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OXY-ACETYLENE PROCESS (OXY)

Learner Guide

TABLE OF CONTENTS INTRODUCTION PAGE 1 LEARNERS INSTRUCTIONS PAGE 2 PROGRAMME 1 PART 1 – OXY-ACETYLENE EQUIPMENT PAGE 3 SELF-TEST EXERCISE 1 PAGE 8 PART 2 - EQUIPMENT PREPARATION PAGE 11 SELF-TEST EXERCISE 2 PAGE 15 GENERAL SAFETY PAGE 17 SELF-TEST EXERCISE 3 PAGE 22 PROGRAMME 2 BASIC WELDING SKILLS PAGE 24 EXERCISE 1 WELDING POOL PAGE 25 EXERCISE 2 WELD POOL AND FILLER ROD PAGE 28 BASIC JOINTS AND WELDING TECHNIQUES PAGE 31 EXERCISE 3 PREPARE A BUTT-JOINT (TACK WELD) PAGE 34 EXERCISE 4 WELD A BUTT JOINT PAGE 37 EXERCISE 5 LAP JOINT (FILLET WELD) PAGE 40 EXERCISE 6 CORNER WELD PAGE 42 ADDITIONAL WELDING NOTES PAGE 44 PROGRAMME 3 FLAME CUTTING PAGE 47 SELF-TEST EXERCISE 4 (EQUIPMENT) PAGE 51 SELF-TEST EXERCISE 5 (PREPARATION) PAGE 56 EXERCISE 7 FREEHAND CUTTING PAGE 59 EXERCISE 8 USING A CUTTING-GUIDE PAGE 61 EXERCISE 9 CUTTING ANGLE-IRON PAGE 63 EXERCISE 10 CUTTING STEEL PIPES PAGE 65 NOZZLE TIP MAINTENANCE PAGE 67

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INTRODUCTION This Learning aid consists of this workbook and a video programme that has been designed to assist you to learn the BASIC SKILLS involved in using oxy-acetylene sets for welding and for flame-cutting. OBJECTIVES (What purpose does this training material serve?) This series of lessons serves to assist you, the Learner, in reaching for a "Learnership" in any of the engineering fields where welding is given as a "unit" of your learning. PURPOSE STATEMENT (What you will learn) You, the Learner, will be shown how to:

o Identify, by name, the components involved in a typical "portable" gas welding-set. o Prepare the system for welding or flame cutting processes. o Describe "safe working practices" during the use of oxy-acetylene

equipment/processes. o Perform basic welding processes on metal plate up to 3.2 mm. o Perform flame-cutting processes on steel plates and pipe.

LEARNING ASSUMED TO BE IN PLACE (What you should already know)

o You should have an understanding of industry and the work environment in terms of "Occupational Health and Safety" relevant to engineering and metal work operations.

o You should be familiar with the various materials, such as metals, that are used throughout engineering and metal work operations.

LEARNING OUTCOMES (What you will be able to do after completing this series of instruction) Upon successful completion of this series you, the Learner, will be able to:

o Prepare an oxyacetylene welding set for welding and for flame cutting processes. o Operate a welding torch in a responsible and safe manner. o Perform basic "down-hand" welding procedures in the processes of:

Tack welding. Welding a "butt-joint". Welding a "Lap-joint". Welding an "Outside Corner Joint".

o Perform basic "Flame Cutting Processes" in the manual processes of: Free-hand cutting. Using a cutting-guide to create straight and bevel cuts. Cut angle-iron. Cut steel pipes.


LEARNERS INSTRUCTIONS (How to use this Learning Aid) Step 1 - Read the Resource Notes and follow the written instructions. Step 2 - View the relevant video section (where applicable). Step 3 - Complete the relevant "Self-Test Exercise" (where applicable). Step 4 - Perform any practical exercise (when applicable). Step 5 - Have your Facilitator/Mentor check your work.


OXY-ACETYLENE PROCESSES EQUIPMENT & EQUIPMENT PREPARATION (DVD PROGRAMME-1)

PART ONE - BASIC EQUIPMENT AND ACCESSORIES In this part of the programme you will be introduced to the basic equipment and accessories that constitute a typical "gas welding / cutting set". When you have completed this section you will be able to:

o Identify oxygen and acetylene cylinders by their colours, shape and size. o Identify, and explain the purpose of regulators. o Identify and explain the purpose of flashback arresters. o Identify welding hoses by colour. o Identify a welding torch and a cutting torch. o Identify a spark lighter. o Describe and select appropriate Personal Protective Equipment that should be worn

/ used during welding and flame-cutting processes.

BEGIN NOW BY READING THROUGH THE RESOURCE NOTES (PART 1).


RESOURCE NOTES - PART 1 OXYACETYLENE EQUIPMENT

1. BASIC EQUIPMENT CYLINDERS There are two cylinders in a standard gas welding/cutting set namely:

o An Oxygen cylinder. o An Acetylene cylinder.

The cylinders can be identified by their colours, size and by the suppliers' labels. Oxygen cylinders are painted BLACK and are taller and narrower than acetylene cylinders. Acetylene cylinders are painted MAROON and are shorter and "fatter" than oxygen cylinders. Oxygen cylinders, when full, contain oxygen at a pressure of approximately 15 000 kPa. (1,5 mPa) Acetylene cylinders, when full, contain a vapour-pressure of approximately 1800 kPa. Both cylinders should be stored and used in an UPRIGHT position. N.B.: This is especially important with acetylene cylinders. All "portable" equipment must be supported and transported using a "welding trolley". Cylinders must be chained or otherwise secured to the trolley so that they cannot topple over during use. When a cylinder is to be moved for a short distance (over level ground only) then it should be kept upright and "walked" into position. This is achieved by rotating the cylinder as you lean it slightly toward you. At the top of each cylinder is a "cylinder-valve". The purpose of a cylinder valve is to open or close the gas supply to the system. The valves shown in the video are surrounded, and therefore protected with a metal "protection-collar". The protection collar prevents the valves from damage, especially during transportation. Note that not all cylinders have this feature. Older designs may be found whereby the valves are protected using a "protection-cap" threaded onto the cylinder. This cap is used for transportation and storage and has to be removed in order to use the gas, thereby leaving the valve "unprotected" during normal use. Cylinder valves may be operated with a hand-wheel, like the type featured in the video or, with a "spindle-key".


REGULATORS The pressures contained inside the cylinders are far in excess of the pressure needed to operate a torch. In order to control the pressure leaving a cylinder and entering the welding hoses we need a "pressure-regulator" to prevent the hoses and the torch from "blowing up". In "everyday language" these devices are simply known as "regulators". There are various types and makes of regulators, however those featured in the video are most commonly encountered. Regulators are made specifically for the type of gas that they must control and for the degree of pressure that they must withstand. For these reasons regulators are made in such a way that they cannot be fitted to the wrong cylinder. A regulator is connected to a cylinder-valve with a special connector known as a "bull-nose". The threads on the Acetylene regulators' bull-nose are "left-handed" whereas the threads on an Oxygen regulator are "right-handed". This feature makes it "almost impossible" to get things mixed up. As an added precaution, you will find that regulators are "colour coded". Blue is the colour used to denote "oxygen", and red is the colour used to denote acetylene. An oxygen regulator will bear a blue label with the word "oxygen" on it. The acetylene regulator will bear a red label with the word "acetylene" on it. As if this were not enough to avoid confusion, you will also notice that the connector-nut of the acetylene bull-nose has a groove machined into it. Any threaded fitting that features a groove indicates that the threads are "left-hand". (This is an international identification mark). Regulators most usually have two pressure gauges. One gauge (normally the one nearest to the bull-nose) is a "high-pressure gauge" that registers the pressure within the cylinder. This is known as the "cylinder-gauge". The other gauge, called the "working gauge", registers the pressure that is leaving the regulator and entering the hose and torch. This gauge (working gauge) carries much lower pressure than the cylinder gauge. A prominent feature of any regulator is the "pressure adjusting-screw". This screw is used to "set" the working pressure into the hose/torch. On ALL regulators the "Line pressure" (working pressure) is INCREASED by turning the pressure adjusting screw inward, that is, to the right (your right). Pressure is DECREASED by turning the screw outward, that is, to the left. When you operate the equipment, you must know this! Gas leaves the regulator through the outlet port. FLASHBACK ARRESTERS A "flashback" arrester is a special device that should be connected to the regulator at the outlet nipple. The purpose of this device is to prevent an explosion of the cylinder in the event that a "flashback" occurs in the hose. A "flashback" is when a


flame travels back into the torch and on into the hose toward the cylinder. This can happen for a variety of reasons, not least of which is "negligence" on the part of the Operator! NOTE: It is extremely "risky" to operate without flashback arresters fitted to the regulator end of each welding hose. Many operators will fit these devices to the "torch end" of the hoses as well, just to be on the SAFE side! WELDING HOSES Welding hoses carry the gases from the regulator to the torch. These hoses are specially manufactured from materials that can withstand pressure and chemical reactions. NO OTHER HOSE TYPE MAY BE USED! Hoses are colour coded to avoid accidental switching between gas types. The colours are the same as for regulators, that is, RED for acetylene, and BLUE for oxygen. The hoses connect to the regulator, or to the flashback arrester, and at the other end to the torch. The Acetylene connectors (at both ends of the red hose) are "Left Handed". Oxygen connectors are "right-handed". This is intended to prevent the "accidental" swapping of hoses. TORCHES There are two types of torches normally associated with oxy-acetylene equipment, namely:

1. Welding torches. 2. Cutting torches (flame cutting).

A welding torch is used in the joining of materials, whereas the cutting torch is used in the "separation" of materials. The function of each type however is to "apply heat" to material via a "flame" created at the nozzle or the cutting tip. It is in the torch that acetylene and oxygen are "mixed". The mixture is affected through "control-valves" set into the hose end of the torch handle. The torch control-valves are manually adjusted by the operator in order to achieve the desired flame (more on this in the next part of this programme). Once again, you will see the colours RED and BLUE featured, this time on the control valve hand-wheels. The control valves "control" the volume or flow of gases into the torch. The flow is "shut off' when the hand-wheel is turned fully in (to the right) and "open" when turned out (to the left). On some torches, you will find "non-return valves" fitted to the inlet connections. A "non-return valve" permits gas to flow in one direction only, namely from the hose and into the torch. The purpose of the non- return valve is to prevent the accidental flow of gas, from the torch, into either hose. NOTE: It must always be kept in mind that when the gases are "mixed" there is an increased chance of combustion taking place. If a welding hose ever contains "mixed gases" then a "flashback" can happen with alarming speed!


