Jib cranes can have varying boom styles, including some that articulate or pivot. Jib cranes may also mount to walls, ceilings or floors, or may be portable.
The Working Load Limits (WLL) listed in
the tables below are the maximum weights which slings are designed to
sustain in general lifting service, according to the standard uniform load
method of rating. In exceptionally hazardous conditions, or in any other
circumstances which might indicate a need for a WLL lower than the designed
figure, the degree of hazard should be assessed by a competent person and
the working load limit adjusted accordingly.
Safety factor 4:1. Working load limits are based upon equally loaded and disposed sling legs.
Tonnes, Grade 8
|Factor of safety
(FoS), also known as safety factor (SF), is a term
describing the structural capacity of a system beyond the expected loads or
actual loads. Essentially, how much stronger the system is than it usually
needs to be for an intended load. Safety factors are often calculated using
detailed analysis because comprehensive testing is impractical on many
projects, such as bridges and buildings, but the structure's ability to
carry load must be determined to a reasonable accuracy.
Many systems are purposefully built much stronger than needed
for normal usage to allow for emergency situations, unexpected loads,
misuse, or degradation.
Ultimate load, strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit loads multiplied by prescribed factors of safety). With respect to aircraft structure and design, ultimate load is the amount of load applied to a component beyond which the component will fail.
A chain is a series of connected links which are typically made of metal. A chain may consist of two or more links.
Chains are usually made in one of two styles, according to their intended use:
Wire rope is a type of rope which consists of several strands of metal wire laid (or 'twisted') into a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes.
Historically wire rope evolved from steel chains which had a record of mechanical failure. While flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel cable are less critical as the other wires easily take up the load. Friction between the individual wires and strands, as a consequence of their twist, further compensates for any flaws.
The basic hoist has two important characteristics to define it: Lifting medium and power type. The lifting medium is either wire rope, wrapped around a drum, or load-chain, raised by a pulley with a special profile to engage the chain. The power can be provided by different means. Common means are hydraulics, electrical and air driven motors. Both the wire rope hoist and chain hoist have been in common use since the 1800s. however; Mass production of an electric hoist did not start until the early 1900's and was first adapted by Germany. A hoist can be built as one integral-package unit, designed for cost-effective purchasing and moderate use, or it can be built as a built-up custom unit, designed for durability and performance. The built-up hoist will be much more expensive, but will also be easier to repair and more durable. Package units where once regarded as being designed for light to moderate usage, but since the 60's this has changed. Built-up units are designed for heavy to severe service, but over the years that market has decreased in size since the advent of the more durable packaged hoist. A machine shop or fabricating shop will use an integral-package hoist, while a Steel Mill or NASA would use a built-up unit to meet durability, performance, and repairability requirements.
|A hoist is a suspended machinery unit that is used for lifting or lowering a freely suspended (unguided) load. It may be manually operated, electrically operated or pneumatically driven and may use chain or wire rope as its lifting medium.|
|An electric hoist is a suspended (overhead) hoist that is powered by electrically driven motors and is used to lift or lower a freely suspended (unguided) load. It generally uses chain or wire rope as its lifting medium|
A manual hoist is a suspended machinery unit that, by use of manual operation, is used for the lifting and lowering of a freely suspended (unguided) load. A manual hoist generally uses chain (roller or link) as its lifting medium.
Manual hoists have a wide range of lifting
capacities and can be used either for vertical lifting and
lowering or for horizontal pulling.
|Generally, a chain hoist is any hoist
which utilizes link or roller chain as its lifting medium. Chain hoists can
be manually operated (hand or lever), pneumatically driven or electrically
A lever hoist is a manual device used to lift, lower, or pull a load and to apply or release tension. It utilizes a ratchet and pawl mechanical configuration to incrementally raise or lower a load or to apply or release tension.
Lever hoists and pullers have the advantage of being easy to transport, require minimum set-up, and are a practical option in confined spaces. They are suitable for different applications ranging from heavy-duty construction work to day-to-day maintenance and repair jobs.
|A ratchet lever hoist or "ratchet
hoist" is a lever operated manual device used to lift, lower, or pull a load
and to apply or release tension. It utilizes a ratchet and pawl mechanical
configuration to incrementally raise or lower a load or to apply or release
The ratchet lever hoist is a versatile tool used in a wide variety of applications, both in industry and in the private sector. Its versatility allows it to be used in confined spaces, and also allows for heavy loads to be maneuvered and positioned safely and efficiently。
A trolley hoist is a hoist suspended from a trolley. A hoist can be connected to a trolley by hook or clevis, or a hoist can be integral with the trolley.
Trolley Hoists are available with varying spans and capacities. Trolley Hoists feature adjustable I-beams and heights for optimal use. Trolley Hoists are weather and moisture proof. Trolley Hoists need only one operator and are capable of heavy-duty lifting.
A trolley is a wheeled carriage, cage or basket that is suspended from and travels on an overhead track.
|A monorail is a single run of overhead track on which carriers (trolleys) travel|
|A single girder crane is an overhead travelling crane that utilizes a single bridge beam attached to the two runway/end trucks. This bridge beam or single girder supports a lifting mechanism or hoist that "runs" on the bottom flange of the bridge beam.|
|A double girder crane is an overhead traveling bridge crane that utilizes two bridge beams set atop the runway (end) trucks. Generally this type of crane utilizes a top running trolley hoist, which moves along the top of the two bridge beams on its own set of trucks/trolley wheels. The hook from the hoist "falls" between the two bridge beams. Headroom under the crane is increased by utilizing this hoist/crane configuration|
An overhead crane is a crane with a single or multiple girder (bridge girder) bridge carrying a movable or fixed hoisting mechanism and traveling on an overhead fixed runway structure.
