Introduction to Machine Rigging 111

abrasion

The scraping or rubbing away of material from an object's surface. Abrasion will eventually cause a rope to fail.

alloy steel

A steel that contains intentionally added materials that improve certain properties of the metal. Alloy steel is used to make chains because of its strength and durability.

American National Standards Institute

ANSI. A private, non-profit organization that administers and coordinates voluntary standards and systems for products, services, and systems in the United States. The American National Standards Institute establishes safety codes for overhead and gantry cranes.

axle

A shaft around which a wheel or gear rotates. The axle in a pulley block may have several sheaves around it.

block

A pulley that consists of one or multiple sheaves encased in a shell with an attachment device to connect it to a load, a stationary object, or another attachment device. Blocks are linked by lines to form block and tackle systems.

block and tackle

A pulley system consisting of at least one movable block and at least one fixed block. Block and tackle systems can be simple, one-line systems or complex, multiple-line systems.

boom

An arm-like structure on a crane or derrick that can swivel or pivot around a fixed location. A boom provides horizontal movement, while a hoist attached to it provides vertical movement.

breaking strength

The amount of stress that will break a rope or chain. The breaking strength of a rope or chain is usually three to four times higher than its working load limit.

breech

The side opening on the shell of a pulley block. The breech allows the line to access the sheave.

bridge

The railed, beam-like part of a crane that carries the trolley. The bridge may be permanently attached to the ceiling or walls of a workplace or be supported by legs.

carbon steel

A common metal that is an alloy of iron and carbon. The amount of carbon in a carbon steel affects its strength, ductility, and malleability.

center of gravity

The point on an object at which all the weight is distributed evenly. The center of gravity is positioned beneath the lifting mechanism to ensure the load stays balanced while in motion.

chain slings

A sling that consists of interconnected metal links. Chain slings are durable and used for lifting heavy loads.

chains

A series of interlocking metal rings. Chains are used to connect loads to rigging equipment.

charring

The darkening of a component that is caused by burning or scorching. Charring decreases a rope's working load limit.

choke

A loop of rope that becomes tighter under tension. Chokes can be created with choker hitches or by looping rope through a shackle.

clevis hook

A hook with a removable pin or bolt at its base. Clevis hooks can be detached from lifting devices by removing the pin or bolt.

compound block and tackle

A block and tackle system with at least one fixed block, two or more movable blocks, and two or more lines. The more lines a compound block and tackle has, the greater the mechanical advantage.

corrosion

A process by which a material gradually degrades or wears away. Corrosion typically occurs when a material is exposed to atmosphere, moisture, or other substances.

cotton

A soft material that comes from the cotton plant. Cotton has the lowest strength of fibers used for rope, but it offers great flexibility.

cranes

A large industrial machine with a hoisting mechanism for lifting and moving extremely heavy loads. Cranes provide both vertical and horizontal movement.

cubic foot

ft.³. A unit of volume measurement in the English system. One cubic foot is equal to 1,728 cubic inches and 0.028 cubic meters.

cylinder

A part of a hydraulic jack that has a cavity in which fluid becomes pressurized when the pump plunger is used. Cylinders contain a narrower column, called a ram, that is forced upward out of the top of the column.

derrick

A three-legged crane with a vertical mast. Derricks may include a boom to provide additional movement.

drum

A large, cylindrical device used to wind and unwind ropes and chains. Drums are used in hoists to raise and lower loads.

elongation

The stretching of a link in a chain. Elongation occurs just before a chain fails.

eyebolt

A bolt with a forged hole or loop at one end. Eyebolts come in two varieties: standard and shoulder.

eyehook

A hook with a circular opening at its base. Eyehooks attach permanently to lifting devices at the opening.

fail

To break, malfunction, or be unable to operate correctly. Damage and wear are the first signs that a component will fail.

fiber rope

Rope made from strands of natural or synthetic materials. Fiber rope is flexible and used for lighter loads.

fiber rope slings

A sling made of natural or synthetic fiber rope. Fiber rope slings are very flexible but not as strong as other types of slings.

fibers

A thin length of a flexible material. Fibers are twisted together to make strands for fiber rope.

fittings

A piece of hardware used to reinforce and secure ropes. Fittings must be checked for pitting, corrosion, cracks, and breaks.