ACCESSORIES Various accessories can be obtained as aids to welding or cutting processes. Two accessories need special mention, namely:

o Spark-Lighter -used to light the torch in a "safe" manner. o Nozzle Tip cleaners -used to clear blockages in torch tips and nozzles.

PERSONAL PROTECTIVE EQUIPMENT Personal protective equipment (also known as PPE) should always be used whenever using oxy-acetylene sets. The following items should always be available and used whenever the need arises. SPATS These leather coverings are worn over the shoes or boots in order to prevent sparks or "slag" (molten metal) from falling and burning your feet. WELDERS APRON If you want to protect your upper body and your clothes from burns caused by sparks then the welder’s apron should be worn. WELDING GOGGLES Goggles are "essential" if you want to protect your eyes from injury. Gas welding goggles have specially shaded lenses that "filter out" harmful rays that are generated in the welding or the cutting processes. Goggles also protect your eyes from flying particles (sparks). It is "mandatory" for you to wear proper "Welding Goggles" in terms of all occupational health and safety acts around the world. NOTE: Sun-glasses are NOT considered safe for use with welding operations. WELDING GLOVES These are designed to prevent hand injury, as a result of sparks, heat from the welding / cutting process and from the accidental handling of hot material. NOTE: All leather PPE articles are made using a specially prepared "Chrome- Leather". Standard leather and other materials (such as PVC) are not suitable for use in the presence of heat, flame or sparks.

NOW VIEW THE VIDEO -PART 1 “OXYACETYLENE EQUIPMENT" THEN COMPLETE SELF -TEST NO. 1.




SELF-TEST NO. 1 BASIC OXY-ACETYLENE EQUIPMENT

INSTRUCTIONS Complete the following exercise without reference to your notes or the video. When you have completed the exercise check your answers / responses by:

o Referring to your notes. o Reviewing the video material. o Asking your Facilitator / Mentor.

QUESTION (tick correct answer/s) YES NO

1. Oxygen cylinders, used for welding equipment, are painted (what colour) _________________. Acetylene cylinders are painted (what colour) ______________.

2. The pressure within a “full” oxygen cylinder is what? a) 15 kPa. b) 15 000 kPa. c) 1 500 psig.

3. The pressure within a “full” acetylene cylinder is what? a) 1 800 kPa. b) 18 000 kPa. c) 1 800 bars.

4. The purpose of a “Regulator” is what? a) To increase the gas pressure to the torch. b) To control the gas pressure and flow from the cylinder. c) To prevent the waste of gas.

5. The colour-coding used for all “oxygen” fittings and hoses is what? ANS: ________________________________________________

6. The colour-coding used for all “acetylene” fittings and hoses is what? ANS: ________________________________________________


7. All the threaded fittings of the “oxygen” supply have what type of threads? ANS: ________________________________________________

8. The “notch” or “groove” in all the threaded fittings of the acetylene supply indicates that these fittings are what? ANS: ________________________________________________

9. If the “pressure adjusting screw” on a regulator is turned “in” (clockwise) what effect will this have? ANS: ________________________________________________

10. How will you notice the effect mentioned in question 9? ANS: ________________________________________________

11. What does the other gauge on the regulator indicate? ANS: ________________________________________________

12. What do you normally find fitted to the output connection of a regulator? a) Non-return valve. b) Flashback arrester.

13. What might you find at the “torch-end” of a welding hose? a) Flashback arrester. b) Non-return valve.

14. To which “torch connection” is the “red” welding hose attached? ANS: ________________________________________________

15. List 4 items of PPE that should be worn when you use oxy-acetylene equipment. i) _______________________________________________ ii) _______________________________________________ iii) _______________________________________________ iv) _______________________________________________


NOW READ THROUGH THE RESOURCE NOTES (PART 2).


RESOURCE NOTES - PART TWO PREPARATION OF EQUIPMENT

1. FITTING OF REGULATORS Regulators have to be fitted (exchanged) from time to time. Whenever an empty cylinder has to be replaced then it is necessary to remove the existing regulator and replace it onto the "fresh" cylinder. The task of fitting a regulator is not complicated and, if you follow the procedures demonstrated in the video, the job will be done "safely". The procedure is summarised below.

1) When the replacement cylinder has been installed and secured in the trolley, remove the protection cap or plug from the cylinder valve. 2) Standing aside (not facing the valve), quickly open and then close the cylinder valve for a "short burst". This is done to blowout any foreign matter that could enter the regulator. 3) Remove (if fitted) the protection cap from the "bull-nose" of the regulator. Note that a regulator should never be stored without a cover over the bull- nose and the outlet connection, as dirt will enter the working components. 4) Thread the bull-nose into the cylinder valve and tighten it with "hand pressure" until it "seats". Remember that the acetylene connector has a "left-hand thread" so you must turn the connecting nut "backward". 5) Secure the connecting nut firmly using a "correctly fitting spanner". It is strongly recommended that you do not use a "shifting spanner" or any other "adjustable device" to secure the nut. Use of such tools in this application will generally cause damage to the nut. 6) Connect the welding hose, together with the flashback arrester, to the regulators' outlet connecting nipple. Again, we strongly recommend the use of "correctly fitting spanners" in order to avoid damage to the connecting nuts. Use two spanners where necessary, to avoid twisting the fittings. 7) Connect the welding hose to the torch, if necessary. 8) Ensure that the regulator "pressure adjusting screw" is turned fully out (minimum pressure) before attempting to open the cylinder valve.

2. PREPARE THE GAS SUPPLY-WELDING OPERATIONS In this section it will be assumed that a "welding torch" has been connected and that our need for the equipment is to perform a "welding operation". At this time we need make a "general statement" that is applicable no matter what process you will be using: Always-reduce the pressure regulator to "minimum working pressure" before opening the cylinder valve. If you ignore this warning then you run the risk of destroying the regulator and putting yourself at high risk.


Follow this procedure for setting up your gas supply to a torch: 1) Making sure that the regulator pressure adjusting screw has been fully turned out (minimum working pressure), and then standing aside (not facing the gauges) open the cylinder valve SLOWLY. Open the valve about 1/2, turn but no more than one full turn of the hand wheel (or spindle). NOTE: Opening this valve "rapidly" will result in serious regulator damage and the possible "explosion" of the cylinder pressure gauge. 2) Observe the cylinder pressure gauge (after opening the valve). This gauge will show the remaining pressure within the cylinder. The pressure must not exceed that stated on the cylinder label. if the pressure is higher than stated on the label then immediately close the cylinder valve and notify your Supervisor or call your gas dealer. 3) Observe that the gas pressure is not in the "empty zone" on the gauge. Do not continue to operate (or attempt to operate) with an empty cylinder. 4) Set the "working pressures" on each regulator to 60 kPa. This pressure is suitable for welding operations. When setting the "working pressure" observe the following procedure:

o Set one gas at a time. o Open the torch valve for the gas you are adjusting. o Turn the pressure adjusting screw in (to the right) and observe the

gauge all the time. o Stop turning the screw when the needle sits over the 60 kPa mark. o Shut off the torch control valve. o Repeat the procedure for the remaining regulator. o Make sure that the torch valves are shut off. o Direct the torch nozzle away from your face and body during the

adjusting process. o Do not perform this operation within a "confined space".

5) Check for leaks throughout the whole assembly. Note that leaks will increase the risk of fire within your work area. Acetylene leaks are easier to notice than oxygen leaks as acetylene has a "distinctive odour" (garlic like smell). Oxygen is "odourless" and therefore difficult to notice unless you can "hear" a leak. In a noisy area you should use a safe "leak detection fluid", obtainable from your gas supplier. NOTE: Do not use any liquid that might contain a "flammable element", and NEVER use oil to check for leaks. In the presence of excessive oxygen oil, and oil based substances, can ignite. 6) Correct, repair or report any leaks that you may discover, but on no account must you continue to operate the equipment until all leaks have been rectified.

