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%f there is no nameplate you must refer to a manufacturer2s handbook, orany other documentation that will give some idea of the weight of theload. %f there is no indication as to the weight of the load an estimatemust be obtained. There is two ways of doing this but both needconsiderable experience. 3ne method is to compare it with the weightof a similar load which is known. The trained men who do rigging workare called riggers. Riggers should have sufficient experience toestimate a load2s weight in this way.

Another, more complicated method is estimate the weight by doing acalculation by multiplying the density and the volume of the load.

)i"$ ,-4-%$ an#fa!t#rer.s Identifi!ation /late$

0$& 'ETERINING T*E BALANCE

To be lifted safely a load must be correctly balanced. 'nbalancedloads tend to tilt and swing when they are lifted. Regular shaped loadsare easy to balance, i.e. by lifting in the middle. %rregular shapes canmore difficult. ee (ig. /0+0$.

4very ob#ect has a point at which it will balance perfectly.

This point is called the ob#ect centre of gravity.

%f a load is lifted from a point directly above its centre of gravity it willremain stable. (rom any other point it will tilt until the centre of gravityis directly below the hook.

Therefore, the Rigger will find the centre of gravity and lift from thatpoint.

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)i"$ %1-4-($ Usin" a odel to find !enter of "ra2it3$

4$& C*ECING CLEARANCES

The third step to take when planning a rigging #ob is to check theclearances.

5efore you move any load, check the si6e of the corridors or gaps thatthe load will have to take when it is moving. When the load is movingit should be kept as close to the floor as possible.

This will make it easier to control and reduce the risk of damage orin#ury if it was to fall. Also loads should not be lifted above otherequipment unless no other route is available.

"eople should be kept out of the way, and loads must never be raisedabove another person.

%f possible barriers and notices must be erected around the areaswhere rigging will take place.

"eople involved in the lifting operation must never put part of theirbodies underneath a suspended load. ee (ig. /0+0&.

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)i"$ ,-4-0$ Che!5in" Clearan!es.

6$& SELECTING T*E E7UI/ENT

When the load2s weight, its balance, and the clearances have beendetermined we can now select the equipment to carry out the #ob. Riggingequipment can generally be grouped into four categories they are

a. 7oists and cranes 0 to provide the lift.

b. lings 0 short lengths of wire rope, chain, or syntheticfibers used to attach a load to the hoist or crane.

c. *onnectors 0 eye bolts, hooks, shackles used to link thedifferent pieces of rigging together.

d. Ad#usters 0 load levelers and turnbuckles used tobalance loads.

1$& SLINGS

When loads are lifted by hoists or cranes, short lengths of wire rope,chain, or synthetic fibers called slings, are used to secure the load tothe lifting devices. lings made of any of these materials can made aseither endless slings or single0leg slings. There are several ways torig each kind of sling, all of which are called a hitch. ince differencekinds of loads require different hitches, riggers must be familiar with allof them. ee a figure /0+0+ for single0leg wire rope sling.

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)i"$ %1-4-4$ Sin"le-le" wire ro8e slin"$

*hain slings may also be either endless or single0leg. ingle0leg chainslings may have rings or hooks at each end.

ome single0led chain slings have a hook at an eye at the other, as shownin (ig. /0+08. 9ike any other chain, chain slings should be inspected forcracks, broken welds, excessive wear and over stretching before each use.

ynthetic fiber slings (ig. /0+0:1 are typically made of braided nylon orpolyester.

Although synthetic fiber slings are light and strong, they are not as durable

as wire rope or chain slings.

ince synthetic slings are easily cut, special care must be taken to protectthem where sharp corners or rough spots are a problem.

Additionally, the material may melt if it is placed near hot pipes or othersources of heat.

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)i"$ %1-4-6$ Sin"le-le" !hain slin"$

)i"$ %1-4-1$ S3ntheti! )ier Slin"$

9$& CONNECTORS

*onnectors are rigging attachments used to link separate pieces ofequipment.

