24 rigging elementsthatcanaffecthoistingsafety · pdf filelifting tackle. the combined weight...

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RIGGING

24 RIGGINGIt is important that workers involved withhoisting and rigging activities are trained in bothsafety and operating procedures. Hoistingequipment should be operated only by trainedpersonnel.

The cause of rigging accidents can often betraced to a lack of knowledge on the part of arigger. Training programs such as CSAO’s BasicSafety Training for Hoisting and Rigging provideworkers with a basic knowledge of principlesrelating to safe hoisting and rigging practices inthe construction industry.

A safe rigging operation requires the rigger toknow

• the weight of the load and rigginghardware

• the capacity of the hoisting device

• the working load limit of the hoisting rope,slings, and hardware.

When the weights and capacities are known,the rigger must then determine how to lift theload so that it is stable.

Training and experience enable riggers torecognize hazards that can have an impact on ahoisting operation. Riggers must be aware ofelements that can affect hoisting safety, factorsthat reduce capacity, and safe practices inrigging, lifting, and landing loads. Riggers mustalso be familiar with the proper inspection anduse of slings and other rigging hardware.

Most crane and rigging accidents can beprevented by field personnel following basicsafe hoisting and rigging practices. When acrane operator is working with a rigger or arigging crew, it is vital that the operator is awareof the all aspects of the lift and that a means ofcommunication has been agreed upon,including what signals will be used.

Elements that can Affect Hoisting Safety

– Working Load Limit (WLL) notknown. Don’t assume. Know the workingload limits of the equipment being used.Never exceed these limits.

– Defective components. Examine allhardware, tackle, and slings before use.Destroy defective components. Defectiveequipment that is merely discarded may bepicked up and used by someone unawareof its defects.

– Questionable equipment. Do not useequipment that is suspected to be unsafeor unsuitable, until its suitability has beenverified by a competent person.

– Hazardous wind conditions. Nevercarry out a hoisting or rigging operationwhen winds create hazards for workers,the general public, or property. Assessload size and shape to determine whetherwind conditions may cause problems. Forexample, even though the weight of theload may be within the capacity of theequipment, loads with large wind-catchingsurfaces may swing or rotate out of controlduring the lift in high or gusting winds.Swinging and rotating loads not onlypresent a danger to riggers—there is thepotential for the forces to overload thehoisting equipment.

– Weather conditions. When the visibilityof riggers or hoist crew is impaired bysnow, fog, rain, darkness, or dust, extracaution must be exercised. For example,operate in “all slow”, and if necessary, thelift should be postponed. At sub-freezingtemperatures, be aware that loads arelikely to be frozen to the ground orstructure they are resting on. In extremecold conditions avoid shock-loading orimpacting the hoist equipment andhardware, which may have become brittle.

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RIGGING

– Electrical contact. One of the mostfrequent killers of riggers is electrocution.An electrical path can be created when apart of the hoist, load line, or load comesinto close proximity to an energizedoverhead powerline. When a crane isoperating near a live powerline and theload, hoist lines, or any other part of thehoisting operation could encroach on theminimum permitted distance (see tablebelow), specific measures described in theConstruction Regulation must be taken. Forexample, constructors must have writtenprocedures to prevent contact wheneverequipment operates within the minimumpermitted distance from a live overheadpowerline. The constructor must havecopies of the procedure available for everyemployer on the project.

– Hoist line not plumb. The working loadlimits of hoisting equipment apply only tofreely suspended loads on plumb hoist

lines. If the hoist line is not plumb duringload handling, side loads are createdwhich can destabilize the equipment andcause structural failure or tip-over, withlittle warning.

Factors that Reduce Capacity

The working load limits of hoisting and riggingequipment are based on ideal conditions. Suchideal circumstances are seldom achieved in thefield. Riggers must therefore recognize thefactors that can reduce the capacity of the hoist.

– Swing. The swinging of suspended loadscreates additional dynamic forces on thehoist in addition to the weight of the load.The additional dynamic forces (see pointbelow) are difficult to quantify and accountfor, and could cause tip-over of the craneor failure of hoisting hardware. The forceof the swinging action makes the load driftaway from the machine, increasing theradius and side-loading on the equipment.The load should be kept directly below theboom point or upper load block. This isbest accomplished by controlling the load’smovement with slow motions.

– Condition of equipment. The ratedworking load limits apply only toequipment and hardware in goodcondition. Any equipment damaged inservice should be taken out of service andrepaired or destroyed.

This crane boom could reach withinthe minimum distance.

Normal phase-to-phase voltage rating Minimumdistance

750 or more volts, but no more than 150,000 volts

Over 150,000 volts, but no more than 250,000 volts

More than 250,000 volts

Beware:The wind can blow powerlines, hoist lines, or your load.This can cause them to cross the minimum distance.

6 metres

4.5 metres

3 metres

Keep the Minimum Distance from Powerlines

Wrong.The hoist line must be plumb at all times.

DANGER!

STOP!

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RIGGING

– Dynamic forces. The working load limitsof rigging and hoisting equipment aredetermined for static loads. The design safetyfactor is applied to account, in part, for thedynamic motions of the load and equipment.To ensure that the working load limit is notexceeded during operation, allow for windloading and other dynamic forces created bythe movements of the machine and its load.Avoid sudden snatching, swinging, andstopping of suspended loads. Rapidacceleration and deceleration also increasesthese dynamic forces.

– Weight of tackle. The rated load ofhoisting equipment does not account forthe weight of hook blocks, hooks, slings,equalizer beams, and other parts of thelifting tackle. The combined weight ofthese items must be added to the totalweight of the load, and the capacity of thehoisting equipment, including design safetyfactors, must be large enough to accountfor the extra load to be lifted.

