05-1 How Do SMAW Piping

8/20/2019 05-1 How Do SMAW Piping

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Teknologi Las Kapal

How doHow do

Shielded Metal Arc WeldingShielded Metal Arc Welding on pipingon piping


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Teknologi dan Rekayasa

I G position

Pipe rotated, Electrode is always at the topEither a split bead or weave technique

may be used


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2G Position

Pipe Axis Vertical, Weld isHorizontal, Pipe isconsidered in a “ixed!position"

Always use a split beadtechnique

Always wor# rom the

bottom up"


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5G Position

Axis o the Pipe is Horizontal, $he weld invertical"

Pro%ression may be up or down"

A weave bead is best used"


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6G Position

Pipe axis is ixedin position at a &'de%ree incline"$hhe position

includes lat,horizontal,vertical, andoverhead welds"

A split beadtecvhnique is bestused"


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lectrode

The SMAW process uses a consumable electrode. Electrode must be compatible with base metal.

Electrodes are available for different metals.

Carbon steels

Low alloy steels Corrosion resisting steels

Cast irons

Aluminum and alloys

Copper and alloys

Nickel and alloys


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lectrode

The AWS systemdistinguishes thetensile strength, weldposition and, coatingand current.

Manufactures mayand do use there ownnumbering systemand produceelectrodes that do not

fit in the AWS system.



Welding !"rrents

Not all electrodes are designed to wor with allcurrents.

!ommon SMAW currents.

Alternating Current (AC)

irect Current straight polarity (C!") or (CEN)

irect Current Re#erse polarity (CR") or (CE")



lectrode Gro"ping

Electrodes are also grouped according to thereperformance characteristics.

#ast$%ree&e

$ Mild steel

$ '"ick solidi%ication o% weld pool

$ (eep penetrating

$ )eco**ended %or o"t o% position welds

$ (eep penetrating arc

#ast$%ill

$ Highest deposition rate$ Sta+le arc

$ Thick %l",

$ #lat position and hori&ontal laps onl-



lectrode Gro"ping

%ill&'reee$ eneral purpose electrodes

$ Characteristics o' 'ast&'reee and 'ast&'ill

Low hydrogen

$ *elding characteristics o' 'ill&'reee

$ esigned 'or medium carbon and alloy steels


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Selecting lectrode Si&e

The optimum electrode diameter is determined bythe thicness of the base metal, the welding positionand the capacity of the welding power supply.

A smaller diameter is usually recommended for out ofposition welding.

When completing root passes in #$%oints, a smallerdiameter maybe used and then a larger diameter isused for the filler passes.

A diameter of &'&( or )'* inch can be used onmetals up to )'+ inches thic without %ointpreparation.

-T the diameter of the electrode should not e"ceedthe thicness of the metal.



SMAW Welding Process

%lu+ Electrode

Electrode

metal

"enetration,olten

puddle-ead-ase metal

!lag

as

shield



3"ip*ent

Power S"ppl- Polarit- Switch

lectrode

4ase Metal

/work Piece1

Gro"nd !la*pGro"nd !a+le

A*perage

Scale

Power Switch

A*perage

Ad"st*ent

lectrode !a+le

lectrode Holder

Power

!ord



A rectifier allows current to flow in one direction only. The direction of the current flow determines the /!

polarity. /!$ or direct current electrode negative is the

arrangement of direct current arc weldingcables'leads in which the electrode is the negative

pole and the worpiece is the positive pole of thewelding arc. When using /!$ polarity, the ma%ority of the heat is

directed at the electrode. The electrodes designed for /!$ polarity produce

weld deposits with shallow penetration. 0rimary

applications are fast travel speeds on sheet metal.

(irect !"rrent straight polarit-

/(!SP1 or /(!1



(irect !"rrent straight polarit-

/(!SP1 or /(!1



/!1 or direct current electrode positive is theopposite of /!$ or direct current electrode negative.

2n this case, the electrode is the positive pole and theworpiece is the negative pole.

When using /!1 polarity, the ma%ority of the heat isdirected at the wor piece.

