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Conduit 1

BENDINGCONDUIT/TUBINGUSINGHANDBENDERS


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Conduitisarugged,protectivetubethroughwhichwiresarepulled

Carefulplanningandpracticewillresultinaprofessionallookingelectrical

system

Aconduitwiringsystemisprobablythemostchallengingoftheelectrical

systemstoinstall

Althoughseveraltypesofconduitareusedinelectricalwork,onlythe

followingtypeswillbediscussedinthissubcourse:rigidsteel,electrical

metallictubing(EMT),rigidnonmetallic(polyvinyl chloride [PVC]),and

flexiblemetallicandnonmetallicconduit.


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RigidSteelConduitRigid

steel

conduit

is

a

heavy

duty

pipe

that

is

similar

in

appearancetometalwaterpipe.Itisthreadedatbothends.Rigidsteelconduitprovidesthebestprotectionfromphysicalabusebecauseofitsstrength.Article349inthe

NEC

covers

rigid

steel

conduit

(Figure

1

1,

page

1

2).

Thesizeofrigidsteelconduitistheinsidediametermeasurement.Rigidsteelconduitisavailableinsizesfrom

1/2inchto6inches.Thesesizeswillaccommodateanyjob.Abreakdownofthesizesofrigidsteelconduitininchesfollows:1/2,3/4,1,11/2,2,21/2,3,31/2,4,5,and6.

Afulllengthpieceorstickofrigidsteelconduitis10feetlong.Galvanizedsteelconduitisavailableforapplicationinwetareasorunderground.Galvanizingpreventstherustingof

conduit

from

moisture.


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EMTConduitEMT conduit is a light-gauge pipe often referred to as thin-wall

conduit (Figure 1-2). The wall thickness of EMT conduit is

about 40 percent less than that of rigid-steel conduit, and

because of the thickness of EMT conduit, it can be easily bent.Article 348 in the NEC covers EMT conduit.

EMT (thin-wall) conduit

EMT conduit is available in inside diameters ranging from 1/2

inch to 4 inches. Like rigid-steel conduit, EMT conduit comes

in 10-foot lengths. A breakdown of the sizes of EMT conduit

in inches follows: 1/2, 3/4, 1, 1 1/2, 2, 2 1/2, 3, 3 1/2, and 4.


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EMTConduitEMT conduit is a light-gauge pipe often referred to as thin-wall

conduit (Figure 1-2). The wall thickness of EMT conduit is

about 40 percent less than that of rigid-steel conduit, and

because of the thickness of EMT conduit, it can be easily bent.Article 348 in the NEC covers EMT conduit.

EMT (thin-wall) conduit

EMT conduit is available in inside diameters ranging from 1/2

inch to 4 inches. Like rigid-steel conduit, EMT conduit comes

in 10-foot lengths. A breakdown of the sizes of EMT conduit

in inches follows: 1/2, 3/4, 1, 1 1/2, 2, 2 1/2, 3, 3 1/2, and 4.


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RigidNonmetallic(PVC)ConduitPVC conduit is produced and used for below-ground (direct

burial or concrete encasement) installation. It provides highstrength, a low absorption rate, watertight joints, and low

installation costs. It is available in inside diameters ranging

from 1/2 inch to 5 inches. PVC conduit comes in lengths of upto 20 feet (Figure 1-3). Article 347 in the NEC covers PVC

conduit.

PVC conduit

A breakdown of the sizes of PVC conduit in inches follows: 1/2,

3/4, 1, 1 1/4, 1 1/2, 2, 2 1/2, 3, 3 1/2, 4, and 5.


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CuttingConduitRegardlessofthetypeofconduitbeinginstalled,

youwilloftenhavetocutittomakeitfit.All

conduitsshouldbecutata90 angle.Rigid

steelconduitcanbecutwitheitherahacksaw

orapipecutter.Althoughaviseisnot

absolutelynecessary,itmakescuttingwith

eithertoolmucheasier(Figure21).


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Typesoftools


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When cutting any conduit with a hacksaw, use a blade with 18 to 32 teeth per

inch

A blade with fewer teeth hangs up, binds, or even breaks

Put the blade in the hacksaw frame (with the teeth pointing forward) so that theteeth cut when you push the saw forward

Place the pipe in the vise so that there is ample room between the vise and the

cut

This lets you saw without hitting your hands on the vise and allows enough

room for threading purposes after the cut is made

Remember, let the saw work for you, do not force it

Use a steady forward cutting stroke with light to medium pressure.


