BASIC RIGGINGBASIC RIGGING

MSHA REGULATIONSMSHA REGULATIONS

• 56/57.16007 Taglines, Hitches, and Slings (a) Taglines shall be attached to loads that may

require steadying or guidance while suspended.

(b) Hitches and slings used to hoist materials shall be suitable for the particular material handled.

• 56/57.16009 Suspended Loads Persons shall stay clear of suspended loads.

TOOLS OF RIGGINGTOOLS OF RIGGING

• Hoists

• Cranes

• Slings• Special

lifting devices

HOISTS AND CRANESHOISTS AND CRANES

• Different types of hoisting equipment– Manual and

powered devices– underhung and top

running cranes– monorails– various types of jig

cranes

SLINGS SLINGS • Main purpose is to suspend a load from a

hoist• Commonly made of wire rope or welded

link chain• Can be constructed from fiber

rope,synthetic webbing or metal mesh• Most slings are assembled by sling

manufacturers• Can be assembled at the job site

The rigging systemThe rigging system• Load• Sling• Hoisting equipment• Rigger (Designer and

Operator of the system)

• = Single, complex rigging system

The RiggerThe Rigger

• Must apply intelligence, common sense and experience

• Anticipate what will happen when the load is moved

• Thought process must take place before the work is started

• Must answer the following questions…..

Questions that must be Questions that must be answered by riggeranswered by rigger

• What is to be done with the load?

• What tools are needed?

• Do the tools have the capacity to handle the loads and forces involved?

Questions that must be Questions that must be answered by riggeranswered by rigger

• How can the hookup be made?

• What will happen when the load is first moved?

• What will be the travel path of the load to reach the desired location?

Questions that must be Questions that must be answered by riggeranswered by rigger

• How will the load be set down at the desired location?

• What other factors are involved (weather, electrical wires, sloping grades, visibility)?

• Are additional personnel needed to control the load safely during the process?

Planning a rigging systemPlanning a rigging system

• Determine the weight of the load• Locating the center of gravity of a load• Distinguishing the force components

(horizontal and vertical) at work in a diagonal force(loads at some angles other than 90 degrees to the horizontal)

• Limitations of each component of the rigging system

Determining the weight of Determining the weight of the loadthe load

• Shipping paper• Manufacturers information attached

to the load• Catalogs or blueprints• Tables of weights from

manufacturers or handbooks• Make sure the weight has not

changed

Volume & Area FormulasVolume & Area Formulas

Calculating an allowable Calculating an allowable loadload

• Determine the breaking strength of the rope– Load which will cause the rope to break– Refer to standard tables in rigging

handbooks– Listed according to the diameter and

kind of rope– Design or safety factor usually 5

Calculating an allowable Calculating an allowable loadload

• Find the load limit by dividing the breaking strength of the rope by the design factor

• Example-– If the table indicates that the breaking

strength of the rope you are using is 27,000 pounds. Dividing this figure by the design factor of 5 gives you a 5400 pound maximum allowable load.

Determine the center of Determine the center of gravitygravity

• The point at which the load will balance• Whole weight of the load is considered

concentrated at this balance point• When suspended from a point, the load

tends to move so that the center of gravity is directly below the point of support.

• Make sure the center of gravity is located directly below the hoisting hook

Determine the center of Determine the center of gravitygravity

• Stable load–Balanced about its center of

gravity–Directly below the hoisting hook

• Unstable load– has a tendency to tip or topple–Creates a hazard to personnel and

equipment

Before Lifting any load Before Lifting any load check for hazardscheck for hazards

• If not directly below the hook the load is unstable

• If the sling is free to slide across the hook the center of gravity will shift directly below the hook

• If two slings are used one will assume the greater share of the load

Before Lifting any load Before Lifting any load check for hazardscheck for hazards

• The sling must not be attached to the load at a point lower than the loads center of gravity– Exception to this

rule when lifting loads on pallets or skids

– Then apex of sling must be above the center of gravity

Determining the center of Determining the center of gravitygravity

• Marked on the load by manufacturer

• Located in catalogs or blueprints

• Some objects have lifting lugs

• Calculate or estimate it

–Make an educated guess and correct through trial and error before making the lift