The electrodes designed for /!1 polarity produceweld deposits with deep penetration.

0rimary applications are for pipe welding, generalpurpose and maintenance welding, deep penetrationapplications, and on base material with surfacecontaminants.

(irect !"rrent )eerse polarit-

/(!)P1 or /(!P1


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(irect !"rrent )eerse polarit-

/(!)P1 or /(!P1


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STA)TIG TH A)!

(eore you start to weld, ensure that you have all the requiredequipment and accessories" )isted below are some additional

weldin% rules that should be ollowed"

!lear the welding area o% all de+ris and cl"tter.

(o not "se gloes or clothing that contains oil or grease.

!heck that all wiring and ca+les are installed properl-. ns"re that the *achine is gro"nded and dr-.

#ollow all *an"%act"rer7s directions on operating the welding*achine.

Hae on hand a protectie screen to protect others in the

welding area %ro* #LASH +"*s. Alwa-s keep %ire$%ighting e3"ip*ent on hand.

!lean r"st8 scale8 paint8 or dirt %ro* the oints that are to +ewelded.


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Striking The Arc

Select the best electrode

Set the welder 34ig (5$*6

Turn on welder

Warn bystanders

7ower helmet

Start arc 3two methods6

4r"shing

Tapping


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4r"shing Method

Hold end o% electrode a+o"t 9:; $ 9:2 inch a+oe the s"r%ace.

Lower hel*et

Gentl- +r"sh s"r%ace o% the *etal with the end o% the electrode.

When arc starts8 li%t electrode 9:< inch.

2f electrode stics, twist it bac and forth. 2f it does

not brea loose, release electrode from electrodeholder.

(o not sh"t o%% the welder with the electrode st"ck to the*etal.


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Tapping Method

Set up welder

8old the electrode at the travel angle and )'+ $ )'(inch above the metal.

9uicly lower the electrode until it touches the metaland then lift it )'* inch.


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lectrode Angle

The electrode angle influences theplacement of the heat.

Two angles are important Trael Work

The travel angle is the angle of the

electrode parallel to the %oint. The correct travel angle must be

used for each %oint. 4eads = 95o %ro* ertical or >5o %ro* the

work. 4"tt oint = 95o %ro* ertical or >5o %ro*

the work. Lap oint = ;5o. T oint = ;5o. !orner = 95o %ro* ertical or >5o %ro*

the work.


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lectrode Angle$cont.

The wor angle is the angle of the electrodeperpendicular to the %oint.


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lectrode Angle$cont.

The appropriate angle must beused for each %oint.:eads ; o!orner ;


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Arc Length

When an arc is too long8 the*etal *elts o%% the electrode in

large glo+"les and the arc *a-

+reak %re3"entl-. This prod"ces a

wide8 spattered8 and irreg"lar

deposit with ins"%%icient %"sion

+etween the +ase *etal and theweld. When an arc is too short8 it

%ails to generate eno"gh heat to

*elt the +ase *etal properl-8

ca"ses the electrode to stick

%re3"entl- to the +ase *etal8 and

prod"ces "neen deposits withirreg"lar ripples. The

reco**ended length o% the arc is

e3"al to the dia*eter o% the +are

end o% the electrode


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Arc Length

The arc length is the distance from the metal part ofthe electrode to the weld puddle.

The best arc length is not a fi"ed distance, but shouldbe appro"imately e?ual to the diameter of theelectrode.

Arc length can be ad%usted slightly to change thewelding process.

E"cessive length

,cessie spatter

)ed"ced penetration

Poor 3"alit- weld

2nsufficient length

lectrode sticks

arrow weld

Poor 3"alit- weld


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Speed o% Trael

The speed of travel 3inches per minute6 is animportant factor when arc welding.

The best speed of travel 3welding speed6 isdetermined by several factors

The si&e o% the oint8

The t-pe o% electrode The si&e o% the electrode

The a*perage setting on the *achine

(eposition rate o% the electrode /c"+ic inches per *in"te1

The deposition rate of an electrode will change with

the welding amperage.


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Speed$cont.

The ideal speed can becalculated using the volume ofthe %oint and the depositionrate of the electrode.

