Crane & Hoist Terminology

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.

Access platform

A limited length platform, located on one end of the crane only, typically for inspection or service.

Administrative or regulatory authority

Governmental agency, industry regulating body or the employer.


Above Finish Floor; used on engineered drawings as an elevation measurement reference to the height of specific items where the floor is shown as 0” or 100’-0”. The floor can also sometimes be more specifically stated as the actual elevation above sea level.

Allied equipment

Devices that are not an integral part of the crane’s main components but can be added-on to help in controlling or handling the load. These can include, but are not limited to; radio controls, anti-collision systems, horns and lights or below-the-hook type devices such as magnets, spreader bars, sheet lifters, c-hooks, vacuum lifters, etc.

Ambient temperature

The temperature of the atmosphere surrounding the crane system.


The current carrying capacity of the crane or one of its components, expressed in amperes.

Anchor bolts

Bolts used to level and hold runway column base plates in-place. If foundations are poured for these column base plates the anchors are typically tied into place to the re-bar. If the floor can support the applied loads then the floor can be drilled and either chemical (epoxy type) or expansion anchors can be used.

Annual inspection

Mandatory inspection of all overhead lifting equipment as required by OSHA. These records must be kept on-site by the end user for future review in case of an accident or injury occurs while using this equipment.


American National Standards Institute.

Anti-collision sensors

These can be photo eye-to-reflector or laser-to-target type systems. These are most often employed to keep two or more cranes separated by a predetermined distance due to runway capacity limitations or simply to keep multiple bridges or trolleys from impacting each other for safety reasons.

Applied loadings

A combination of the dead load, live load and the impact allowance, as well as the lateral and longitudinal loads, on a structural support system of a bridge crane or monorail system. Also to be considered are the axial, shear and moment loads of the supporting structure on the floor or foundations.

ASCE rails

American Society of Civil Engineers, this looks a lot like railroad rail but is designed for top running crane cranes and trolley travel and may be affixed with “J” shape bolts that wrap around the top flange of a profile shape beam or held in place by a variety of clips that clamp to the bottom flange of the ASCE sections.


Appointed by a duly constituted administrative or regulatory authority.

Automatic crane

A crane which, when activated, operates through a preset cycle or cycles.

Auxiliary hoist

A supplemental hoisting unit, usually designed to handle lighter loads at a higher sped than the main host.


American Welding Society; one of the regulatory agencies of our industry.

Axial load

Vertical load applied to floor by free standing crane column.


Back panel

A board or plate to which different electrical controlling devices are mounted. This panel is then bolted to the back surface inside the control enclosure.

Base or deck mounted hoist

A type of mounting where the hoist is mounted to the top side of a horizontal structural supporting surface.

Battery backup system

Battery bank used on a crane that is operating with an electro-magnet, to guard against inadvertent load release due to loss of primary power to the crane and/or magnet system.

Bearing life

The L-10 life of an anti-friction bearing is the minimum expected life, hours, of 90 percent 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.

Below-the-hook accessories

There are a variety of this type of equipment; magnets, c-hooks, sheet lifters, vacuum lifters, tongs, clamps, etc. The capacity of the crane or hoist must include the dead weight of this device as well as the live lifted load when specifying the requirement.

Below-the-hook lifting devices

Devices that are not normally reeved onto the hoist rope or chain, such as hook-on-buckets, magnets, grabs and other supplemental devices used for ease of handling certain types of loads. The weight of these devices is to be considered part of the load to be lifted.


Brinell Hardness Number; measurement of material hardness. Typically used when referring to wheel hardness.

Block loads

An action that facilitates the removal of slings or other lifting devices from under the load, accomplished by bringing the load to rest on wood, metal or other spacers between the floor and load.

Body bound bolt

Structural connections will usually allow for the holes to be 1/16” larger than the bolts that are used in the connection. However, when there is no allowance for the sections to “give”, normally in the elevation of the two sections, the hole-to-bolt tolerances will be much tighter in order to keep the sections from dropping in relative elevation.

