Crane Glossary of Terms

A

Abnormal Operating Conditions:

Environmental conditions that are unfavorable, harmful or detrimental to or for the operation of a crane or hoist; conditions such as excessively high or low temperatures, corrosive fumes, dust laden or moisture laden atmospheres 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 or cycles.

Auxiliary Hoist:

A backup 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 a load would otherwise impose on the main girder.

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B

Bearing Life Expectancy:

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

BHN:

Brinell hardness number, measurement of material hardness.

Boom (Overhead Crane):

A horizontal member used to permit hoisting as well as lowering the load at a point other than directly under the hoist drum or trolley, it is mounted on the trolley.

Boom (Gantry Crane):

A trolley runway extension often used to obtain clearance for gantry travel by retracting or raising.

Box Section:

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

Brake:

A device, other than a motor, that stops or pauses motion by power or friction.

Branch Circuit:

The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).

Bridge:

That part of an overhead crane consisting of girders, end trucks, end ties, walkway and rive 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 and hoisting machineries.

Bridge Rail:

The rail supported by the bridge girders on which the trolley travels.

Bumper (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.

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C

Camber:

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

Capacity:

The maximum rated load which a crane is designed to handle.

Clearance:

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

CMAA:

Crane Manufacturers Association of America.

CSA:

Canadian Standards Association. Crane, as an entire assembly, must be CSA certified.

CSA "NRTL/C":

Indicator appearing adjacent to the CSA mark signifies that the industrial control equipment meets U.S. standards.

Collectors:

Contacting devices for collecting current from the runway or bridge conductors. The mainline collectors are mounted on the bridge to transmit current form 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 opening and closing an electric power circuit.

Controller:

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

Corrosion Resistant:

Equipment is designed and manufactured with different materials to prevent corrosion of materials.

Counter-Torque Braking:

A method of speed control by which the motor is reversed to develop power to the opposite direction.

Cross Shaft:

The shaft extending across the bridge used to transmit torque from motor to bridge drive wheels.

Crab:

See trolley.

Cushioned Start:

An electrical or mechanical method for reducing the rate of acceleration of a travel motion.

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D

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 unites, 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 the member.

Drive:

The assembly of the motor and gear unit used to propel the bridge or trolley.

Drive Girder:

The girder on which side the bridge drive machinery is mounted.

Drum:

The cylindrical member around which the hoisting ropes are wound for lifting and lowering the load.

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.

Dynamic Lowering:

A method of control by which the hoist motor is so connected in the lower direction, that when it is over-hauled by the load, it acts as a generator and forces current either through the resistor or back into the life. i.e., regenerative braking.

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E

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 Top Running 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 when in an overhauling condition, 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 the NEMA or CSA 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 Tie:

A structural member other than the end truck which 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.

Endstop:

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

Explosion Proof:

Equipment designed in accordance with existing codes and standards such that it will operate in a specified hazardous environment without causing an explosion. If there is a spark, explosion proof ensures that there will be no explosion as a result of the spark.

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F

Fail-Safe

A provision designed to automatically stop or safely control any motion in which a malfunction occurs.

Field Wiring:

The wiring required after erection of the crane.

Fixed Axle:

An axle which is fixed in the end 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 platform.

Footwalk:

The walkway with handrail and toeboards attached to the bridge or trolley for access purposes.

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G

Gantry Crane:

A crane similar to a top running crane except that the bridge for carrying the trolley or trolleys is rigidly supported on one or more legs running on fixed rails.

Gantry Cranes

Single Leg
A Single leg Gantry Crane is a crane that is designed to have one ‘leg’ of the crane support an end of the bridge while the other end is supported by an end truck that runs along an elevated rail.

Double Leg
A Double Leg Gantry Crane is a crane that is designed to be supported by two or more ‘legs’ that move along fixed rails that are embedded in the floor.

Portable
A Portable Gantry Crane is a normal gantry crane that is not fixed to the floor but is instead fixed to a wheel base. This design is allows for easy movement of hard to budge equipment.

Girders:

The principle horizontal beams of the crane bridge, which supports the trolley, and are supported by the end trucks.

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.

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H

Hoist:

A machinery unity that is used for lifting and lowering a load.

Hoists:

Air Chain Hoists
An air driven machinery unit, utilizing chain as its lifting medium, and used for the lifting and lowering of a freely suspended (unguided) load. Often used in an environment that requires electric spark avoidance due to a potentially explosive atmosphere.

Air Wire Rope Hoists
An air driven machinery unit, utilizing chain as its lifting medium, and used for the lifting and lowering of a freely suspended (unguided) load. Often used in an environment that requires electric spark avoidance due to a potentially explosive atmosphere.

