Teknologi Dan Rekayasa OXY-ACETYLENE WELDING. Teknologi dan Rekayasa The setting of oxy-acetylene...

Teknologi Dan Rekayasa

OXY-ACETYLENE WELDING

Teknologi dan Rekayasa

The setting of oxy-acetylene The setting of oxy-acetylene welding equipmentwelding equipment

OBJECTIVE :OBJECTIVE :

After studying this lesson, the After studying this lesson, the students can be to explain the students can be to explain the setting of oxy-acetylene welding setting of oxy-acetylene welding equipment.equipment.


The oxy-acetylene welding setThe oxy-acetylene welding set

The high pressure oxy-acetylene welding set is The high pressure oxy-acetylene welding set is consist of two steel cylinders that contain oxygen consist of two steel cylinders that contain oxygen and acetylene gases.and acetylene gases.

Attached to these cylinders are two regulators. Attached to these cylinders are two regulators. The function of these regulators is to reduce the The function of these regulators is to reduce the cylinder pressure to a suitable working pressure cylinder pressure to a suitable working pressure and hold that pressure constant regardless of the and hold that pressure constant regardless of the size of flame being used.size of flame being used.

The regulators are connected by two rubber The regulators are connected by two rubber hoses to a hand torch.hoses to a hand torch.

The torch has two valves to control the gas flow The torch has two valves to control the gas flow and interchangeable tips of different sizes to and interchangeable tips of different sizes to provide different sizes of flame.provide different sizes of flame.


The oxy-acetylene welding set


Safety precautions of the Safety precautions of the oxygen cylinderoxygen cylinder

1.1. Cylinders should not be used as rollers or Cylinders should not be used as rollers or anvils as this may damage the case. Also, if anvils as this may damage the case. Also, if the brass valve is broken off the cylinder, the the brass valve is broken off the cylinder, the gas will exhaust at a violent rate.gas will exhaust at a violent rate.

2.2. The cylinder valve should be opened only The cylinder valve should be opened only two or three turns. If gas leaks around the two or three turns. If gas leaks around the valve stem, the brass gland-nut should be valve stem, the brass gland-nut should be tightened.tightened.



3.3. No oil or grease should be used on oxygen or No oil or grease should be used on oxygen or other gas connections. If even a very small other gas connections. If even a very small quantity of oil is placed under pressure in quantity of oil is placed under pressure in glass line, it will explode in much the same glass line, it will explode in much the same way as the oil fuel in a diesel engine cylinder.way as the oil fuel in a diesel engine cylinder.

Note that gas connections are all made of Note that gas connections are all made of brass, so oil is not needed to join these brass, so oil is not needed to join these together.together.

4.4. Cylinders should not be heated as this tends Cylinders should not be heated as this tends to expand their contents with sub-sequent risk to expand their contents with sub-sequent risk of explosion.of explosion.



Liquid OxygenLiquid Oxygen. . When oxygen is compressed and cooled to When oxygen is compressed and cooled to liquid state, there are 814 litres of gas available liquid state, there are 814 litres of gas available from every litre of liquid. For this reason. It is from every litre of liquid. For this reason. It is very economical to transport large quantites of very economical to transport large quantites of oxygen in liquid form.oxygen in liquid form.Large users of oxygen may have an insulated Large users of oxygen may have an insulated container of liquid oxygen installed on their container of liquid oxygen installed on their premises together with an evaporator unit that premises together with an evaporator unit that turns the liquid oxygen back into oxygen gas.turns the liquid oxygen back into oxygen gas.The insulated storage tank is kept filled by and The insulated storage tank is kept filled by and insulated road tanker from the manufacturer.insulated road tanker from the manufacturer.



Precautions withPrecautions with Liquid oxygenLiquid oxygen..

Liquid oxygen is intensely cold and must Liquid oxygen is intensely cold and must never be allowed to touch human flesh. The never be allowed to touch human flesh. The temperatures involved can cause human temperatures involved can cause human tissue to freeze and be permanently tissue to freeze and be permanently destroyed.destroyed.