Bogie truck

A short end truck attached to the end of one girder (or to a connecting member if more than one bogie is used per girder). This type of end truck is used when more than four wheels are required on a crane due to the design of the runway or for ease of installation of the crane bridge girders.


Load bearing beam of a jib crane.

Bottom entry conductors

This is where the rigid conductor bars are mounted in such a way as to allow the collectors to enter the bars from the bottom. This is in contrast to side entry or lateral mount type. The bottom entry is preferred due to the collectors not needing both vertical and horizontal springs to keep them in alignment as are required by the side entry type. Bottom entry bars will also not have the tendency to collect and hold metal shavings that come from normal wear of the bars and collectors that can cause arcing, resulting in short circuits or other conductivity problems.

Box section

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


A device, other than a motor, used for retarding or stopping motion by friction or power means.

Brake, holding

A friction brake for a hoist that is automatically applied and prevents motion when power to the brake is de-energized.

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 or hand chain wheel to lower a load but does not impose any additional load on the motor or hand chain wheel when the hoist is lifting a load. A mechanical load brake is a mechanical control braking means.

Braking means

A method or device used for stopping or holding motion by friction or power.

Braking means, control

A method of controlling speed by removing energy from the moving body or by imparting energy in the opposite direction.

Braking means, countertorque (plugging)

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

Braking means, dynamic

A method of controlling speed by using the motor as a generator, with the energy being dissipated by resistance.

Braking means, eddy current

A method of controlling or reducing speed by means of an energy induction load brake.

Braking means, mechanical

A method of controlling or reducing speed by friction.

Braking means, pneumatic (air)

A method of controlling or reducing speed by means of a compressed gas.

Braking means, regenerative

A method of controlling speed in which the electrical energy generated by the motor is fed back into the power system.


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.

Bridge (cross) conductors

The electrical conductors located across the bridge structure of a crane to provide power and control capacity for all bridge, trolley, hoist and auxiliary functions.

Bridge disconnect

As required by code to allow for disconnecting the mainline power across the bridge and to the trolley, hoist and other electrically controlled devices on the crane, while still leaving the main control panel “hot” for maintenance purposes.

Bridge/crane girder(s)

Crane member on which carriers or trolleys travel, horizontally mounted between and supported by the end trucks.

Bridge (cross) conductors

The electrical conductors located across the bridge structure of a crane to provide power and/or control capacity for all bridge, trolley and hoist functions.

Bridge rail

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

Bridge travel

The crane movement in a direction along the length of the crane runway.

Building structure

The structural members of a building which support the building and roof loads and on which the loads of a crane or monorail system, and the load to be moved, can possibly be imposed.

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.



An elevated operator’s compartment attached to a crane, typically located on one end of the bridge structure or the trolley frame.

Cab-operated crane

A bridge crane controlled by an operator in a cab located on the bridge or trolley.

Cable guide

This is a device that regulates the wire rope as it wraps around the hoist drum in order to keep the rope in the proper grooves.

Cable reel

Usually spring loaded, this is a reel with conductor cable wrapped around it to be used for mainline power delivery along a runway or monorail and is also, when mounted to a trolley, used to deliver power and control to a powered below hook device.


The slight upward vertical curve designed and fabricated into crane bridge girders (and sometimes runway and monorail sections) to compensate partially for deflection due to the weight of the hoist and the lifted load.

Cantilevered column

A runway or monorail upright column that is unsupported, laterally or longitudinally, at the top.


The maximum rated (SWL).

Ceiling mounted

A type of crane or monorail system mounting where hanger brackets, clamps or bolted connections suspend the components. 

Certified welder

In order to ensure quality and safety, it is strongly suggested that crane and runway welder/fabricators be certified to AWS (American Welding Society) Specifications D1.1 for structural work and D14.1 for overhead cranes and other material handling equipment. Ask to see their certification before the work starts and be sure that they are using the welding method as shown on the certificates (i.e. mig or tig wire, or stick).

Chain guide

See Guide, chain.

Chain, hand

The chain grasped by a person to apply force required for the lifting or lowering motion.