3. LIGHTING THE TORCH The objective when lighting a torch is to obtain a flame that burns "efficiently" with the correct proportions of fuel (acetylene) and oxygen. An efficient flame is


known as a "neutral flame". The following details should assist you to achieve a neutral flame, and of course, you will be shown how to do this as you watch the video demonstration.

o Make sure that the nozzle is secure in the torch. o With the nozzle directed away from your body and face (and away from the

cylinders too!), open the acetylene control-valve (on the torch) about 1/4 turn.

o Using your "spark lighter" strike a spark directly in front of the nozzle. Move your hand away smartly as the acetylene ignites.

o Adjust the acetylene torch control valve until the acetylene flame does the following: a. Burns directly against the nozzle tip. b. Just stops producing black smoke.

o Next, open the oxygen control valve very slowly and observe the change in the nature of the flame. Continue in this way until the "feather" that surrounds the "cone" just disappears. At this time you will have a "neutral-flame". (See diagrams below)

A Neutral Flame (The correct one) looks like this

By comparison we see here a "carburising flame", or, a flame that is burning too much acetylene.

You will notice the "feather around the "cone". A "feather" is produced by acetylene. The other type of flame is the "Oxidising flame", or the flame with too much oxygen! Notice that the inner-cone is rather "pointed" and not nice and rounded like the "neutral flame".


4. SHUTTING DOWN

When you have finished using a torch then it must be shut down and the equipment made safe. The following procedure must always be used in order to ensure maximum safety.

o Always close the acetylene torch-control-valve first. This is an absolute MUST. Do not close the oxygen before the acetylene, or you run a great risk of the flame not being extinguished and for "burning" to continue within the torch.

o When the torch has been extinguished, close both cylinder valves. o Open the acetylene (torch) control-valve. Watch the gauges on the acetylene

regulator; they should both drop to zero. o Close the torch valve (acetylene). o Open the oxygen (torch) control-valve. Watch the gauges on the oxygen

regulator drop to zero. o Close the torch control valve. o Turn out the pressure adjusting screws on both regulators (set both

regulators to "minimum"). o Wrap the hoses around their storage brackets (on trolley). DO NOT wrap the

hoses around the cylinders. NOTE: If your cylinders have "spindle-valves", then make sure that you place the "spindle-key" in a place where it will be easily accessible for other "authorised users". 5. PURGING The process called purging should be performed before lighting a torch, especially if the equipment was "carelessly" left in a pressurised state (had not been correctly shut down). Purging ensures that the only gas in either of the hoses is the gas that's supposed to be there! To purge a hose simply open the torch control-valve (one gas at a time) and permit the gas to run through the hose for about 5 seconds. This will drive out any "mixed gases", including air, and reduce the risk of flashback or a fire in the hose. NOTE: It should be unnecessary to purge the hoses if the system has been properly closed down as you will automatically "purge" the hoses when you set the working pressures.

NOW VIEW THE VIDEO -PART 2 “EQUIPMENT PREPARATION" THEN COMPLETE SELF -TEST NO. 2.




SELF-TEST NO. 2 EQUIPMENT PREPARATION



QUESTION YES NO

1. What, on a threaded fitting, does a “groove” indicate? ANS: ________________________________________________

2. On which part of the equipment will you find the fitting mentioned in question one? ANS: __________________________________________

3. What must you always check FIRST before opening a gas cylinder valve? ANS: ________________________________________________ _____________________________________________________

4. Why should you open a cylinder valve slowly? ANS: ________________________________________________ _____________________________________________________

5. To what “working pressure” must we set both gases for welding? ANS: ________________________________________________

6. What leak detection method is used to detect a gas leak if you are in a noisy work place? ANS: ________________________________________________

7. Which torch control-valve should always be closed FIRST when you shut down? ANS: ________________________________________________


8. Before leaving the gas equipment and when the work is completed you must do what? ANS: ________________________________________________

9. In what state must the regulators be left in, when the work is completed? ANS: ________________________________________________ _____________________________________________________

10. What is the purpose of “purging” the hoses? ANS: ________________________________________________ ____________________________________________________

NOW READ THROUGH THE RESOURCE NOTES ON "GENERAL SAFETY".


RESOURCE NOTES GENERAL SAFETY

NOTE: There is no video for this section. Safety is an "on-going" issue at every stage of the welding process. In this session we shall overview the general points of safety in terms of your work environment and the equipment you will be using. WORK ENVIRONMENT Perhaps the highest risk from any welding process is that of fire. Fire can devastate a business and more seriously it can cost lives. Any person involved in welding processes must take every precaution to ensure that the risk of starting a fire is minimised. Your part in minimising the risk of starting a fire is made when you do the following:

o Remove, wherever possible, any flammable material from the area. This would include such items as: Paper. Oil or fuel drums. Paint containers and associated products. Wooden articles. Fabrics. Plastics and associated materials.

o If you have to weld in areas that have "fixed" flammable materials, such as wooden floors then take the time to protect from possible ignition by "wetting down" the area using water.

o Always make sure that there is a fire extinguisher available nearby. o Place a metal tray filled with sand beneath the work area. This is to catch any "slag"

that might drop as you work. This practice will be essential if you are "flame cutting". o During the working process you will always need to be aware of fire hazards. If there

are workers around you ask them to keep an eye on the area. If you are working alone make it a habit to "look around" every few minutes in order to assess the area.

THE ATMOSPHERE AND VENTILATION We must also consider "ventilation". Many accidents, some resulting in death, have been caused because an area did not have "adequate ventilation". It must be kept in mind that the process of gas-welding, or the use of any "flame", consumes "oxygen" from the atmosphere. If you are going to weld within any area defined as being a "confined space" provision MUST be made for extra ventilation to be available. (You can learn more about "confined spaces" by viewing Tech AV programme CS-1). Always make sure that there are no gas leaks from your cylinders or related equipment. A gas leak from either cylinder will result in a potentially "explosive atmosphere" especially in a confined area/space.


Acetylene will create an "explosive atmosphere" in concentrations between 2.5% and 80% by volume. Never use oxygen (from your cylinder) as a way of "blowing down" (removing dust or debris). This is a very risky practice that can easily result in an "oxygen enriched atmosphere". HANDLING AND USE OF EQUIPMENT CYLINDERS We learnt that the pressures in gas-cylinders (full cylinders) are very high and this fact alone makes any cylinder a "high risk" item in the workshop. Cylinders MUST be handled with care and respect! A full "industrial sized cylinder" is heavy and cannot be safely lifted by a single person so we advise, strongly, that you make no attempt to lift and carry a cylinder by yourself. A cylinder must NEVER be dropped as this can result in a very serious situation. Should the regulator (or the connector) break off; the cylinder can take off like a rocket and devastate anything it strikes. Do not "roll" cylinders along the ground (horizontally) as this could also result in the same problem. Of course a rolling cylinder if uncontrolled can run away from you on a slope and cause major havoc "en-route"! If you have to move a loose cylinder it must be kept upright and "walked" by rotating it along the ground. This practice is for moving cylinders over "short distances" and over level ground only. Never lift a cylinder by the spindle-valve. If the cylinder has a protection-collar or a safety-cap, then you may use these to "support" the cylinder, but not to lift. Cylinders must be stored (and used) in an upright position, (especially acetylene) and portable units must be transported on a trolley, as mentioned earlier. The cylinders must be secured in position with a chain or other suitable devise that will prevent the cylinders toppling over. Do not "park" the trolley close to any source of heat or ignition. This means that your cylinders must be placed as far as possible away from the working nozzle. Never allow an electric arc (arc weld electrode) to be struck against a cylinder. Keep the hand-wheel or the spindle-key (as applicable) attached to the cylinder at all times during operation. In the event that you must close a cylinder-valve in an emergency, the last thing you need is to spend time searching for this item! All equipment should be kept as clean as possible. This is not simply done for "appearance sake". Clean equipment is safe equipment. Oil and grease on hoses, torches and on regulators will result in damage and deterioration.


‘Oil is "bad news" anywhere near the oxygen supply too!. Oil will ignite "spontaneously" if brought into the presence of high-pressure oxygen. Do not "assume" that a cylinder contains a certain gas unless that cylinder has a LABEL specifying the contents. An unlabelled cylinder should be returned to the supplier. Do not use a cylinder that has a leaking cylinder-valve. Return such a cylinder to the supplier. EMERGENCY SITUATIONS It must always be kept in mind that cylinders contain gas that is normally at a high pressure. Gas pressure however is directly affected by temperature. Gas pressure can INCREASE considerably when a cylinder is heated. When a cylinder is exposed to heat, even the heat of the sun through a window, then the internal pressure can rise to "dangerous levels". Concerning an acetylene cylinder the internal pressure must never rise above 2 750 kPa. In the event that you notice that the pressure is close to, or exceeding this figure then action must be taken.

o Your very first reaction must be to get away from the cylinder and sound a warning (call your supervisor or safety officer).

o If you are using the equipment at the time, then immediately shut down and close off the cylinders.

o Where possible, get hold of a water hose and spray the cylinder, from a distance, in order to try and cool it down.

WHAT TO DO IN THE EVENT OF FIRE!

o Remove the cylinders away from the area if it is safe to do so. o If cylinders are too close to the fire then cool them using water sprayed from a safe

distance. o Evacuate the area and follow your companies’ standard "fire drill".

