Glossary of overhead crane and component terminology
We think about cranes all day (and some of us even dream about them at night), but for those whose responsibility is understanding and maintaining all the equipment in a plant, specialized crane-speak may be confusing. Use this glossary of crane and component terminology whenever you come across a word or phrase associated with your cranes that is unfamiliar.
ABNORMAL OPERATING CONDITIONS
Environmental conditions that are unfavorable, harmful or detrimental to or for the operation of a hoist; such as excessively high (over 100ºF) or low (below 0ºF) ambient temperatures, corrosive fumes, dust or moisture-laden environments and hazardous locations.
ADJUSTABLE OR VARIABLE VOLTAGE
A method of control by which the motor supply voltage can be adjusted.
AUTOMATIC CRANE
A crane which, when activated, operates through a preset cycle(s).
AUXILIARY HOIST
A supplemental hoisting unit, usually designed to handle lighter loads at a higher speed than the main hoist.
AUXILIARY GIRDER
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 loads would otherwise impose on the main girder.
BEARING LIFE
See L10 bearing life
BHN
Brinell Hardness Number, a measurement of material hardness.
BOX SECTION
The rectangular cross section of girders, trucks or other members enclosed by four sides.
BRAKE
A device, other than a motor, used for retarding or stopping motion by means of friction or power.
BRANCH CIRCUIT
The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
BRIDGE
The part of an overhead crane consisting of girders, trucks, end ties, a walkway and a drive mechanism that 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.
BRIDGE RAIL
The rail supported by the bridge girders on which the trolley travels.
BUFFER
See bumper.
BUMPER
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.
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) that a crane is designed to handle.
CLASS
A 6-item system for classifying cranes based on their speed, how often they can be used, their rated capacity, maintenance requirements, the distance material needs to be moved and their service conditions. Class A cranes are infrequent or standby cranes. Class F cranes can handle continuous severe service. Learn more about crane classes.
CLEARANCE
The minimum distance required from the extremity of a crane to the nearest obstruction.
COLLECTOR
A contacting device 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.
CONTROLLER
A device for regulating in a pre-determined way the power delivered to the motor or other equipment.
COUNTER-TORQUE
A method of control by which the motor is reversed to develop power to the opposite side.
COVER PLATE
The top or bottom plate of a box girder.
CROSS SHAFT
The shaft extending across the bridge. It is used to transmit torque from the motor to the bridge drive wheels.
CUSHIONED START
An electrical or mechanical method for reducing the rate of acceleration of a travel motion.
CAB-OPERATED CRANE
A crane controlled by an operator in a cab located on the bridge or trolley.
DEAD LOADS
The loads on a structure that remain in a fixed position relative to the structure. On a crane bridge, such loads include the girders, footwalk, cross shaft, drive units and panels.
DEFLECTION
Displacement due to bending or twisting in a vertical or lateral plane, caused by imposed live and dead loads.
DIAPHRAGM
A plate or partition between opposite parts of a member that serves a particular purpose in the structural design of the member.
DRIVE GIRDER
The girder on which the bridge drive machinery is mounted.
DUMMY CAB
A compartment or platform on a pendant or radio controlled crane that has no permanently mounted electrical controls in which an operator may ride while controlling the crane.
DYNAMIC LOWERING
A method of control by which the hoist motor acts as a generator and forces current either through the resistors or back into the line.
EDDY-CURRENT BRAKING
A method of control by which the motor drives through an electrical induction load brake.
EFFICIENCY OF GEARING AND SHEAVES
The percentage of force transmitted through these components that is not lost to friction.
ELECTRIC OVERHEAD TRAVELING CRANE
An electrically operated machine for lifting, lowering and transporting loads, consisting of a moveable bridge carrying a fixed or moveable hoisting mechanism and traveling on an overhead runway structure.
ELECTRICAL BRAKING SYSTEM
A method of controlling crane motor speed when in an overhauling condition without the use of friction braking.
ENCLOSED CONDUCTOR
A conductor or group of conductors substantially enclosed to prevent accidental contact.
ENCLOSURE
A conductor or group of conductors substantially enclosed to prevent accidental contact.
END APPROACH
The minimum horizontal distance, parallel to the runway, between the outermost extremities of the crane and the centerline of the hook.
END TIE
A structural member, other than the end truck, that connects the ends of the girders to maintain the squareness of the bridge.
END TRUCK
The unit consisting of truck frame, wheels, bearings, axles, etc., which supports the bridge girders.
FAIL-SAFE
A provision designed to automatically stop or safely control any motion during which a malfunction occurs.
FIELD WIRING
The wiring required after erection of the crane.
FIXED AXLE
An axle that is fixed in the truck and on which the wheel revolves.
FLOOR-OPERATED CRANE
A crane that is pendant-controlled by an operator on the floor or an independent track.
FOOTWALK
A walkway with handrail and toeboards that is attached to the bridge or trolley for access purposes.
GANTRY CRANE
A portable crane that is similar to an overhead crane except that the bridge for carrying the trolley(s) is rigidly supported on two or more legs running on fixed rails or other runway. Also known as a gantry crane.
GIRDERS
The principal horizontal beams of the crane bridge that supports the trolley and is supported by the end trucks.