Chain, load

The load-bearing chain in a hoist.

Chain, roller

A series of alternately assembled roller links and pin links in which the pins articulate inside the busihings and the rollers are free to turn on the bushings. Pins and bushings are press fit in their respective link plates.

Chain, welded link

A chain consisting of a series of interwoven links formed and welded.


A type of crane or monorail suspension method used to sup­port tracks from an overhead structure and fastened to the structure by means of pressure rather than welding or direct bolting.


Minimum distance from the physical boundaries of a crane to the nearest obstruction.


Crane Manufacturers Association of America, Inc. (formerly EQOI—Electric Overhead Crane Institute).


Contacting devices for collecting current from the runway, bridge or monorail conductors. The mainline collectors are mounted in a manner so as to transmit current from the mainline conductors to the equipment being energized. These can be of the shoe type for enclosed conductors, or in the case of older equipment, the wheel type for open conductors.


An electro-mechanical device for opening and closing an electric power circuit.

Control trolley

The C-track suspended rolling box at the lead of the control festoon across the bridge where the push button station plugs in.


A device for regulating, in a predetermined way, the power delivered to the motor or other equipment, usually by means of a pushbutton pendant station or radio remote.

Coped connection

This type of connection allows for a section of the runway or bridge girder to be cut out and re-plated in order for the beam to sit lower on the seat of the runway haunch or bridge end truck. This is done most often to satisfy an elevation requirement or limitation.

Counter torque

A method of controlling speed where the motor energized in the direction opposite to the direction is rotating.

Cover plate

The top or bottom plate of a box girder.


A machine for moving, lifting and lowering a load comprised of a bridge, hoist and trolley. Cranes may be of the traveling, portable, or fixed type.

Crane girder(s)

Single and double girders are typical and can be profile (wide flange or S-beam shape) or fabricated box girder sections.

Crane service rating

Service ratings are defined by CMAA and are determined by number and length of the lifts and the percentage of rated crane capacity per lift, usually as counted per hour.

Cross shaft

The shaft extending across the bridge or trolley, used to transmit torque from motor to the drive wheels


The “C” shaped track is mounted so the opening of the “C” is facing downward and allows the festoon trolleys to roll across the bridge or along the runway or monorail, enabling the flat cable conductors to deliver power and/or control from the source to the controlled device.

Cushioned start

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


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.


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


This is a test designed to measure the deflection of the bridge girder(s) and/or runway beams. As this is a design criterion, it is recommended that this test be conducted at 100% of the rated capacity of the equipment being tested and not measured with the load test weights, which are most often 125% of rated capacity. Should the deflection test be conducted with this larger load test weight, you will get a false record of the true deflection of the member as designed.

Designated perso

Selected or assigned by the employer or the employer’s representative as being competent to perform specific duties relative to operating, inspecting or servicing the crane.


A plate or partition between opposite parts of a member serving a definite purpose in the structural design of the member. Sometimes called a stiffener, which is welded into a box section bridge girder or end truck.


A device whereby the conductors of a circuit can be disconnected from their power source.

Drive girder (G-1)

The girder on which the bridge drive machinery is mounted, on double girder cranes only.


The cylindrical member around which the wire rope is wound for lifting or lowering the load.

Dual drive

Modern configuration to motor drive bridge crane end trucks using separate synchronous motors and gear boxes, one for each end truck. Large capacity trolleys may also use this technology when needed.

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.

Duty cycle

The working requirements of a crane or hoist as defined by HMI, CMAA or FEM classifications.

Dynamic operation

A method of controlling directional speed by using the motor as a generator, with the energy being dissipated by resistance.



The alignment of the center lines of stacked structural sections in order to maintain the capacity as designed and to minimize torsion; such as the web of the runway ASCE crane running rails and the web of the supporting runway beams or the trolley rail being centered over the inside web plate of a torsional box girder bridge beam.


Equivalent Center Loading; a factor used for determining the actual downward load applied to a horizontal structural member from an end truck or trolley; based on the number of wheels, the individual wheel loads and the overall wheel base.