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To use a pipe cutter, place the conduit in the vise as described above for cutting

with a hacksaw. Put the cutter over the conduit and adjust it until the

cutting wheel makes contact at the point of the cut

Tightenthecutterjustenoughtoscorethepipeonthefirstturn.Then,screwthe

handleinaboutonefourthofaturnforeachturnaroundtheconduituntilthecutis

complete.Cuttingoilcanbeusedtoeasethecuttingaction.Rigidsteelconduitiscut

thesameway.


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EMT and PVC conduit should be cut with a hacksaw because pipe cutters may

flatten the end of the pipe.

Pipe cutters also leave a ridge on the inside of the pipe that is very hard toremove. There are tubing cutters made specifically for cutting EMT or

PVC, but be sure you have the correct cutter for the job.

As stated before, when cutting conduit with a hacksaw or tubing cutter, using

the vise will make the job much easier.

The tubing cutter is used the same way as the pipe cutter.


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Flexiblemetallicandnonmetallicconduitshould

alsobecutwithahacksawata90 angleCuttinganytypeofconduitleavesasharpedge

or

burrs

on

the

inside

of

it

that

must

be

removedbyreaming


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To ream rigid-steel conduit, use the reamer.

A rat-tail file does a good job on any type of conduit.

Use pliers, such as needle-nose or side-cutting pliers, to ream

EMT that has been cut with a hacksaw.

The important thing is to remove any sharp edge or burrs inside

the conduit that might cut the insulation when the conductors

are pulled into it.


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ThreadingConduitOnce rigid-steel conduit is cut, it must be threaded for use with

threaded couplings, locknuts, and bushings.

To thread conduit, use a pipe-cutting die with a standard pipe

thread of 3/4-inch taper per foot.This die cuts a deeper thread on the end of the conduit and then

tapers the cut at the rear or shoulder of the thread. This is just

the opposite of a running thread on a bolt.


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The dies used for threading smaller sizes of conduit are usually

hand-driven

The handle may be solidly attached to the die, or the die assembly

may be a ratchet-type

When using larger sizes or installing large amounts of conduit

that require considerable threading, a motor-driven, pipe-

threading machine is recommend


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The most common rigid-steel conduit threader is a nonadjustable

ratchet and dies, which come in sizes to fit conduit from 1/2

inch to 2 inchesBefore threading the conduit, inspect the dies to see that they are

sharp and free from nicks and wear.

Next, insert the conduit into the vise, place the guide end of thepipe threader on the conduit, and push the threading dies

against the conduit with the heel of your hand


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With pressure against the threader, take three or four short, clockwise

strokes downward to start the threads.

Continue the threading with clockwise strokes, mixed with a reverse

stroke every now and then, until two or three threads extend beyond

the die.

To reverse the threader, pull the ratchet lock out and turn it a half turn.The reverse turns keep the threads and dies clean and free of bits of

metal.

Cutting oil applied during the threading helps the cutting process byreducing friction. To remove the threader, release the ratchet lock

and turn the die by hand counterclockwise. Removal of the die also

cleans the threads.

It is important that the right amount of threads be cut for the job. Inother words, a full thread must be cut so that the ends of the conduit

come together in the coupling


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Full threads are also necessary for the conduit to make a firm seat in the endthreads of the hub.

Cutting threads until two or three threads extend beyond the die usually givesyou a full thread.

However, if too many threads are cut, the conduit will fit too loosely in thecoupling or against the hub.

Power threaders come in the following two types: stationary threaders built for

use in the shop and portable threaders built for use in the field.

Both types are driven by electric motors that have adjustable chucks and diesfor use on different sizes of conduit.

Portable threaders normally handle conduit up to 2 inches.

Shop threaders may be built to handle conduit up to 6 inches.


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MethodsofBendingConduitWhenyouareinstallingconduit,youwillneedtomakebendstogooveror

aroundobstacles.

Thesebendsmustbemadewithoutreducingtheinsidediameterofthe

conduitatthebend.

Youwillmakemostbendsonthejobasapartoftheinstallationprocedure.

Thesearecalledfieldbends.

Factorymadebendsmaybeusedinsteadoffieldbends;however,they

increasethecostofthejobbecausetheyareanaddedcostandmay

requiremorecutting,threading,andbending.