Procedures to determine Procedures to determine center of gravitycenter of gravity

• Connect slings and hoist based on estimate of object’s center of gravity

• Take up slack in slings or hoist• Lift the load just enough to check stability• If stable, continue to lift• If unstable, lower load and adjust the rigging– Lift point should be moved closer to end

that dips• Repeat until load is stable

Horizontal ForceHorizontal Force

• Very often sling legs are attached at an angle less than 900

• Then a horizontal force is added to the vertical force

• Resulting Combined force is greater than the weight of the load

• Horizontal force increases as the angle becomes smaller

Horizontal ForceHorizontal Force

• When a sling angle is 300 the total force is twice that of the load

• Sling Angles of 450 are not recommended

Horizontal ForceHorizontal Force• Horizontal forces act

on the load causing damage by compression or buckling

• Horizontal forces are absorbed by using a spreader beam making the sling legs between beam and load vertical

Sling ComponentsSling Components

• Hooks• Coupling Links• Fittings• Sling Legs• Can be assembled at the job site but must

use recommended components and assembly procedures– May also require some sort of weight test

Hook HazardsHook Hazards• Attachments should never be field welded to a

hook• Heat should not be applied in an attempt to

reshape a hook– Can reduce strength of hook– Could result in hook failure at loads lower than the

rated load

• If handles or attachments are required they should be obtained from the hook manufacturer

Purpose of a latch?Purpose of a latch?• Purpose is to retain slings in the hook– Not intended to support the load– Should be sturdy enough to retain the sling

if the moving load should catch on something

• Latches are used to close the throat opening• Must be provided on hoist and crane hooks

Reasons For Removing a Reasons For Removing a Hook From Service Hook From Service

• Hook throat has increased by more than 15%

• Wear exceeds 10% of the original hook section dimension, or there is a bend or twist of more than 10% from the plane of the unbent hook

• Hook shows cracks, excessive nicks, or gouges

Factors Affecting Wire-Rope Factors Affecting Wire-Rope StrengthStrength

• Three major signs of loss of strength– Flat spots worn on outer wires– Broken wires– reduction of rope diameter

• Other factors that can reduce strength– Bending the rope over a curved surface– Temperature– Corrosion and environment– Rope fittings or terminations

Bending The Rope Over A Bending The Rope Over A Curved SurfaceCurved Surface

• Normal curved surfaces that ropes are curved over include sheaves, pins and other curved surfaces

• The rope is subjected to bending stress• Reduces rope efficiency/nominal strength

by a certain percentage• Efficiency depends upon the:– D = Diameter of curved surface– d = Nominal diameter of rope

Example (You will need to refer Example (You will need to refer to Fig. 2-5 and Table 2-1)to Fig. 2-5 and Table 2-1)

• Fiber-core 6 x 37 wire rope, 1” in diameter (d)

• Sheave with a 30” diameter (D)

• D/d ratio is 30/1• Efficiency is 95%• Load Rating

dropped 95% from 83,600 lb. To 79,420 lb.

Wire Rope ClipsWire Rope Clips• Two basic designs• U section contacts dead end of the rope• Tends to crush some wires• Affects strength if u-bolt clip is installed wrong• Fist Grip can be installed either way• Use only forged steel for lifting slings

Removal From ServiceRemoval From Service• Rope Distortion such as

kinking, crushing, unstranding, birdcaging or core protrusion

• Heat Damage from any source– Look for damage from

weld and weld splatter• Cracked or deformed end

fittings(hooks particularly)• Corrosive failure of one

wire adjacent to end fitting

Removal From ServiceRemoval From Service

• One broken or cut strand

• Pitting due to corrosion

• For Single Wire Rope Either:– 10 broken wires in a section the length of one

rope lay– 5 broken wires in one strand within a distance

of one rope lay

Chain HazardsChain Hazards

• Similar force acts on the links if the chain is knotted or twisted

• Never shorten a sling by twisting or knotting

• Never use bolts and nuts or other fasteners to shorten a sling