GROUND FAULTS
An accidental conducting connection between the electrical circuit or equipment and the earth or some conducting body that serves in place of the earth.
HOIST
A machinery unit that is used for lifting and lowering loads.
HOLDING BRAKE
A brake that automatically prevents motion when power is off.
HOOK APPROACH
The minimum horizontal distance between the center of the runway rail and the hook.
HYDRAULIC BRAKE
A brake that uses hydraulics to slow or stop motion.
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.
IMPACT ALLOWANCE
Additional hook load assumed to result from the dynamic effect of the live load.
INSULATION CLASS
A motor winding insulation rating that indicates its ability to withstand heat and moisture.
JIB CRANE
A crane that does not use a runway or track system and typically offers up to 360° o rotation. Can be stand-alone or mounted to a column or wall.
KSI
Kips per square inch, a measurement of stress intensity. See kip.
KIP
A unit of force that is equivalent to 1000 pounds.
KIT CRANE
See modular crane.
KNEE BRACE
The diagonal structural member joining the building column and roof truss.
L10 BEARING LIFE
The minimum expected life, in hours, of 90% of a group of anti-friction bearings that are operating at a given speed and loading. The average expected life of the bearings is approximately five times the L-10 life.
LATERAL FORCES
Horizontal forces perpendicular to the axis of the member being considered.
LIFT
The maximum 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, that are 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 that moves relative to the structure under consideration.
LOAD BLOCK
An assembly consisting of a hook, swivel, bearing, sheaves, pins and frame, suspended by hoisting ropes.
LOAD CARRYING PART
Any part of the crane in which the induced stress is influenced by the load on the hook.
LOAD CYCLE
One lift cycle with load plus one lift cycle without load.
LONGITUDINAL STIFFENERS
Horizontal members attached to the web of the bridge girder to prevent the web from buckling.
MAGNETIC CONTACTOR
An electro-magnetic device for opening and closing an electric power circuit.
MAGNETIC CONTROL
A means of controlling direction and speed by using magnetic contactors and relays.
MAINLINE CONTACTORS
A magnetic contactor used in the incoming power circuit from the mainline collectors.
MAINLINE DISCONNECT SWITCH
A manual switch that breaks the power lines leading from the mainline collectors.
MANUAL-MAGNETIC DISCONNECT SWITCH
A means of disconnecting power, consisting of a magnetic contactor that can be operated by remote pushbutton and can be manually operated by a handle on the switch.
MASTER SWITCH
A manually operated device that serves to govern the operation of the contactors and auxiliary devices of an electric control.
MATCH MARKING
Identification of non-interchangeable parts for re-assembly after shipment.
MECHANICAL LOAD BRAKE
An automatic type of friction brake used for controlling loads that are being lowered. 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.
MEAN EFFECTIVE LOAD
A load used in durability calculations that accounts for both maximum and minimum loads.
MODULAR CRANE
An economical, lighter duty (usually Class C) crane that consists of a basic hoist, trolley and bridge and is used to move material in smaller manufacturing facilities, mills and machine shops. Although it is also known as a kit crane, a modular crane will still require some customization to ensure it meets the needs of individual applications.
MONORAIL CRANE
Instead of using a bridge or girder, the trolley runs along a single path using the flat surface or flange on the bottom of an I-beam.
MULTIPLE GIRDER CRANE
A crane that has two or more girders for supporting a live load.
NON-COASTING MECHANICAL BRAKE
A drive with coasting characteristics such that it will stop the motion within a distance to 10% of the rated speed in feet per minute when traveling at rated speed with rated load.
OPERATOR CAB
The operator compartment from which movements of the crane are controlled. To be specified by the manufacturer as open, meaning it has only sides or a railing around the operator, or enclosed, which means it comes complete with roof, windows, etc.
OUTRIGGER
See auxiliary girder.
OVERCURRENT
A situation where more current than intended runs through a conductor. Also known as overload.
OVERLOAD
Any load greater than the rated load.
OVERLOAD PROTECTION
A device that causes and maintains the interruption or reduction of current flow to the equipment in the case of excessive current.
PENDANT PUSHBUTTON STATION
A way to control the crane where the controllers are beneath the crane, for example, on the floor.
PITCH DIAMETER
Distance through the centre of a drum or sheave from centre to centre of a rope passed around the periphery.
PLAIN REVERSING CONTROL
A reversing control that has identical characteristics for both directions of motor rotation.
PLUGGING
A control function that accomplishes braking by reversing the motor line voltage polarity or phase sequence.
PORTAL CRANE
See gantry crane.
PROCESS CRANE
A heavy duty (Class D and E), custom-engineered crane that performs high capacity lifts or a specific task in constant (or near-constant) succession. Usually top-running, double-girder design
PROTECTIVE PANEL
An assembly containing overload and under-voltage protection for all crane motions.
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.
RATED LOAD
The maximum load which the crane is designed to handle as designed by the manufacturer.
TOP RUNNING CRANE
A type of bridge or girder crane where the trolley and hoist run on a rail installed on top of the bridge girder(s).
UNDER RUNNING CRANE
A type of bridge or girder crane where the trolley and hoist run on the bottom flange of the bridge. Also known as an underhung crane.
WORKSTATION CRANE
A lighter-duty crane of modular design that can typically lift up to two tons.