WHAT TO DO WHEN A CYLINDER BECOMES EMPTY

o Remove the cylinder from service after making sure that the cylinder valve has been firmly shut-off.

o Mark the cylinder with the letters "MT" using a suitable "non-permanent" marker or chalk.

o Fit the protective cover to the cylinder (if equipped) or, fit the cap to the cylinder valve opening.

o Store the cylinder away from full cylinders (in an upright position) in. a shaded area (or in your cylinder store if available) until your gas dealer comes to exchange them.

WHAT TO DO IF THE CYLINDER VALVE IS "LEAKY" The commonest cause of a leaking cylinder valve is dirt on the valve seat. An attempt may be made to dislodge dirt by opening the cylinder valve (without the regulator) for a brief


time (approximately 1-2 seconds). Quickly close the valve and re-check for leaks. If the valve still leaks, DO NOT USE the cylinder. Contact your gas dealer (or report this to a supervisor). Label the cylinder so that it can be identified as having a leaking valve. Do not store the leaking cylinder in a closed area. It must be kept out in the open so that there is no danger of creating an explosive atmosphere. WELDING-HOSES AND FITTINGS These are often subject to bad abuse in many "care-less" workshops! Follow these simple rules for hoses:

o Keep hoses clean and free of grease and oil by wiping with a dry cloth when necessary.

o Wrap hoses neatly and store them on the hose bracket of the trolley when not in use. Don't just leave them lying around on the floor/ground.

o During the work operation arrange the hoses in such a way that they don't lie upon or over: Walkways or gangways, where they will be crushed by vehicles etc. Over hot work, where of course you run the risk of a fire! Below the work, where sparks or slag will drop on them. Directly beneath your work, in which case they will be subject to the full heat

of the torch and the metal being welded. o Do not leave hoses in a "pressurised state". o Inspect the hoses frequently for signs of "deterioration" such as cracking or

perishing, cuts and abrasions. Hoses that show any such signs are dangerous to use. Replace any damaged or worn hose with a new one. NEVER fit any hose other than one supplied by an authorised dealer.

o Any hose that has been involved in a "flashback" must be replaced. o Check-valves and "flashback arresters" should always be fitted to "oxy-fuel

equipment". REGULATORS AND GAUGES

o Regulators must be kept clean and "OIL FREE". *Never oil the threads of a regulator and never use "thread sealant" on the fittings.

o The gauges must be easy to read. If you can't see the pressure readings on any of the gauges, as a result of damage to the face, then new or "serviced" gauges should be installed by your dealer.

o Always check that the gauges are suitably "rated" for the cylinders. o Never leave a regulator in a "pressurised state". Always release the pressure from

the line when you have finished using the set. o Do not set the "working pressure" for acetylene above 1 00 kPa (15 psig). o Check that there is no "internal pressure leakage" within a regulator. To do this,

make sure that the pressure-setting screw is turned fully "counter-clockwise" (set to minimum pressure). Close the torch control valve. Open the cylinder-valve and


observe the "working gauge" which must be reading zero (or a very low reading). Observe the gauge for several minutes during which time there should be no pressure rise. If the pressure does rise, then the regulator is faulty, and should be removed from service.

o When opening a cylinder-valve, do not place your face in front of the gauges. Always stand aside so that, in the event of a gauge "blowout", you will not be injured.

TORCHES Because the torch is "handled" a great deal we can expect it to collect dirt and grime. At the end of the day’s work you should spend a minute or two wiping it clean. Do not use solvents or "fuel" to clean the torch. In fact don't use such substances "anywhere on the system!" Check your torch to make sure that the control-valves are in good order. By this we mean that the valves open and close easily and the control-knobs are not damaged or broken. Inspect the working tips or nozzles as molten metal or other "debris" may be accumulated in the orifices or built up around the tip. Remove and clean any tip or nozzle that requires this action. Renew any nozzle or tip that is badly damaged from overheating or other "misuse". PERSONAL SAFETY The main objectives concerning "personal safety" are to avoid being burned and to avoid eye injury/damage. You have already been introduced to the PPE items and all that is left to say is "wear the protective equipment" if you want to avoid being injured. Remember that all PPE must be "approved" by a qualifying authority.

NOW COMPLETE THE SELF-TEST 3 ON THE NEXT PAGE.


SELF-TEST NO. 3 GENERALSAFETY

INSTRUCTIONS Complete the following exercise without reference to the notes. When you have finished, check your answers / responses by:

o Referring to your notes. o Asking your Facilitator / Mentor.

QUESTION YES NO

1. The major “risk” when using oxy-acetylene equipment is what? ANS: ________________________________________________

2. What must be considered when working with a flame in a confined space? ANS:_________________________________________________

3. How should you move a gas cylinder, over level ground, if you have no assistant? ANS: ________________________________________________

4. What position must gas cylinders be in during use and during storage? ANS: ________________________________________________

5. If a cylinder has no “supplier labels” attached, what action should you take? ANS: ________________________________________________ _____________________________________________________

6. What action should you take with an empty bottle? ANS: ________________________________________________ _____________________________________________________


7. What action should you take concerning a leaking cylinder valve that cannot be closed off? ANS: ________________________________________________ _____________________________________________________

8. Why should a bottle NOT be stored near a “source of heat”? ANS: ________________________________________________ _____________________________________________________

9. What action must you take if you notice that the gas pressure in a cylinder is above the maximum allowable pressure? ANS: ________________________________________________ _____________________________________________________

10. Why must you not look at the gauges whilst you are opening a cylinder valve? ANS: ________________________________________________ _____________________________________________________

11. What substance should you NOT allow to come into contact with either of the two gases? ANS: Oil or grease,

NOW READ THROUGH THE RESOURCE NOTES ON "BASIC WELDING SKILLS".


RESOURCE NOTES BASIC WELDING SKILLS (VIDEO PROGRAMME – 2)

In this programme you will learn how to:

a) Select the appropriate nozzle for the metal to be welded. b) Use the welding torch and make a "welding pool". c) Introduce metal into the pool with a filler -rod. d) Make a “Tack weld". e) Weld a “Butt -joint". f) Weld a “Fillet -joint". g) Weld a “Corner -joint".

PART 1 - "SELECT THE CORRECT NOZZLE" The major consideration for selection of the nozzle size is the metal thickness. The thicker the metal, the bigger the nozzle. The chart offered below can be used to select the correct nozzle. Note that it would be a rare occurrence to perform "gas-welding" on steel plate thicker than 3,2 mm.

PLATE THICKNESS NOZZLE SIZE 0.8 mm 1 1.2 mm 2 1.6 mm 3 2.4 mm 5 3.2 mm 7

PART 2 - " USING THE TORCH" Part of the "secret" about making a "professional weld" is the way you hold and "work" the torch. The majority of welds are made using what is called "Leftward Welding". This technique requires that welding begins (commences) at the "right-hand" side of the work and progresses "leftward" along the joint to be welded.

NOW VIEW THE VIDEO -PARTS 1 & 2 AND THEN PERFORM EXERCISE NO. 1 ON THE NEXT PAGE.



EXERCISE 1 - MAKING A "WELDING POOL" (PUDDLE-RUN) This is purely a training (learning) exercise and is to be performed on 1,6 mm mild-steel plate The purpose of the exercise is to assist you develop the basic "manipulative skill" involved in using a welding torch. When you have mastered the following exercise you will be able to control a welding torch in such a way that you create a "welding pool" (or puddle) and keep it running along the length of the work. Practice making a weld - pool in your workplace. Remember the following while practicing:

o Position the work-piece (plate) onto your welding bench or a suitable support. o Prepare your welding set in the manner described earlier. o Fit a NO.3 nozzle to the torch and make sure that it is secure. o Light up your torch and set a "neutral flame". o Bring the nozzle to the right hand edge of the plate. Hold the torch in such a way

that the torch (handle) is parallel to the plate and the nozzle forms an angle of between 60 and 70 degrees to the surface (of the plate).

o Apply the flame to the plate and maintain a distance of about 2 mm between the "cone" and the surface.

o At the same time, set up a small "oscillating movement" of the nozzle (either rotate a little circle or a slight side to side action) as you apply heat to the plate. The object here is to create a "puddle" (or pool) of "molten metal" about 6 mm in diameter.

o As the puddle forms begin to move the torch to the left. Maintain the torch angle, and the distance between the cone and the surface of the plate.

o Move the torch at a slow speed, keeping the "puddle" running as you move the torch along.

o Make a full length run from end to end on your work-piece. o When you reach approximately 40 mm from the end of the run, increase your speed

of movement (travel) in order to compensate for the rapid heat build-up that will occur at this point.

o When you have finished the run, shut off your equipment. o Allow the work to cool before inspecting the run.

NOTE: This basic practice should be done until you are able to make a full run without stopping and without the puddle "drying out"(moving too fast) ,or burning holes though the plate (moving too slowly).

CHECK YOUR WORK BY COMPLETING THE "CHECK-LIST" FOR EXERCISE NO. 1.


CHECK-LIST For Practical Exercise No. 1 - Basic "Weld pool"

o Check your completed exercise against the criteria in the listing below. o Score a "YES" response (tick the block) if the work meets the criteria described. Score

a "NO" response if the work does not meet the criteria described. o Repeat the exercise, if necessary, until you are able to score a "YES" response to all

the criteria. o Have your Facilitator / Mentor check your work and sign off this exercise when

completed.