DETERMINING LOADSThe first step in planning a rigging operation isto calculate or estimate the weight of thematerial to be lifted or moved.

When this information is not included inshipping papers, design plans, catalogue data,or other dependable sources, it may benecessary to calculate the weight based onweight tables for specific materials.

Taking the time to calculate load weights canprevent serious accidents in rigging, hoisting,and moving material.

Remember: The weight of all riggingequipment must be included as part of theload to be lifted (Figure 1).

The next step is to select the right rope for thejob — fibre rope or wire rope.

FIBRE ROPESThe fibres in these ropes are either natural orsynthetic. Natural fibre ropes should not beused for rigging since their strength is morevariable than that of synthetic fibre ropes andthey are much more subject to deteriorationfrom rot, mildew, and chemicals.

Polypropylene is the most common fibre ropeused in rigging. It floats but does not absorbwater. It stretches less than other synthetic fibressuch as nylon. It is affected, however, by theultraviolet rays in sunlight and should not beleft outside for long periods. It also softens withheat and is not recommended for workinvolving exposure to high heat.

Nylon fibre is remarkable for its strength. Anylon rope is considerably stronger than the samesize and construction of polypropylene rope. Butnylon stretches and hence is not used much forrigging. It is also more expensive, loses strengthwhen wet, and has low resistance to acids.

Polyester ropes are stronger than polypropylenebut not as strong as nylon. They have goodresistance to acids, alkalis, and abrasion; do notstretch as much as nylon; resist degradation fromultraviolet rays; and don’t soften in heat.

All rigging equipment such as hooks,

slings, blocks, spreader beams, and

hoisting lines must be counted as part of

the load.

Figure 1

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RIGGING

All fibre ropes conduct electricity when wet. Whendry, however, polypropylene and polyester havemuch better insulating properties than nylon.

Inspection

Inspect fibre rope regularly and before eachuse. Any estimate of its capacity should bebased on the portion of rope showing the mostdeterioration.

Check first for external wear and cuts, variationsin the size and shape of strands, discolouration,and the elasticity or “life” remaining in the rope.

Untwist the strands without kinking or distortingthem. The inside of the rope should be as brightand clean as when it was new. Check for brokenyarns, excessively loose strands and yarns, or anaccumulation of powdery dust, which indicatesexcessive internal wear between strands as therope is flexed back and forth in use.

If the inside of the rope is dirty, if strands havestarted to unlay, or if the rope has lost life andelasticity, do not use it for hoisting.

Check for distortion in hardware. If thimbles areloose in the eyes, seize the eye to tighten thethimble (Figure 2). Ensure that all splices are ingood condition and all tucks are done up(Figure 3).

Defective or damaged fibre rope should bedestroyed or cut up so that it cannot be usedfor hoisting.

Design Factors

Fibre rope must have a design factor to accountfor loads over and above the weight beinghoisted and for reduced capacity due to

• wear, broken fibres, broken yarns, age,variations in size and quality

If rope or eyestretches,

thimble will rock.

Whip rope totighten up

thimble in eye.

Check fortucks

popping free.

To securesplice, usewhipping.

Figure 2 Figure 3

Manila Rope

Manila rope is not recommended forconstruction use and is illegal forlifelines and lanyards.

Dusty residuewhen twisted open

Wear from inside out.Overloading. If extensive,replace rope.

Broken strands,fraying, spongytexture

Replace rope.

Wet Strength could be reduced.

Frozen Thaw and dry at roomtemperature.

Mildew, dry rot Replace rope.

Dry and brittle Do not oil. Wash withcold water and hang incoils to dry.

Polypropylene and Nylon Rope

Chalky exteriorappearance

Overexposed to sunlight(UV) rays. Possibly leftunprotected outside. Donot use. Discard.

Dusty residuewhen twisted open

Worn from inside out. Ifextensive, replace.

Frayed exterior Abraded by sharp edges.Strength could be reduced.

Broken strands Destroy and discard.

Cold or frozen Thaw, dry at roomtemperature before use.

Size reduction Usually indicatesoverloading and excessivewear. Use caution. Reducecapacity accordingly.

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RIGGING

• loads imposed by starting, stopping,swinging, and jerking

• increases in line pull caused by frictionover sheaves

• decreases in strength caused by bendingover sheaves

• inaccuracies in load weight

• getting wet and drying out, mildew and rot

• strength reductions caused by knots

• yarns weakened by ground-in dirt andabrasives.

The design factor for all fibre rope is 5. Forhoisting or supporting personnel, the designfactor is 10.

The design factor does not provide extra usablecapacity. Working load limits must never beexceeded.

Working Load Limits

Working load limits (WLLs) can be calculated asshown in Figure 4.

The two tables below (Figures 5 and 6) are forpurposes of illustration only. Checkmanufacturer's ratings for the WLL of the ropeyou are using, which may well differ from whatis shown in these tables.

Breaking strengthWLL = ___________________Design Factor

Breaking strength= ___________________5

For example, a rope rated at 1500 lbs.breaking strength has a working loadlimit of 300 lbs.

1500 lbs._________ = 300 lbs.5

Figure 4

Caution: This table contains sample values for thepurposes of illustration only. Refer to the manufacturer ofthe equipment you’re using for precise values.

Figure 5

Caution: This table contains sample values for thepurposes of illustration only. Refer to the manufacturer ofthe equipment you’re using for precise values.

Figure 6

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RIGGING

WLLs are for the common three-strand fibreropes generally used for rigging. Figures arebased on ropes with no knots or hitches.