Electric Chain Hoists
A suspended machinery unit that is powered by electrically driven motors and is used to lift or lower a freely suspended (unguided) load, using chain as its lifting medium.

Electric Wire Rope Hoists
A suspended machinery unit that is powered by electrically driven motors and is used to lift or lower a feely suspended (unguided) load, using wire as its lifting medium.

Hand Chain Hoists
A suspended machinery unit that, by use of manual operation, is used for lifting or lowering of a freely suspended (unguided) load and uses chain as its lifting medium.

Ratchet Lever Hoists (Pullers)
A lever operated manual device used to lift, lower or pull a load and to apply or release tension. Utilizes a ratchet and pawl mechanical configuration to incrementally raise or lower a load or to apply or release tension.

Holding Brake:

A friction 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 provides retarding or stopping motion by hydraulic means.

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I

Idler Sheave:

A sheave used to equalize tension in opposite parts of a rope. Because of its slight movement, it is not termed as a running sheave.

Impact Allowance:

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

Indoor/Outdoor Use

Equipment is designed and manufactured to be weatherproofed for outdoor use.

Industrial Duty Crane:

Service classification covered by CMAA Specification No. 70 and Specification No. 73, 'Specification for Electric Overhead Traveling Cranes'.

Insulation Class:

Motor winding insulation rating which indicates its ability to withstand heat and moisture.

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J

Jib Cranes

Floor Supported
A Floor Supported Jib Crane is a jib crane where the boom is connected to a heavy pipe column and is base plated to the floor/foundation and is designed to rotate 360 degrees.

Column Supported (Tie Rod)
A Column Supported (Tie Rod) Jib Crane is a jib crane that is supported by a wall column and has an additional tie rod connected to the boom and is designed to allow for 180 degrees of rotation.

Column Supported (Full Cantilever)
A Column Supported (Full Cantilever) is a jib crane where the boom is connected directly to a wall column. A full cantilever jib crane is ideal for a lower ceiling where maximum head room is required and is designed to allow for 180 degrees of rotation.

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K

K.S.I:

Kips per square inch, measurement of stress intensity.

Kip:

A unit of force, equivalent to 1000 pounds.

KN:

KiloNewton, a metric unit of force, equivalent to mass (kg) times gravity (9,81).

Knee Brace:

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

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L

Lateral Forces:

Horizontal forces perpendicular to the axis of the member being considered.

Lift:

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

Lift Cycle:

Single lifting and lowering motion (with or without load).

Lifting Devices:

Buckets, magnets, grab 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 Block:

The assembly of hook, swivel, bearing, sheaves, pins and frame suspended by the hoisting ropes.

Load Carry 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 web buckling.

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M

Magnetic Control:

A means of controlling direction and speed by using magnetic contactors and relays.

Main Line Disconnect Switch:

A manual switch which breaks the power lines leading from the main line collectors.

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.

Master Switch:

A manually operated device which serves to govern the operation of contractors 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 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.

Mean Effective Load:

A load used in durability calculations accounting for both maximum and minimum loads.

Mill Duty Crane:

Service classification covered by AISE Standard No. 6, ‘Specification for Electric Overhead Traveling Cranes for Steel Mill Services’.

Monorails

Curved
A Curved Monorail System allows for transportation of product along a fixed, curved path along a single beam. The monorail system is mounted to an existing overhead structure to allow for more floor space.

Switches
A Monorail System with Switches allows for transportation of product along a fixed path to anywhere in the facility along a single beam.

Multiple Girder Crane:

A crane which has two or more girders for supporting the live load.

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N

Non-Coasting Mechanical Drive:

A drive which 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 a rated speed with rated load.

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O

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.

Outdoor/Indoor Use:

Equipment is designed and manufactured to be weatherproofed for outdoor use.

Overload:

Any load greater than the rated load.

Overload Limit Device:

Mechanical or electrical apparatus that prevents the crane from lifting loads greater than the safe working load.

Overload Protection (Overcurrent):

A device operative on excessive current to cause and maintain the interruption or reduction of current flow to the equipment governed.

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P

Pendant Pushbutton Station:

Means suspended from the crane operating the controllers from the floor or other level beneath the crane.

Pitch Diameter (Rope):

Distance through the center of a drum or sheave from center to center of a rope passed about the periphery.

Plain Reversing Control:

A reversing control which has identical characteristics for both directions of motor rotation.

Plugging

A control function which accomplishes braking by reversing the motor line voltage polarity or phase sequence.

Protective Panel:

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

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Q

Qualified:

A person who, buy possession of a recognized degree, certificate of professional standing or excessive knowledge, training and experience, has successfully demonstrated the ability to solve or resolve problems relating to the subject matter and work.