CRITERIA YES NO

1. Is the weld bead about 6mm wide along the complete length?

2. Is the weld bead free of holes burned through the metal?

3. Is the welding set correctly and safely closed down?

FACILITATOR / MENTOR SIGNATURE: ___________________ DATE: __________________

NOW MOVE ON TO PART 3 "USING A FILLER -ROD".


PART 3 - "USING A FILLER -ROD" In this exercise we are going to introduce the "filler rod". Again we stress that this is a training exercise and not a "normal situation". The objective of this exercise is to have you gain experience in applying metal into the puddle with a filler rod. Filler rods are made of the same material as the "base metal". The rod that we select must be the same thickness as the work-piece, that is 1,6 mm in our exercise. The purpose of a "filler-rod" is to add metal thereby "reinforcing" the welded section of a joint.

NOW VIEW THE VIDEO -PART 3 "USING A FILLER -ROD" AND THEN PERFORM EXERCISE NO. 2.



EXERCISE 2 - INTRODUCING A FILLER-ROD INTO THE WELD POOL (CREATING A BEAD) Follow the procedure as outlined below and as demonstrated in the video:

o Obtain (from your Facilitator) a 1,6 mm MIS filler-rod. o Set up your work-piece as you did previously, and then prepare a "neutral flame". o Start by creating a pool at the right hand end of the work-piece. Remember to keep

the correct nozzle-angle (60 - 70 degrees). o Hold the filler-rod in your (other) hand. Allow about 200 mm of rod to protrude. o Keep the filler rod at an angle of about 30 to 40 degrees (This forms a 90 - 100

degree angle between the rod and the nozzle). o "Oscillate" the nozzle to create 1.6 mm welding-pool (puddle) and then "introduce"

the filler-rod. NOTE: The action is to dip the filler-rod in and out of the puddle as the nozzle moves along. This is a definite "skill" requiring the co-ordination of both hands. o Make a "bead" weld along the work-piece using the filler rod. o At about 40mm from the end of the run you will find it necessary to increase the

speed of the torch movement as the base metal will have become very hot and melting will occur faster.

o Allow the metal to cool before inspecting the work. o Shut down your equipment. o Inspect your work once it has cooled.

SOME CONCLUSIONS Not everyone manages to perform the exercises without hitting a "snag" or two! During your practice you will probably experience at least one of the following problems:

o A hole blew through the metal. o The puddle kept "drying up". o The torch began "screeching". o The flame "blew out". o The filler rod kept "sticking".


Let's explain what these problems are and what to do about them.

PROBLEM POSSIBLE CAUSE REMEDY

Hole blows through the plate. Excessive heat applied. Use smaller size nozzle.

Move faster.

Puddle dries up. Not enough heat applied. Maintain correct nozzle distance from work. Slow down the rate of travel.

Torch “screeches”. Nozzle / Flame too close to the weld pool ( Nozzle too hot).

Lift nozzle to correct distance above work.

Flame blows out. Incorrect gas settings or Blocked orifice.

Reset gas supply and working pressures. Clean the nozzle orifice.

Filler rod sticks to metal. Lifting the nozzle from the weld pool. Not weaving the nozzle.

Maintain correct distance of nozzle from the work. Maintain a 6mm pool by weaving the nozzle.

NOTE: A "screeching" torch is a sign that combustion is occurring inside the nozzle or even in the torch "mixing chamber". This can result in a flashback!



CHECK-LIST For Practical Exercise No. 2 - "Weld pool with Filler-rod material"




completed.

CRITERIA YES NO

1. Does the weld bead look neat?

2. Is the bead an even 6mm wide from end to end?

3. Is the bead free of “blow holes”?

4. Have you shut down the equipment correctly?

FACILITATOR/MENTOR SIGNATURE: _______________________ DATE: ________________

NOW MOVE ON TO - "BASIC JOINTS AND WELDING TECHNIQUES".


BASIC JOINTS AND WELDING TECHNIQUES In this lesson we shall explain the features of basic joints. We will then explain how to weld these joints in the "down-hand position". BASIC JOINTS / JOINT WELDING Metal plates can be joined in various ways. The type of joint used in any application is generally based on the required strength of the joint or the shape of the object. The 4 basic joints are:

1. Butt joints. 2. Lap joints. 3. Corner joints. 4. Tee joints.

These 4 joints can be welded in various positions. The easiest position is known as the "down-hand position". As the term suggests, welding is performed with the joint pointing upward so that you can work with the nozzle of your torch facing "downward". Sometimes the work (welding) has to be done 'in-situ', or “where the job cannot be done on your bench. The kinds of positions that you will encounter include: HORIZONTAL / VERTICAL

VERTICAL UP

In the video we demonstrate 3 basic welds, namely:

o A Butt weld / joint. o A Fillet weld on a lap joint. o An outside -corner weld.


PART 4A - PREPARING A BUTT - JOINT In this section we demonstrate the setting up of a Butt-Joint using 3.2 mm plate. The general procedure is to arrange the two plates so that their edges are parallel and a "root gap" of between O.8mm and 3.2 mm exists between them. When this has been achieved the plates are then "tacked" together with "tack-welds". A final weld is made having first secured the plates with "tacks". Let us explain these terms: 1. ROOT GAP This is the term given to the gap into which molten metal "penetrates" during the welding process. The strength of a weld is determined primarily by the degree of penetration.

2. TACK WELD A tack-weld is a "temporary weld", usually 5 millimetres long. The purpose of this weld is to hold adjacent material in place whilst the main welding is in progress. Tack welds are placed about 75 -100mm apart along the seam to be welded.

The material to be welded must be set-up in such a way that:

o The plates are raised off the welding-bench surface (2 pieces of channel iron can be used).

o The plates are supported in a flat position for "down-hand" welding on a welding bench.

o A parallel GAP of 3.2 mm exists between the two plates.( To achieve this you can a spare piece of 3,2 mm plate as a gauge.

o The work is now ready to be "tacked".


VIEW THE VIDEO -PART 4A AND THEN PERFORM EXERCISE NO. 3.



EXERCISE 3 - PREPARING A BUTT -JOINT Practice preparing and tack welding a butt -joint in your workplace. The following procedure is recommended: Step 1 Prepare your welding torch with a NO. 7 nozzle (according to the nozzle

chart). Step 2 Light the torch and set a neutral flame as you learnt earlier. Step 3 Make sure that you have a 3.2 mm mild-steel filler rod. Step 4 Commence at the centre of your work-piece and bring your flame over the

join. Distribute the heat evenly between the two plates and use a "weaving or an oscillating action with the torch. As soon as the pool forms, dip the filler rod into the pool and make a short "bead" of about 5 mm long.

Step 5 Check that the root gap has not altered after performing the centre weld. It is most usual that the gap will pull in at one end or the other, and increase slightly at the opposite end.

Step 6 Make a second tack weld, spaced 75 mm on the "wide gap side" of the first tack. In this manner the wide gap will pull in, and hopefully the narrow gap will open.

Step 7 Make subsequent tack welds at 75 mm intervals on the wide side. Step 8 Check that the narrow gap has opened up, using the filler rod as a gauge. Step 9 Assuming that the gap is still too narrow, place the work onto a flat and solid

surface and then give the first tack (centre) one or two firm and flat blows with a 1 Kg hammer. This will tend to "spread" the tack weld and thereby open the gap slightly. Check once more that the gap has increased (using the filler rod).

NOTE: Another method involves deliberately creating a "tapered" root gap thus providing for the normal "pull in" that occurs as a tack weld cools. This method assumes that you have a great deal of experience and knowledge of the metal that you are working with. Tacking proceeds at the "narrow-end" of the joint and progresses at 75mm intervals. As the tacking progresses the gap will tend to close as each weld cools.


CHECK-LIST For Practical Exercise No. 3 - Prepare a butt joint (Tack Weld).




completed.

CRITERIA YES NO

1. Root gap is correct width (thickness of rod).

2. Root gap is uniform in width along the joint.

3. Tacks are spaced 75 mm apart.

4. Tacks penetrate into the root.

FACILITATOR / MENTOR SIGNATURE: _____________________ DATE: _________________


PART 4B -WELDING THE BUTT - JOINT

VIEW THE VIDEO - PART 4B “WELDING THE BUTT - JOINT" THEN PERFORM EXERCISE NO. 4.

EXERCISE 4 - WELDING THE BUTT - JOINT Practice the process of performing a "butt-weld". Remember the following when you are practicing:

o Welding commences on the right hand edge for "leftward welding". o The nozzle is always "weaving" in order to maintain a 6mm weld-pool, distributed

equally across the weld-seam. o When the pool has been created a steady forward movement must be maintained. o The nozzle tip angle is held steady at 60 - 70 degrees to the line of travel, and the

filler rod held at 30 - 40 degrees (making an "included angle" of 90 degrees). o Filler material is introduced (added) continuously in order to build up the desired

"reinforcement". o Speed up the rate of travel as you approach the end of the run to allow for the rapid

heat build-up at this stage.




CHECK-LIST For Practical Exercise No. 4 - Butt Joint Weld.




completed.