When load tables are not available, thefollowing procedures work well for new nylon,polypropylene, polyester, and polyethyleneropes.

Since rope on the job is rarely new, you willhave to judge what figures to use.

If you have any doubt about the type orcondition of the rope, don’t use it. There is nosubstitute for safety.

Nylon Rope

1. Change the rope diameter into eighths ofan inch.

2. Square the numerator and multiply by 60.

Example: 1/2 inch rope = 4/8 inch diameter

WLL = 4 x 4 x 60 = 960 lbs.

Polypropylene Rope



Example: 1/2 inch polypropylene rope =4/8 inch diameter

WLL = 4 x 4 x 40 = 640 lbs.

Polyester Rope



Example: 1/2 inch polyester rope =4/8 inch diameter

WLL = 4 x 4 x 60 = 960 lbs.

Polyethylene Rope



Example: 1 inch polyethylene rope =8/8 inch diameter

WLL = 8 x 8 x 35 = 2,240 lbs.

Care

• Remove kinks carefully. Never try to pullthem straight. This will severely damagethe rope and reduce its strength.

• When a fibre rope is cut, the ends must bebound or whipped to keep the strandsfrom untwisting. Figure 7 shows the rightway to do this.

Storage

• Store fibre ropes in a dry cool room withgood air circulation — temperature10-21°C (50-70°F), humidity 40-60%.

• Hang fibre ropes in loose coils on large-diameter wooden pegs well above thefloor (Figure 8).

Figure 7

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RIGGING

• Protect fibre ropes from weather,dampness, and sunlight. Keep them awayfrom exhaust gases, chemical fumes,boilers, radiators, steam pipes, and otherheat sources.

• Let fibre ropes dry before storing them.Moisture hastens rot and causes rope tokink easily. Let a frozen rope thawcompletely before you handle it. Otherwisefibres can break. Let wet or frozen ropedry naturally.

• Wash dirty ropes in clean cool water andhang to dry.

Use

• Never overload a rope. Apply the designfactor of 5 (10 for ropes used to support orhoist personnel). Then make furtherallowances for the rope’s age andcondition.

• Never drag a rope along the ground.Abrasive action will wear, cut, and fill theoutside surfaces with grit.

• Never drag a rope over rough or sharpedges or across itself. Use softeners toprotect rope at the sharp corners andedges of a load.

• Avoid all but straight line pulls with fibrerope. Bends interfere with stressdistribution in fibres.

• Always use thimbles in rope eyes.Thimbles cut down on wear and stress.

• Never use fibre rope near welding orflame cutting. Sparks and molten metal cancut through the rope or set it on fire.

• Keep fibre rope away from high heat.Don’t leave it unnecessarily exposed tostrong sunlight, which weakens anddegrades the rope.

• Never couple left-lay rope to right-lay.

• When coupling wire and fibre ropes,always use metal thimbles in both eyes tokeep the wire rope from cutting the fibrerope.

• Make sure that fibre rope used with tackleis the right size for the sheaves. Sheavesshould have diameters at least six —preferably ten— times greater than therope diameter.

Knots

Wherever practical, avoid tying knots in rope.Knots, bends, and hitches reduce rope strengthconsiderably. Just how much depends on theknot and how it is applied. Use a spliced endwith a hook or other standard rigging hardwaresuch as slings and shackles to attach ropes toloads.

In some cases, however, knots are morepractical and efficient than other riggingmethods, as for lifting and lowering tools orlight material.

For knot tying, a rope is considered to havethree parts (Figure 9).

The end is where you tiethe knot. The standingpart is inactive. Thebight is in between.

Following the rightsequence is essential intying knots. Equallyimportant is the directionthe end is to take and

Figure 8

End

StandingPart

Bight

Figure 9

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RIGGING

whether it goes over, under, or around otherparts of the rope.

There are overhand loops, underhand loops,and turns (Figure 10).

WARNING: When tying knots, alwaysfollow the directions over and underprecisely. If one part of the rope must gounder another, do it that way. Otherwise anentirely different knot — or no knot at all —will result.

Once knots are tied, they should be drawnup slowly and carefully to make sure thatsections tighten evenly and stay in properposition.

The following illustrations show how to tiesome knots and hitches useful in the mechanicaltrades.

Bowline — Never jams or slips when properlytied. A universal knot if properly tied and untied.Two interlocking bowlines can be used to jointwo ropes together. Single bowlines can be usedfor hoisting or hitching directly around a ring.

Bowline on the Bight — Used to tie abowline in the middle of a line or to make a set

of double-leg spreaders for lifting pipe. Can alsobe used as a sling — sit in one loop and putthe other around the back and under the arms.

Figure-Eight Knot — Tied at the end of arope to keep strands from unlaying. Useful inpreventing end of rope from slipping through ablock or eye.

Reef or Square Knot— Can be used for tyingtwo ropes of the samediameter together. It isunsuitable for wet orslippery ropes andshould be used withcaution since it untieseasily when either freeend is jerked. Both thelive and dead ends of therope must come out ofthe loops at the sametime.

Overhand Loop Underhand Loop Turn

Figure 10

Bowline

1

2

3

4

Bowline on the Bight1 2

3

Figure 8 Knot

12 3

4

Reef orSquare Knot

1

2

3

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RIGGING

Two Half-Hitches — Two half hitches, whichcan be quickly tied, are reliable and can be putto almost any general use.

Running Bowline — The running bowline ismainly used for hanging objects with ropes ofdifferent diameters. The weight of the objectdetermines the tension necessary for the knot togrip.

