2 gas welding

7/25/2019 2 Gas Welding

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Gas Welding (Oxy-acetylene)

A number of welding processes use a flameproduced by burning a mixture offuel gasand

oxygen. The gas usually used isAcetylenebut

other gases are also used.eparate cylinders and

a hose pipe from each

cylinder transports the

gases to a torch.

Gas and fuel mix in

the torch burns !

"#$$%&.


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Gas Welding


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'uring the welding heat from the flame is

concentrated on the oint edges until the

metal melts and starts to flow. When the

molten metal from both sides melts it starts to

fuse when the metal cools down the two parts

becomePermanentlyoined

AdditionalFiller

Metalis fed in by

hand into the weld

pool at regularinter*als where it

becomes molten

and oins with the

parent metal.


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Oxy-acetylene

fames


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Carburising Neutral Oxidising

The Oxy-acetylene welding +lame


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Equipment used in Oxy-

Acetylene welding

The oxygen and acetylene hose pipes

Gases used

Gas pressure ,egulators

+lashbac arrestor

Welding torchWelding no//le

+iller rods and fluxes


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The oxygen and acetylene hose pipes

,einforced rubber hoses.

Acetylene hose has left hand thread couplings and colour

coded red.

Oxygen hose has right handed thread couplings and colour

coded blue


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Gases used O0 and &010

Oxygen extracted from air and compressed into cylinders at high

pressure. &ylinder is blac.

Acetylene (&010) is a fuel gas. &annot be compressed directly as

explodes at high pressures.

&ylinders are paced with porous material which is filled withacetone.

Acetone absorbs acetylene. &ylinder colour coded maroon


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Gas 2ressure ,egulators

One gauge indicates the pressure of the cylinder and the

other indicates the pressure in the supply pipe to the torch.


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Welding torch

Oxygen and acetylene are deli*ered to the torch by separate hoses.

3ach gas is controlled by a *al*e on the torch.

The two gases mix in the torch and after they are ignited burn at

the no//le.

4ixer 5eedle *al*es


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+lashbac Arrestors

These are positioned on both the fuel gas and oxygen

supply between the hose and the regulator. Their purpose

is to pre*ent the return of a flame through the hose into

the regulator.


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+iller ,ods and fluxes

+iller rods are used when additional filler metal is re6uired in the

weld area they come in different diameters.

+luxes protect the weld pool from contamination by oxygen andnitrogen they are normally in paste form placed on a heated

filler rod before welding begins


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'angers of OAW

The combination of acetylene and oxygen is highly

flammable and the en*ironment in which OAW is performed

is therefore ha/ardous.

ome of the dangers relate specifically to the acetylene.

1) Pure C2H2 is a clrless! drless gas"

olution7 +or safety reasons commercial acetylene isprocessed to ha*e a characteristic garlic odor.


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'angers of OAW

2) One # t$e p$ysical limitatins # t$e gas is t$at it is

unstable at pressures muc$ ab%e 1 atm &'"1 (Pa).

lutin7 Accordingly acetylene storage cylinders are pacedwith a porous filler material (such as asbestos balsa wood and

other materials) saturated with acetone (&1"&O&1").

Acetylene dissol*es in li6uid acetone8 in fact acetone dissol*es

about 09 times its own *olume of acetylene thus pro*iding arelati*ely safe means of storing this welding gas.


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2lease study the

ad*antages and

disad*antages from*ideo

2 gas welding

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