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OXYACETYLENE

DOWNSTREAM EQUIPMENT (ODE)

Learner Guide

TABLE OF CONTENTS

INTRODUCTION PAGE 1 OXY/ACETYLENE EQUIPMENT INTRODUCTION PAGE 3 MODULE NO. 1 - PRESSURE REGULATORS PART 1 - PURPOSE AND TYPES PAGE 4 PART 2 - SELECTION CRITERIA PAGE 7 PART 3 - SAFE PRACTICES PAGE 12 SELF TEST NO. 1 PAGE 16 NOTES PAGE 20 MODULE NO. 2 - GAS HOSES AND CONNECTIONS PART 1 - PURPOSE AND TYPES PAGE 21 PART 2 - HOSE AND CONNECTION MAINTENANCE PAGE 26 SELF TEST NO. 2 PAGE 30 NOTES PAGE 34 MODULE NO. 3 - GAS WELDING TORCHES PART 1 - TYPES OF TORCHES SELECTION CRITERIA PAGE 35 PART 2 - NOZZLES (WELDING TIPS) PAGE 37 PART 3 - TORCH PREPARATION PAGE 40 SELF TEST NO. 3 PAGE 45 NOTES PAGE 47 MODULE NO. 4 - CUTTING TORCHES PART 1 - TYPES OF CUTTING TORCHES PAGE 48 PART 2 - TORCH PREPARATION AND USE PAGE 51 SELF TEST NO. 4 PAGE 58 APPENDIX 1 - MSDS PAGE 61 APPENDIX 2 - USEFUL CONVERSIONS PAGE 71 APPENDIX 3 - INTERNATIONAL STANDARDS PAGE 72 NOTES PAGE 73

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OXYACETYLENE "DOWNSTREAM" EQUIPMENT

INTRODUCTION This learning aid has been designed to assist you to master the BASIC SKILLS and KNOWLEDGE involved for the handling and preparation of oxyacetylene devices associated with "portable gas cylinders". OBJECTIVES (PURPOSE OF THIS MATERIAL) This series serves to assist you, the "Learner", in achieving a "Learner-ship" in any of the engineering fields where Portable Oxyacetylene equipment is involved. PURPOSE STATEMENT (WHAT YOU WILL LEARN) During this learning programme you will learn:

o To identify and select gas pressure regulators, gas hoses and their associated connectors, including safety devices that must be in place.

o To fit and test equipment prior to putting it into service. o To assemble and prepare both welding torches and hand-held cutting torches of

popular design.

LEARNING ASSUMED TO BE IN PLACE (WHAT YOU SHOULD ALREADY KNOW / BE ABLE TO DO)

o General industrial safety. o Handling and identification of industrial gas cylinders. o Use of basic hand tools. o Interpret gas-pressure values from "bourdon-tube" gauges.

LEARNING OUTCOMES (WHAT YOU WILL BE ABLE TO DO)

o Prepare portable oxyacetylene equipment for use with a welding torch or a hand held cutting torch.

o Identify and fit appropriate flashback arresters to gas hoses / lines. o Prepare a welding torch for work. o Prepare a cutting torch for work. o Light up, adjust flame and shut down a torch in an acceptably safe manner. o Perform a full and safe "shut down" procedure.

INSTRUCTIONAL AIDS (INCLUDED IN THIS PACKAGE) 1. This Learner Guide. 2. Video No. 1 (ODE-1) - Pressure . 3. Video No. 2 (ODE-2) - Hoses and Connections. 4. Video No. 3 (ODE-3) - Gas welding torches. 5. Video No. 4 (ODE-4) - Cutting torches (Hand Held).


LEARNERS INSTRUCTIONS (HOW TO USE THIS LEARNING AID) Step 1 - Read the Resource Notes and follow any written instructions. Step 2 - View the relevant video section (where applicable). Step 3 - Complete any "Self-Test Exercise" (as applicable). Step 4 - Perform a practical exercise (as applicable). Step 5 - Have your Mentor / Instructor assess your work.

START LEARNING BY READING THE NOTES THAT BEGIN ON THE NEXT PAGE.


OXY / ACETYLENE EQUIPMENT Please make sure you have video No. 1 available (ODE-1). INTRODUCTION Oxy / acetylene equipment and processes can present a number of potential hazards to the operator, as well as to others within the vicinity. An understanding of these hazards as well as adherence to some, recommended safe practices, will greatly minimize the risk of a serious accident when using this equipment. Other related Tech AV programmes include:

o Gas Safety - "Gas Hazard Awareness". o Gas Safety - " Safe Handling of Portable Cylinders". o Oxy / acetylene Processes - "Manual Gas Welding and Flame Cutting". o Brazing and Braze Welding - General Welding Safety.

In this series of programmes you will learn more about oxyacetylene "downstream" equipment, namely:

o Pressure - regulators, gas hoses and their connectors, flash - back arrestors, welding torches and cutting torches, with an emphasis upon "recommended safe practices".


MODULE NO. 1 - PRESSURE REGULATORS Identification of parts.

PART 1 - PURPOSE AND TYPES The function of a pressure - regulator, just as the name suggests, is to regulate or "control" gas pressure. The pressure existing in a freshly filled "Standard Oxygen cylinder" is normally somewhere between 170 and 200 bars (17000 kPa - 20000 kPa). With the advent of improved design, cylinders capable of withstanding pressures up to 300 bars - 30 000 kPa will soon be available. The pressure existing within an acetylene cylinder is in the region of 17 bars (1700 kPa) with a maximum of 20 bars (2000 kPa) permitted. In order to use either gas (oxygen or acetylene) the pressure must be reduced to a safe and practical "working pressure", and maintained at that pressure whilst welding, cutting or brazing. This then is the primary purpose of any pressure regulator. Although "gauge less" regulators are sometimes used it is most usual, especially in industrial applications, to use regulators that have two gauges namely,

o High pressure gauge -reading cylinder pressure. o Low pressure gauge (working gauge) - reading outlet pressure (working pressure.

Gauges may be calibrated (marked) in "bars" (bar), kilopascals (kPa), or kilogram's per square centimetre (kg/cm²) and in some countries "pounds per square inch" (psi). Some gauges are often marked in dual scale calibrations. For example they may give units in both psi and bars or psi and kPa.


CONSTRUCTION OF TYPES

NOTE: In the event of accidental rupture (bursting) of a regulator, those types assembled with vertical components are considered to be less hazardous because flying parts are directed downward, whereas with horizontally assembled types, the flying parts would be directed outward (toward the operator). TYPES Pressure regulators are available in 3 configurations, in respect to their operation, namely: 1. Single Acting (Also called "single stage"). 2. Single stage - Pressure Compensating. 3. Double Acting (Also called "2 stage" and "dual stage"). SINGLE ACTING TYPES This type of regulator, being the simplest of the 3 designs, performs pressure reduction in a "single step". Owing to its design however it does have a limitation in that the outlet pressure (working pressure) tends to increase as the cylinder pressure drops (decays) during use. This means that the "operator" (welder) must be vigilant and make necessary adjustments to compensate for this factor. Single acting regulators are the most commonly encountered for most "manual operations" primarily owing to their relatively low cost and the fact that, for most operations, the slow pressure change seldom has any significant effect on the work (weld or flame cut). It is also a very simple and quick task to "re-set" the working pressure when the need arises but this is dependent upon the "operator" actually "observing his gauges" from time to time. DOUBLE ACTING Also known as "multi-stage" and "dual-stage" regulators, this type performs pressure reduction in 2 steps (stages) therefore delivering a steady and consistent working pressure regardless of cylinder pressure decay. The application for a multi-stage regulator is essentially the same as for PC single-stage units. The double acting regulator is favoured for


operations that require consistent working pressures and finer control over the outlet pressure with a minimum of "operator" attendance. SINGLE STAGE - PRESSURE COMPENSATING (PC) Although constructed in a similar design to the normal single-stage type, a "pressure-compensating" type features a mechanism that maintains a constant working -pressure regardless of cylinder pressure decay. In many applications the PC regulator has superseded the dual stage owing to its comparative low cost and the fact that it delivers a steady outlet pressure regardless of cylinder decay. The PC type is ideally suited to all manual welding and cutting processes, and especially processes that require precise and steady working pressures. PC types are recommended for use with "balanced-pressure" torches as well as for "automatic welding / flame cutting" processes where operator monitoring is minimal.


PART 2 - SELECTION CRITERIA Although most welders, boilermakers and other users of oxyacetylene equipment seldom get to choose their equipment (the bosses do this for you!). It is never less important for you to be able to recognise a "safe" and acceptable regulator. STANDARDS In the manner of most "critical equipment", pressure regulators must meet certain manufacturing and safety standards in order to qualify for "international acceptance". Standards are set by a variety of "standards authorities" around the world and, depending on which country you happen to be in, your local "standards authority" will have either set its own standards or dictate which international standard they recognise. The ISO standard for pressure regulators used in welding, cutting and related processes with GAS CYLINDERS up to 300 bar is: ISO 2503. Other references that you may encounter include:

o BS EN ISO 2503 (replaced BS 7650 & EN 585). o DIN EN ISO 2503 (Germany).

NOTE: Good (Safe) quality products that meet these standards will clearly display this fact, either on the regulator itself or within the written specifications of that particular unit. If in doubt, consult your equipment supplier or dealer for confirmation of a standard. The main point is that if a regulator has not been "approved", by your local standards authority, or against one of any international standards, then that unit is probably "unsafe" due to possible inferior materials or manufacturing methods. AGE OF REGULATORS Certain components (specifically the "diaphragms") within most pressure regulators are made of "elastomeric material" (Plastic like substances). Over a period of time most elastomer material tends to deteriorate and loose its "elastic properties". This in turn means that a regulator will eventually fail! When a regulator "fails" the consequences could be very serious indeed! International standards (codes of practice)1 limit the "life" of oxygen and acetylene regulators to 5 years. Any regulator that is 5 years old (or older!) should be removed from service, or removed from the "shelf". This means that any regulator, USED OR NOT, shouldn't be fitted to a cylinder if it is older than 5 years! It is indeed common practice for most operators, users or owners of equipment to continue using regulators for years after the "expiry date" and "nothing happens"! The point however is that the RISK of regulator failure is very high, and increases daily, as an old regulator remains in service.