Make an overhand loop with the end of therope held toward you (1 in illustration). Holdthe loop with your thumb and fingers and bringthe standing part of the rope back so that it liesbehind the loop (2). Take the end of the ropein behind the standing part, bring it up, andfeed it through the loop (3). Pass it behind thestanding part at the top of the loop and bring itback down through the loop (4).

WIRE ROPEWire rope consists of three elements arranged indifferent ways to yield advantages for specificjobs. The three basics are

1.wires that form the strand

2. multi-wire strands laid helically around acore

3. the core, which can be fibre rope (FC),independent wire rope core (IWRC), orwire strand core (WSC). See Figure 11.

Strand Constructions

Wires in a strand are commonly arranged in oneof four basic constructions or combinations(Figure 12).

Pipe Hitch Two Half Hitches

Running Bowline

1

2

3

4

Figure 11

Wire Rope

Wire

Strand

Core

Ordinary The basic strand construction haswires of the same size woundaround a centre.

Seale Large outer wires with the samenumber of smaller inner wiresaround a core wire. Providesexcellent abrasion resistance butless fatigue resistance. When usedwith an IWRC, it offers excellentcrush resistance over drums.

Filler Wire Small wires fill spaces betweenlarge wires to produce crushresistance and a good balance ofstrength, flexibility, and resistanceto abrasion.

Warrington Outer layer of alternately large andsmall wires provides goodflexibility and strength but lowabrasion and crush resistance.

Figure 12

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RIGGING

Lay

The strands of a rope can be configured indifferent arrangements by lay. Each lay hascharacteristics suited to certain applications.

Grades of Steel

Ropes are not only of different sizesand construction but may also bemade of different grades of steel.

EEIPS: Grade 125/140 ExtraExtra Improved Plow Steel. Usedchiefly in applications whereresistance to fatigue is not animportant factor.

SIPS: Grade 120/130 SpecialImproved Plow Steel, Type 2.Steel of remarkable strength andductility, specially made for hoistingrequirements where weight is not animportant factor.

SIPS: Grade 115/125 Special ImprovedPlow Steel, Type 1. Used for specialapplications where breaking strengths somewhathigher than those of grade 110/120 are desiredand where other conditions such as sheave anddrum diameters are favourable to its use.

IPS: Grade 110/120 Improved Plow Steel.Because of its well-balanced combination ofstrength, wear resistance, and toughness, this isthe most widely used grade of steel for general-purpose wire ropes.

PS: Grade 100/110 Plow Steel. Although ithas lower tensile strength and wear resistancethan grade 110/120, it retains high fatigueresistance and can be used when strength issecondary to wear resistance.

The most common grade is 110/120 improvedplow steel. This intermediate grade combinesflexibility with strength and is used for generalrigging purposes in items such as slings.

Common Wire Ropes

Figure 13 shows the construction, characteristics,and typical applications for some common typesof wire rope.

Regular Lay Most common layin which thewires wind in onedirection and thestrands theopposite direction(right lay shown).

Less likely to kinkand untwist; easierto handle; morecrush resistantthan lang lay.

Lay Lay Wires in strandand strands ofrope wind thesame direction(right lay shown).

Increasedresistance toabrasion; greaterflexibility andfatigue resistancethan regular lay;will kink anduntwist.

Right Lay Strands wound tothe right aroundthe core (regularlay shown).

The most commonconstruction.

Left Lay Strands wound tothe left aroundthe core (regularlay shown).

Used in a fewspecial situations— cable tooldrilling line, forexample.

Alternate Lay Alternate strandsof right regularlay and right langlay.

Combines the bestfeatures of regularand lang lay forboom hoist orwinch lines.

6 x 19 Seale

Resistant to abrasion andcrushing; medium fatigueresistance.

6 x 21 Filler Wire

Less abrasion resistance; morebending fatigue resistance.

6 x 25 Filler Wire

Most flexible rope inclassification; best balance ofabrasion and fatigue resistance.

6 x 26 Warrington Seale

Good balance of abrasion andfatigue resistance.

Used for haulage rope, chokerrope, rotary drilling line.

Used for pull ropes, loadlines, back-haul ropes,draglines.

Most widely used of all wireropes — crane joists, skiphoists, haulage, mooring lines,conveyors, etc.

For boom hoists, logging andtubing lines.

Figure 13

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RIGGING

Wire Rope Slings

The use of wire rope slings for lifting materialsprovides several advantages over other types ofslings. It has good flexibility with minimumweight. Outer wires breaking warn of failureand allow time to react. Properly fabricated wirerope slings are very safe for generalconstruction use.

Braided Slings

Fabricated from six or eightsmall diameter ropes braidedtogether to form a single ropethat provides a large bearingsurface, tremendous strength,and flexibility in all directions.They are very easy to handle and almostimpossible to kink. Especially useful for baskethitches where low bearing pressure is desirableor where the bend is extremely sharp.

Inspection

Wire rope must be inspected regularly andoften. Figure 14 shows some of the moreobvious warning signs to look for.

BraidedSlings

Replace rope if there are• 6 or more broken wires in one lay• 3 of more broken wires in one

strand in one lay• 3 or more broken wires in one lay

in standing ropes• more than one broken wire at

end connector in standing ropes.

Estimate rope’s condition at sectionshowing maximum deterioration.

Wornsection

Enlargedview ofsinglestrand

Where the surface wiresare worn by 1/3 or moreof their diameter, therope must be replaced.

Multi-strand rope “bird-cages” dueto torsional unbalance. Typical ofbuild-up seen at anchorage end ofmulti-fall crane application.

A “bird cage” caused by suddenrelease of tension and resultantrebound of rope from overloadedcondition. These strands and wireswill not return to their originalpositions.

Core protrusion as a resultof torsional unbalance

created by shock loading.

