We are pleased to provide you with a variety of crane resources which will allow you to get a good understanding of crane systems. You will find key information such as: terms, diagrams and industry websites, to ensure you are making the right choices when purchasing a crane or seeking crane services.

Crane Classifications:

There are six types of crane classifications covered under CMAA Specification No. 70, each dependent on duty cycle. They are generally by CMAA are as follows:


Class A (Standby or Infrequent Service)

  • This service class covers cranes where precise handling of equipment at slow speeds with long idle periods between lifts are required.
  • Capacity loads may be handled for initial installation of equipment and for infrequent maintenance.
  • Typical examples include cranes used in powerhouses, public utilities, turbine rooms, motor rooms and transformer stations.

Class B (Light Service)

  • This service class covers cranes where service requirements are light and the speed is slow.
  • Loads may vary from no load to occasional full-rated loads with 2 to 5 lifts per hour, averaging 10 feet per lift.
  • Typical examples include cranes in repair shops, light assembly operations, service buildings, light warehousing, etc.

Class C (Moderate Service)

  • This service covers cranes where service requirements are deemed moderate and to handle loads that average 50 percent of the rated capacity with 5 to 10 lifts per hour, averaging 15 feet, with not over 50 percent of the lifts at rated capacity.
  • Typical examples are cranes used in machine shops, paper mill machine rooms, etc.

Class D (Heavy Service)

  • In this type of service, loads approaching 50 percent of the rated capacity will be handled constantly during the work period.
  • High speeds are desirable for this type of service with 10 to 20 lifts per hour averaging 15 feet, with not over 65 percent of the lifts at rated capacity.
  • Typical examples include cranes used in heavy machine shops, foundries, fabricating plants, steel warehouses, container yards, lumber mills, and standard duty bucket and magnet operations where heavy duty production is required.

Class E (Severe Service)

  • This type of service requires a crane capable of handling loads approaching the rated capacity throughout its life with 20 or more lifts per hour at or near the rated capacity.
  • Typical examples are magnet, bucket, magnet/bucket combination cranes for scrap yards, cement mills, lumber mills, fertilizer plants, container handling, etc.

Class F (Continuous Severe Service)

  • In this type of service, the crane must be capable of handling loads approaching rated capacity continuously under severe service conditions throughout its life.
  • Typical examples are custom designed specialty cranes essential to performing the critical work tasks affecting the total production facility, providing the highest reliability with special attention to ease of maintenance features.

    Useful Websites:

AIST: Association for Iron & Steel Technology -
ANSI: American National Standards Institute -
ASME: The American Society of Mechanical Engineers -
ASTM: American Society for Testing & Materials -
AWS: American Welding Society -
CMAA: Crane Manufacturers Association of America -
HMI: Hoist Manufacturers Institute -
MBMA: Metal Building Manufacturer's Association -
OSHA: Occupation Safety and Health Administration -

 Crane and Hoist terms and definitions:

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.

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 hoist 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]- 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, stretch or a rope.

Exposed- Capable of 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 the 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)- The 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 pressed to 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 an 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 or 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 by controlling the motions which allows for smooth acceleration and deceleration.

Wall Crane- A crane that has a jib with or without a trolley and is 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).