Reputable manufacturers will display either a "date of manufacture" or an "expiry date" upon the regulator body or within the supplied literature. Ask your supplier or dealer to explain where this information is displayed on any given unit that they provide. 1. According to British and European regulations. regulators that are over 5 years old and designed for use with oxyacetylene, should be replaced! GAS TYPE Regulators are designed for use with specific gas types, which in our case is Oxygen and Acetylene. The gas type for which any given regulator is to be used is identified by one or more of the following:

o Colour coding ( usually red for acetylene and blue for oxygen). NOTE: Colour coding should never be used as the only means of identification. Colour codes may vary between different countries and manufacturers!

o The name of the gas type printed upon the gauges. o The name of the gas type upon a decal attached to the regulators pressure adjusting

knob, or upon the body of the regulator. NOTE: "If you cannot POSITIVELY identify a regulator as to the type of gas it is to be

used with , then DO NOT ATTACH IT TO A CYLINDER!" PRESSURE GAUGES (STANDARD: ISO 5171) The regulators most commonly attached to portable "industrial" oxyacetylene equipment feature two gauges, namely, a "high -pressure" gauge (also known as the "cylinder gauge"), and a "low-pressure gauge" (also known as the "working -pressure gauge"). The gauge closest to the "bull-nose" or "inlet connection" is the "high pressure gauge". This gauge indicates the pressure within the cylinder. The low-pressure gauge indicates the working-pressure within the hoses and the torch at any given moment. Gauges may be calibrated (marked) in "bars" (bar), kilopascals (kPa), "pounds per square inch" (psi), or sometimes in "kilogram's per square centimetre" (kg/cm²). Some gauges may feature "dual scales". Be careful that you observe the scale that indicates the pressure-units that you are working with or those with which you are familiar. Confusion can lead to accidents! All pressure gauges should also be marked with the gas type for which they are to be used. The gauges used with pressure regulators are designed to withstand more pressure than "normally expected", this offers protection against the possibility of a gauge burst if, for any reason the pressure rises beyond "normal". Gauges should also display a "maximum pressure" marking on the scale. This is normally a RED line or sometimes a red area (zone) on the high end of the gauge scale.


Gauges should always indicate readings in excess of this maximum pressure reading so that the operator can easily identify a fault and / or a potentially hazardous situation. LOW PRESSURE GAUGE If a low pressure gauge (either oxygen or acetylene) shows a reading above the maximum rated pressure or within the red zone, it is almost certain that the fault is within the regulator. The immediate action to be taken is as follows:

o Close the cylinder valve. o Open the shut off valve (if fitted). o Open the torch valve(s) -to release pressure. o Wind out the regulator pressure adjusting screw. o Remove the regulator and have an authorised agent attend to it.

HIGH PRESSURE GAUGE (CYLINDER GAUGE) If a high pressure gauge indicates an "over maximum pressure reading" then the situation must be assessed quickly by your supervisor as it is most likely to be of HIGH RISK! Possible causes of excess cylinder gauge reading:

o A faulty gauge (not impossible, but unlikely where good quality and well maintained equipment is installed.).

o Cylinder overfilled (also not impossible, but an unlikely event if you purchase gas from a reputable dealer).

o Cylinder has become "overheated" externally. (For example, if near a fire or other heat source).

o In the case of "acetylene", the problem can be caused from "internal heating" as a result of "acetylene decomposition" within the cylinder.

PRESSURE RATINGS INLET PRESSURE Every regulator must state the maximum inlet pressure for which that unit is designed. This figure may be located:

o On the body / bonnet of the regulator. o On a decal on the unit (often on the pressure-adjusting knob). o On the face of the "high pressure gauge" (Maximum pressure rating - Thick Red Line

on the outside of the scale or beginning of the Red Zone). o Within the manufacturers data sheets (for model and type).

Always take note of the maximum cylinder pressure before you attach a regulator. Cylinder (max.) pressure rating is displayed on the cylinder, both on the manufacturers' label and stamped into the metal near the cylinders' neck. The maximum stated "inlet-pressure" of the regulator (inlet) must be equal to or greater than the maximum rated cylinder pressure. The basic rule is:


"If Cylinder Pressure rating is greater (higher) than stated Regulator Inlet Pressure, DO NOT ATTACH the unit to the cylinder!" WORKING PRESSURE Also known as the "outlet pressure", this is adjustable within a "range" that MUST be stated upon the regulator, or provided in the written specifications of the unit. Outlet pressure is determined by the position of the "pressure adjusting screw". If the screw is turned all the way out (anti-clockwise) then the outlet pressure will be at its MINIMUM setting (Zero). When the pressure adjusting screw is turned all the way in (clockwise) the outlet pressure will be at its "regulated" maximum. The outlet or working pressure can therefore be set to any figure lying between zero and "maximum" depending on the position of the adjusting screw. SAFE WORKING -PRESSURE RANGES FOR REGULATORS USED WITH "PORTABLE GAS EQUIPMENT" 1. Oxygen Regulator: 0 - 10 bar (0 -1000 kPa). 2. Acetylene: 0 - 1.5 bar (0 -150 kPa). IMPORTANT: In the case of an ACETYLENE regulator the maximum outlet pressure is restricted to, and will never exceed 150 kPa. ACETYLENE FACTS "If pressure rises above the critical level, adiabatic combustion leads to decomposition of acetylene" - which, in non-scientific terms, means that acetylene, in its "gaseous state" (not dissolved), becomes highly unstable if compressed to pressures in excess of 2 bars (200 kPa). RELATED MATERIAL SAFETY DATA SHEET INFORMATION MSDS Nr.: 001. Chemical formula: C2H2. Stability and reactivity:

o Can form explosive mixture with air. o May decompose violently at high temperature and/or pressure or in the presence of

a catalyst o Forms explosive "acetyl ides" with copper, silver and mercury. o Do not use alloys containing more than 70% copper. o Dissolved in a solvent supported in a porous mass. o May react violently with oxidants.


(See Appendix -1 for full MSDS Nr. 001 Acetylene). ACETYLENE STORAGE The reason that acetylene within a cylinder exists at a pressure of around 18 bar (1800 kPa) is because it is held in a "dissolved state" with acetone. Facts:

o Acetylene is soluble in water and in acetone (will dissolve). o 1 Litre of water will dissolve 1 litre of acetylene. o 1 Litre of acetone will dissolve 24 litres of acetylene. o Acetylene is an extremely flammable gas and can react violently under certain

conditions. Keep these facts in mind when next you use this gas, it demands a little more respect than we sometimes give it!


PART 3 - SAFE PRACTICES In this section we shall consider those actions we need take toward ensuring that a pressure regulator remains in a safe and reliable condition. Inspection In accordance with modern safety practices (Code of practice), all regulators in service should be given a thorough "physical inspection" on a weekly basis. In order to perform a full inspection it is necessary to remove a regulator from the cylinder. Before removal always ensure that: 1. The cylinder valve is fully closed. 2. The pressure has been released. 3. The regulator adjusting screw is turned fully out (regulator is closed). 4. Correctly fitting spanner is used to turn the bull-nose connector. Inspect the regulator as follows:

1. Inspect the pressure gauges for obvious things such as a broken gauge cover (glass). Make sure that you are able to clearly read the gauges figures or markings. 2. Examine the bull-nose seating surface for damage such as scratching and corrosion. Remember that this area has to withstand the full force of cylinder pressure and that any imperfection can result in a potentially dangerous gas leak. 3. Inspect the threads of both the bull nose and the outlet connection. Damaged or worn threads can prevent an effective seal. Whilst in this area, check the "hexagons" on the connectors and connector nuts. Rounded corners and "bite marks" offer evidence of someone using incorrect tools to loosen or tighten the fittings. If damage is bad (if a spanner no longer fits) the unit must be repaired by your agent. 4. Check the condition and operation of the pressure adjusting screw. Broken knobs make it difficult to operate adjusting screws (and dangerous too!). The screw should turn easily, without sticking or jamming, all the way in and all the way back out. If the screw is hard to turn, have the unit checked by your agent. 5. Check the condition and operation of the stop-valve (where fitted) in the same manner as the adjuster screw. 6. Inspect the pressure relief valve (also called the "excess pressure device"). You won't be able to test this but, by "looking at it", you will see if it has been damaged "physically".


REMEMBER Do NOT attempt to repair a regulator, no matter how "simple" the task appears. Should anything go wrong and an accident happen as a result of a regulator failure, after YOU have worked on it, then you can be sure that YOU will be called to question in the accident enquiry! FITTING AND TESTING OF REGULATORS This is not a difficult task but one in which a little care and attention must be paid in order to avoid damage to the unit or worse, personal injury! For "safety sake" follow these recommendations: SAFETY TIP: During the following procedures it is recommended that safety goggles be worn. FITTING (TO A CYLINDER)

o Remove (where fitted) the protective plug from cylinder valve port. o Blowout dirt etc from the valve port by quickly opening and closing the cylinder

valve. Remember the safety rules: Stand to the side, make sure you are wearing goggles and ensure that no one is in the immediate area.

o Remove protection cover /cap from regulator bullnose. o Ensure that you have the correct regulator (gas type and pressure rating). Attach to

cylinder valve and tighten connector nut by hand. o Select correctly fitting spanner. Support the unit in an upright position (gauges at

top). Do NOT hold on to the gauges whilst you tighten the connector. This can result in damage to gauges or even cause them to "snap away" from the body.

o Tighten the connector nut firmly, but do not over tighten. o Connect hose as applicable to the outlet connector. ALWAYS fit the correct flashback

arrester between hose and regulator outlet. If applicable, use two spanners here to prevent the turning of the outlet adapter in the regulator body.

TESTING (EXTERNAL LEAK) External leaks, on or around the regulator, will not only result in gas wastage but can also create a hazardous environment. Check for leaks in the following manner:

o Close off the regulators outlet connection. If a shut-off valve is not featured then attach a suitable device such as a flashback arrester that has a quick-coupler outlet connection.

o Open the cylinder valve. Do this in accordance with standard safety practices, namely: Stand aside the cylinder so as not to "face" the gauges. Open the cylinder-valve slowly in order to avoid a sudden pressure rush into

the regulator. o Adjust the "working pressure" by turning in the pressure adjusting screw. Set the

pressure to "nominal" for the torch / nozzle that you will be using. o Apply a safe leak detection fluid" (available from your equipment supplier) to each

joint and connection, including the gauge fittings and body joints.


o Observe if bubbles appear and note their position. Bubbles obviously indicate a leak. o If leaks occur at bullnose or outlet connection, then check the tightness of

connectors but do NOT over tighten. (If leaking persists after tightening connections the unit should be removed and sent for repairs*).

o If leaks occur at gauges or around body joints then the regulator needs attention from an authorised agent. DO NOT attempt to tighten gauges.

o If no leaks exist then test the regulator for internal leaks! IMPORTANT: NEVER APPL Y sealing compounds, including PTFE tape. to leaking joints. TESTING (INTERNAL LEAK) NOTE: The following check can be made at time of performing an "external leak check". The procedure that follows assumes that the regulator has been depressurised and that the cylinder valve is closed.

o Make sure that the pressure adjusting screw is turned all the way OUT (anti clockwise).

o Make sure that either the stop valve is closed (if equipped) or the outlet is "blanked off' using a suitable device such as a quick -couple flash -back arrester.

o If not already open, then, in the manner explained earlier, SLOWLY open the cylinder valve.

o Observe the cylinder gauge (high pressure) to make sure that there is pressure in the cylinder.