Protrusion of IWRC resultingfrom shock loading.

Figure 14Wire Rope Inspection

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RIGGING

Wire Rope Slings

Broken wires Up to six allowed in one ropelay or three in one strand inone rope lay with no morethan one at an attached fitting.Otherwise, destroy and replacerope.

Kinks,bird-caging

Replace and destroy.

Crushed andjammedstrands


Coreprotrusion


Bulges in rope Replace and destroy.

Gaps betweenstrands


Wire rope clips Check proper installation andtightness before each lift.Remember, wire rope stretcheswhen loaded, which maycause clips to loosen.

Attachedfittings

Check for broken wires.Replace and destroy if one ormore are broken.

Frozen Do not use. Avoid suddenloading of cold ropes toprevent failure.

Sharp bends Avoid sharp corners. Use padssuch as old carpet, rubberhose, or soft wood to preventdamage.

Wire Rope

Rusty, lack oflubrication

Apply light, clean oil. Do notuse engine oil.

Excessiveoutside wear

Used over rough surfaces, withmisaligned or wrong sheavesizes. Reduce load capacityaccording to wear. If outsidediameter wire is more than 1/3worn away, the rope must bereplaced.

Broken wires Up to six allowed in one ropelay, OR three in one strand inone rope lay, with no morethan one at an attached fitting.Otherwise, destroy and replacerope.

Crushed,jammed, orflattenedstrands

Replace rope.

Bulges in rope Replace, especially non-rotating types.

Gaps betweenstrands

Replace rope.

Coreprotrusion

Replace rope.

Heat damage,torch burns, orelectric arcstrikes

Replace rope

Frozen rope Do not use. Avoid suddenloading of cold rope.

Kinks, bird-caging

Replace rope. Destroydefective rope.

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RIGGING

NYLON SLINGS

Synthetic web slings offer a number ofadvantages for rigging purposes.

• Their relative softness and width createmuch less tendency to mar or scratchfinely machined, highly polished orpainted surfaces and less tendency tocrush fragile objects than fibre rope, wirerope or chain slings (Figure A).

• Because of their flexibility, they tend tomold themselves to the shape of the load(Figure B).

The rated capacity of synthetic web slings isbased on the tensile strength of the webbing, adesign factor of 5 and the fabrication efficiency.Fabrication efficiency accounts for loss ofstrength in the webbing after it is stitched andotherwise modified during manufacture.Fabrication efficiency is typically 80 to 85% forsingle-ply slings but will be lower for multi-plyslings and very wide slings.

Although manufacturers provide tables for bridleand basket configurations, these should be usedwith extreme caution. At low sling angles, oneedge of the web will be overloaded and thesling will tend to tear (Figure C).

Nylon and polyester slings must not be used attemperatures above 90°C (194°F).

Polypropylene and Nylon Web Slings

Chalky exteriorappearance

Overexposed to sunlight (UV)rays. Should be checked bymanufacturer.

Frayed exterior Could have been shock-loadedor abraded. Inspect verycarefully for signs of damage.

Breaks, tears,or patches

Destroy. Do not use.

Frozen Thaw and dry at roomtemperature before use.

Oilcontaminated

Destroy.

Figure A

Synthetic web slingsdo not damage orcrush loads

Figure B

Web slings moldthemselves to the load

Figure C

If the sling angle istoo low, the webcan tear here

Effect of low sling angle on webbing

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RIGGING

Inspect synthetic web slings regularly. Damageis usually easy to detect. Cuts, holes, tears, frays,broken stitching, worn eyes and worn ordistorted fittings, and burns from acid, causticsor heat are immediately evident and signal theneed for replacement. Do not attempt repairsyourself.

Synthetic web slings must be labelled toindicate their load rating capacity.

CHAIN SLINGS

Chain slings are made for abrasionand high temperature resistance.The only chain suitable for lifting isgrade 80 or 100 alloy steel chain.Grade 80 chain is marked with an8, 80, or 800. Grade 100 is markedwith a 10, 100, or 1000. The chainmust be embossed with this grademarking every 3 feet or 20 links, whichever isshorter – although some manufacturers markevery link. Chain must be padded on sharpcorners to prevent bending stresses.

METAL MESH SLINGSMetal mesh slings, also known as wire or chainmesh slings, are well adapted for use whereloads are abrasive, hot or tend to cut fabricslings and wire ropes. They resist abrasion andcutting, grip the load firmly without stretchingand can withstand temperatures up to 288°C(550°F). They have smooth, flat bearing surfaces,conform to irregular shapes, do not kink ortangle and resist corrosion (Figure D).

For handling loads that would damage themesh, or for handling loads that the meshwould damage, the slings can be coated withrubber or plastic.

Chain Slings

Use only alloy steel for overhead lifting.

Elongated orstretched links

Return to manufacturer forrepair.

Failure to hangstraight


Bent, twisted,or crackedlinks


Gouges, chips,or scores

Ground out and reducecapacity according to amountof material removed.

Chain repairs are best left to the manufacturer.Chain beyond repair should be cut with torchinto short pieces.

ChainSlings

Figure D

Chain mesh slings

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RIGGING

Note that there is no reduction in working loadlimit for the choker hitch. This is because thehinge action of the mesh prevents any bendingof individual wire spirals.

RIGGING HARDWAREKnow what hardware to use, how to use it, andhow its working load limit (WLL) compares withthe rope or chain used with it.

All fittings must be of adequate strength for theapplication. Only forged alloy steel load-ratedhardware should be used for overhead lifting.Load-rated hardware is stamped with its WLL(Figure 15).

Inspect hardware regularly and before each lift.Telltale signs include

• wear

• cracks

• severe corrosion

• deformation/bends

• mismatched parts

• obvious damage.