CRITERIA YES NO

1. Is the weld bead of neat appearance?

2. Is there the correct "penetration" into the root?

3. Is the bead of 6mm "consistent" width?

4. Are the plates (surfaces) level?



PART 5 - FILLET WELDS In this section you will learn how to perform a basic "fillet-weld" on 3.2mm mild-steel plate. A fillet-weld is generally one where the welding bead has to be laid into an "inside-corner", or as in the example that we shall use, onto a "lap-joint". One of the considerations that we must take into account with any fillet weld is that of "irregular heat transfer". Heat will always move more rapidly into thinner material, therefore if the two adjoining plates are of different thickness, or of different surface areas, then the "lesser" material will reach its melting point before the "greater". In order to compensate for this, the welder must apply the heat in such a way that a "balance" is created and that fusion of metal occurs equally across the joint. The technique and the process of heat application and filler material inclusion are expertly demonstrated in the video. NOTE: In the video demonstration the practice plates have been set-up purely for purposes of demonstrating the "welding technique", and as such do not necessarily reflect all setting up processes.

VIEW THE VIDEO - PART 5“FILLET WELDS " THEN PERFORM EXERCISE NO. 5.



EXERCISE 5 - " FILLET WELD" ( LAP JOINT) Practice making fillet-welds in your workplace. Remember the following when practicing:

o The important point to note is that the adjoining plates in the lap-joint must be positioned "flat" upon each other (their centre-lines must be parallel).

o The two plates must be in "tight contact" with each other. If a gap exists, owing to buckling for example, then this must be corrected before welding commences.

o Plates are tacked together on both sides (back then front) to ensure proper alignment during the welding process.

o The nozzle (flame) is directed toward the plate that will absorb the most heat, which in the demonstration is the lower section. In this way a "balance" of heat can be ensured.

o The actual welding technique is very similar to that which you used in the "butt-weld" process. The torch angle, and filler rod angle, remain the same along the line of travel. The weld pool must be maintained at about 6mm diameter by "weaving the nozzle". The weld-pool must be kept moving and the filler material must be added continuously in a regular pattern.

o The result of the process is a neat looking bead that is consistent in width and in the "herring-bone pattern" along the full weld.



CHECK-LIST For Practical Exercise No.5 - Lap-Joint / Fillet-Weld.




completed.

CRITERIA YES NO

1. Is the weld bead evenly distributed over the join?

2. Is the weld bead of a consistent width along the full weld?

3. Are the two plates level / parallel?



PART 6 - OUTSIDE-CORNER JOINT The "outside corner joint" is a popular joint used to create many fabricated items such as boxes, trays , bins and hoppers to name a few. Although the welding of this joint is often made on site in all sorts of positions, you will first need to practice in the "down-hand position". The DVD demonstration provides excellent visual explanation on how to create the "outside corner joint".

NOW VIEW THE VIDEO - PART 6 “WELDING THE OUTSIDE -CORNER JOINT" AND THEN PERFORM EXERCISE NO. 6.

EXERCISE 6 - WELDING AN OUTSIDE (CORNER JOINT) Take note of the following pointers as you practice welding a corner-joint.

o A special "jig" has been constructed in order to support the plates for this training exercise. You can make up such a jig should you wish in your own 'training workshop.

o The two plates (3.2 mm mild-steel) when set up in the jig at 90 degrees to each other form a "natural root" in the form of a "Vee".

o Whether making a "tack weld" or a "final weld" the method of welding must remain the same.

o The flame is directed into the root, but the nozzle and filler rod angles remain the same as for a "butt-weld".

o Care must be taken to confine the welding pool to the "apex" of the joint. Nozzle movement (weave) must be controlled in order to prevent the pool from becoming too wide.

o When you watch the DVD, pay attention to the way in which the welder manipulates his torch, control the welding pool and applies the filler material.

CHECK YOUR WORK BY COMPLETING THE "CHECK-LIST" FOR EXERCISE NO. 6 ON THE NEXT PAGE.




CHECK-LIST For Practical Exercise No. 6 - "Outside Corner Joint".




completed.

CRITERIA YES NO

1. Is the completed weld neat in appearance?

2. Is there a “trace” of root penetration on the underside?

3. Is the width of the bead consistent along the full weld?


READ THROUGH THE ADDITIONAL NOTES ON WELDING AND THEN MOVE ON TO THE NEXT SECTION.


NOTES DESIRABLE FEATURES OF WELDS It must always be kept in mind that welding is performed in order to "permanently" attach parts together. Once two parts have been welded we generally intend them to stay that way for years. The aim therefore is to create a "mechanically strong" weld. Welders tend to be rather proud of a "good looking weld" not simply because it looks "professional" but because they know that it is also an "effective weld" too! The diagram below illustrates a typical weld in "sectional view".

The physical features of an effective (strong) weld are:

o Full depth of fusion into the root. o Equally distributed fusion along the top of the joint. o Adjoining plates in correct alignment. o Underside bead (root bead) is uniform and blended into the parent material. There is

no "excessive protrusion" of the root bead. Some "physical features" of poor or weak welds are as follows:

Misalignment of plates caused by:

o Faulty setting up. o Thermal movement.


Lack of penetration caused by:

o Failure to set or maintain an adequate "root gap". o Welding speed too high. o Poor manipulation of torch (angle and weave). o Nozzle size too small.

Excessive penetration caused by: o Nozzle size too large. o Incorrect manipulation of the nozzle (angle and weave). o Welding speed too slow.

Excessive reinforcement caused by:

o Excessive rod size or amount of feed into pool. o Incorrect torch manipulation. o Nozzle size too small.

Insufficient reinforcement caused by: o Inadequate rod size or feed speed. o Welding speed too slow. o Nozzle size too large.


Undercut on weld face caused by: o Nozzle size too large. o Welding speed too slow. o Insufficient rod (filler) feed.

NOZZLE MAINTENANCE It is an overlooked FACT that the condition of the welding nozzle has a direct effect on the quality of the weld. Nozzles tend to become clogged with solids and this effectively distorts the flame and causes uneven heat distribution to the parent metal. In severe cases a clogged nozzle will effectively reduce the amount of heat that is transferred into the metal and result in poor fusion/weld penetration. After each welding operation, and sometimes during the welding operation, the nozzles should be inspected and cleaned. Nozzle cleaning involves the removal of deposits from the nozzle-orifice using a "nozzle-cleaning wire". Cleaning wires are usually contained in handy packs that contain several "standard wire sizes". The normal practice is to select a wire that will fit comfortably into the orifice and "file" away any deposit. The wire size is gradually increased until the orifice has been returned to its correct diameter. On no account should you "increase" the diameter of the orifice as this will defeat the object of "sizing”. This concludes the "Welding Section" of the series.

MOVE ON TO THE NEXT SECTION "FLAME CUTTING".


FLAME-CUTTING (VIDEO PROGRAMME 3)

BEGIN NOW BY READING THROUGH THE FOLLOWING RESOURCE NOTES.

INTRODUCTION Flame cutting is a process used in the "cutting" of certain metals, primarily steel, using heat energy to cause rapid "oxidation". This method of cutting is widely used in many fabrication and repair industries, specifically in the "heavy duty" industries such as ship building and steel construction work. Cutting may be done using hand-held equipment or using complicated, automatically controlled equipment. In this programme you are going to learn about the use of "hand-operated" equipment. PART - 1 "THE CUTTING PROCESS" Most people assume that flame cutting involves the controlled "melting" of metal. This is not true as the process actually involves the "burning" of metal. All substances, including steel (and other metals) will burn, that is, they will "ignite", under certain conditions. The conditions required for any material to burn are: Correct temperature and sufficient "oxygen". It is not necessary for you to understand all the "chemistry" involved in the flame cutting process but in essence the following will help you understand what is going on: "Mild-steel" will "ignite" (burn) at 816°C in the presence of "pure oxygen". The colour of steel will change from its normal "grey", to red/orange when it reaches 816°C. The "flame-cutting" process creates the conditions for "igniting steel" by:

a) Heating steel to a "red hot condition" (bringing it to temperature). b) Directing a jet of pure oxygen into the hot steel (forcing it to burn / ignite).

The tool used to create these conditions is the "Cutting Torch". There are various types of cutting torches, some that are operated by hand and others by automatic machines. We will only be looking at "hand operated devices" in this programme.


THE (HAND OPERATED) CUTTING TORCH A cutting torch is similar in many ways to the welding torch that you are by now quite familiar with. The torch connects to the gas equipment in exactly the same manner as the welding torch. Gases flow into the torch via an oxygen control-valve and an acetylene control-valve. Non-return valves are most usually fitted to the torch end of the welding hoses, and, of course, flashback arresters are always fitted to the gas regulators. The primary differences between the torches are:

o A cutting torch has a special "nozzle", called the "cutting-tip" (But usually referred to as a cutting "nozzle").

o A cutting torch has a special "control lever", called the "cutting-lever".

CUTTING TIPS The cutting tip, (or cutting nozzle), normally contains several orifices. One orifice is placed in the centre of the tip. This is the "cutting orifice" through which is supplied the "cutting oxygen". Surrounding the cutting-orifice are several (normally) smaller (in diameter) "pre-heating orifices". At the opposite end of the tip there are 3 "tapered" surfaces, known as "seats". When the tip is installed into the "cutting-head" of the torch, these seats make contact with corresponding seats inside the head. A "tip-nut" secures the tip into the head and, when correctly tightened, presses the tip firmly upon the seats thereby creating "gas-tight seals".