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Sincemostofthebendingyoudowillbedonewithmanualbenders,the

bendingprocedurestaughtwillbemadewiththosetypesoftools.

Therearebasicallytwotypesofmanualbendersusedforbendingrigidsteel

conduitandEMT.

Theyaretherigidbender,calledthehickeys,andtheEMTbender.

TheEMTbenderisnormallymadeforEMT,butsomearemadetobeusedfor

bothEMTandrigidsteelconduit.

TheEMTbenderiscapableofmakingafull90 bendwithasinglemotion.

Conduit

sizes

up

to

1

inch

for

rigid

steel

and

1

1/4

inch

for

EMT

can

be

bentusingmanualbenders.

Largersizesareusuallybentwithpowerbenders


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TypesofBendsConduitinstallationsarenormallyreferredtoasrunsofconduit.

Arunofconduitistheconduit,fittings,straps,conductors,andbends

neededfromoneopeningtothenext(forexample,fromthepanelboard

tothefirstoutletboxorfromthefirstoutletboxtothesecondoutlet

box).

Inarunofconduit,therecannotbemorethantheequivalentoffour90

bends,foratotalof360.

Thepurposeofallowingonlysomanybendsinarunofconduitistohelpin

pullingconductorsintotheconduit.

Experiencehastaughtthatifmorethan360 ofbendsareused,itisvery

difficulttopullconductorsthroughthebends


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Theabilitytobendconduitandtubingisarequirementforallelectricians

Thereare fivemainbendsthatareusedbyelectricianstheseare:

stubupbacktoback

offset,boxoffset3

point

saddle

fourpointsaddleTheelectricianmustusecautionwhenbendingracewaystomakesurethatit

maintainsitsroundshapethroughoutthebentportionoftheraceway,in

ordertohelppreventjammingwhenpullingthewiresintoit

EMTisveryeasytobendbyhand

Itisathinwallgalvanizedmetaltubingthatisusedmostlyforinteriorconstruction

EMTbendersaresweepbendersoronesweep,onepiecebenders

Theyhaveacurvedtrackthattheracewayfollowsastheelectricianbendsthe

raceway


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TheracewayfitsintoacurvedtrackorslotintheEMTbenderwhichkeeps

theracewayfromspreadingoutasitisbent

Thiskeepstheracewayroundinthebendandalsokeepsitfromkinking


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RigidandIMCconduitarethehardestracewaystobendbecausetheyhaveamuchthickerandharderwallandrigidorIMCcanbebentbyhandusingahickey(orsegmentbender)

Ahickeybenderisusedtobendconduitinsmallbendswithshortsegments,forinstance,inordertobenda90 bendwiththistypeofbenderyouwouldbend9each10 bendswithshortgapsinbetweenthem

AnotherwaytobendrigidorIMCconduitbyhandistouseafullsweepbenderforrigidoruseanEMTbender

TouseanEMTbender,theelectricianwoulduseaEMTbenderforrigidorIMCandforrigidorIMC,hewouldusea1EMTbender

ThehickeybenderisonlyusedforRigidorIMC

ItwouldnormallykinkEMTtubing(exceptforverysmallbends)Largesizesofracewayscanbebentwithhydraulicbendersorwithmechanicalbenders,

suchasChicagobenders,thatincorporatearatchetingaction


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PVCconduitcanbebentwithheat.Heatbendersareusedonbigjobs,butfor

smalljobs,45 and90 elbowscanbepurchasedandgluedtogetherto

complete

the

run

if

no

heat

benders

are

available

Also,anEMTbendercanbeusedtobendsmalldegreebendsorkicksin

PVC.UseanEMTbendertobend30 kickinthePVCconduitbybendingit

to60 andthentheconduitwillspringbackto30

ThiswillonlyworkonorPVCandonlyforsmallbends,butitisfast

andprettyaccurate.


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TheEMTbenderhasdegreemarksonitformakingprecise10,221/2,30,

45 and60 bends

Thereisnota90 markonthebender.Thisbendismadebybendingtheracewayuntilitlooksliketheracewayisbentto90

Thiswillgeteasierwithexperience

TheEMTbenderalsohasseveralmarksthatareusedtolineupvarioustypes

ofbends.Thesearethearrow,thestarandtheteardrop

Theteardrop(ortherimmark)isusedforthecenterbendon3pointsaddles

Thestarisusedonbacktobackbends.Thearrowisusedforallotherbends

Date post:	08-Apr-2018
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