(It's a bit pointless doing all this with an empty cylinder!) o Turn in the pressure adjusting-screw to obtain approximately "nominal" working

pressure for the torch. o Now observe the low -pressure gauge. If after about 5 - 10 minutes there is no

increase in the low -pressure gauge reading then the regulator is in good order. o However, should there be a rise or "creep" in pressure (low -pressure gauge) then an

internal leak exists within the regulator. This is a hazardous condition! o In this situation do the following (in this order);

1. Close the cylinder valve immediately. 2. Release the pressure in the regulator. Do this by opening the shut-off valve, or loosening the connector at the outlet. 3. Close the regulator (turn adjuster screw fully out). 4. Remove the regulator from the cylinder. 5. Send the regulator away for inspection by an authorised agent. CARE & MAINTENANCE Follow these simple recommendations:

o Keep the unit clean and free of dirt. o Do NOT use solvents, petrol or any substance that is even "remotely flammable" to

clean a regulator. A dry brush, paper towel or oil free cloth is usually sufficient to dislodge most deposits.

o Never "oil" the threads, or any other part of the regulator. A regulator will not "rust" and needs NO lubrication. Substances that contain hydrocarbons such as oil, grease etc. in the presence of pressurised oxidising gases, such as oxygen, will react and result in fire or explosion.


o When a regulator is removed from a cylinder, and is to be stored for any period of time, cover the inlet (bullnose) and the outlet connection to prevent dirt, vapours etc from entering. Use the plastic caps supplied when the unit was purchased to protect the unit.

o Always make sure that the pressure adjusting screw has been turned all the way OUT.

o Place the unit in its original box or other suitable container in order to protect from being knocked about by other objects.

o Store the unit safely and separately from other tools and equipment, don't leave it lying around to get damaged.

FOR YOUR OWN SAFETY, AND THAT OF YOUR COLLEAGUES

o Only install and use quality equipment that meets local or international standards of manufacture.

o Perform regular inspections on your equipment. o Follow recommended safe practices. o Understand the hazards associated with your particular processes. o Maintain your equipment in good working order. o Develop a safe working attitude.

INSTRUCTIONS 1. View video (ODE-1). 2. Complete the Self Test exercise on the following page. 3. Proceed to module 2.



SELF TEST NO. 1 REGULATORS

INSTRUCTIONS Answer the questions below without reference to your notes or the video. 1. Label the following parts of a regulator.

2. Explain, in your own words, the correct procedure for pressurising a regulator. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ 3. Explain, in your own words the correct procedure for depressurising and closing of a regulator. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________


MULTIPLE - CHOICE (Note that some questions may have more than one correct response.)

QUESTION YES NO

1. a) b) c)

What is the primary function of a pressure regulator? Tick correct response.) To slow to flow of gas into the hoses and torch. To reduce and control gas pressure. To increase pressure to the torch.

2. a) b) c)

What pressure can be expected in a standard oxygen cylinder? (Tick correct response.) 20 bar. 2000 bar. 200 bar.

3. a) b) c)

What pressure can be expected in a standard acetylene cylinder? (Tick correct response.) 170 bar. 1700 bar. 17 bar.

4. a) b) c)

What is the main purpose for fitting a pressure-regulator? (Tick correct response.) Reduce cylinder outlet pressure to a safe working pressure. Maintain a steady working pressure. Stop gas leaking from cylinder.

5. a) b) c)

The type of regulator most commonly used in conjunction with portable oxyacetylene equipment is? (Tick correct response.) Dual stage. Single stage. Pressure compensating.

6. a) b) c)

When purchasing a regulator one should always? (Tick correct response.) Buy the cheapest brand available. Buy the brand that has been approved by a recognised "standards authority". Buy the type that has a known brand name.


7. a) b) c)

A regulator should be replaced when it has reached the age of ... ? (Tick correct response.) 1 year. 2 years. 5 years.

8. a) b) c) d)

In order to positively determine which "gas type" a regulator is suited for we need note, what ... ? (Tick correct response.) Colour code. Gas type name on gauges. The gas name on a decal. The manufacturers specifications.

9. 1. 2. 3.

List the 3 most common "units of pressure" used with pressure gauges. ____________________________ (bar) ____________________________ (kPa) ____________________________ (psi)

10. a) b) c)

In terms of pressure ratings, which of the following must be checked before you attach a regulator to a cylinder? (Tick correct response.) Regulator working pressure range. Cylinder pressure rating. Regulator input rating.

11. a) b) c)

What is the maximum working pressure that an acetylene regulator should deliver? (Tick correct response.) 150 kPa. 150 bar. 150 psi.

12. a) b) c)

Why does a pressure gauge offer scale readings above indicated maximum figures? (Tick correct response.) To indicate excessive and dangerous pressure. So that they can be attached to bigger cylinders. To deliver more Gas flow.

13. a) b) c)

What is the working-pressure range required for an oxygen regulator used with portable gas equipment? (Tick correct response.) 0 - 100 bar. 0 - 10 bar. 0 - 100 psi.


14. a) b) c)

Turning the pressure adjusting screw "clockwise" does what? (Tick correct response.) Increases the working pressure. Increases the cylinder pressure. Closes the regulator.

15. a) b) c)

To close a regulator we should do what? (Tick correct response.) Turn the pressure adjusting screw fully in. Turn the pressure adjusting screw fully out. Shut the cylinder valve.

16. a) b) c)

A regulator can be damaged internally if .... ? (Tick correct response.) The cylinder valve is opened too quickly. The cylinder valve is opened too slowly. The cylinder valve is shut too tight.

17. a) b) c)

It is considered to be "safe practice" to always stand aside a cylinder whenever opening the valve, why is this? (Tick correct response.) So we can reach the valve easily. To avoid gas hitting our face. To avoid possible injury from an exploding gauge.

18. a) b) c)

If you cannot stop a leak at the regulators inlet connection to the cylinder you should ... ? (Tick correct response.) Use a longer spanner. Remove the regulator for inspection. Apply sealing compound to the threads.

19. a) b) c)

When testing a regulator, what would indicate an internal leak? (Tick correct response.) The high pressure gauge dropping. The low pressure gauge rising. The sound of a gas leak.

20. a) b) c)

If a regulator is faulty or damaged you should do what? (Tick correct response.) Remove it from service. Repair it. Work very carefully with it.

CHECK YOUR RESPONSES WITH YOUR INSTRUCTOR / MENTOR.


NOTES


MODULE NO. 2 - GAS HOSES AND CONNECTIONS Please ensure that you have video programme No. 2 available (ODE-2). INTRODUCTION Hoses are commonly the most neglected part of all oxyacetylene equipment. Accidents arising from hose related incidents are relatively common but can be reduced by applying some simple criteria. PART 1 - PURPOSE AND TYPES The primary purpose of a gas hose is to convey gas from a cylinder to the torch in the safest possible manner. A hose needs to be as flexible and lightweight as possible yet strong enough to withstand external and internal influences. Gas hose consists of an inner "extrusion" made of synthetic rubber (Styrene Butadiene) with a wall thickness of 1.5mm or more. Surrounding the inner extrusion is an outer "protective layer", (minimum thickness 1 mm) which may be "single braid" or "double braid" made with fabric-reinforced synthetic rubber. The outer protective layer is colour coded for purposes of identification as to the gas type to be used. In the case of oxyacetylene equipment the standard colours are:

o Blue - Carrying oxygen. o Red - Carrying acetylene.

HOSE SELECTION CRITERIA Gas hose meeting the international standard ISO 3821 or EN 559 (old British Standard BS 5120) should always be selected. Never select gas hose on the basis of cost alone as this can prove to be very unsafe. Selection based upon ISO or equivalent standards, will ensure the following safety related attributes:

o Resistance to fire and heat. o Resistance to chemicals that may feed through with gases (such as acetone). o Flexibility at temperatures as low as -25°C. o Resistance to ignition in oxygen enriched atmosphere. o Resistance to crushing or kinking. o Resistance to "weathering" or "ozone attack". o Ability to resist pressure of flashback (bursting pressure). o Good flow of gases (least possible flow resistance).

The standard, along with other information such as hose size, is imprinted along the length of all gas hoses. Gas hose is obtainable in any length requested. For "average" conditions hose length of approximately 5 metres is considered adequate. Use the shortest length that is practical as


long hoses present difficulty with placing, storing and handling on the job. Remember too that the longer the' hose the greater the amount of gas it will contain! HOSE SIZE The size of gas hose is based upon the "bore diameter" of the inner extrusion. Sizes available are listed in the table below.

Manufacturing Tolerances Nominal Size Minimum (mm) Maximum (mm) Size marked on Hose

4.45 5.55 5.0 mm 5.75 6.85 6.3 mm 7.35 8.65 8.0 mm 9.35 10.65 10.0 mm

There are no "absolute rules" governing the selection of size other than "operator experience". Selection of a suitable hose size is dependent upon the required gas flow (in "litres per minute" or "cubic feet per hour") and this, in turn, is normally decided by the type of torch, length of hose and the nozzle size. The most "commonly selected" size is 8mm as this size is suitable for most operations involving oxyacetylene welding, brazing and flame cutting etc. COLOUR OF HOSES Standard colour coding for oxyacetylene equipment is:

o Acetylene - RED. o Oxygen - BLUE (Except USA).

Do not use any other colours as this will lead to confusion and possible accidents! NOTE: That in USA oxygen hoses are GREEN. BUNDLING OF HOSES The two "welding hoses" are commonly tied or "bundled" together so as to form a compact arrangement. Special "Hose-Ties" (clips) of the "break-apart" type should be used to provide a means of keeping the two hoses together. Proper clips offer a separation, or gap between the hoses through which sparks and slag can pass. DO NOT tape or "wire" hoses together as this practice provides no "spark gap" and also prevents the break apart of hoses in emergency situations. The use of "Siamese hose" (Moulded double hose) is NOT RECOMMENDED owing to the high risk of a burn through.