On modem nozzles (cutting tips) you will see the letters NM stamped or etched onto the body. These letters literally mean "Nozzle Mixing". In this type of torch the following process takes place. No mixing of gases takes place in the torch. The gases (oxygen and acetylene) enter the nozzle body by way of separate chambers (called annular grooves). Tubes carry each gas from the control-valves to the cutting-head and into their respective "annular chambers". From there each gas flows into the "nozzle section" where they finally join up and become mixed. The mixed gases exit the torch via the "pre-heating orifices". A further separate chamber, usually in the back of the cutting-head, is fed with pure oxygen when the "cutting lever" is depressed. Pure oxygen is then directed into the tip and delivered directly to the work surface in the form of a "jet-stream". It is only the heated metal, receiving the blast of oxygen from the cutting orifice, which "ignites" and bums away. NOTE: It is important that the "seating surfaces" both in the cutting-head and on the nozzle body, are kept free from dirt and from damage. Any imperfections on these surfaces will result in gases leaking from one chamber into another within the cutting-head. This could result in a very dangerous condition owing to the "mixed" condition within the torch. Nozzles (cutting tips) are available in various types and sizes. Information about a tip is (usually) stamped into the nozzle body. For example suppose you see the following information on a nozzle: A-NM 6 and then 0.8 This information tells us:

o "A" - The nozzle is designed for use with "Acetylene" (ONLY). o "NM" - The gases are "Nozzle Mixed". o "6" - There are 6 pre-heat orifices. o "0.8" - The "cutting orifice" is 0.8 mm in diameter.

This example is typical of a "general purpose" nozzle for use on metal up to 6 mm thick.


NOW VIEW THE FIRST SECTION OF VIDEO - NO. 3 “FLAME CUTTING" AND THEN COMPLETE SELF -TEST NO. 4.




SELF-TEST NO. 4 OXY-ACETYLENE FLAME CUTTING EQUIPMENT



QUESTION (tick correct answer/s) YES NO

1. Most materials will burn provided what is present? ANS: ________________________________________________

2. The purpose of the “pre-heating” orifices in a cutting tip is? a) To raise the temperature of the material to melting point. b) To melt the material. c) To cut through the material.

3. The purpose of the centre hole in a cutting tip is to? a) Cool the metal and the cutting tip. b) Blow oxygen into the melting metal. c) Raise the temperature of the metal.

4. When the “cutting lever” is depressed on the torch the following happens… a) Oxygen is forced through the pre-heating orifices. b) Oxygen is forced out of the centre orifice. c) Acetylene is forced out of the centre orifice.

5. The letters “NM” stamped onto a cutting tip means what? a) Nozzle Mixing. b) No Mixing. c) Nozzle type “m”.

6. The letter “A” before the NM means what? a) For use with “A” type torch. b) For use with acetylene. c) Afrox.


7. If you see the numbers “6” and “0.8” on a nozzle body what does this tell you? ANS: ________________________________________________ _____________________________________________________

NOW READ SECTION 2 - “PREPARING THE TORCH".


SECTION 2 - PREPARING THE TORCH In this section we will explain how to set up the equipment in preparation for using a cutting-torch, and then we shall explain how to shut down. CONNECTION TO WELDING HOSES The torch connects directly to standard welding hoses. The connectors are identical to the welding torch, i.e., red hose with left-hand fittings for acetylene, and blue hose with right-hand fittings for the oxygen hose. NOTE: It is strongly recommended that "non-return valves" be fitted to the torch end of the hoses. SELECTION OF A CUTTING-TIP (NOZZLE) A cutting tip is selected according to the thickness of material to be cut (most usually). The nozzle size is determined by the size (diameter) of the cutting-orifice. For "general purpose" work there are 7 nozzle sizes namely: 0.8 – 1.2 – 1.6 – 2.0 – 2.4 – 2.8 – 3.2 (all sizes in mm). NOZZLE INSPECTION A nozzle should be inspected before it is fitted to the torch. The following should be inspected, and corrected where applicable:

o Orifices -must be clean and open. Any dirt, debris or adhering metal slag etc will affect the flow of gas and result in a poor cut.

o Tip shape-at the "nose" must be flat and a sharp, well defined "edge" apparent. A rounded tip will yield poor cutting results.

o Seating surfaces -these MUST be free of any defect that would result in a leak. Even small scratches on these surfaces will permit gases to escape.

We will discuss nozzle maintenance at the end of the programme. FITTING A NOZZLE Follow the simple instructions listed for "safe" results:

o Use only a "correct fitting spanner" to loosen and tighten the "tip-nut". o Make sure that the seating surfaces in the "cutting-head" are clean. If you have to

clean inside a cutting head use only soft cloth or tissue. Do not use a rag, or any other material that has oil or grease on it.

o Insert the selected nozzle (tip) carefully into the cutting-head. Ensure that it is fully "seated" by giving it a slight twist as you feel it enter the seats.


o Take care when fitting the "tip-nut". Do not "cross-thread" the nut. Always fit it by HAND until it is fully entered within the head. Tighten the nut with the correct spanner. DO NOT over-tighten this nut as this will possibly "strip" the threads and distort the seating surfaces.

PREPARING THE GAS SUPPLY The gas supply is prepared in exactly the same manner as you were taught in the welding section. The only difference is that the OXYGEN working pressure is set higher than for welding. Let's itemise the preparation procedure:

o Ensure that torch valves are both closed (shut-off) and that both regulator "pressure adjusting screws" are backed off (set to minimum).

o Open the cylinder-valves and check the "remaining pressure" in each bottle. Do not proceed if the pressures indicate that the supply is low. Note that flame cutting requires an adequate supply of oxygen.

o Open the acetylene "torch-valve" and adjust the acetylene "working-pressure" to 60 kPa. (Standard pressure for most operations).

o Close the acetylene torch-valve. o Open the oxygen torch-valve and set the working pressure to suit the nozzle size /

material thickness (see table below). o Close the oxygen "torch-valve".

Operating Data for Hand-Cutting of Mild-Steel

Material Thickness mm 6.0 12.5 25 50 75 100 150 Nozzle size-Type A-NM6 0.8 1.2 1.6 1.6 1.6 2.0 2.4 Oxygen Pressure kPa 170 200 270 340 350 300 300 Acetylene Pressure kPa 60 60 60 60 60 60 60

LIGHT AND ADJUST THE FLAME The procedure for lighting the torch is very similar to the welding torch: The procedure is summarised as follows:

o Open the acetylene valve a small amount (1/8 -y, turn). o Strike the lighter directly in front of the nozzle tip. o Adjust the acetylene torch-valve until the flame burns without black smoke and,

contacts the nozzle-tip. o Open the oxygen torch valve slowly. o Adjust the oxygen valve until a "neutral flame" is achieved. o Check that flame is burning from each "pre-heating orifice". Shut down and clean the

orifices that do not light (if applicable). o Depress the "cutting lever" slowly and observe the flame. o The pre-heating flame should not alter when the cutting oxygen is flowing.

NOTE: It may be necessary to adjust the pre-heating flames to a "neutral condition" with the oxygen lever depressed.


SHUTTING DOWN On completion of your work shut down in the following manner:

o Release the cutting lever. o Close the acetylene torch control-valve (This valve first). o Close the oxygen torch control-valve. o Close both cylinder valves (oxygen and acetylene). o Open each torch control-valve, in turn, to release the pressure within each hose. o Close both torch control-valves. o Set both regulators to their minimum pressure (turn the adjusting screws fully out). o Wrap the hoses on their support brackets on the back of the trolley.

NOW VIEW THE VIDEO SECTION “PREPARING THE TORCH" THEN COMPLETE SELF -TEST NO 5.



SELF-TEST NO. 5 PREPARATION OF FLAME CUTTING EQUIPMENT



QUESTION (tick correct question/s) YES NO

1. A cutting tip, or nozzle, is selected according to what? a) The desired cutting speed. b) The width of the metal to be cut. c) The thickness of the metal to be cut.

2. Before you fit a nozzle to the torch you should check, what? a) That the tapered seating surfaces are clean and not damaged. b) That the threads in the torch head are not damaged. c) That the gas bottles are full.

3. The preparation of the gas supply is almost identical to the “welding set-up”, with one exception, what is this exception? ANS: ________________________________________________ _____________________________________________________

4. The oxygen “working –pressure” is adjusted /set according to what? ANS: ________________________________________________

5. What can you expect to happen to your cut if the pre-heating flames tend to carburise when the oxygen lever is depressed? ANS: ________________________________________________ _____________________________________________________


6. List the actions that you must take, in sequence, when shutting off a cutting-torch. i) _______________________________________________ ii) _______________________________________________ iii) _______________________________________________ iv) _______________________________________________ v) _______________________________________________ vi) _______________________________________________ vii) _______________________________________________

NOW READ SECTION 3 - "FREE -HAND CUTTING".


SECTION 3 - "FREE-HAND CUTTING" The term "free-hand" means to operate and control the torch without mechanical aids. When you have developed the ability to perform an acceptable "free-hand" cut through metal plate then you will have no problem with any other flame cutting process. Wherever it is practically possible, flame cutting should be carried out on a suitable "cutting table". If however you do not have such a device available then the work should be set up in a safe manner on a suitable metal support structure. (You will need to discuss this with your Facilitator / Mentor).

NOW VIEW THE VIDEO SECTION “FREE -HAND CUTTING" THEN PERFORM EXERCISE NO. 7.

