Overhead Crane and Hoist Terminology
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.
Anchor Bolt : A bolt used with its head embedded in masonry or concrete and its threaded part protruding to hold a jib crane in place.
Anchor Bolt Load: The total amount of force that is applied to each supporting anchor bolt in a jib crane; usually measured in kips.
ANSI: American National Standards Institute
Appointed: Assigned specific responsibilities by the employer or the employer’s representative.
ASCE Rail : The runway rails on top running cranes that the bridge travels on.
Automatic Crane : A crane which when activated operates through a preset cycle or cycles.
Auxiliary Hoist: A supplemental hoisting unit of lighter capacity and usually higher speed than provided for the main hoist.
Axial load : The total vertical force applied to the supporting structure in a jib crane. Formula: Axial load= (overall weight of the crane) + (design factor x weight of load)
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.
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, which is a 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. The boom is mounted on a 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, on a hoist or crane 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: The part of an overhead crane consisting of girders, end trucks, end ties, walkway and drive mechanism which carries the trolley and travels in a direction parallel to the runway.
Bridge Conductors: The electrical conductors located along the bridge structure of a crane to provide power to the trolley 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.
Bay: The space between the building frames measured parallel to the crest of the building.
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.
Boom: The horizontal beam (track) upon which a hoist trolley travels. The “jib” of the jib crane.
Bracket Center: The distance, center line to center line, between two supporting brackets of a wall mounted jib crane (i.e. the distance between the two wall mounting points).
Brake: A device for slowing or, stopping motion by friction or by electrical means.
Brake, Mechanical Load: An automatic type of friction brake in the hoist that is 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 of the hoist by friction or power.
Braking Means, Control: A method of controlling hoist speed by removing energy from the moving body or by imparting energy in the opposite direction.
Braking Means, Counter-torque (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 hoist 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 hoist speed by means of an energy induction load brake.
Braking Means, Mechanical: A method of controlling or reducing hoist speed by friction.
Braking Means, Pneumatic: A method of controlling or reducing hoist speed by means of a compressed gas.
Braking Means, Regenerative: A method of controlling hoist speed in which the electrical energy generated by the motor is fed back into the power system.
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.
Bridge: The main travelling structure of the crane which spans the width of the bay. The bridge consists of two end trucks and one or two bridge girders.
Bridge Girder(s): The primary horizontal beam of the crane bridge which supports the trolley and is supported by the end trucks.
Bridge Travel: The crane movement in a direction parallel to the crane runway.
Bridge, Trolley and Lift Speeds: The rate at which the bridge or trolley travels, or at which the hoist lifts, usually in feet per minute or FPM.
Building Aisle: A space defined by the length of a building and the space between building columns.
Bumper [buffer]: An energy absorbing device for reducing the impact when a moving crane or trolley reaches the end of its permitted travel; or when two moving cranes or trolleys come in contact.
Cab: The operator’s compartment on a crane
Cab Operated Crane: A crane controlled by an operator in a cab located on the bridge or trolley.
Camber: The slight upward vertical curve given to girders to compensate partially for deflection due to hook load and dead weight of the overhead crane.
Cantilever Gantry Crane : A gantry or semi-gantry crane in which the bridge girders or trusses extend transversely beyond the crane runway on one or both sides.
Capacity: The maximum rated load which a crane is designed to handle. Usually in tons (1 ton= 2,000 LBS).
Chain Guide: A means to guide the hoist load chain at the load sprocket.
Chain Hoist: A hoists used for lower capacity, lighter duty applications and for projects in which cost is a primary deciding factor.
Clearance: The distance from any part of the crane to a point of nearest obstruction.
CMAA: Crane Manufacturers Association of America Collectors: Contacting devices for collecting current from the runway conductors. The mainline collectors are mounted on the bridge to convey electrical current from the runway conductors.
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.
Column load: The load on the column transmitted from the crane or monorail loading.
Conductors, bridge: The electrical conductors located along the bridge structure of a crane to provide power to the trolley.
Conductors, runway [main]: are the electrical conductors located along a crane runway to provide power to the crane.
Control Pendant: A device that gives an operator precise control over the motions of the crane.
Controller, spring return: a controller which when released will return automatically to a neutral position.
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.
Crane: A machine for lifting and lowering a load and moving it horizontally with the hoisting integral part of the machine. Cranes whether fixed or mobile are driven manually or by power.