Burn-through results when hot metal (slag) drops onto a hose and remains trapped between the oxygen and the acetylene hose sections. HOSE CONNECTIONS All hoses must be connected by mechanical means to the gas supply and to the torch. The devices used are called "hose connectors". At either end of every hose you will find a "hose-end connector" of one type or another. There are various types and sizes of hose-end connectors but all of them must be permanently attached and secured into the gas hose. Hose end connectors feature a tapered and barbed "tail-piece". The tail-piece is inserted fully into the hose where the barbs assist in preventing the fitting from being pulled out. As an added prevention against being pulled out, a hose clip or clamp is attached over the hose end. The hose clip, once tightened (or in some types "crimped") firmly secures the hose to the end connectors' tailpiece. Hose clamps must be of the type that resist snagging on clothing and which will retain a positive grip upon the hose. It must be noted that "jubilee clamps" (worm drive type) are no longer considered suitable for use as "gas hose connection clamps". It accordance with improved safety practices, is becoming common to encounter safety devices called "flashback arresters" attached to both ends of oxyacetylene hoses. Some flashback arrestors are fitted "permanently to the torch end of gas hoses and, when this occurs, the flashback arrestor also acts as a "hose-end connector". The purpose of a flashback arrester is to prevent a "flashback" (back burn) from entering a gas hose or a regulator. End connectors may be of threaded type of "quick-connector" type (Also called "quick couplers"). THREADED CONNECTORS (ISO 3253) As the term suggests a threaded connector features threaded couplings usually a "swivel nut" on the "hose-end connection", and an "adapter" (male threads) upon the device to which the hose is to be attached. The two most usual thread sizes are ¼" and ⅜" BSP. QUICK-CONNECT COUPLERS (ISO 7289) A "quick-connect" coupler eliminates the need for tools to be used when either connecting or disconnecting a torch from the hoses, or a set of hoses from the gas supply. This type of coupler is commonly used with "manifold-supply systems" and for "user stations".


A "quick-connect" coupling consists of two sections, a socket section and a coupler pin (also known as a "spigot"). A positive and "gas tight" connection is made when the coupling pin is inserted into the socket and a spring loaded collar "snaps" into the "locked position". Disconnection is made by pulling back the collar which in turn releases the "lock" and frees the coupler pin. It is important that you are aware that quick-couplers are made in such a way that you cannot easily confuse the "oxygen connection" with the "fuel connection" (acetylene) as the connectors have different features. Incorrect connection is possible however if the couplers are incorrectly fitted at the time of making up a hose or during a joint repair operation. Quick-connect sockets are colour coded (as per standard hoses) and must be fitted in accordance, namely BLUE with oxygen and RED with acetylene (fuel gas). A further important point to note is the "flow direction". Quick-connect sockets feature a "shut-off valve" that automatically closes when the coupling pin is removed. The socket section therefore MUST be positioned "UPSTREAM" (cylinder side) of the connection. If you fit the connector the wrong way round gas will escape from the supply side. Most connectors have "flow direction arrows" printed upon the label to remind you of the correct positioning. ADAPTERS Adapters may be required in order to "configure" a device (usually the torch) for quick-connect coupling. Coupling adapters consist of a "quick-connect pin" coupled to a threaded nut. When attached to the threaded input connector (torch inlet) the pin is secured and provides the means to connect the torch to a quick-connect socket. As the nut is usually a "loose" component (non-captive) it can happen that you may inadvertently attach the oxygen pin to the acetylene nut (or vice versa). Always make sure that the pins are installed with the correct nuts. Although the oxygen connector cannot fit an acetylene pin (and vice versa) it is possible that you may attach hoses the wrong way round (if you don't observe input connections) if the pins have been switched over! FLASHBACK ARRESTERS Detailed explanation of these very important safety devices is offered in other modules however it is important at this time that you are aware of some important facts concerning their fitting , viz:

o Make sure that the "flow direction arrows" (on the label) point AWAY from the regulator, that is, TOWARD the torch end of a hose. Failure to observe this basic convention will result in NO GAS FLOW to the torch.

o * Fit only a "REGULATOR MOUNTED" FBA at the regulator.


o * Fit only a "BLOWPIPE MOUNTED" FBA at the "torch-end" of a hose. * Consult the manufacturers' brochure or package instructions for details. Be aware that certain INTERNAL components differ between "Regulator mounted" and "Blowpipe mounted" FBA's. Incorrect installation can result in malfunction of devices. STANDARDS: RELEVANT TO CONNECTORS AND HOSE ASSEMBLIES The following standards are applicable to hose end couplers and associated devices.

o (ISO 3253) (BS) EN 560 for standard Hose Connectors. o (ISO 7289) (BS) EN 561 for "Quick Coupling" Connectors. o (BS) EN 1256 for Hose Assemblies (Made up with connectors). o (ISO 5175) EN 730 for Flashback Arresters.

CONFIGURATION OF CONNECTORS Owing to "preferences" of operators and users of gas supply systems there are a variety of configurations possible for the connection of hoses and flashback arrestors. This becomes very pronounced at the "torch end". Some operators prefer their FBA's to be attached "permanently" to the TORCH, whilst others prefer their FBA's to be a permanent feature of the HOSE connection. It is however MOST usual (and most sensible!) for the REGULATOR MOUNTED FBA to be "permanently" attached to the regulators' threaded "outlet adapter". By consulting the manufacturers' pamphlets, or by asking your equipment supplier, you will be able to determine, and obtain a suitable configuration to suit your system.


PART 2 - HOSE AND CONNECTION MAINTENANCE In this section we shall be concerned with practical aspects involved with hoses and relevant connections. We begin by first explaining those "basic procedures" involved in attaching hose-fittings. 1. CUTTING A HOSE Hose cutting is necessary when removing old fittings, trimming off or when making a "repair" such as cutting out a damaged or leaking section. The most important point about hose cutting is that you use a "sharp knife" as this produces a clean cut. Do not cut gas hose using a hacksaw as this will result in debris (particles of rubber) entering the hose. This in turn can lead to clogging and failure of delicate mechanisms within FBA's and torches. 2. ATTACHING A "PERMANENT" HOSE-END FITTING A permanent "hose-end fitting" is identified by the tapered and "barbed" tailpiece. Essentially the task involves pushing the tailpiece into the hose until the tapered section has FULLY entered and then securing the fitting with an externally mounted "hose clamp". Although an uncomplicated task, the assembly of an "end fitting" can present "challenges" so, follow these guidelines:

o Ensure that the "tailpiece fittings" are matched in terms of hose size. For example you will experience "extreme difficulty" with attempting to fit an 8 mm fitting into a 6 mm hose!

o When fitting (installing) a threaded fitting (featuring a swivel nut) secure the nut with an adapter tool (see video example) where possible. Push in the fitting with hand pressure (usually considerable effort will be necessary!)

o Push against a clean and firm surface, such as timber or rubber matting in the absence of an "installing tool".

o Use lubricant ONLY if necessary. "Dry" fitting offers the most positive grip. o Use only a "safe" lubricant, such as "leak detection fluid". NEVER use oil or

any other "petroleum based product. o Insert the tailpiece fully into the hose. There is usually a "shoulder" on the

tailpiece against which the end of the hose should "butt". o Fit and secure a suitable "hose clamp" over the hose end (See video

demonstrations for methods of securing clamps). 3. HOSE JOINERS Hose joining may be necessary when making a "temporary repair" or when a hose has to be extended because it is impractical or unsafe to bring cylinders closer to the work. One major safety point that you must be aware of is that the hose-joiner MUST be suitable for oxyacetylene. Essentially this means that the use of COPPER fittings must


be avoided , especially on the acetylene hose. Copper will react with acetylene to form an explosive chemical compound (Copper acetylide). 3.1 QUICK-CONNECT HOSE JOINERS This type deserves special mention because: a) They are becoming increasingly popular and, b) There are important considerations to keep in mind when fitting and when using hoses equipped with them. The following guidelines will assist in the selection and fitting of the devices. 1) Select those types that have tailpiece sizes to match your hose size. 2) Select those bearing standard colour codes so as to avoid confusion later (Blue and red). 3) Install the "socket portion" on the "UPSTREAM" side of the joint. Most quick- connect joiners feature a "close-off valve" that shuts when the connector pin is removed. Fitting the device the wrong way round will result in gas escaping from the supply when you disconnect! 4) DO NOT confuse a "hose connector" with a "flashback arrester". This may happen when you collect hoses that have been fitted with quick-connect joiners and you mistake them for FBA's. 4. TESTING FOR LEAKS Before putting a hose in to service it must be checked to ensure that there are no leaks at connecting points or at any position along the length of a hose. The usual method of checking for leaks is to install the hose and set up your equipment as if for normal operation, in other words apply gas working-pressure into the hose. At this time apply leak detection fluid to every joint and observe for bubbles. To assess for leaks along the "trailing section" of hoses you can immerse sections in water (in the manner used to check a puncture in a bicycle tube). This technique is useful only for the sections of hoses that are at "ground level". For those sections leading up to the cylinders use leak detection fluid (spray). Some operators prefer to use an INERT gas such as argon to apply pressure to a newly made (or repaired) hose. IMPORTANT NOTE Do not use compressed air, (as supplied by a normal air compressor) for testing purposes. Such air contains "oil vapour" and this will impregnate the hose resulting in a highly flammable situation when connected to the normal gas supply.


5. INSPECTION OF HOSES Hoses should be examined on a regular basis (at least weekly) for evidence of damage or deterioration. The following points of inspection should be attended to:

o Cracks and splits* (Excessive surface cracking). o Burn through of outer layer. o Cuts or punctures. o Swelling (Indicating separation of reinforcement from the inner extrusion. o Brittleness (indicating a badly weathered or a burned hose). o Wear from scuffing or dragging.

*Bend the hose sharply and examine depth of cracking. If you can see the inner extrusion then the hose must be replaced. Light "surface cracking is considered as being "acceptable". All other defects require the renewal of a hose. Remember that a hose may appear to be in good condition on an external inspection but we cannot see inside. Any hose that has been exposed to a flashback must be renewed , as internal damage will be highly probable. Further inspection must include:

o Security of hose end fittings. Security of clamps. o Condition of the end fittings. These tend to become damaged from being

"scuffed " when hoses are dragged along the ground. o Missing or broken bundling clips. Replace where required.

6. STORING HOSES The correct and SAFE procedure for hose storage is as follows:

Ensure that all gas has been bled from each hose. Wrap hoses around the trolley handles, or if equipped, around the hose

support bracket. Store equipment in sheltered position (under cover) and away from main

work area. NEVER X Leave welding gases in the hoses. X Wrap hoses around the cylinders. Fire in a coiled hose is exceedingly difficult to control and around a cylinder this situation could prove "disastrous". X Leave hoses lying upon the ground when not in use. X Leave hoses outside and exposed to direct climatic factors (Sunshine, freezing etc).