EXERCISE NO. 7 - " FREE -HAND CUTTING" In the video demonstration you saw a skilled operator making a freehand cut through a section of 6mm mild-steel plate. Practice the free-hand cutting technique in your workplace taking note of the following:

o The free-hand cut is made "across the body". o The torch is supported in the hands. o The hands are firmly supported on the bench / table. o The cut is started on the edge of the work. o The torch movement (travel and speed) is controlled. o The nozzle tip is kept "flat" to the surface of the work and the heating flames are at 3

to 4 mm from the surface. o The cut only occurs directly beneath the "cutting orifice" and that the cut itself is

very narrow (Usually around 1 mm wider than the cutting orifice size). Here are some handy tips:

1. If, during cutting, the flame cuts out (snaps off) then one or more of the following problems has occurred:

o The working line gas pressures have altered. o The nozzle is blocked. o The nozzle is being held too close to the work. o The nozzle has become overheated.

If you experience this problem then do the following:



o Shut both the torch control-valves fully. o Allow the nozzle to cool, or if overheated, plunge the nozzle into cold water. o Check the condition of the nozzle and clear any blockages if applicable. o Purge the lines. o Re-set the gas pressures as outlined in the preparation section.

2. If you "lose the cut" then the following has probably occurred:

o You are moving the torch too fast along the cutting line. o You have lifted the nozzle too far from the work.

To regain the cut, do the following:

o Release the cutting lever. o Bring the nozzle back the point where the cut is lost and apply the pre-heat

flame. o Continue the cut as normal.

When metal is cut at the correct speed, and the nozzle tip held at the correct distance from the work, then the cut (also known as the "kerf') will be clean and free of "slag". (Slag is the name given to the melted and re-solidified blobs of metal that adhere to the underside of the work) A good cut will provide a "slag free" result. The bottom edge of the cut should be "sharp" and the "drag-lines" (the pattern created by the oxygen jet) will be square to the plate and barely visible.

Example of good cut



CHECK-LIST For Practical Exercise No. 7 - Free-hand Flame Cutting.




completed.

CRITERIA YES NO

1. The cut is straight.

2. The cut is "clean" (little or no slag on underside).

3. The drag-lines indicate that the cutting speed was correct.

4. The equipment has been shut-down and made safe.


NOW READ SECTION 4 " - USING A CUTTING -GUIDE".


SECTION 4 - USING A CUTTING GUIDE It is not always convenient or practical to make every cut using the "free-hand" method. No matter how skilled you become you will not be able to produce a perfectly straight cut in this way. Although flame-cutting cannot be used for producing a "machined edge", we can however create a clean and straight edge that would meet the requirements for a welded joint for example. To produce a straight cut we must use a cutting-guide. There is nothing "fancy" about a cutting guide, in fact most welders favour a length of "angle-iron" for this purpose. The guide simply assists the operator to maintain a straight cutting line by offering "support" to the nozzle. Depending on the situation the cutting guide may be "hand held" or "clamped" to the work surface. A guide is (most usually) necessary when you have to "bevel" an edge. In the DVD demonstrations you will see our expert using a cutting guide to create normal "straight" cut and a "bevelled cut", using "angle-iron" as his cutting-guide.

NOW VIEW THE VIDEO SECTION - “CUTTING WITH A GUIDE" THEN PERFORM EXERCISE NO. 8.

EXERCISE 8 - CUTTING WITH A GUIDE Practice cutting both straight and bevelled cuts using a guide. Remember the following whilst you practice:

o Position the work in such a way that you will perform the cut "toward" your body. o Place the cutting guide in such a way that it is parallel to your cutting line. When the

nozzle is placed against the guide the "cutting orifice" must be directly over the line. o The pre-heating cones should be spread equally over the cutting line.





CHECK-LIST

For Practical Exercise No. 8 - " Using a Cutting Guide".




completed.

CRITERIA YES NO

1. The square cut is “square” to the plate.

2. The cut is neat and clean (little or no slag on underside).

3. The cut is on the line.

4. The bevel cut is neat and cut to 45 degrees.

5. The bevel is cut to the line.

6. Equipment has been shut down and made safe.



SECTION 5 - CUTTING ANGLE-IRON Now that you are getting a little more skilful in the use of the cutting-torch the next tasks that you might tackle will be the cutting of typical "sections". The 2 sections that you will see demonstrated are:

o Angle iron. o Steel pipe.

Both of these tasks require certain "manipulative skills" that you need acquire. There are really two things that you need to do in order to learn these skills, namely:

1. Watch an expert do it. 2. Practice doing it yourself.

VIEW THE VIDEO SECTION “CUTTING ANGLE -IRON" THEN PERFORM EXERCISE NO. 9.

EXERCISE 9 - CUTTING ANGLE – IRON Practice this procedure in your own training workshop. Take particular note of the following:

o The way that you hold and move the torch. o The angle of the torch nozzle. o The "switch" from an upward cut to a downward cut.




CHECK-LIST For Practical Exercise No. 9 - "Cutting Angle Iron".



the criteria. o Have your Facilitator/Mentor check your work and sign off this exercise when

completed.

CRITERIA YES NO

1. Angle-iron cut is clean and on line.

2. Little or no slag on the underside.

3. Correct nozzle was selected for material thickness.

4. Equipment is shut down and made safe.



SECTION 6 - CUTTING STEEL PIPE Steel pipe can be cut accurately and neatly with a cutting torch. Steel piping is an expensive commodity and you certainly don't want to waste money (yours or your companies') by making an inaccurate cut.

o You will learn valuable information simply by observing the techniques demonstrated in the DVD section.

VIEW THE VIDEO SECTION - “CUTTING STEEL PIPE" THEN PERFORM EXERCISE NO.10.

EXERCISE 10 - CUTTING STEEL PIPE As you perform this exercise, pay attention to the following:

o The method of marking out the cutting line. o The method of supporting and manipulating the torch. o The constant angle of the nozzle directed toward the centre of the pipe.




CHECK-LIST For Practical Exercise No. 10 - "Cutting Steel Pipe".



the criteria. o Have your Facilitator/Mentor check your work and sign off this exercise when

completed.

CRITERIA YES NO

1. Angle-iron cut is clean and on line.

2. Little or no slag on the underside.

3. Pipe cut is on the line and pipe end is square.

4. Correct nozzle was selected for material thickness.

5. Equipment is shut down and made safe.



SECTION 7 -NOZZLE TIP CARE AND MAINTENANCE We have already mentioned that a good, clean and neat cut is largely dependent upon a cutting tip (nozzle) that is in good order. In the hands of an experienced operator a tip can last for years. In the hands of an "inexperienced operator" a tip may last only a couple of hours! When it is discovered that you are struggling to obtain a neat cut, the torch keeps "popping out" or you are getting a lot of "back-fires", then it is time to stop the operation and inspect the nozzle. A common cause of such problems is a "poor tip". It is possible, and certainly desirable, to restore a tip to working condition with some simple maintenance. If you examine a new nozzle the following features will be found:

o The tip is "flat" with a well-defined, "sharp" edge. o The pre-heating holes are open and clear, as is the "cutting orifice".

If you examine a nozzle that has been in use for some time you may find the following:

o The tip has become "rounded" or eroded (The sharp edge has gone). o The orifices are no longer "round", and some may even be totally clogged. o These defects can be the result of heat and "spatter" during normal use. Sometimes

the defects are the result of "misuse". NOTE: A cutting torch should never be used as a "hammer", chipping tool, lever or any other purpose except to "cut". TIP (HEATING END) MAINTENANCE Tips are maintained, under normal circumstances, using the nozzle cleaning kit. Using the file, clean away any deposits of "spatter" from the "nose". If the tip is "eroded" then use a small flat smooth file (mill file) to restore the tip to a "flat condition". Having restored the nose then the orifices must be cleaned. For this you will use the "cleaning wires". Select a wire size that is smaller (thinner) than the orifice to begin the procedure. Insert the wire into the orifice and move it in and out. Do not use a twisting motion as this can enlarge the hole. Select the next size (larger) cleaning wire and repeat the procedure. NOTE: The important point to keep in mind is that an orifice must not be enlarged beyond its "manufactured size". If you do enlarge an orifice the tip will produce excessive heat (from the pre-heating holes) and excessive oxygen from the cutting-orifice, thereby increasing the width of the "kerf'. If you are not sure which size cleaning wire to use .then obtain a new tip of the same specification to that you are cleaning, and select the wire(s) to match the new tip.


STORING NOZZLES When a new nozzle is purchased it will generally be fitted with a plastic "protection cap". This cap protects the "seating surfaces" from damage such as scratching. Do not discard this protection cap as it can be used when you store the nozzle. Nozzles can also be set out on a tool rack in your cupboard. The tool rack not only protects the nozzles from damage but also makes it easy to select and "keep track" of where the nozzles are. Do not throw your nozzles into your toolbox amongst all the other tools. This will most certainly result in damage to the seating surfaces and may be the cause of an unpleasant accident! CONCLUSION This concludes the basic training module on "Oxyacetylene Processes". Practice the skills you have learnt at every possible opportunity. Other processes that involve the use of oxyacetylene kits include:

o Bronze Welding (usually called "Brazing" although this is not the correct term). o Silver brazing (Also called silver soldering). o Hardening and "annealing".

You can learn more about other technical skills by participating in other TECH AV programmes in the Basic Industrial Skills series.

(OXY) - TechAV · There are two types of torches normally associated with oxy-acetylene equipment,...

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