fixed block

A pulley block that is connected to a stationary point. Fixed blocks, or fixed pulleys, are paired with movable blocks in block and tackle systems.

fixed pulley

A pulley block that is connected to a stationary point. Fixed pulleys, or fixed blocks, are paired with movable pulleys in block and tackle systems.

flange

A raised section around a cylindrical component such as the shank of a fastener. The flange on a shoulder eyebolt prevents the bolt from moving from side to side when side forces impact the load.

gantry crane

A crane with a trolley that runs along a bridge supported by two or more legs that rest on the floor of the workplace. Gantry cranes are typically portable.

grade designation

A standardized classification that indicates a chain's strength. A higher grade designation indicates a stronger chain.

hard hat

A lightweight, protective head covering used to protect the head from impacts, bumps, and electric shock. Hard hats have a shock-absorbing lining with a headband and straps that suspend the shell away from the skull.

hemp

A coarse material that comes from hemp plants. Hemp was one of the first materials used to make rope for rigging.

hoist

A motor-powered device that raises or lowers a load as a line winds or unwinds around a drum. A hoist may be part of a crane or used alone.

hook

A curved device designed to fit into a hole or loop. Hooks are usually used with chains, hoists, and slings.

hydraulic jack

A jack that uses a pump plunger to create pressure in a fluid cylinder to raise the top surface. Hydraulic jacks use pressure to hold a load in place but leak pressure over time.

International Organization for Standardization

ISO. A non-governmental organization based in Switzerland that develops and establishes standards, rules, and guidelines designed to ensure that products, processes, and services are fit for their purposes. The International Organization for Standardization publishes standards for a broad range of industries.

jack

A device that is placed under a load and expanded to lift large or heavy objects. Jacks come in three basic varieties: ratchet jacks, screw jacks, and hydraulic jacks.

jib hoist

A hoist mounted to a movable arm. A jib hoist may be mounted to the arm of a derrick or to the arm of a post secured to the floor.

lay

The direction in which strands of rope are twisted. The lay is one factor that determines the strength and flexibility of a rope.

line

A rope, chain, or wire that is used to attach loads to lifting devices. Lines may pass through the sheave of a pulley or wrap around the drum of a hoist.

loads

The object that a lifting device must move. Loads must not weigh more than the working load limit of the equipment.

mast

The upright structure of a derrick. The mast is responsible for lifting and bearing the weight of the load.

mechanical advantage

The difference between the applied force and the work accomplished. Mechanical advantage allows loads to be lifted with less effort.

millwright

A person who specializes in rigging. Millwrights oversee the rigging and moving of loads as well as the installation and leveling of equipment.

movable block

A pulley block that moves as a load is moved. Movable blocks, or movable pulleys, are paired with fixed blocks in block and tackle systems.

movable pulley

A pulley block that moves as a load is moved. Movable pulleys, or movable blocks, are paired with fixed pulleys in block and tackle systems.

natural

Occurring in nature and not human-made. Natural fibers used in rope include hemp, sisal, coir, and cotton.

nylon

A synthetic polymer material that is strong, flexible, and resilient. Nylon is used to make synthetic fiber rope.

Occupational Safety and Health Administration

OSHA. A government agency dedicated to reducing injuries, illnesses, and deaths in the workplace. The Occupational Safety and Health Administration sets standards to maintain accident-free workplaces.

overhead crane

A crane with a trolley that runs along a bridge mounted to the ceiling or walls of the workplace. Overhead cranes are permanent structures.

overhead hoists

A hoist that is mounted above a load, either to a fixed point on the ceiling or to a trolley on an overhead or gantry crane. Overhead hoists move loads over longer vertical distances than jib hoists.

pawl

A device that hinges or pivots to fit into the notches of a ratchet wheel, gear, or toothed shaft. A pawl inside a ratchet jack holds the jack in place.

personal protective equipment

PPE. Any article of clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment may include safety glasses, gloves, ear plugs, respirators, or steel-toed boots.

pin

A thin, cylindrical, non-threaded fastener used to secure the position of two or more parts. Pins are inserted through holes to close the end of a shackle or clevis hook.