Hoisting Hooks

• Should be equipped with safety catches(except for sorting or grab hooks).

• Should be forged alloy steel with WLLstamped or marked on the saddle.

• Should be loaded at the middle of thehook. Applying the load to the tip willload the hook eccentrically and reduce theWLL considerably.

• Should be inspected regularly and often.Look for wear, cracks, corrosion, andtwisting—especially at the tip—and checkthroat for signs of opening up (Figure 16).

Swivels

• Reduce bending loads on riggingattachments by allowing the load to orientitself freely.

• Should be used instead of shackles insituations where the shackle may twist andbecome eccentrically loaded.

• Can provide approximate capacities shownin Figure 17. See manufacturer’s table forthe exact WLL of the swivel you are using.

Check for wearand deformation.

Check for signsof opening up.

Check for wear and cracks.

Check for cracksand twisting.

Hook Inspection Areas

Figure 16

Figure 15

Swivels (All Types)

• Weldless Construction• Forged Alloy Steel

Stock Diameter(Inches)

Maximum WorkingLoad Limit (Pounds)

1/45/163/81/25/83/47/81

1-1/81-1/41-1/2

8501,2502,2503,6005,2007,200

10,00012,50015,20018,00045,200

Caution: This table contains sample values for the purposes of illustration only.Refer to the manufacturer of the equipment you’re using for precise values.

Figure 17

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RIGGING

Shackles

• Available in various types (Figure 18).

• For hoisting, should be manufactured offorged alloy steel.

• Do not replace shackle pins with bolts(Figure 19). Pins are designed andmanufactured to match shackle capacity.

• Check for wear, distortion, and opening up(Figure 20). Check crown regularly forwear. Discard shackles noticeably worn atthe crown.

• Do not use a shackle where it will bepulled or loaded at an angle. This severelyreduces its capacity and opens up the legs(Figure 21)

• Do not use screw pin shackles if the pin canroll under load and unscrew (Figure 22).

Turnbuckles

• Can be supplied with eye end fittings,hook end fittings, jaw end fittings, stubend fittings, and any combination of these(Figure 23).

• Rated loads are based on the outsidediameter of the threaded portion of theend fitting and on the type of end fitting.Jaw, eye, and stub types are rated equally;hook types are rated lower.

• Should be weldless alloy steel.

• Lock frames to end fittings on turnbucklesexposed to vibration. This will prevent

Figure 19

Never replace ashackle pin with a bolt.

The load willbend the bolt

Figure 20

Check for wear

Check for wear &straightness

Figure 21

Packings Hook

Poor PracticeNever allow shackle to bepulled at an angle — the

legs will open up.

Good PracticePack the pin with washersto centre the shackle

Figure 22

If the load shifts, the sling willunscrew the shackle pin

WARNING

Don't run the sling through a hook or shackle.The sling can slide in the hook or shackleand allow an unbalanced load to tip.

Check that pin isalways seated

Check that shackleis not “opening up”

Figure 18

24 – 17

RIGGING

turning and loosening. Lockor jam nuts are ineffectiveand can overload the screwthread. Use wire to preventturning (Figure 24).

• When tightening aturnbuckle, do not applymore torque than youwould to a bolt of equalsize.

• Inspect turnbucklesfrequently for cracks in endfittings (especially at theneck of the shank),deformed end fittings,deformed and bent rodsand bodies, cracks andbends around the internally threadedportion, and signs of thread damage.

Eye Bolts

• For hoisting, use eye or ringbolts made of forged alloysteel.

• Use bolts with shoulders orcollars. Shoulderless bolts arefine for vertical loading butcan bend and loseconsiderable capacity underangle loading (Figure 25).Even with shoulders, eye andring bolts lose somecapacity when loaded on anangle.

• Make sure that bolts are atright angles to hole, makecontact with workingsurface, and have nutsproperly torqued (Figure26).

• Pack bolts with washerswhen necessary to ensurefirm, uniform contact withworking surface (Figure 26).

• Make sure that tapped holes for screwbolts are deep enough for uniform grip(Figure 26).

• Apply loads to the plane of the eye, neverin the other direction (Figure 27). This is

Swivel eye bolt

Figure 25

Turnbuckle End Fittings

Eye Jaw Hook(has reduced

capacity)

Stub

Jaw and Eye Combination

Jaw and Jaw Combination

Hook and Hook Combination

Hook and Eye Combination

Jaw and Eye Combination

Figure 23

Figure 24

Do not use jam nuts Lock wire will holdEnd fittings must be secured

Correct for Shoulder-Type Eye & Ring Bolts

Nut must beproperlytorqued

Ensure thatbolt is

tightenedinto place

Pack withwashers toensure thatshoulder is

firmly incontact with

surfaceEnsure thattapped hole

is deepenough

Assuming that loads are reducedto account for angular loading

Incorrect

Shoulder must bein full contact with

surface

Figure 26

24 – 18

RIGGING

particularlyimportant withbridle slings,which alwaysdevelop anangular pull ineye bolts unlessa spreader baris used.

• Never insert thepoint of a hookin any eye bolt.Use a shackle instead (Figure 28).

• Do not reeve a sling through a pair ofbolts. Attach a separate sling to each bolt.

Snatch Blocks

• A single or multi-sheave blockthat opens on one side so arope can be slipped over thesheave rather than threadedthrough the block (Figure 29).

• Available with hook, shackle,eye, and swivel end fittings.

• Normally used when it’snecessary to change thedirection of pull on a line.Stress on the snatch blockvaries tremendously with the anglebetween the lead and load lines. With bothlines parallel, 1000 pounds on the lead lineresults in 2000 pounds on the block, hook,

and anchorage. As the angle between thelines increases, the stress is reduced(Figure 30).