Crane Aisle: The portion of the building aisle in which the crane operates, defined by the crane span and the continuous length of the crane runway.
Crane girder(s): See Bridge Girder(s).
Crane Span: The horizontal distance center to center of the both runway beams.
Cross Shaft: The shaft extending across the bridge used to transmit torque from motor to bridge drive wheels.
Cushioned Start: An electrical or mechanical method for reducing the rate of acceleration of a travel motion.
CSA: Canadian Standards Association. In Canada, a 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.
Deflection : The difference in elevation at the tip of the boom between an unloaded jib crane and a fully loaded jib crane; usually measured in inches. Our Jib Crane designs tend to have stricter deflection criteria than others in the industry.
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.
Designated Person: A person selected or assigned by the employer or the employer’s representative as being competent to perform specific duties.
Diaphragm: A plate or partition between opposite parts of a member, serving a definite purpose in the structural design of the member.
Double Girder: An overhead crane consisting of two end trucks, two bridge girders and the trolley hoist unit. The trolley runs on rails on top of the bridge girders.
Drag Brake: A brake which provides retarding force without external control.
Drift Point: A point on a travel motion controller which releases the brake while the motor is not energized. This allows for coasting before the brake is set.
Drive: The assembly of the motor and gear unit used to propel the bridge or trolley.
Drive Girder: he girder on which side the bridge drive machinery is mounted.
Drop stops: Means to limit the drop of a bridge or trolley in case of wheel or axle failure.
Drum: The cylindrical member around which the ropes are wound for raising or 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: a method of controlling crane motor speeds when in the overhauling condition to provide a retarding force.
Dynamic Lowering: A method of control by which the hoist motor is 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.
ECL (Equivalent Center Load): The effective loading on the center of the beam caused by one or more loaded wheels of the end truck or trolley.
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.
Electrification System: The various parts of the crane structure that supply and apply electricity to the trolley hoist.
Emergency Stop Switch: A manually or automatically operated electric switch to cut off electric power independently of the regular operating controls.
Enclosed Conductor(s): A conductor or group of conductors substantially enclosed to prevent accidental contact.
Enclosures: The enclosures house all of the electrical components on the crane.
End Approach: The minimum horizontal distance, parallel to the runway, between the outermost extremities of the crane and the centerline of the hook.
End Stop: A device to limit the travel of a trolley or crane bridge. This device normally is attached to a fixed structure and does not normally have energy absorbing capability.
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 Trucks: Located on either side of the span, the end trucks house the wheels on which the entire crane travels. These wheels ride on the runway beam allowing access to the entire length of the bay.
Equalizer or Equalizer Sheave: A device or sheave which compensates for unequal length or stretch or a rope.
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 reduces the risk of explosion as a result of the spark.
Exposed: Capable or being contacted inadvertently. Applied to hazardous objects not adequately guarded or isolated.
Fail-safe: A provision designed to automatically stop or safely control any motion in which a malfunction occurs.
Festooning: Wiring and support system that delivers power to a trolley hoist across bridge or runway beam.
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 which is pendant or nonconductive rope controlled by an operator on the floor or independent platform.
Footwalk: A walkway with handrail, attached to the bridge or trolley for accessibility purposes.
Foundation: Free Standing jib cranes require that a special foundation, usually of concrete and steel, be used to support the crane and prevent the crane from tipping over. Foundation recommendations can be found in the price pages and in the installation manual.
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.
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 fixed to a wheel base (as opposed to the floor). This design allows for 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.
Hand Chain: The chain grasped by a person to apply force required for the lifting or lowering motion of the hoist.
Hand Chain Wheel: A wheel with formed pockets on its periphery to allow torque to be transmitted when a force is applied to the hoist hand chain.
Hand Geared: The operation of the bridge, hoist, or trolley of a crane by the manual use of chain and gear without electric power.
Headroom: The distance from where suspension of the track to the palm of the bottom hook.
Height Under Boom (HUB): The distance from the floor to the underside of a jib crane’s boom. The minimum height under boom equals the height of the load, plus the maximum distance the load is to be lifted, plus the headroom required for the hoist, trolley, and attachments.
Hoist Chain – The load bearing chain in a hoist.
Hoist: A machinery unity that is used for lifting and lowering a load.
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 wire 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 aka Come- Along Hoist: 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.