Eddy-current braking

A method of control by which the motor drives through an electrical induction load brake. 

Electric overhead traveling crane (EOT)

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 one or more of the crane motor speeds without the use of friction braking. 


A bracket supported track mounted conductor system by which the moving equipment receives its electrical power.

Emergency stop

This is a button, usually a mushroom head style located on the controlling push button station or radio transmitter that shuts off the mainline contactor in the main panel thereby stopping all functionality of the crane or hoist when depressed.

Enclosed track

A light capacity crane or monorail system that includes an extruded track made of steel or aluminum, similar to a uni-strut shape, free rolling end trucks and trolleys that ride on the inside of the track allowing for a smooth and ergonomically low effort of movement. These can be free standing or ceiling supported and some can be supplied with motor drives, track switches, curves and a variety of electrification configurations.


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 face of the runway end stop and the centerline of the load hook.

End stop

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

End tie

A structural member, other than the end truck, which connects the ends of the bridge girders to maintain the squareness of the crane bridge. 

End truck

An assembly consisting of the frame, wheels with axles and drive train, which support the crane girder(s) and facilitate crane movement along the runway.

End user

The owner and physical location of the user of the overhead lifting equipment in question.

Engineered lift

This is a lift of more that the rated capacity of a crane or hoist that allows for the rare occurrence when there is no other real alternative. First the manufacturer of unit must be notified and respond in writing that the detailed lift is permissible, then the crane must be inspected to be sure all of the components are operating correctly, the lift is then made, once the area is cleared of all unnecessary personnel. After the lift cycle is completed, the crane must be inspected again to make certain that no damage was done to the crane and its components and is safe to put back into normal operation. Detailed records of this entire event must be maintained by the end user.


Engineer Of Record; the original engineer that designed a structure or building that must be consulted when alterations or new forces are being applied to this structure or building in order to accommodate an overhead lifting system. This is also the individual to be contacted should there be some question with the way the old or new structural design is functioning.


Electric Overhead Traveling crane.

Explosion proof

This is an electrical specification and includes a variety of electrical components that must be supplied as per the demands of the Group, Class and Division of the hazardous area in which they are expected to operate.



A provision designed to automatically stop or safely control any of the crane’s motions in which a malfunction may occur.

Failure rating

For standard hoists and cranes, the ratio for strength to failure is 5:1.


European crane and hoist duty rating system, similar the U.S. HMI and CMAA rating systems. 

Festoon cables

Looped wires, now commonly flat cable, that carry power and control across a bridge or along a runway or monorail. 

Field wiring

The wiring required after erection of the crane. 

Fire watch

A designated individual that is in-place to watch for fire hazards when “hot” work such as welding or torch cutting is being performed in the field.

Fixed axle

An axle which is fixed in the truck and on which a wheel revolves when driven by a pinion.

Fleet angle

The angle formed by the wire rope and the drum or sheave grooves.

Floor controlled crane

Motor driven cranes which are controlled by an operator on the floor by means of pushbutton station suspended from the overhead equipment. 

Foot walk (service platform)

The full length walkway with handrail and toeboards, attached to the bridge or trolley for access purposes. Typically attached to the G-1, or drive-side girder, allowing access to main control panels and most wiring connections.

Footing / Foundation

Concrete foundation, usually re-bar reinforced, designed by a Professional Engineer, that is excavated and poured to support the axial, shear and moment loads applied by crane or monorail upright column base plates.


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 floor mounted rails or other runway. These can typically come in two styles; a semi-gantry (or single leg) which has one leg fixed to a floor running truck and one truck fixed to the other end of the bridge that runs on a more conventional runway beam and rail that is supported by the building columns at bridge height. The other type is a full gantry (or double leg) which has legs at both ends of the bridge with trucks running on two floor mounted rails.   


The principal horizontal beam(s) of a bridge crane, which support the trolley, is attached to the end trucks.

Grade 5

Technical specification of the preferred fasteners used to make structural connections for a crane, runway or monorail system.

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.

Guide, chain

A means to guide the load chain at the load sprocket.