• To determine the load on block, hook, andanchorage, multiply the pull on the leadline or the weight of the load being lifted

Correct Orientation- Load is in theplane of the eye

Load

Incorrect OrientationWhen the load is

applied to the eye

Figure 27

Load

Result

CorrectUse a shackle

Incorrect

Figure 28

When open

Multiplication Factorsfor Snatch Block Loads

Angle Between Leadand Load Lines

Multiplication Factor

10°20°30°40°50°60°70°80°90°100°110°120°130°140°150°160°170°180°

1.991.971.931.871.811.731.641.531.411.291.151.00.84.68.52.35.17.00

Figure 31

Figure 29

Safety Tip

Whenever two or more ropes are to beplaced over a hook, use a shackle to reducewear and tear on thimble eyes.

24 – 19

RIGGING

by a suitable factor from the table inFigure 31 and add 10% for sheave friction.

Wire Rope Clips

Wire rope clips are widely used for making endterminations. Clips are available in two basicdesigns: U-bolt and fist grip.

When using U-bolt clips, make sure you havethe right clip. Never stock malleable wire ropeclips. They may be inadvertently used for criticalheavy-duty applications. Always make certainthe U-bolt clips are attached correctly. TheU-section must be in contact with the dead endof the rope. Tighten and retighten nuts asrequired by the manufacturer.

To determine the number of clips and thetorque required for specific diameters of rope,

Figure 30

Installation of Wire Rope Clips

RopeDiameter(Inches)

MinimumNumber of

Clips

Amount ofRope Turn-back fromThimble(inches)

Torque inFoot-PoundsUnlubricated

Bolts

5/16

3/8

7/16

1/2

9/16

5/8

3/4

7/8

2

2

2

3

3

3

4

4

5-1/2

6-1/2

7

11-1/2

12

12

18

19

30

45

65

65

95

95

130

225

Caution: This table contains sample values for the purposes of illustration only.Refer to the manufacturer of the equipment you’re using for precise values.

Figure 32

24 – 20

RIGGING

refer to Figure 32. For step-by-step instructionson attaching clips, refer to Figure 33.

WrongRight

Figure 33

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

APPLY FIRST CLIP one base width fromdead end of wire rope. U-Bolt over deadend. Live end rests in clip saddle. Tightennuts evenly to recommended torque.

APPLY SECOND CLIP as close to loop aspossible. U-Bolt over dead end. Turn nutsfirmly but DO NOT TIGHTEN.

APPLY ALL OTHER CLIPS. Space evenlybetween first two and 6-7 rope diametersapart.

APPLY TENSION and tighten all nuts torecommended torque.

CHECK NUT TORQUE after rope hasbeen in operation.

ApplyTension

ApplyTension

24 – 21

RIGGING

SLINGSSlings are often severely worn and abused inconstruction.

Damage is caused by

• failure to provide blocking or softenersbetween slings and the load, therebyallowing sharp edges or corners of theload to cut or abrade the slings

• pulling slings out from under loads,leading to abrasion and kinking

• shock loading that increases the stress onslings that may already be overloaded

• traffic running over slings, especiallytracked equipment.

Because of these and other conditions, as wellas errors in calculating loads and estimatingsling angles, it is strongly recommended thatworking load limits be based on a design factorof at least 5:1.

For the same reasons, slings must be carefullyinspected before each use.

Sling Angles

The rated capacity of any sling depends on itssize and its design.

Keep sling angles greater than 45° wheneverpossible.

The use of any sling at an angle lower than 30°is extremely hazardous. This is especially truewhen an error of only 5° in estimating the slingangle can be so dangerous.

Sling Configurations

Slings are not only made of various materialsuch as wire rope and nylon web. They are alsoused in various configurations for differentpurposes.

Common configurations are shown in thefollowing illustrations.

The term “sling” includes a wide variety ofconfigurations for all fibre ropes, wire ropes,chains, and webs. The most commonly usedtypes in construction are explained here.

500

LBS

1000 LBS

Best Good

1000 LBS

60°500

LBS

577

LBS 577

LBS

1000 LBS

MinimumRecommended

AVOID

1000 LBS

30°45° 1000 LBS1000 LBS707 LBS 707 LBS

Effect of Sling Angle on Sling Load

Figure 34

24 – 22

RIGGING

Single Vertical Hitch

The total weight of the load iscarried by a single leg. Thisconfiguration must not be used forlifting loose material, longmaterial, or anything difficult tobalance. This hitch providesabsolutely no control over theload because it permits rotation.

Bridle Hitch

Two, three, or four singlehitches can be used togetherto form a bridle hitch. Theyprovide excellent stabilitywhen the load is distributedequally among the legs, whenthe hook is directlyover the centre ofgravity of the load,and the load is raisedlevel. The leg lengthmay need adjustmentwith turnbuckles todistribute the load.

Single Basket Hitch

This hitch is ideal for loads withinherent stabilizing characteristics.The load is automatically equalized,with each leg supporting half theload. Do not use on loads that aredifficult to balance because the load can tilt andslip out of the sling.

Double Basket Hitch

Consists of two singlebasket hitches passed underthe load. The legs of thehitches must be kept farenough apart to providebalance without openingexcessive sling angles.

On smooth surfaces, the basket hitch should besnubbed against a step or change of contour to

prevent the ropefrom slipping as theload is applied. Theangle between theload and the slingshould beapproximately 60degrees or greaterto avoid slippage.

