tap and load tap. (CMAA 70-7, CMAA 74-7)
Warning: Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury. (CMAA Crane Operator's Manual)
Warning devices: typical warning devices are gong, bell, siren, horn, rotating beacon, strobe light. (CMAA Crane Operators Manual)
Web Plate: The vertical plate connecting the upper and lower flanges or cover plates of a girder. (CMAA 70-7, CMAA 74-7)
Wheelbase: Distance from center-to-center of outermost wheels. (CMAA 70-7, CMAA 74-7)
Wheel Load: The load without vertical inertia forces on any wheel with the trolley and lifted load (rated capacity) positioned on the bridge to give maximum loading. (CMAA 70-7, CMAA 74-7)
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