The most common connectors are hooks, shackles, and eyebolts.

ince they are common attachments in basic rigging work, all riggersshould know where they are used how they work, and how they areinspected for wear and damage.

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9$% S*ACLES

hackles are '0shaped connectors with pins that are used to coupleslings to hooks, slings to eyes, and hooks to eyes. ee (ig. /0+0;1.

)i"$ %1-4-9$ Sha!5les with olt and with lo!5in" 8in$

9$( E:EBOLTS

4yebolts are threaded connectors used by riggers to provide a place forslings to be attached.

4yebolts are often permanently installed on equipment. When they arepermanently installed they are located in a position so the equipment isperfectly balanced when raised traight shank eyebolts are for straightlifts only, never at an angle.

houlder type eyebolts are stronger and designed so that lifting can bedone at an angle, but never greater than +8 .

9ike other rigging equipment, eyebolts should be inspected before use

see fig. /0+0< = /0+0/1.

MECHANICAL MAINTENANCE COURSEMODULE 16

LESSON 4 PAGE7CRANES AND LIFTING MATERIALS

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)i"$ ,-4-;$ E3eolt witho#t sho#lder$

)i"$ ,-4-,$ E3eolt with Sho#lder$

9$0 *OOS

7ooks are used in basic rigging work as connectors on hoists, cranes,ad#usters, and slings.

7ooks can be connected to shackles, eyebolts, or directly to the eye ofa sling. Although hooks come in various shapes and si6es, all are

similar in function.

(or extra safety hooks should be fitted with safety latches wherepossible. ee (ig. /0+0!>1.

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)i"$ %1-4-%&$ *oo5s with Safet3 Lat!h$

;$& A'JUSTER

When an unbalanced load is to be lifted, sling lengths must bead#usted to place the load hook of the crane of hoist directly above theload2s centre of gravity.

Ad#usters are rigging attachments that are designed for this task. Twotypes of ad#usters are commonly used for balancing loads, they areload levelers and turnbuckles.

5oth devices have advantages and disadvantages, so you must knowhow to select the right ad#uster for the #ob.

;$% LOA' LEVELERS

A load leveler is a device with two chain legs and an ad#ustermechanism that allows the legs to be varied, and, therefore, balances

the load. see fig. /0+0!!1

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)i"$ ,-4-%%$ Load Le2eler$

;$( TURNBUCLES

Turnbuckles are ad#usters that are useful for making small ad#ustmentsto the length of the sling. They have a threaded body with two screws.

3ne screw is threaded at the opposite side to the other so that whenthe turnbuckle2s body is rotated, the screws move either outwards orinwards, thus shortening or lengthening the sling. ee (ig. /0+0!$1.

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)i"$ %1-4-%($ T#rn#!5les$,$& *OISTS

%n the past, heavy loads could only be lifted manually by one or moremen, until overhead pulleys were discovered and made the #ob easier.

"ulleys brought about the discovery of the block and tackle, and thenlater to hoists that are today.

7oists enable one man to lift a heavy load by multiplying his muscularenergy.

They reduce the amount of effort needed to lift a load by using a seriesof reduction gears, thus doing work by mechanical advantage.

With a hoist one man can lift up to ten tons. ?ost hoists are chainoperated, and are therefore, known as chain hoists. ee (ig. /0+0!&1

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)i"$ %1-4-%4$ Co

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!&. True or (alse. With a hoists one man can lift up to ten tons of weight.

!+. *ome0along have several applications.

!. They can be used for@@@@@@@@@@@@@@@@@@@@@$. They can be used for @@@@@@@@@@@@@@@@@@@@&. They can be used as @@@@@@@@@@@@@@@@@@@@@

MECHANICAL MAINTENANCE COURSEMODULE 16

LESSON 4 PAGE15CRANES AND LIFTING MATERIALS