7. CARE The following points must be considered in order to ensure total safety and the reduction of risk from hose related accidents. During operation ensure that hoses are routed in such a way that they:

o Cannot be snagged by passing objects (like vehicles, cranes etc). o Will not be crushed beneath wheels. o Will not become snagged on sharp objects. o Will not lie upon heated materials. o Are not positioned directly beneath a cutting table or platform

Observe the following basic rules:

o Keep hoses far away from oil, grease, tar and chemicals. o Don't drag hoses as this causes the outer layer to become scuffed. o Never attempt to "repair" a hose-leak or a split hose by "taping". Tape will

inevitably burst. Where necessary, cut out a damaged section and effect a proper join the manner explained earlier.

o NEVER attempt use "garden hose" (water hose) as a "cheap substitute" for gas hose. This is a really dangerous practice and deserves no further comment!

o If quick-connect couplers are used these must be checked for leaks regularly. Frequent use of these coupling types results in wear to the elastomeric sealing elements and leaks will occur. Replace or renew couplers when leaks are detected.

o Avoid using chemicals or solvents to "clean" your welding hoses. A water moistened cloth is the only "safe" item to use.

INSTRUCTIONS 1. View video (ODE-2). 2. Complete the Self-Test exercise that begins on the following page.

THIS CONCLUDES THE HOSES AND CONNECTIONS MODULE.



SELF TEST NO. 2 GAS HOSES AND CONNECTIONS

INSTRUCTIONS - PART 1 (MULTIPLE - CHOICE SELECTION) Answer the following questions below without reference to your notes or the video. (Note that some questions may have more than one correct response.)

QUESTION YES NO

1. a) b) c)

When selecting new gas hose for oxyacetylene purposes it is important that ... ? (Tick correct response.) The hose displays standards markings on the outer layer. The hose displays the manufacturers name on the outer layer. The hose displays the date of manufacture on the outer layer.

2. a) b)

The standard colour codes used with gas hose are ... ? (Tick correct response.) Oxygen ... Blue / Red. Acetylene ... Blue / Red.

3. a) b) c)

The size of a hose is determined by, which factor? (Tick correct response.) The external diameter. The length. The internal diameter.

4. a) b) c) d)

The correct type of clips used for the "bundling" of hoses must offer what properties? (Tick correct response.) A spark-gap between the two hoses. Quick separation. Neat appearance. Hold hoses rigidly together.

5. a) b) c)

We must never bundle hoses together using tape, wire or cable ties, why is this? (Tick correct response.) These items can break during operation. They prevent rapid separation in event of emergency. The practice contravenes fire regulations.


6. a) b) c)

Which type of "hose clamp" is no longer considered as suitable for use with gas hose? (Tick correct response.) Wire clamps. Jubilee clamps. Crimp type clamps.

7. a) b) c)

The purpose of a "flashback arrester" is what? (Tick correct response.) To prevent a backfire occurring. To prevent a flashback entering a hose or a regulator. To control the flow of gas through the hose.

8. a) b) c)

Flashback arresters must be installed where? (Tick correct response.) At the cylinder valve. At the torch inlet. At the regulator outlet and the torch inlet.

9. a) b) c)

Arrows on the labels of FBA's and Quick-Connect couplers / joiners indicate what? (Tick correct response.) The top of the device. The flow direction of gas through the device. North and South.

10. a) b) c)

Flashback arresters can be classified as ... ? (Tick correct response.) Blowpipe mounted and Regulator mounted. Cylinder mounted and torch mounted. Hose mounted and non-hose mounted.


INSTRUCTIONS - PART 2 Answer the following in your own words, without reference to your notes or the video. 1. Why is it that you should use a sharp knife and not a hacksaw to cut gas hose? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

2. Why must you install quick-connect couplers with the labels arrows pointed away from the regulator (or toward the torch)? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 3. Describe (briefly) how you would test hoses for leaks. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 4. List those items that you would look for when making a "visual inspection "of a gas hose. 1)_________________________________________________________________ 2)_________________________________________________________________ 3)_________________________________________________________________ 4)_________________________________________________________________ 5)_________________________________________________________________ 6)_________________________________________________________________ 5. Describe the correct manner of storing hoses. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________


6. Describe those things that you must NEVER allow, In respect to hose storage. 1)_________________________________________________________________ 2)_________________________________________________________________ 3)_________________________________________________________________ 4)_________________________________________________________________



NOTES


MODULE NO. 3 - GAS WELDING TORCHES INTRODUCTION Although we use the term "welding", a welding-torch can be used for other processes besides pure "welding". For example, the same torch may be used for "braze-welding" (also called bronze welding), silver brazing and other heating operations. PART 1 - TYPES OF TORCHES Two types of welding torch are in common use, namely:

o Balanced pressure torch, also known as an "equal pressure torch" and o Injector torch, also known as a "low pressure torch".

Although there are many similarities between the types there are some notable differences which you must be aware of in order that you operate either type in a safe manner. SELECTION CRITERIA The selection of a torch type is often a matter of "preference" by the user (Operator) but all torches and related accessories, such as nozzle-tips, must meet with standard EN ISO 5172 or equivalent in order to satisfy international safety requirements. BASIC PARTS AND FUNCTIONS - BOTH BP AND INJECTOR TYPES In its simplest form a welding torch consists of:

o A handle section, also known as the "stock". o Gas hose connections. o Gas control valves, also called "torch valves". o A gas-mixer, or "mixing unit". o A mixing tube. o A nozzle, also called a "tip".

BALANCED PRESSURE TORCH The primary attributes of this type of torch include:

o Gas pressure settings (working pressure) on both oxygen and acetylene are "equal". Typically the pressure setting for most operations and tip sizes is 60 - 70 kPa.

o The mixing unit accommodates various sizes of tip. Only the tip (nozzle) need be changed when you need to change for another size.

INJECTOR (LOW PRESSURE) WELDING-TORCH Although similar in appearance to a balanced pressure torch, an "injector torch" (low-pressure torch) differs in the following ways:

o Gas pressure settings are NOT equal. Normally the acetylene working pressure is set very low, typically below 10kPa. Oxygen pressure is set higher than acetylene. The


actual pressure is determined by the tip size (nozzle number) and the design of the injector and may differ between manufacturers and torch models.

o Mixing tubes are "matched" with tip sizes. You cannot fit any sized tip to a mixing tube, only that size that is "matched". It is necessary to purchase a variety of mixing tubes and matching tips to cover the range of material-thickness, and metal types that you are likely to work with.

It may be of interest to you that the injector torch was developed many years before it was discovered that acetylene could be safely "compressed" by dissolving it in acetone. With the advent of "compressed acetylene" the injector torch has, at least in "oxyacetylene terms", become somewhat redundant, however it still has many advantages over the more "modern" equal-pressure torch, namely: An injector torch can be used when acetylene cylinder delivery-pressure has "decayed" below that of the working-pressure required to operate an "equal pressure" torch. It can be used with "low pressure fuel-gases" (vapour pressure). Injector torches are relatively unaffected by gas pressure fluctuations and provide a much more "consistent flame" than the equal-pressure type.


PART 2 - NOZZLES (WELDING TIPS) A nozzle, also known as a "tip" is a very important part of the torch. Tips are manufactured from copper or copper alloys. Gas flows through the tip via an orifice (small diameter channel). "Back pressure" exists within the tip, and this ensures that a "jet" of mixed gas, passes through the orifice and arrives into the atmosphere at a "constant velocity". The flame burns as result of combustion of the mixed gases combined with the oxygen in the atmosphere. (Around 40% of the oxygen required for the flame is obtained from the surrounding atmosphere). The manner in which gas exits the tip affects the "behaviour" of the flame. A "perfect flame" is achieved only if the tip is in perfect shape. The ideal shape of the tip is flat and the orifice must have sharp edges. During operation a tip tends to become deformed and the orifice tends to become clogged with "spatter". Depending upon the "experience" of the welder (operator) this will occur "sooner or later". A tip will require "dressing" from time to time in order to maintain efficiency and prevent problems such as backfiring. NOZZLE IDENTIFICATION 1. BALANCED PRESSURE TYPE

o Tips are available in varying sizes according to the size of the orifice. o The size of a nozzle is given as a number stamped onto the body of a tip. The number

indicates the "gas volume", in cubic feet per hour, which will pass through the tip when working pressures are correctly set.

o It is not necessary to change a mixer when changing to a different tip-size as all tips, designed for any given torch, are interchangeable.

o Tips are threaded into the mixer-tube and "hand tightened". o Selection of a suitable tip for any given task is most usually decided by the material

thickness to be welded or brazed. As a "guide only" the table below offers basic tip selection data for "mild steel" welding with a balanced pressure torch.

Steel Plate Thickness (mm Tip size selection Working pressure (kPa)

Oxygen & Acetylene 0.8 1 60 1.2 2 60 1.6 3 60 2.4 5 60 3.2 7 60 4 10 60 5 13 60 6 18 60 8 25 60

10 35 60 12 45 60 20 55 60


Table 1 - Setting Guide (Balanced Pressure Torch) INJECTOR TYPE TORCH TIPS (LOW PRESSURE)

o Tips are an "integral" part of the mixing unit. o Tips of different sizes are available but it must be noted that they cannot be

swapped or attached to a mixer that is designed for another size. o Tip sizes are stamped onto the body, but the number does not relate to gas volume. o A new tip, of the size removed or the sizes stated on the mixer body, can be fitted to

the end of a given mixer tube. o An "O-ring" is used to seal the mixer body into the torch stock. Failure of the "O-ring"

will result in air being drawn into the mixing gases. This may cause backfiring and the inability to maintain the desired flame.

o Tips (mixers) are selected by reference to the torch manufacturers' setting guides. Table 2 offers "typical data" for low pressure welding torches.

Nozzle Number Steel Thickness

(mm) Acetylene pressure

Nominal (kPa) Oxygen pressure

Nominal (kPa) 1 0.5 - 1.00 7 60 2 1.00 - 2.00 7 70 3 2.00 - 4.00 7 70 4 4.00 - 6.00 7 75 5 6.00 - 9.00 7 85 6 9.00 - 14.00 7 100 7 14.00 - 20.00 7 110 8 20.00 - 30.00 7 130

Table 2 - Setting guide (injector / Low pressure Torch)

TIP MAINTENANCE Nozzle-tips, after an amount of action, tend to become misshapen and restricted with metal "spatter". These conditions not only yield poor work results but can also cause the torch to "backfire" and may even cause a "flashback". It is therefore necessary to "dress" a tip when the need arises in order to restore the desired flame quality. A tip is dressed, to a flat and square condition using a suitable flat/smooth file. The filing action must be light, in order to remove only a minimal amount of metal and to restore a smooth flat condition. Orifices are cleared of filings and restored to the correct size using a cleaning wire. Always begin by selecting a wire that is smaller than the final size required. Keep the wire straight as you gently move it in and out of the orifice. Gradually increase the wire size until you reach that with the desired size. You can establish the correct size by using a new tip of the same number and locating a wire that just fits neatly into the orifice.