Hand chain wheel

See Wheel, hand chain. 

Hanger rod

A type of crane or monorail suspension method used to support tracks from an overhead structure and fastened to the structure by means of a steel rod together with other fittings.

Hazardous locations (classified as explosion proof and/or spark resistant)

Where fire or explosion hazards may exist and are classified depending on the properties of the flammable vapors, liquids or gases or combustible dusts or fibers which may be present and the likelihood that a flammable or combustible concentration or quantity is present.

  • Class 1: Where flammable gases or vapors are, or may be, present in the air in quantities sufficient to produce explosive or ignitable mixtures
  • Class 2: Which are hazardous because of the presence of combustible dust
  • Class 3: Hazardous be¬cause of the presence of easily ignitable fibers or filings, but in which such fibers or filings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures


The seat fastened to an upright column on which the runway beams for a top running crane sit. These connections are best made when bolted. 


Headroom is the distance measured from the saddle of the load hook, when in it’s highest lift position; typically to the following locations: 

  • Bottom of bridge girder 
  • Top of bridge girder 
  • Clear ceiling 


Hoist Manufacturers Institute, a division of CMAA. 


An under running or top running machinery unit which is used for lifting or lowering a live load. When more than one hoist is mounted on a bridge, the larger capacity unit is typically called out as the Main hoist and the smaller unit is designated as the Auxiliary hoist.

Holding brake

A friction brake for any of the crane’s motions that is automatically applied and prevents motion when power is off.   

Hook approach

The minimum horizontal distance, perpendicular to the runway, between the centerline of the hoist hook and the centerline of the runway rail. 

Hook latch

A normally spring loaded mechanical device to close the throat opening of the hoist hook. 

Hot metal duty

A very specific rating for a crane that handles molten metal. As defined by CMAA and ANSI, these cranes and hoists have a higher failure rating for the components @ 7:1.

Hot pigtail

The 4-wire power connection leads that are provided by the purchaser’s electrical contractor and left at the conductor connection point to be tied into mainline power delivery method by the crane system installer. 

Hot work

A field work term used to call out work that uses heat, such as welding or torch cutting.

Hydraulic Brake

A brake that provides for slowing or stopping of a motion by hydraulic means.


Ice cube relay

A plug-in module in some crane and hoist electrical components, such as the push button station or control panels. Most commonly used by some European manufacturers.

Idler Girder (G-2)

The bridge girder which does not have the bridge drive attached, but which usually carries the bridge conductors, on double girder cranes only.

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.


International Electric Code. 

Impact allowance

Additional load assumed to result from the dynamic effect which occurs at the initial point of lifting the live load and is figured as a percentage of the live load. This would be added to static wheel load, which is typically detailed on quotes and drawings without the impact load included, for an accurate and complete loading that is applied to the support structure of a bridge crane or monorail system.

Independent push button station

C-track supported festoon push button controller that travels across the length of the bridge, independent of the hoist and trolley, and controls all motions of the crane.

Inductive load

An electrical load which has a lagging power factor.

Industrial duty crane

Service classification covered by CMAA Specification No. 70, Specifications for Electric Overhead Traveling Cranes.

Insulation class

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

Insurance certificates

You always want to ask your crane or structural support system builder for a copy of their manufacturer’s liability insurance certificate. Just as important, the installer needs to supply you with copies of their general liability and workers compensation insurance certificates. These need to be supplied prior to any work beginning. You may also want to be named as an additionally insured on these certificates.

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.


Jib crane

Typically a manual type horizontally swinging crane that is supported by a free standing base plate mounted pipe or hung from your building column in a tie-rod configuration or full cantilevered style. The free standing pipe column type can also be motor driven in the rotation direction.

Jogging (or inching)

To move the hook, trolley, or bridge in a series of short, repetitive, depressions of the function controller button.

Junction box (j-box)

A small and secure box in which wiring terminations are made.



Kips per Square Inch, measurement of stress intensity.


A unit of force, equivalent to 1,000 pounds

Knee brace

The diagonal structural member joining a building column to the roof truss, other overhead horizontal structural member or the floor.