Hoist Motion: The motion of a crane which raises and lowers a load.
Holding Brake: A brake that automatically prevents movement when there is no power.
Hook: The attachment portion of the hoist or lifter where the load is attached directly or through a below the hook device or sling.
Hook Approach: The minimum horizontal distance between the center of the runway rail and the hook.
Hook Height: See Lift Height.
Hook Latch: Non-load bearing device attached near the throat of the hook to restrain the sling or load from becoming accidently separated.
Hot Metal Handling Crane: An overhead crane used for transporting or pouring molten material.
Hydraulic Brake: A brake that provides retarding or stopping motion by hydraulic means.
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.
Idler Sprocket: A freely rotating device that changes the direction of the hoist load chain.
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.
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.
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.
Lift Height: The maximum safe vertical distance that the hook can travel from the floor
Limit Device: A device that is operated by some part or motion of a power driven hoist to limit motion.
Limit Switch: A device designed to disconnect 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: The total superimposed weight on the hoist load block or hook.
Load Block: The assembly of hook or shackle, swivel, bearing, sheaves, sprockets, pins, and frame suspended by the hoisting rope or load chain. This shall include any appurtenances reeved in the hoisting rope or load chain.
Load Carry Part: Any part of the crane in which the induced stress is influenced by the load on the hook.
Load Chain: The load-bearing chain in a hoist.
Load Cycle: One lift cycle with load plus one lift cycle without load.
Load Sprocket: A hoist component that transmits motion to the load chain. This hoist component is sometimes called load wheel, load sheave, pocket wheel, or chain wheel.
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.
Longitudinal Stiffeners: Horizontal members attached to the web of the bridge girder to prevent web buckling.
Magnet: An electromagnetic device carried on a crane hook to pick up loads magnetically
Magnetic Control: A means of controlling direction and speed by using magnetic contactors and relays.
Main Hoist: The hoist mechanism provided for lifting the maximum rated load.
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.
Main Switch: A switch controlling the entire power supply to the crane.
Man Trolley: A trolley having an operator’s cab attached thereto.
Mast: The vertical steel component of a jib crane which supports the crane. Free Standing jib cranes (including Work Station Jibs) have a circular pipe for a mast, Wall Cantilever cranes have standard I-beams, and Mast Type cranes have wide flange beams. Wall Bracket cranes do not have a mast.
Master Switch: A switch which dominates the operation of the contactors, relays or other remotely operated devices.
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.
Mechanical: A method of control by friction
Mill Duty Crane: Service classification covered by AISE Standard No. 6, ‘Specification for Electric Overhead Traveling Cranes for Steel Mill Services’.
- 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.
Non-running Sheave: A hoist 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.
Normal Operating Conditions: Conditions during which a hoist is performing functions within the scope of the original design.
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.
Overhead Crane: A crane with a movable bridge carrying a movable or fixed hoisting mechanism and traveling on an overhead fixed runway structure.
Overload: Any hoist 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
Over-travel Restraint: A device used to prevent the hoists 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.
Pendant or 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.
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.
Power-Operated Crane: A crane whose mechanism is driven by electric, air, hydraulic or internal combustion means.
Power Supply: The electrical service available in the building for which the crane is being designed.
Power Transmission Parts: Hoist machinery components including the gears, shafts, clutches, couplings, 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
Protective Panel: An assembly containing overload and undervoltage protection for all crane motions.
Pulpit-Operated Crane: A crane operated from a fixed operator station not attached to the crane.
Qualified Person: A person who, by possession of a recognized degree in an applicable field or a 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.
Radio Remote Control: The radio control performs exactly like the pendant but operates using a radio frequency.
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.
Rated load: The maximum load a crane is designed to handle.
Reeving: A system in which a rope or chain travels around drums, sheaves or sprockets.
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 operated by Radio Remote Controls.
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.
Roller Chain: A series of alternately assembled roller links and pin links in which the pins articulate inside the bushings and the rollers are free to turn on the bushings. Pins and bushings are press fit in their respective link plates.
Rope: A wire rope, unless otherwise specified.
Rotating Axle: An axle which rotates with a wheel.
Running Sheave: A hoist sheave that rotates as the load block is lifted or lowered.
Runway: The rails beams, brackets, and columns on which a crane operates.
Runway Conductors: The main conductors mounted on or parallel to the runway which provide electrical current to the crane.