Be careful to keep the wire straight as it is pushed in and out, as bending it will cause the orifice to become "bell-mouthed" (enlarged at the opening). This condition will result in you never being able to set a correct flame and can also contribute to backfiring. Always remember that a poor flame shape will result in poor heat distribution into the work and that the nozzle tip determines the flame shape.


PART 3 - TORCH PREPARATION ASSEMBLING A torch may, for various reasons, need to be dismantled and assembled. Generally it is necessary to fit the mixing unit and a tip. If the torch is new, it may be necessary to attach gas inlet connectors as well. GENERAL INFORMATION (ALL TYPES) When assembling any torch the following steps need be observed:

o Work with clean hands as oil, grease or other substances may result in problems when gas flows.

o Use only correct fitting spanners, where there is need. Components on modern torches are sometimes secured with "hand connectors".

o Take careful note of any location devices, such as notches or teeth, between the mixer and the stock. Always align the mixer according to the locating notches (where applicable) and ensure a positive connection before tightening the retainer.

o Do NOT apply excess force when tightening connections as this almost always results in damage to sealing surfaces, and of course threads become "stripped".

o With injector torches, be careful when inserting the unit into the stock as it is

possible to damage the "O-ring" during this operation. TEST FOR LEAKS This is something that you will rarely see being done but, according to most "safety codes", it is essential. A leaking torch can present a major hazard in a workplace. TORCH VALVES Valves are a potential source of leaks, and depending on the design may leak at the seat or at the gland packing (or both). Leaks may be detected using "leak detection fluid" when the torch is under operating-pressure. Return the torch to your supplier for repairs if leaks exist here. MIXER JOINT AREA Another common source of gas leakage is the joint between the torch body and the mixing unit, most usually the result of "over tightening", or in the case of "injector types, a worn or damaged "O-ring". A leak in this area can result in various problems, as air will usually be drawn into the mixer via the leaking joint resulting in a greater potential for "backfiring". BALANCED PRESSURE TORCH -MIXER AND NOZZLE JOINT CHECKS To check for leaks in this area on an "equal-pressure (balanced pressure) torch", proceed as follows: 1. Set the specified working pressure at regulator. 2. Open both valves approximately ½ turn. 3. With a gloved hand (finger), block the nozzle.


4. Apply leak detection fluid to the mixer area and observe. (Bubbles indicate a leak) 5. Close torch valves after determining the existence (or not) of leaks. 6. Check the security of the mixer retainer nut and the nozzle. Do NOT over tighten. If leak persists then have the torch checked or repaired by your authorised dealer. INJECTOR OR LOW PRESSURE TORCH - MIXER JOINT CHECKS NOTE: With low-pressure torches (injector) and premix types it is possible that the mixing unit's "o-ring" is damaged (or missing!). The following test will determine the efficiency of the mixer seal of an injector torch:

o Connect the oxygen supply to the torch and set working pressure as specified. o Disconnect the acetylene (fuel gas) from the torch inlet connection. o Open the oxygen valve on the torch. o Open the acetylene valve (torch-valve). o Place your finger onto the fuel gas torch connection (lightly blocking the inlet port). If

the "o-ring seal" is in good order you will feel a slight "suction". If no suction is felt this is an indication of a damaged "o-ring". Remove the mixing tube and check the condition of this important device. Renew the "o-ring", if applicable, using a correct type (supplied by your equipment dealer).

o Close the torch valves when you have completed this test. FULL SYSTEM LEAK TESTING It is actually impractical to leak-test individual components when the whole system is "pressurised". Any external leak between the regulator and the torch should be investigated during a leak test. At this time, if you have been studying this series in sequence, you will be aware that the regulator, the hoses, the connections and now the torch must all be "leak tested" before putting the system into service. Having now effectively put together all the necessary components of an "oxyacetylene welding set" let us describe how we test for "gas tightness" of the complete system. PROCEDURES 1. PURGE 1) Close both torch valves. 2) Open individual gas cylinders and set working pressures in the manner explained in the regulator module. 3) Open in turn, each torch valve, and allow gas to flow for approximately 5 seconds (1 second per metre length of hose). Shut valve and repeat procedure on the other valve. Safety Note: Observe all safety rules, especially those involving "ventilation" and be aware that there will be flammable gas surrounding you for a few minutes! You have now "purged" the hoses, meaning that all "air" has been driven out.


2. ENTRAP GAS IN SYSTEM AND IDENTIFY A LEAK 1) With torch valves both closed and the regulators both set at "normal workin g pressure", CLOSE both the cylinder valves. 2) Observe the cylinder-pressure-gauge. If a leak exists in the system this gauge will indicate a drop in pressure (needle will move "down scale"). 3) Check, using "leak detection fluid " or water, the location of any leaks at all points between the regulator connection and the torch inlet connections. (Assuming that you have noticed the pressure gauge dropping). Mark each point for attention, or as applicable, check and rectify the problem directly. LIGHTING UP AND SHUTTING DOWN The following procedures are offered as a guide only. Please note that actual pressure settings, nozzle size selection and flame adjustments may vary according to your equipment and processes. Please make sure that you read and follow any instructions offered by torch manufacturers. BALANCED PRESSURE TORCH 1. LIGHTING UP 1) Make sure that hoses and torch have been purged in the manner previously described. 2) Set (check) the working pressures of both oxygen and acetylene to around 60 kPa. 3) Ensure that you have a proper spark lighter at hand. 4) Hold the torch in a manner that the nozzle/tip is away from your body and the tip facing upward. 5) Open the acetylene torch-valve by about one quarter to one half turn. 6) Ignite the gas. 7) Adjust the gas using the torch valve until the flame burns without black smoke and slightly away from the tip of the nozzle. Note that the flame will burn far away from the tip if the torch valve is opened too much, or if regulator pressure is too high. 8) Slowly open the oxygen torch-valve and manipulate this until the desired flame is achieved (usually a neutral flame). 2. SHUTTING DOWN (NORMAL PROCEDURE) 1) Lift torch away from the work and allow it to cool for a couple of seconds. 2) Close the acetylene torch-valve. The flame will extinguish. 3) Close the oxygen torch-valve. 4) If you have finished work (or want to break for lunch) then close the cylinder valves. 5) Bleed the gases from each hose in turn by opening the relevant torch valve until gauges read zero. 6) Close both regulators - turn the pressure adjusting screws fully out (counter clockwise. 7) Store away the torch and hoses in appropriate manner.


INJECTOR TORCH 1. LIGHTING UP 1) Make sure that hoses and torch have been purged in the manner previously described. 2) Adjust regulator working-pressures to the figures relevant to nozzle size (manufacturers" data or refer to table 2 in this guide). 3) Ensure that you have a proper spark lighter at hand. 4) Hold the torch away from your body with the nozzle tip pointed upward. 5) Open the oxygen torch-valve by about 1 full turn. 6) Open the acetylene torch-valve by around ¼. turn (Note the difference in the "order" from the BP torch!) 7) Ignite the "mixed gases" using the spark lighter. 8) Adjust the flame with the acetylene torch-valve until the desired flame is achieved. 2. SHUTTING DOWN The shutting down procedure is identical to that described with the BP torch. WATCH THE GAS PRESSURE Gas delivery pressure (working pressure) is a very important factor. If upon opening the torch valves you notice a drop in working pressure (and this is quite usual, especially if you have long hoses) then reset the pressure whilst the torch valve is open. You may need to do this with both gases. CARE OF TORCHES Apply the following "rules" and your torch will last you a lifetime!

o Do not use a torch as a hammer or a lever. o If a nozzle / tip is in poor condition, fix it or replace it. Do this before you light up

and, if required during the welding or cutting procedure. Remember that a bad nozzle tip is a major cause of backfire and can lead to worse situations!

o Do not use pliers or other "gripping tools" in order to secure mixing units to torch handles. Most mixing units are secured with a hand-operated retainer-nut and, as the name suggests, this should be tightened by hand. If a spanner is required the retainer-nut will feature a hexagon or there will be "flats" machined into it (for accommodating a spanner). Over-tightening can result in damage to sealing-elements and the retainer which in turn will result in leakage.

o Store your torch in such a way that it will not be damaged. A torch rack, that offers a hang-up facility, is a very effective storage method.

o Any torch that does not operate correctly, after all checks have been made, should be returned to your equipment supplier for professional attention.


CONCLUSION By following the recommendations offered in this section and by READING the torch manufacturers information regarding their product(s) you will greatly reduce the risk of a "torch related" incident. INSTRUCTION 1. View video (ODE-3). 2. Complete Self-Test Exercise No. 3.



SELF TEST NO. 3 GAS WELDING TORCHES

INSTRUCTIONS Answer the questions below without reference to your notes or the video. (Note that some questions may have more than one correct response.) Answer the following in your own words.

QUESTION YES NO

1. a) b) c)

With a balanced pressure torch, the gas working pressures of both oxygen and acetylene must be adjusted, how? (Tick correct response.) Equally to 60 kPa. Acetylene to 7 kPa and Oxygen to 60 kPa. Both must be the same.

2. a) b) c)

An injector torch is also known as a low-pressure torch, why is this? (Tick correct response.) Because it operates at low oxygen and fuel gas pressure. Because it operates with low fuel gas pressure. Because it operates at low oxygen pressure.

3. a) b) c)

The number stamped upon a "balanced pressure tip" indicates what? (Tick correct response.) The diameter of the orifice. The manufacturers' code. The gas flow -rate.

4. a) b) c)

It is extremely important that both gas hoses are purged before lighting a torch, why is this? (Tick correct response.) To prevent possible explosion of mixed gases. To stop the torch from backfiring. To make the gas light easier.

5. a) b) c)

Under normal operating conditions a torch must be closed down how? (Tick correct response.) Close acetylene torch valve and then close the oxygen torch valve. Close oxygen torch valve and then the acetylene torch valve. Close both the cylinder valves and then close the torch valves.