Knife switch

Type of electrical disconnect that uses a “throw” lever that seats into parallel circuit making connector plates and is usually fused.


Lateral load

Horizontal forces perpendicular to the axis of the member being considered. When used in reference to a crane runway being braced back to your building, you can estimate the lateral load that your structure will realize to be approximately 220 lbs. per ton of lifted load.


The maximum vertical distance (upper and lower) through which a load hook can travel.

Lift cycle

A single lifting and lowering motion (with or without load).

Lifting devices

Devices which are not considered to be a fixed part of the hoist, such as hook suspended buckets, magnets, grabs and other supplemental devices used for ease of handling certain types of loads. The weight of these devices is to be considered part of the load to be lifted when specifying the desired capacity of a crane, hoist, runway or monorail system (including the supporting structure).

Limit switch

A device designed to cut off the power automatically at or near the limit of travel for the hoist, trolley or bridge motions.

Line contactor

A contactor to disconnect power from the supply lines.

Live load

A load which moves relative to the structure under consideration.


The total lifted weight on the load block or hook.

Load block (bottom block)

The assembly of hook, swivel, bearing, sheaves, pins, and frame suspended by the hoisting rope or load chain.

Load chain

See Chain, load.

Load cycle

Lowering of the hook to pick up a load, one lift with the load, one lowering of the load, plus one lift without the load, returning the hook to the original position.

Load, rated

The maximum load for which a hoist is designated by the manufacturer or a qualified person.

Load spectrum

The average daily operating time of a crane or hoist, calculated in order to determine the proper service class of the equipment the application requires.

Load suspension parts

The load suspension parts of the hoist are the means of suspension (hook or lug), the structure or housing which supports the drum or load sprocket, the drum or load sprocket, the rope or load chain, the sheaves or sprockets, and the load block or hook.

Load test

This type of test is performed in the field to determine the integrity of the system as a whole. It is recommended that the test be @ 125% of the rated capacity and include travel to all limitations of the system as well as a timed hoist brake test to detect brake slippage outside the range of acceptance. Do not accept the factory hoist load test certificate alone in lieu of the completed field test as it only verifies the hoist mechanism itself and does not confirm that the entire system is sound and safe to operate.

Lock out – tag out

Method by which a crane system mainline power disconnect is turned off and the knife switch handle is locked in the “off” position by one or more pad locks. These locks have a tag with the name of the individual locking out the crane. It is not permitted to remove someone else’s lock as this could put this individual in great danger of serious injury or death due to electrocution.

Longitudinal stiffeners

Horizontal members attached to the web of the bridge girder to prevent web buckling. These can also be part of a runway, monorail or other crane structural support system.


Magnetic control

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

Mainline conductors

Rigid conductor bars, festoon system or cable reel that delivers the mainline power along the runway or monorail.

Mainline contactor

A magnetic contactor located in the main control panel, used in the incoming power circuit from the main line collectors, to pull in or drop out the power supply, to the crane or hoist.

Mainline disconnect switch

A manual knife type switch which breaks the power leading from the switch to the mainline conductors to the crane or hoist.

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 contactors and auxiliary devices of an electric control.

Match marking

Identification of non-interchangeable parts for reassembly after shipment. These are typically used on the crane, runway and structural support components.

Mean effective load

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

Mechanical load brake

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 additional load on the motor when lifting a load.

Mill duty crane

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

Mill spec

The tolerances to which the steel mills produce their products. These are typically much less exacting than what is required by the hoist and crane industry for bridge girder, runway and monorail sections. This causes the need for the crane fabricators to quite often re-work the straightness and flange relationships on many of the sections before they can be built into an overhead lifting system that meets CMAA tolerances.


Monorail Manufactures Association, a division of CMAA.

Moment load (overturning)

The forces applied to a column and base plate that want to pull it loose from the floor. These are most prevalent with full cantilevered columns.


A single line overhead track, from which a hoist & trolley unit is suspended, used to transport loads. These can be simple straight line tracks or more complicated with switches, curves and interlocks that connect to cross over sections that allow the hoist & trolley to travel onto under running bridge cranes.