pitting

Corrosion in the form of small holes on the surface of metal components. Pitting on metal chains, slings, wire ropes, and metal end fittings reduces their working load limits.

polyester

A synthetic polymer material that is light, strong, and resistant to deterioration. Polyester is used to make synthetic fiber rope.

polypropylene

A synthetic polymer that is lightweight, tough, and resistant to fatigue. Polypropylene is used to make synthetic fiber web slings.

pulleys

A simple machine consisting of a wheel and a rope that is used to raise and lower loads or transmit motion. Pulleys may be movable or fixed.

pump plunger

A part of a hydraulic jack that forces fluid into the cylinder, causing the surface of the jack to raise. Some hydraulic jacks use lever-operated pump plungers, while others use automatic pump plungers.

ratchet jack

A jack with a pawl and a toothed shaft that catches on the pawl to raise or lower the top surface. Ratchet jacks should generally not be used for rigging jobs.

restraints

A device that attaches to a load to prevent unwanted movement. Restraints are used to safely secure loads that are being moved.

rigging

The process of lifting and moving loads with ropes, chains, and mechanical devices. A person who specializes in rigging is called a millwright.

ropes

A length of twisted fiber or wire strands. Ropes are used to connect loads to rigging equipment.

safety shoes

Footwear that protects the feet from impact and heat. Safety shoes may have reinforced toe areas.

screw jack

A jack with a handle that rotates a threaded shaft to raise or lower the top surface. Screw jacks use friction to hold a load in place.

shackle

A U-shaped piece of metal that is closed at the end with a pin or bolt. Shackles often use clevis and cotter pin assemblies.

shank

The cylindrical length of a fastener that extends from the underside of the head to the point. The shank includes the threaded and unthreaded parts of the fastener.

sheave

The wheel of a pulley. The sheave usually features a groove to hold a rope or chain.

shell

The outer covering of a pulley block that surrounds the sheave or sheaves. The shell has breeches on either side.

shoulder eyebolt

An eyebolt that has a flange at the base of the loop. Shoulder eyebolts are used when side forces would impact the load.

simple block and tackle

A block and tackle system with one fixed block, one movable block, and a single line. Simple block and tackle systems provide a 2:1 mechanical advantage.

slings

A length of material used to connect a load to a lifting device. Slings can be made of rope, chain, metal mesh, or webbing.

standard eyebolt

An eyebolt with a shank that leads directly to the loop. The standard eyebolt is used only for vertical lifting.

strands

A length of material made by twisting fibers or wires together. Strands are twisted together to make rope.

swivel hook

A hook with a rotating joint at its base. Swivel hooks attach permanently to lifting devices and may be rotated to make it easier to attach them to loads.

synthetic

Artificial or human-made. Synthetic fibers used in rope include nylon, polyester, polyethylene, and polypropylene.

synthetic fiber web slings

A sling that consists of webbing made from synthetic materials such as nylon, polyester, and polypropylene. Synthetic fiber web slings are suitable for lifting fragile loads.

tag lines

A line that attaches to a load being lifted by a crane to allow personnel on the ground to guide the load. Tag lines should never be wrapped around hands, as this can cause a serious safety hazard.

tensile stress

A force that attempts to pull apart or stretch a material. In rigging, tensile stress comes from the weight of the load.

threads

A long, spiraling ridge around the outside of a cylindrical shaft. Threads allow eyebolts to securely fasten to a load.

trolley

The part of an overhead or gantry crane that travels across the bridge to provide horizontal movement. A hoist attached to the trolley provides vertical movement.

volume

The total space that an object takes up. Volume is found by multiplying the height, length, and width of the object.

wear

The erosion of material as a result of friction. Wear is typically caused by two or more objects rubbing or sliding against each other.

wire mesh slings

A sling made of metal wire mesh. Wire mesh slings are useful for loads that would damage rope slings.

wire rope

Rope made from strands of steel or iron. Wire rope is used for jobs that require extremely strong, abrasion-resistant rope.

wire rope slings

A sling made of wire rope. Wire rope slings are very strong but not as flexible as fiber rope slings.

wires

A thin, elongated piece of metal. Wires are twisted together to make strands for wire rope.

working load limit

The maximum weight a rope or chain can safely lift. The working load limit of a rope depends on its material, elasticity, and number of strands.