Oxygen and acetylene cylinder


Safety precautions of the acetylene Safety precautions of the acetylene cylindercylinder

Acetylene cylinders must not be used as Acetylene cylinders must not be used as anvils or rollers. This is because a dent in anvils or rollers. This is because a dent in the cylinder may pulverize some of the the cylinder may pulverize some of the porous filling and increase the size of the porous filling and increase the size of the storage voids to a dangerous level.storage voids to a dangerous level.

Cylinders must not be heated either in the Cylinders must not be heated either in the hot sun or by a flame. The contents could hot sun or by a flame. The contents could explode if heated. Each cylinder contains explode if heated. Each cylinder contains fusible safety plugs that will melt at 100° fusible safety plugs that will melt at 100° C if the cylinder is heated, these plugs C if the cylinder is heated, these plugs melt and release the gas, preventing melt and release the gas, preventing dangerous pressure from building up dangerous pressure from building up within the cylinder that could explode within the cylinder that could explode violently.violently.


Faults in Gas RegulatorsFaults in Gas Regulators

Regulators are generally very reliable in service Regulators are generally very reliable in service but may suffer at times from the following faults but may suffer at times from the following faults ::

1.1. Creep or surgeCreep or surge : The torch pressure may : The torch pressure may creep up when the torch is turned off or creep up when the torch is turned off or may surge up and down during flame may surge up and down during flame adjustment. This is caused by a leaking adjustment. This is caused by a leaking regulator valve or seat.regulator valve or seat.

CureCure : Replace regulator valve and/or seat. : Replace regulator valve and/or seat.



2.2. FreezingFreezing : Regulators may freeze at very : Regulators may freeze at very high flow rates.high flow rates.

CureCure : Turn off and allow to thaw or pour : Turn off and allow to thaw or pour hot water over the regulator case. hot water over the regulator case. Alternatively, the flow may be reduced by Alternatively, the flow may be reduced by using a number of cylinders with separate using a number of cylinders with separate regulators to supply the necessary flow. A regulators to supply the necessary flow. A two stage regulator will carry larger flows two stage regulator will carry larger flows without freezing.without freezing.



3.3. Leaking Bullnose SpigotLeaking Bullnose Spigot : The bullnose : The bullnose may leak even though it is very tight in the may leak even though it is very tight in the cylinder fitting. This is caused by damage to cylinder fitting. This is caused by damage to the brass face of the cylinder O ring or by the brass face of the cylinder O ring or by dirt deposited in the valve. dirt deposited in the valve.

CureCure : renew or remachine the bullnose : renew or remachine the bullnose face and remove dirt before inserting face and remove dirt before inserting valve.valve.Note : Note : The practice of using a lead washer The practice of using a lead washer between a between a leaking bullnose and cylinder valve is to be leaking bullnose and cylinder valve is to be discouraged as it can cause a blockage in the discouraged as it can cause a blockage in the valve or regulator.valve or regulator.


Safety with RegulatorsSafety with Regulators

1.1. No oil or grease should be used on any part No oil or grease should be used on any part of the regulator or bullnose. This is because of the regulator or bullnose. This is because oil subjected to high pressure can explodeoil subjected to high pressure can explode

2.2. The regulator adjusting knobs should never The regulator adjusting knobs should never be screwed into their limit and left there. This be screwed into their limit and left there. This is because this can stop the regulating valve is because this can stop the regulating valve from working, and a blocked blowpipe tip can from working, and a blocked blowpipe tip can allow high pressure oxygen to enter the allow high pressure oxygen to enter the acetylene line with risk of explosion.acetylene line with risk of explosion.

Safety with HosesSafety with Hoses

The gas is carried between the regulators The gas is carried between the regulators and the blowpipe by flexible reinforced and the blowpipe by flexible reinforced rubber hoses.rubber hoses.

Rubber hoses should not be used for liquified Rubber hoses should not be used for liquified petroleum gas as this gas causes petroleum gas as this gas causes deterioration of the rubber.deterioration of the rubber.

Hose connections are made of brass and Hose connections are made of brass and have threads. Because interchanging of the have threads. Because interchanging of the hoses could cause dangerous gas mixtures hoses could cause dangerous gas mixtures and pressures, the acetylene connections and pressures, the acetylene connections always have left hand threads. always have left hand threads.