National Electric Code.

Normal operating conditions

Conditions during which a crane system is performing functions within the scope of the original design. 

Normal walking speed

A walking speed assumed to be 125-150 feet per minute.


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.


Any load greater than the rated capacity of an overhead lifting system.

Overload limit device

A device that is part of the hoisting unit that senses when an attempt is made to exceed the capacity (safe working load) of the hoist and interrupts the lift circuit.

Overload protection (overcurrent)

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

Overtravel restraint

A device used to prevent the slack load chain from inadvertently being lowered out of the load sprocket.


Parts (lines)

Number of lines of rope or chain supporting the load block or hook.

Patented track

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


Professional Engineer. An individual qualified to design part or all of an overhead lifting system and this design should always bear the engineer’s registration stamp.

Pendant pushbutton station

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

Pendant station

Controls suspended from the hoist for operating the unit from the floor.

Permanent power

The power source on a new construction project that allows for the crane system installation to be energized and tested.

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.

Plug and Play

System that allows for connecting most crane electrical components together with plugs and receptacles, eliminating the need for hard wiring.


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


Point of Lowest Obstruction: Any building structure, i.e. lights, HVAC ductwork, electrical conduit, etc., above the crane operating area.

Power transmission parts

The machinery components including gears, shafts, clutches, couplilngs, bearings, motors and brakes.

Primary upper-limit device

The primary upper-limit device is the first limit device that will be activated to control the upper limit of travel of the load block when a hoist is equipped with more than one upper-limit device.

Profile beam section

Either an “S” or wide flange beam.

Protective panel

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

Push button station (pendant)

An electrical control device, consisting of push button operated contacts, used by the operator for the control of the powered motions of the crane, hoist, and other auxiliary equipment.


Qualified person

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


Radio controlled crane

A crane operated from a radio transmitter located at a point not mechanically attached to the crane being controlled. The bridge main control panel has a receiver that transmits the desired commands to the difference crane functions.

Rail sweep

A device attached to the bridge end trucks (and trolley end trucks for double girder top running trolleys) and is located in front of the truck’s leading wheels to push aside loose obstructions from the running surface.

Rated load

See Load, rated.

Reeving (rope)

The reeving of the hoist is the path of the rope between the hoist and the load block. 

  • Double reeving is two parts of wire rope leading off of the drum, one from each end of the drum, creating a hook movement referred to as True Vertical Lift   
  • Single reeving is one part of the line leading off of the drum in which the hook travels horizontally across the drum during the lift cycle resulting in some measure of hook “drift” 

Regenerative braking

A method of control­ling speed in which the 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.


Request for quote. This should include a detailed specification of the equipment, location for installation, time frame for delivery and any special conditions or terms as anticipated by the requester.

Roller chain

See Chain, roller. 

Rope sheave

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

Rotating axle

An axle which rotates with the wheel and is connected directly to the drive motor or gear box by a splined or keyed shaft.


The rails, beams, brackets and framework on which the crane operates. These can be building column seated on haunches, semi-free standing (braced back to the building) or totally free standing cantilevered columns and may or may not require foundations.

Runway conductors

The main line 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. These can be ASCE type rails which can be attached to the runway beam top flanges by J-bolts or clips or square bar sections that are welded to the beam top flanges.


S-beam section (sometimes called an I-beam)

A standard structural 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.

Service Class

The working requirements of a crane or hoist as defined by HMI, CMAA or FEM classifications.

Shear (friction) connection

Where two sections are connected end-to-end (as opposed to stacked) with plates that are bolted and tightened to specific torque specifications to create adequate friction to hold the load.


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

Sheave, nonrunning

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

Sheave, running

A sheave that rotates as the load block is lifted or lowered.

Side pull

The action of the hoist wire rope pulling horizontally against the grooves of the drum when the hook is not operated straight up and down and can result in an unsafe condition and/or damage to the equipment.