Runway Rail: The rail supported by the runway beams on which the bridge travels.
Semi-Gantry Crane: A gantry crane 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 a truck running on an elevated rail or runway.
Side Pull: The component of the hoist pull acting horizontally when the hoist lines are not operated vertically.
Side Pull: The angle by which the load block is being operated outside of the vertical lifting place.
Sheave: A grooved wheel or pulley used with a rope or chain to change direction and point of application of a pulling force.
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: See Crane Span
Span (Jib Crane): For a jib crane, span is the distance from the center of the pivot point to the end of the boom. Note that “span” is greater than actual “working span” or “hook coverage.”
Spark Resistant: Equipment designed in accordance with existing codes and standards such that it will operate in an environment with no hazardous gas present.
Standby Crane: A crane which is not in regular service, but is used occasionally or intermittently as required.
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.
Stop: A device to limit travel of a trolley or crane bridge. This device is normally attached to a fixed structure and does not have energy absorbing ability.
Storage Bridge Crane: A gantry type crane of long span used for bulk storage of material; the bridge girders or trusses are rigidly or non-rigidly supported on one of more legs. It may have one or more fixed or hinged cantilever ends.
Strength, Average Ultimate: The average tensile force per unite of cross sectional are required to rupture the material as determined by test.
Support Column: A separate column which supports the runway beam of a top running crane.
Supporting Structure (Jib Crane): For a free standing jib crane the supporting structure is the foundation which the crane is bolted to or implanted in. For a wall bracket or wall cantilever jib crane, the supporting structure is the wall or column to which the crane is bolted. Mast type jib cranes have a supporting structure at both the ceiling and the floor.
Suspension system: The system (rigid or flexible) used to suspend the runway beams of under hung or monorail cranes from the rafter of the building frames.
Switch: A device for making, breaking, or changing the connections in an electric or pneumatic circuit (valve).
Tieback or Runway Tieback: A mechanical connection from the runway girder to the column to provide structural connection and support of the top of the girder.
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.
Torsion Box Girder: Girder in which the trolley rail is located over one web.
Torsional Forces: Forces which can cause twisting of a member.
Thrust and Pull: Forces exerted by a jib crane on its supporting structure. Thrust is the pushing (or compressive) force exerted on the structure, while Pull is the tensile force. Thrust and Pull are thus equal (but opposite in direction) to each other. The maximum thrust and pull occurs when the crane is loaded at full capacity.
Trolley: The mechanism that carries the hoist across the bay along the bridge girder(s) navigating the span.
Manual Trolley or Push Trolley: 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 Electric Trolley: A machinery unit that runs along the top or the underside of a bridge beam by an electric motor.
Motor Driven Air Trolley: A machinery unit that runs along the top or the underside of a bridge beam by an air motor.
Trolley Frame: The basic structure of the trolley on which are mounted the hoisting and traversing mechanisms.
Trolley Hoist: The unit consisting of both the hoist and the trolley frame.
Trolley Travel: The trolley movement perpendicular to the crane runway
Truck [Endtruck]: The unit consisting of a frame, wheels, bearings, and axles which supports the bridge, girders or trolleys.
Top Running: The crane bridge travels on top of rails mounted on a runway beam supported by either the building columns or columns specifically engineered for the crane.
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.
Under Running: The crane bridge travels on the bottom flange of the runway beam which is usually supported by the roof structure.
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: 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.
Variable Frequency Drive (VFD): A device used in conjunction with a pendant to vary the frequency of the motors controlling the motions allowing for smooth acceleration and deceleration.
Wall Crane: A crane having a jib with or without trolley and supported from a side wall or line of columns of a building. It is a traveling type and operates on a runway attached to the side wall or columns
Welded Link Chain: A hoist chain consisting of a series of interwoven links formed and welded.
Wheel Base: The distance from center to center of the outermost wheels.
Wheel Load: The load without impact on any wheel with the trolley and lifted load (rated capacity)
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. positioned on the bridge to give maximum loading.
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.
Wire Rope Hoist: A very durable hoist that will provide long term, reliable usage.
Working Span: The working span (or hook coverage) of a jib crane is less than the span of the crane. It is a function of the maximum hook reach and the ability to get the trolley close to the mast. Working span = (distance between trolley stops): (hoist trolley length)
Voltage Drop: The loss of voltage in an electric conductor between supply tap and load tap.