Step one determine the areaof the weld. 3Assuming )')5inch penetration.6

Step Two nowing thedeposition rate of theelectrode, determine thewelding speed. 3/eposition

rate ; (.> in&'min.6

Area = 1

2bh = 0.25 in x 0.25 in

2= 0.0625 in

2

in

min=2.5 in

3

min x

1

0.0625 in2= 40

in

min


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Speed$cont.

The correct welding speed is indicated by theshape of the ripples.

Too %ast = narrower width8elongated ripple pattern8shallow penetration.

)eco**ended = width 2$?ti*es dia*eter o% electrode8

"ni%or* ripple pattern8 %"llpenetration.

Too slow = e,cessie width8

e,cessie penetration


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,a*ples o% SMAW Welds


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#lat Position @ 4"tt oints piping

arlier ree,plained that welding can +e done in an- position8 +"t itis *"ch si*pler when done in the %lat position. In this position8

the work is less tiring8 welding speed is %aster8 the *olten p"ddle

is not as likel- to r"n8 and +etter penetration can +e achieed.

Wheneer possi+le8 tr- to position the work so -o" can weld in

the %lat position. In the %lat position8 the %ace o% the weld is

appro,i*atel- hori&ontal.


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#lat Position @ 4"tt oints M"ltipass

piping


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Weaing Motions

Bo" *a- "se oneo% the weaing

*otions shown8

depending "pon

the t-pe o% oint

and si&e o%

electrode.


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Hori&ontal Position

*ou will discover that it is impossible to weld allpieces in the lat position" +ten the wor# must bedone in the horizontal position" $he horizontalposition has two basic orms, dependin% uponwhether it is used with a %roove weld or a illet

weld" n a %roove weld, the axis o the weld lies in arelative horizontal plane and the ace o the weld isin a vertical plane" n a illet weld, the weldin% isperormed on the upper side o a relativelyhorizontal surace and a%ainst an approximately

vertical plane


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Certical Position

A Dertical weldE is de%ined as a weld that is applied to a erticals"r%ace or one that is inclined ;5 degrees or less. recting

str"ct"res8 s"ch as +"ildings8 pontoons8 tanks8 and pipelines8

re3"ire welding in this position. Welding on a ertical s"r%ace is

*"ch *ore di%%ic"lt than welding in the %lat or hori&ontal position

d"e to the %orce o% grait-. Grait- p"lls the *olten *etal down.

To co"nteract this %orce8 -o" sho"ld "se %ast$%ree&e or %ill$%ree&e

electrodes. Certical welding is done in either an "pward or

downward position. The ter*s "sed %or the direction o% welding

are vertical up or vertical down.

Vertical down welding is s"ited %or welding light ga"ge *etal+eca"se the penetration is shallow and di*inishes the possi+ilit-

o% +"rning thro"gh the *etal. #"rther*ore8 ertical down welding

is %aster which is er- i*portant in prod"ction work.


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0erhead Position

0erhead welding is the *ost di%%ic"lt position in welding. ot onl- do

-o" hae to contend with the %orce o% grait- +"t the *aorit- o% the ti*e

-o" also hae to ass"*e an awkward stance. eertheless8 with practice

it is possi+le to *ake welds e3"al to those *ade in the other positions.

!"rrent Settings and lectrode Moe*ent

To retain co*plete control o% the *olten p"ddle8 "se a er- short arc andred"ce the a*perage as reco**ended. As in the ertical position o%

welding8 grait- ca"ses the *olten *etal to drop or sag %ro* the plate.

When too long an arc is held8 the trans%er o% *etal %ro* the electrode to

the +ase *etal +eco*es increasingl- di%%ic"lt8 and the chances o% large

glo+"les o% *olten *etal dropping %ro* the electrode increase.When -o" ro"tinel- shorten and lengthen the arc8 the dropping o% *olten

*etal can +e preentedF howeer8 -o" will de%eat -o"r p"rpose sho"ld

-o" carr- too large a pool o% *olten *etal in the weld.


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Show SMAW piping


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05-1 How Do SMAW Piping

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