Double Wrap Basket Hitch

A basket hitch that is wrappedcompletely around the load. Thismethod is excellent for handlingloose materials, pipes, rods, orsmooth cylindrical loads because therope or chain exerts a full 360-degree contactwith load and tends to draw it together.

Single Choker Hitch

This forms a noose in the ropeand tightens as the load is lifted.It does not provide full contactand must not be used to liftloose bundles or loads difficultto balance.

Double Choker Hitch

Consists of two single chokersattached to the load and spreadto provide load stability. Doesnot grip the load completely butcan balance the load. Can beused for handling loosebundles.

Double Wrap Choker Hitch

The rope or chain is wrappedcompletely around the loadbefore being hookedinto the vertical partof the sling. Makesfull contact with loadand tends to draw it together.

SingleVerticalHitch

BridleHitch

SingleBasketHitch

Caution: Load maybe carried by only2 legs while 3rdand 4th merely

balance it.

Detail

RIGHT

WRONGLegs will

slide together.

DoubleWrapChokerHitch

SingleChokerHitch

DoubleWrapBasketHitch

DoubleChokerHitch

DoubleBasketHitch

24 – 23

RIGGING

WORKING LOAD LIMITS

Tables

Working load limits (WLLs) for slings can beobtained from manufacturers’ tables such asthose in Figures 35 and 36 (one type of wirerope sling).

Rules

There are general rules for estimating the WLLsof common sling configurations. Each rule for agiven configuration, material, and size is basedon the WLL of that sling in a single verticalhitch.

Bridle Hitches (2, 3, and 4 leg) — Measurethe length of the sling legs (L) and measure thehead room between the hook and the load (H).

WLL = WLL (of single vertical hitch)x H/L x 2 for a two-leg hitch

3- and 4-Leg Bridle Hitches

WLL = WLL (of single vertical hitch) x H/L x 3

Generally, 4-leg and 3-leg bridle hitches shouldbe rated as 2-leg hitches because there is noway of knowing that all legs are sharing theload. It is possible for only 2 legs to carry theload while the others merely balance it.

Rigging Safety Tips

With two or more slingson a hook, use a shackle.

Use tag lines for control.

Block loose loads before unhooking. Make sure loads are secure.

When legs are notof equal length,use smallestH/L ratio.

WLL =WLL (of single vertical hitch) x H/L x 2

When legs are not of equallength, use smallest H/L ratio.

Note: Load may be carried by only 2 legs whilethird and fourth legs merely balance it. Therefore:WLL =WLL (of single vertical hitch) x H/L x 2

Determining capacity of 4-leg bridle hitch

24 – 24

RIGGING

Figure 35

Caut

ion:Thistablecontains

samplevalues

forthepurposes

ofillustrationonly.Refer

tothemanufactureroftheequipm

entyou’re

usingforprecisevalues.

24 – 25

RIGGING

Figure 36

Caut

ion:Thistablecontains

samplevalues

forthepurposes

ofillustrationonly.Refer

tothemanufactureroftheequipm

entyou’re

usingforprecisevalues.

24 – 26

RIGGING

Single Basket HitchFor vertical legs: WLL = WLL (ofSingle Vertical Hitch) x 2.For inclined legs: WLL = WLL (ofSingle Vertical Hitch) x H x 2.—

L

Double Basket Hitch Figure 37For vertical legs: WLL = WLL (ofSingle Vertical Hitch) x 4.For inclined legs: WLL = WLL (ofSingle Vertical Hitch) x H x 4.—

L

Double Wrap Basket HitchDepending on the configurations, theWLLs are the same as for the SingleBasket Hitch or the Double Basket Hitch.

Single Choker Hitch Figure 38For sling angles of 45° or more.WLL = WLL (of Single Vertical Hitch)

x 3/4.Sling angles of less than 45° are notrecommended.

Double Choker Hitch Figure 39

For sling angles of 45° or more (formed bythe choker).WLL = WLL (of Single Vertical Hitch)

x 3/4 x H/L x 2Sling angles of less than 45° (formed by thechoker) are not recommended.

HOISTING TIPS• Never wrap a wire rope sling completely

around a hook. The tight radius willdamage the sling.

• Make sure the load is balanced in thehook. Eccentric loading can reducecapacity dangerously.

• Never point-load a hook unless it is

Figure 37

When the choker angle isgreater than 45°,

WLL =WLL (of singlevertical hitch)x 3/4 x H/L x 2

Figure 39

WLL =WLL (of single vertical hitch)x H/L x 4

When this angle is greaterthan 45°, WLL =WLL (ofsingle vertical hitch) x 3/4

Figure 38

24 – 27

RIGGING

designed and ratedfor such use. Point-loading can cutcapacity by morethan half (Figure 40).

• Never wrap thecrane hoist ropearound the load. Attach the load to the

crane hook by slings or other riggingdevices.

• Avoid bending wire rope slings nearattached fittings or at eye sections.

• The hoist line must be plumb at all times.

• Know the standard hand signals forhoisting (Figure 41).

HAND SIGNALS FOR HOISTING OPERATIONS

Load Up Load Down Load Up Slowly Load DownSlowly

Boom Up

Boom Down Boom Up Slowly Boom DownSlowly

Boom UpLoad Down

Boom DownLoad Up

EverythingSlowly

Use WhipLine

Use MainLine

Travel Forward Turn Right

Turn Left ShortenHydraulic Boom

Extend HydraulicBoom

Swing Load Stop

Close Clam Open Clam Dog Everything

No response should bemade to unclear signals.

1

6

11

16

21

2

7

12

17

22

3

8

13

18

23

4

9

14

19

5

10

15

20

Figure 41

Figure 40Point Loading

Capacity Severely Reduced

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