Simultaneous and independent control

Method by which two or more movements of a crane system can be operated together or separately. Either actuated by a selector switch, or separate control buttons for each function, on the controller.

Skewing forces

Lateral forces on the bridge truck wheels caused by the bridge girders not running in a perpendicular direction to the runways. Some normal skewing occurs in all bridges.


The horizontal distance center-to-center of runway rails.

Spark resistant

This is a mechanical specification and includes a variety of alterations to the components of the unit that must be supplied as per the demands of the Group, Class and Division of the hazardous area in which they are expected to operate.


A mechanical device used to join the adjacent ends of runway, monorail and/or ASCE runway rail sections.

Sprocket, idler

A freely rotating device that changes the direction of the load chain.

Sprocket, load

A hoist component that transmits motion to the load chain. This component is sometimes called load wheel, load sheave, pocket wheel or chain wheel.

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 speed.

Stepped control

A type of control system with fixed speed points.

Strength, average ultimate

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


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

Supporting structure

The structure used for the support of a crane and runway or monorail system.

Suspension fittings

Fittings used to attach an under running runway or monorail track to the supporting structure.


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


A device for making, breaking or changing the connection in an electric or pneumatic circuit (valve).

Switch, emergency stop

A manually actuated switch to disconnect power independently of the regular operating controls.


Safe Working Load; another way to callout the rated capacity of a hoist, crane or monorail system.


Tag out

Procedure by which a qualified service technician shuts down the availability of an overhead lifting system due to an unsafe or damaged condition that needs to be corrected or repaired. DO NOT use this equipment as long as it remains tagged out.


An electrical conductor system employing flexible steel wire cables for suspension of the conductor cables either by “S” hooks or small rolling trolleys.


Totally enclosed fan cooled, motor type.

Tensile strength

Measures the force required to pull something, such as a wire rope or a structural beam, to the point where it breaks.


Totally enclosed non-ventilated, motor type.

Top running crane

An electric overhead traveling crane having the end trucks supported on rails attached to the top of the crane runway beams.

Torque, full load (motor)

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

Torsional box girder

Double box girder construction in which the trolley rail is located over the inside webs of both girders.

Torsional forces

Forces which can cause twisting of a structural member.


The structural member of an under running crane or monorail that supports the carrier or crane wheels.

Tractor drive

A motor driven unit supported from wheels and propelled by friction drive wheel bearing on the underside of the track.


Other contractors on a job site that your installer needs to work with, or around, in order to get the installation completed.

Transfer switch

A switch, usually located on the face of the main control panel, that allows for changing the method of control from a push button station to a radio, and back.


A wheeled mechanism that carries a hoist and which provides horizontal motion of the hoist along a beam.

Trolley frame

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

Trolley hoist

A hoist and trolley unit consisting of a hoist suspended from or mounted to a trolley, or a hoist with an integral trolley.

True vertical lift

In true vertical lift, the load hook travels in an exactly vertical path between the lower limit and the upper limit of lift.

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. This is a very dangerous condition and can result in the hoist motor pulling the rope until it breaks, dropping the load.


Under running crane

An electric overhead traveling crane where the end trucks are supported from the bottom flanges of tracks attached to a structure or sup­ported on bottom flanges of beams. These tracks or beams make up the crane runway.

Undervoltage 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 thereby allowing for controlled acceleration and deceleration of the driven hoist, trolley or bridge.

Voltage drop

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


W-beam section

A wide flange beam shape as defined by the American Institute of Steel Construction.

Web plate

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

Welded link chain

See Chain, welded link.

Welded, hand chain

A wheel with formed pockets on its periphery to allow torque to be transmitted when a force is applied to the hand chain.

Welding procedure

A written, and repeatable, progression of steps that will yield the best result for a certain type of welded connection.

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.


Distance from center-to-center of outermost wheels on a trolley or end truck.

Wire markers

Small labels that wrap around the power and control wires in a control panel or junction box that allow the technician to see how things are supposed to be connected and make it easier for them to trouble shoot when there is a problem. Similar markers will also be stuck to the connecting locations on the terminal strips in the panel or j-box.