An overhead crane, also known as a bridge crane, is a type of crane where the hook-and-line mechanism runs along a horizontal beam that itself runs along two widely separated rails. Often it is in a long factory building and runs along rails along the building's two long walls. It is similar to a gantry crane. Overhead cranes typically consist of a hoist to lift the items, the bridge, which spans the area covered by the crane, and a trolley to move along the bridge.
A crane (also known as a bridge crane
or overhead crane) is a type of machine used for lifting,
generally equipped with a hoist) (also called a wire rope drum),
wire ropes or chains and sheaves, that can be used both to lift
and lower materials and to move them horizontally. It uses one
or more simple machines like a hoist to create mechanical
advantage and thus move loads beyond the normal capability of a
human. Cranes are commonly employed in the transport industry
for the loading and unloading of freight, in the construction
industry for the movement of materials and in the manufacturing
industry for the assembling of heavy equipment.
The first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilised where the provision of power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use. Sometimes sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. For a while, mini - cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.
This article also covers lifting machines that
do not strictly fit the above definition of a crane, but are
generally known as cranes, such as stacker cranes and loader
|A top running crane is an electric overhead traveling crane having the end trucks supported on rails attached to the top of the crane runways|
|An overhead traveling crane is a crane with a single or multiple girder (bridge girder) bridge carrying a movable or fixed hoisting mechanism and traveling on an overhead fixed runway structure|
|A runway is an assembly of rails, beams, girders, brackets and framework on which a crane or trolley travels|
|An I-beam crane is an overhead traveling bridge crane that utilizes standard I-beams (S beams) as the bridge girder and at times, also utilizes I-beams as the runway beams. Cranes that utilize H-beams (structural beams) as girders and runways are sometimes referred to as I-beam cranes as opposed to patented track cranes|
|A box girder crane is an overhead travelling crane that utilizes a "box" configuration in fabricating the bridge girder. This box girder design incorporates a four-sided box with a running surface plate for the hoist trolley attached to the bottom of the box. The advantage of the box girder is that it possesses greater loading capabilities and is able to span greater bridge distances. The crane is generally utilized in pairs with the hoisting mechanism operating on rails attached to the top of each box girder|
A jib crane is a stationary or fixed crane that utilizes a cantilevered bridge (girder) supported from a stationary vertical support. A jib crane consists of a hoist attached to a rotating arm that functions as a manipulator. The arm can rotate 360 degrees and is mounted on a wall or attached to a floor-mounted support.
Jib cranes can have varying boom styles, including some that articulate or pivot. Jib cranes may also mount to walls, ceilings or floors, or may be portable.
|The bottom block is the device at the bottom of a hoist's lifting medium (chain/wire rope) through which the medium is reeved and supports the hook and/or an attachment. It may be stationary or rotating depending upon the requirements for the piece of lifting equipment|
|Material handling is the movement, storage, control and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption and disposal. The focus is on the methods, mechanical equipment, systems and related controls used to achieve these functions. See also, supply chain, supply chain management, logistics and third party logistics. Note that all of referenced terms are highly interrelated and their definitions are frequently intermingled.|
Abnormal Operating Conditions - Environmental conditions that are unfavorable, harmful, or detrimental to or for the operation of a hoist, such as excessively high or low ambient temperatures, exposure to weather, corrosive fumes, dust laden or moisture laden atmospheres, and hazardous locations.
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)
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.
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 weight in tons the crane will be required to lift.
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.
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.
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.
Counter-Torque – A method of control by which the power to the motor is reversed to develop torque in 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.
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.
Designated Person - A person selected or assigned by the employer or the employer's representative as being competent to perform specific duties.
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.
Drum – The cylindrical member around which the ropes are wound for raising or lowering the load.
Dynamic – a method of controlling crane motor speeds when in the overhauling condition to provide a retarding force.
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.
Enclosures - The enclosures house all of the electrical components on the crane.
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 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 – A device which compensates for unequal length or stretch or a rope.
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.
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 Cranes - An overhead crane where the bridge girder(s) are connected to “legs” on either side of the span. These “legs” eliminate the supporting runway and column system and connect to end trucks which run on a rail either embedded in, or laid on top of, the floor.
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.
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 - A mechanical unit that is used for lifting and lowering a load via a hook or lifting attachment.
Hoist Chain – The load bearing chain in a hoist.
NOTE: Chain properties do not conform to those shown in ANSI B30.9-1971, Safety code for slings
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 Height -See Lift Height.
Hot Metal Handling Crane – An overhead crane used for transporting or pouring molten material.
Idler Sprocket - A freely rotating device that changes the direction of the hoist load chain.
Jib Crane - A crane consisting of a boom which is supported as a cantilever on a column.
Lift Height - The maximum safe vertical distance that the hook can travel from the floor
Lifting Devices - See Below-the-hook Lifting Devices
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.
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 Chain - The load-bearing chain in a hoist.
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.
Magnet – An electromagnetic device carried on a crane hook to pick up loads magnetically
Main Hoist – The hoist mechanism provided for lifting the maximum rated load.
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.
Mechanical – A method of control by friction
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.
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.
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 - The pendant gives the operator precise control over the motions of the crane.
Pendant Station - Controls suspended from the hoist for operating the unit from the floor.
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
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.
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.
Remote Operated Crane - A crane operated by Radio Remote Controls.
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.
Single Girder - An overhead crane consisting of two end trucks, a single bridge girder and the trolley hoist unit. The trolley runs on the bottom flange of the bridge girder.
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.”
Standby Crane – A crane which is not in regular service, but is used occasionally or intermittently as required.
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.
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).
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.
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.
Under Running - The crane bridge travels on the bottom flange of the runway beam which is usually supported by the roof structure.
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) positioned on the bridge to give maximum loading.
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)
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