Lighting the BlowpipeLighting the Blowpipe1.1. With a valve key open the valve on each cylinder With a valve key open the valve on each cylinder

slowly. This allows the gas to fill the regulators.slowly. This allows the gas to fill the regulators.2.2. The regulators adjusting knobs are screwed in The regulators adjusting knobs are screwed in

until the working pressure gauge reads the until the working pressure gauge reads the correct pressure for the welding blowpipe –34 correct pressure for the welding blowpipe –34 kPa for acetylene and 69 kPa for oxygen.kPa for acetylene and 69 kPa for oxygen.

3.3. Having screwed a welding tip onto the torch Having screwed a welding tip onto the torch (say, a size 15), turn on the blowpipe acetylene (say, a size 15), turn on the blowpipe acetylene and light the gas flowing from the tip. A sooty, and light the gas flowing from the tip. A sooty, yellow flame will result.yellow flame will result.

4.4. Gradually turn on the blowpipe oxygen and outer Gradually turn on the blowpipe oxygen and outer cone. If the flame is too fierce, turn both cone. If the flame is too fierce, turn both blowpipe valves off a little. If the flame is too blowpipe valves off a little. If the flame is too small, turn both blowpipe valves on little.small, turn both blowpipe valves on little.

To Turn Off the BlowpipeTo Turn Off the Blowpipe

1.1. Turn off the blowpipe acetylene valve. (This stops Turn off the blowpipe acetylene valve. (This stops the flame immediately). the flame immediately).

2.2. Turn off the blowpipe oxygen valveTurn off the blowpipe oxygen valve3.3. Turn off the gas at the cylinder with the cylinder Turn off the gas at the cylinder with the cylinder

key.key.4.4. Open and close the blowpipe valves one by one Open and close the blowpipe valves one by one

to remove the gas from the regulators and hoses.to remove the gas from the regulators and hoses.5.5. Unscrew both regulator adjusting knobs so that Unscrew both regulator adjusting knobs so that

there is no spring tension remaining against the there is no spring tension remaining against the diaphragm.diaphragm.

Always turn off the welding set and remove the gas Always turn off the welding set and remove the gas and the tension from each regulator diaphragm. This and the tension from each regulator diaphragm. This prevent gas leakage and stops excessive wear of the prevent gas leakage and stops excessive wear of the regulator valves seats.regulator valves seats.

Flame AdjustmentFlame Adjustment The flame used for welding must be hot The flame used for welding must be hot

enough to easily raise the metal to be enough to easily raise the metal to be welded to its melting point.welded to its melting point.

There are three types of oxy-acetylene There are three types of oxy-acetylene welding flames. These are called welding flames. These are called neutral, oxidising and carburising.neutral, oxidising and carburising.

The blowpipe flame may be adjusted to The blowpipe flame may be adjusted to a neutral, oxidising or carburising a neutral, oxidising or carburising flame. Each type of flame has its own flame. Each type of flame has its own special use, and careful adjustment it special use, and careful adjustment it necessary before welding commences.necessary before welding commences.

Flame Adjustment

Oxidising flame

Neutral flame

Carburising flame

Unburnt gases

Short fierce inner cone

Hottest part of flame

5 mm

Flame AdjustmentFlame Adjustment Neutral flame :Neutral flame :

Equal volumes of oxygen and Equal volumes of oxygen and acetylene. Greatest heat 5 mm from acetylene. Greatest heat 5 mm from end of inner cone. Used for welding. end of inner cone. Used for welding.

Oxidising flame :Oxidising flame :Excess oxygen causes oxidation of the Excess oxygen causes oxidation of the weld pool. Used for brazing.weld pool. Used for brazing.

Carburising flame :Carburising flame :Excess of acetylene turns into carbon Excess of acetylene turns into carbon which mixes with the weld pool. Used which mixes with the weld pool. Used for Linde welding.for Linde welding.


THE ENDTHE END

THANK YOUTHANK YOU

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Teknologi Dan Rekayasa OXY-ACETYLENE WELDING. Teknologi dan Rekayasa The setting of oxy-acetylene...

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