Answer the following in your own words. 1. Describe how you would purge the gas hoses and set regulator working- pressures prior to lighting your torch. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 2. Describe the procedure for a "full shut down" of your torch and oxyacetylene set. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________



NOTES


MODULE NO.4 - CUTTING TORCHES Please ensure that you are in possession of video No. 4 (ODE-4). INTRODUCTION The most notable feature of a cutting torch is a "cutting lever" that, when depressed, results in a stream of pure oxygen being discharged via the nozzle or "cutting tip". Cutting or "burning" occurs when oxygen is introduced into "pre-heated" steel. Preheating is achieved with a normal "oxyacetylene flame" using "mixed gases". The mixed gases are discharged via several "pre-heat orifices" contained within the "cutting tip". Cutting torches are usually classified by the method in which pre-heat gases are mixed. PART 1 - TYPES OF CUTTING TORCHES There are essentially 2 main classifications of cutting-torch namely,

o Nozzle mix type, and o Pre-mix type.

By far the most widely encountered type is the "nozzle mix" variety and it is this type that we shall be primarily concerned with for the remainder of this module. Within these classifications there are: 1) Straight Torches - designed purely as cutting torches. 2) Combination torches - designed to be adapted to a welding torch handle (stock). NOZZLE MIX TORCH As the name suggests, gas mixing occurs within the nozzle, not (as with pre-mix types) within the handle (stock) section. It is this feature that offers added safety because, under normal conditions, there are no "mixed gases" within the torch handle (galleries). This safety feature assumes that everything else in the system is in proper order, especially the regulator settings and the condition of the nozzle. When a nozzle is attached, and properly secured within the cutting-head by a "retaining nut, the nozzle seating shoulders create a "gas tight fit" between the separate gas fed galleries within the head. However if there is dirt, carbon or scratches on any of these surfaces then gas can "bypass" the seat and either leak into the atmosphere or enter into an adjacent gallery. The result of this situation can be a sooty flame (acetylene) seen burning around the tip, a backfire or even a flashback.


PRE-MIX CUTTING TORCHES The term "premix" means that gases for preheating are mixed before they reach the nozzle tip. There are essentially two designs in the premix classification namely: 1. Body Mix types (by far the most common in this classification) and, 2. Head Mix types (Injector in head). BODY MIX TORCH TYPE This type can be identified by its "physical appearance, in that you will notice only two gas feed tubes emanating from the handle and connecting to the cutting head. Mixing of the fuel gas and oxygen, which is normally of the "injector design", occurs within the handle (stock) section. The mixed gases are then directed through a single gallery (tube) to the cutting head. The other gallery, upon depressing the cutting-lever, directs pure oxygen to the head. HEAD MIX TYPE This type has an "injector-mixing unit" built into its "cutting head". The primary reason for this arrangement or design is intended to minimise the volume of potentially dangerous "mixed gases" contained within a torch. Although similar in appearance to the "Nozzle mix torch" (as you will observe 3 gas tubes), a "head mixer" tip and a "nozzle mix" tip cannot be interchanged. Head mix type torches are uncommon and are mentioned here because it is possible that you may come across them. SELECTION CRITERIA The selection of a torch is often a matter of "preference" by the user (Operator) but all torches and related accessories, such as nozzle-tips, must meet with standard EN ISO 5172 in order to comply with safety requirements. IDENTIFYING CUTTING TIPS

o Cutting-tips are manufactured in many shapes and sizes by various manufacturers. o Not all types are "interchangeable" between the different types of torches. o As a general rule one should purchase only "genuine tips" made specifically for the

torch types that you are using. o The tips used with a "nozzle-mix" torch are very different from those used with

"premix torches". o Nozzle-tips may have "tapered seats" or they may have "flat seats".

NOZZLE MIX TIPS Tapered Seat types: are identified by the fact that you will notice three tapered "shoulders". Labelling stamped upon the nozzle body also offers information about that particular tip. One popular type of nozzle can be identified by the following alpha / numerical references:


Example 1: ANM - 6 Explanation: A = For use with "acetylene" (fuel gas). NM = Indicates that it is a "nozzle mix". 6 = That there are 6 pre-heat orifices. Example 2: ANME - 4 Explanation: ANM = As above.

E = Extended body (for use with cutting jigs or attachments).

4 = Four pre-heat orifices. NOTE: Tips designed for use with propane will be marked with the letter "P", not with an "A". Also stamped upon the nozzle body will be the nozzle size. The size of a cutting tip is determined by the diameter of the "cutting orifice" (centre orifice). Sizes are stated either in millimetres or "inch" system. Typical sizes are listed in the table below:

Size mm 0.8 1.2 1.6 2.0 2.4 2.8 3.2 4.0 Size inch 1/32 3/64 1/16 5/64 3/32 7/64 1/8 5/32

FLAT-SEAT CUTTING TIPS Certain torch manufacturers produce nozzle mix torches that feature "flat seats". Some flat seated nozzles may feature special sealing washers or seats. Use ONLY those tips designed by. or recommended by. the torch manufacturer.


PART 2 - TORCH PREPARATION AND USE GENERAL RULES: WHENEVER PERFORMING MAINTENANCE UPON TORCHES.

o Work with clean hands as oil, grease or other substances may result in problems when gas flows.

o Use only a correct fitting spanner where applicable. A short spanner should be used to avoid the risk of over-tightening.

NOTE 1: The use of adjustable spanners, pliers, vise-grips, "stilson-wrenches" and similar tools will inevitably result in damage. NOTE 2: Do NOT apply excessive force when tightening nozzle retainers as this will distort seats and damage threads. ASSEMBLING A STRAIGHT TORCH As a rule the only "assembling" required with a straight cutting-torch is the occasional replacement of the tip. All other components of the torch, namely the stock, cutting lever, valves etc. are not, under normal circumstances, removed. ASSEMBLING A COMBINATION TORCH This task involves attaching a "cutting head" to a standard welding torch. The welding mixer unit (Tube) must be removed and the cutting head fitted in its place. REPLACING NOZZLE-MIX TIPS (TAPERED SEAT)

o Slacken the retainer using the correct size spanner. Remove the nut together with the tip.

o Place the tip in a rack to prevent it being damaged whilst in storage. Plastic caps prevent shoulder damage.

o Inspect the seating surfaces within the cutting head. Wipe out loose carbon using a dry cloth or paper towel. If seats are damaged then do NOT use the torch. Your supplier or dealer may be able to have the seats reconditioned.

o Select the appropriately sized replacement tip. o Check that the seating shoulders are undamaged and free of deposits. o Check the condition of the retainer-nut. Damaged threads or a nut that has become

"oval" indicate that a new retainer should be fitted. o Insert the tip into the cutting head and apply a slight twisting motion, in order to

positively engage the seats. o Engage the retainer into the threads being careful not to cause a "cross thread". o Screw the retainer all the way into the head by hand and then check to ensure that

the nozzle has seated. If the tip is loose or floppy then it hasn't seated. o Using a correctly fitting spanner, secure the retainer. Note that the retainer should

never be forced. "Wrist pressure" is all that should be necessary in order to create a leak free connection.


REPLACING TIPS (WITH FLAT SEATS) The following procedure applies to most flat seat types:

o Ensure that the seats inside the cutting-head are clean and damage free. o Select appropriate tip for metal to be cut (or heated). o Inspect nozzle to ensure that washers are present and in good condition. o Insert nozzle carefully into the cutting head. No twisting required or recommended. o Insert and screw in the retainer nut, by hand. Secure the nut firmly by hand if the tip

is a "used tip". o If the tip is "brand new", nip it firmly using a correctly fitting spanner.

NOTE: Excessive tightening will result in seat damage and a severe gas leakage. NOZZLE MAINTENANCE One of the most important tasks that must be done, on a regular basis, is nozzle tip maintenance. As can be imagined the tip of a nozzle is exposed to severe conditions from heat and from "spatter" and will not remain in "pristine condition" indefinitely. The main conditions that can seriously affect the SAFE operation of your torches include the following.

o Orifice(s) becomes blocked with spatter and / or carbon (soot) and must be unblocked using a suitably sized nozzle wire-file. A blocked nozzle is a major cause of backfiring.

o The "nose" of a nozzle becomes burned or slightly melted. In this condition the heating flame is poorly dispersed (poor shape to the flame). Nozzle tip edges must be filed perfectly flat (square) using a flat smooth file.

o An orifice may also develop a "bell mouth" as a result of incorrect use of the nozzle-cleaner (wire). A "bell mouth" is an enlargement of the nozzle orifice at the point where the gas exits. This condition causes results in "flow problem" which in turn is a cause of backfires.

o The seats can become coated with soot as a result of backfires. Dirty or damaged seating surfaces will allow the "bypass" of gases from one gallery to another within the cutting head . This condition will seriously increase the risk of backfiring and even a "flashback".

TIP DRESSING / CLEANING Inspect the mixing head seats (easily visible when nozzle-tip is removed) and if necessary wipe clean using a dry and clean cloth or paper towel. Do not scrape the shoulders or the seats as this will result in leaks. If the seats are damaged then the torch must be repaired via your gas equipment supplier. NOTE: Where excessive carbon deposits are encountered it may be necessary to soak the head and nozzles in a solution of "carbon remover". Consult your equipment dealer for carbon removal products, and always follow the manufacturers' instructions.

o Wipe away any "soot" from the sealing surfaces. If these are damaged (scratched or pitted) then replace the tip (do not use a damaged tip for risk of flashback).

o Dress the tip as required by filing the "nose" to a perfectly flat condition.


o Select a wire-cleaner to suit the pre-heat orifices. It is important that you do not force an "oversized" wire into an orifice as this will enlarge the diameter resulting in poor flame performance.

o Be careful that you do not bend the wire as you clean the orifice because this will cause a "bell mouth" at the opening.

o Clean the cutting-orifice (oxygen) using an appropriately sized wire. o Replace the tip into the cutting head in the manner previously described. o Light up the torch (after observing all procedures) and check that the pre-heat

flames emit from each orifice. o Ensure that all flames are of the same basic shape and length. Any variation means

that some orifices are probably "enlarged" or "bell mouthed". IMPORTANT NOTE: DO NOT attempt to rectify a nozzle tip leak by forcing the nozzle securing-nut tighter! If the nozzle tip is leaking (sometimes identified by a sooty flame burning from the nut area) then remove the tip and check the seat area for dirt or damage. Refit and twist the tip upon its seats (shoulders) before securing the retainer nut. TESTING TORCH FOR LEAKS A leaking torch can present a major hazard in a workplace. All torches should be periodically tested for leaks as a matter of "routine". The leak-testing procedure is essentially the same for both nozzle-mix and for pre-mix types. Note that leak detection fluid should be used in preference to "soapy water" for the following checks:

o Connect the torch to the gas supply in the manner described under "Lighting up" (described later).

o Purge the hoses. o With both torch-valve closed, apply leak-detection fluid to the inlet connection and

to the torch-valves. Bubbles indicate that a leak exists. If all is well, proceed to next step.

o Apply leak detection fluid to the nozzle-retainer nut. Block the nozzle orifices using a gloved hand or use a "pencil eraser".

o Open the acetylene valve. o Observe for bubbles around the retainer. The presence of bubbles indicates leakage

past the acetylene seat in a nozzle-mix head or the failure of the low-pressure seat in a pre-mix head . In either case the nozzle / tip will require removal and attention.