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R

Rail Sweep:

A mechanical device attached to the end truck of a bridge or trolley, located in front of the leading wheels, to remove foreign objects form the rail.

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.

Remote Operated Crane:

A crane controlled by an operator now in a pulpit of in the cab attached to the crane, by any method other than pendant or rope control.

Remote Radio Control:

A cordless means of control, utilizing analytical or digital radio signals to secure controls even in noisy environments.

Resistor Rating:

Rating established by NEMA, which classifies resistors according to percent of full load current on first point and duty cycle.

Rotating Axle:

An axle which rotates with the wheel.

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.

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S

Shall:

This work indicates that the requirement is based upon sound engineering judgment at the time of publication of this specification.

Sheave:

A grooved wheel or pulley used with a rope or chain to change direction and point of application of a pulling force.

Should:

This work indicates that the requirement is a recommendation, the advisability of which depend on the facts in each situation.

Side Pull:

The angle by which the load block is being operated outside of the vertical lifting place (not recommended).

Skeleton Cab:

Same as a 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.

Spark Resistant:

Equipment designed in accordance with existing codes and standards such that it will operate in an environment with no hazardous gas present.

Static Control:

A method of switching electrical circuits without the use of contacts.

Stepless Control:

A type of control system with infinite speed control between minimum speed and full force.

Stepped Control:

A type of control system with fixed speed points.

Strength, Average Ultimate:

The average tensile force per unite of cross sectional are required to rupture the material as determined by test.

Sweep:

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

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T

TEFC:

Totally enclosed fan cooled.

TENV:

Totally enclosed non-ventilated.

Top Running Cranes

Single Girder
A Single Girder Bridge Crane is an overhead bridge crane that has one bridge girder that supports the trolley and hoist. The trolley and hoist ride on the bottom flange of the bridge girder. The single girder bridge crane is considered top running when the bridge girder rides on top of the runway beams and can hold between 250lbs and 15 ton.

Double Girder
A Double Girder Bridge Crane is an overhead bridge crane that has two bridge girders that support the trolley and hoist. The trolley and hoist ride on top of the two bridge girders. The double girder bridge crane is considered top running when the bridge girders ride on the top of the runway beams and can hold between 10 ton and 160 ton.

Torque, Full Load (Motor):

The torque produced by a motor operating at its rated horsepower and speed.

Torsional Box Girder:

Girder in which the trolley rail is located over one web.

Torsional Forces:

Forces which can cause twisting of a member.

Trolley:

The unit carrying the hoisting mechanism which travels on the bridge rails.

Trolleys:

Manual Trolleys
A machinery unit that runs along the top or the underside of a bridge beam either by pulling or pushing.

Geared Trolleys
A machinery unit that runs along the top or the underside of a bridge beam by gears which are controlled by a manual chain.

Motor Driven Trolleys (Electric/Air)
A machinery unit that runs along the top or the underside of a bridge beam by a motor that is either driven by electric or air.

Trolley Frame:

The basic structure of the trolley on which are mounted the hoisting and traversing mechanisms.

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. Can also be inadvertent physical contact between the load black and the upper block or other part of the trolley.

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U

Under Running Cranes

Single Girder
A Single Girder Under Running Bridge Crane is a bridge crane where the bridge girder rides below the runway beam. In contrast to a top running bridge crane where the bridge girder rides on the top of the runway beams. The runway beam for an under running bridge crane is typically ceiling mounted. Under running bridge cranes usually do not exceed 10 tons in capacity.

Double Girder
A Double Girder Under Running Bridge Crane is two bridge girders that ride below the runway beam as opposed to on top in a top running bridge crane. The runway beam for an under running bridge crane is typically ceiling mounted and can hold up to 25 tons but the practical limit is more like 15 tons.

Patented Track
A Patented Track Crane is a standard under running crane with one exception. The bottom flange is wider with a raised tread, creating the perfect rolling surface. Patented Track Cranes are designed for high-repetition and harsh environments as well as for precise engineering and installation tolerances you would find in military or aircraft maintenance facilities.

Undervoltage Protection:

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

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V

Variable Frequency:

A method of control by which the motor supply frequency can be adjusted.

Voltage Drop:

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

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W

Web Plate:

The vertical plate connecting the upper and lower flanges or cover plates of a girder.

Winches:

A stationary machinery unit that, geared by either electricity or air, pulls a load along a relatively level surface.

Wheelbase:

Distance from center-to-center of outermost wheels.

Wheel Load, Bridge:

The vertical force (without impact) produced on any bridge wheel by the sum of the rated load, trolley weight and bridge weight, with the trolley so positioned on the bridge as to give maximum loading.

Wheel Load, Trolley:

The vertical force (without impact) produced on any trolley wheel by the sum of the rated load and the trolley weight.

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X

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Y

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Z