SAFE APPLICATION OF TORCHES The primary safety considerations when using any cutting-torch are as follows:

o Working (gas) pressure settings at regulators must be correct. o Nozzle / Tip size and type must be relevant to operation. o Nozzles must be in good condition, and where necessary they should be cleaned and

"dressed". o Torch (all aspects) must be in good order, notably it must be free of leaks at any of

the connections or joints. o Torch should be used in a safe manner according to the task (as explained in the

practical application modules).


REGULATOR PRESSURE SETTING The following information (Table 1) may be used as a GUIDE for the HAND cutting of mild steel plate using a nozzle-mix, straight cutting-torch.

Metal Thickness mm

Nozzle size (Type A-NM6)

Oxygen working pressure (kPa)

Acetylene working pressure (kPa)

6.0 0.8 170 60 12.5 1.2 200 60 25 1.6 270 60 50 1.6 340 60 75 1.6 400 60

100 2.0 300 60

Tabel 1 - Setting Guide Please note that the data offered is "nominal" and assumes: Hose size 8 mm and hose length 5 metres. Correction of working pressures may be required for conditions such as, length of hoses, additional safety devices in the line and condition of tip. LIGHT-UP AND SHUT DOWN TORCHES It is very important, from the safety perspective, that you are familiar with the procedures for the torch type that you intend using. Wherever possible always follow the procedures offered by the written information in the torch manufacturers brochure. In the case of ANY torch type there is one very important rule that must be observed namely: Always purge the hoses before lighting up. This must be done to expel air or mixed gases that may be present in hoses and the torch galleries. STANDARD PROCEDURES 1. STRAIGHT TORCH (NOZZLE MIX CUTTERS) - LIGHTING

o Set the oxygen working pressure to that specified for the nozzle size. o Depress the cutting Oxygen lever and re-adjust the regulator as necessary

whilst gas is flowing. Allow sufficient gas to flow to completely purge the system before releasing the cutting Oxygen lever (one second per metre length hose).

o Open the acetylene regulator and set nominal working-pressure. o Open the acetylene torch valve to purge hose and reset acetylene pressure

whilst gas is flowing.


o Once sufficient gas has been allowed to flow to purge the system close the torch-valve. Allow a short time for gases to dissipate into the atmosphere before lighting the torch.

o Open the acetylene torch-valve by approximately ¼ to ⅓ turn and ignite at the tip using your spark lighter. NOTE: When lighting acetylene, the tip should face upward. When lighting propane the tip should face downward.

o Adjust the fuel gas (acetylene) valve on shank until the black sooty smoke just disappears.

o Slowly open the oxygen valve on shank and adjust oxygen to obtain the desired flame (usually neutral).

o Observe that a flame can be seen burning from all 4 or 6 preheating orifices. No flame indicates a blocked orifice and the torch must not be used until this has been rectified.

o Observe that all preheating flames are of equal length. If some of the flames are seen to be notably shorter than others then the following may assist: Close the torch down. Loosen the tip retainer nut and rotate the tip by a few degrees. Re-tighten the nut and follow the lighting up procedure.

o Depress the cutting lever and observe if the preheat flames remain unchanged. It is sometimes necessary to adjust the acetylene flow, with the cutting lever depressed, in order to obtain "neutral" flames of equal length.

2. COMBINATION TORCHES-LIGHTING UP We pick up the process after the cylinder-valves have been opened:

o Close the "fine-adjustment" valve, that is, the "oxygen-valve" on the cutting-attachment.

o Fully open the oxygen valve on the shank (body). This will remain in the fully open position from now on.

o Set the working pressures of both the oxygen and the acetylene using the torch valves (on shank) in closed position.

o Holding the torch away from you and others around you, depress the cutting-oxygen lever and at the same time reset the working oxygen pressure as necessary.

o Release the cutting oxygen lever. o Open the acetylene torch (stock) valve and purge the hose whilst checking

and adjusting the working pressure as necessary. Remember to allow at least 5 seconds for purging. Also remember that acetylene will be entering the atmosphere!

o Close the acetylene valve, and allow a short time for gases to dissipate into the atmosphere before lighting the torch.

o Open the acetylene valve by about ¼ - ⅓ turn. o Hold torch away from your body and the cylinders. Keep the nozzle/tip facing

upward (for acetylene). o Ignite the acetylene, and adjust the flame to just stop delivering black smoke.


o Slowly open the "fine adjustment oxygen-valve" on the torch head. Adjust the pre-heat flames, by manipulating the torch head oxygen-valve, to produce neutral pre-heat flames.

o *Ensure that all pre-heat orifices are producing flame of equal length. o Press the cutting oxygen-lever and observe that the pre-heat flames remain

unaffected. *NOTE: Unequal flame lengths, especially if they are "yellow looking" indicate an excess of acetylene. It must be made clear that not all torches behave "to the book". It is often necessary to make several "manipulations" of the torch-valves and also of the regulator working pressures in order to obtain the "correct flame". Flames should burn slightly ahead of the tip. Always keep in mind that too much pressure is a safer condition than too little pressure! Flashbacks are most likely to occur when the nozzle pressure is too low. In an "ideal" situation the pre-heat flames will appear to burn just slightly away from the nozzle when the cutting lever is depressed. Obtaining this condition is, as mentioned earlier, a matter of carefully manipulating torch valves and/or regulator pressures. Another point we must mention is that no matter what you attempt to do with torch-valves and regulator settings you will NEVER achieve a satisfactory flame if the nozzle / tip is restricted. Only a clean and properly "dressed" tip will yield a correct "cutting flame". SHUT DOWN PROCEDURE -FOR BOTH TYPES OF CUTTING TORCH

o Release the cutting Oxygen lever. o Close the acetylene control valve and the flame will extinguish. o Close the Oxygen control valve on the stock. o Close both cylinder valves. o Open one and then the other of the torch valves for long enough to bleed gas from

the system. o Check that all gauges now read zero and then turn the regulator pressure-adjuster

screws fully out. o Pack away your hoses and equipment.

EMERGENCY SHUT DOWN If ever you should experience a situation in which your torch issues loud and rapid "machine-gun" like backfiring, accompanied with a screeching noise and black smoke issuing from the nozzle then you have an "emergency situation" on your hands! Literally your torch is burning on the "inside" and the following action must be taken immediately:

o Close the OXYGEN VALVE (Torch). o Close the acetylene valve. o Plunge the torch into cold water (NOT the sand bucket!).


o Shut off the cylinder valves. o Remove torch from service as it will require professional attention. o Report the incident to your supervisor.

CARE OF TORCHES Basic Rules Apply the following "rules" and your torch will last you a lifetime!

o Do not use a torch as a hammer or a lever. o If a nozzle/tip is in poor condition, fix it or replace it. Do this before you light up and,

if required , during the welding or cutting procedure. Remember that a bad nozzle tip is a major cause of backfire and can lead to worse situations!

o Do not use pliers or other "gripping tools" in order to secure mixing units to torch handles. Most mixing units are secured with a hand-operated retainer-nut and, as the name suggests, this should be tightened by hand. If a spanner is required the retainer-nut will feature a hexagon or there will be "flats" machined into it (for accommodating a spanner). Over-tightening can result in damage to sealing-elements and the retainer, which in turn will result in leakage.

o Store your torch in such a way that it will not be damaged. A torch rack, that offers a hang-up facility, is a very effective storage method.

o Any torch that does not operate correctly, after all checks have been made, should be returned to your equipment supplier for professional attention.

CONCLUSION By following the recommendations offered in this section and by READING the torch manufacturers information regarding their product(s) you will greatly reduce the risk of a "torch related" incident. INSTRUCTIONS 1. View the video (ODE-4). 2. Complete the Self-Test exercise beginning on the following page.



SELF TEST NO. 4 GAS CUTTING TORCHES

INSTRUCTIONS Answer the questions below without reference to your notes or the video. (Note that some questions may have more than one correct response)

QUESTION YES NO

1. a) b) c)

The mixing of the pre-heat gases in a "nozzle mix" torch takes place, where? (Tick correct response.) Within the body of the nozzle. Within the cutting head. Within the gas delivery tubes.

2. a) b) c)

A premix torch is identified by what feature(s)? (Tick correct response.) Six preheat orifices in the tip. Two gas delivery tubes between stock and cutting head. Three deliver tubes between stock and cutting head.

3. a) b) c)

The letters "ANM" stamped upon a nozzle body, indicate what? (Tick correct response.) American Nozzle Manufacturers. Acetylene -Nozzle Mix. Acetone -Nozzle Mixture.

4. a) b) c)

The "size" of a cutting tip is in reference to what? (Tick correct response.) The diameter of the cutting orifice. The length of the nozzle body. The diameter of the nozzle body.

5. a) b) c)

The control valve on a "cutting attachment" performs what function? (Tick correct response.) Controls oxygen flow to the cutting orifice. Controls pre-heat oxygen flow. Controls acetylene flow to the nozzle.

6. a) b) c)

The oxygen torch valve should remain fully opened during operation of which type of torch? (Tick correct response.) Combination torch. Premix torch. Straight torch.


7. a) b) c)

Before lighting ANY torch, and especially a pre-mix type it is vital that you first do what? (Tick correct response.) Purge both of the gas hoses. Open the torch valves fully. Close the cylinder valves.


Answer the following in your own words. 1. Describe how you would select and install a tapered seat nozzle for your nozzle- mix torch. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________

___________________________________________________________________ 2. Describe the lighting up procedure for a "straight nozzle-mix torch". ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 3. Describe the lighting up procedure for a "combination nozzle-mix torch". ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 4 Describe a "full shut down procedure" regardless of torch type. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________



APPENDIX 1 - MSDS DATA SHEETS (COURTESY - AIR PRODUCTS) Version: 1.17 Date : 23/06/1999 1. IDENTIFICATION OF THE SUBSTANCE / PREPARATION AND OF THE COMPANY. MSDS NR. 001. PRODUCT NAME Acetylene (dissolved). CHEMICAL FORMULA C2H2. COMPANY IDENTIFICATION see heading and / or footer. Emergency phone numbers see heading and / or footer. 2. COMPOSITION / INFORMATION ON INGREDIENTS SUBSTANCE / PREPARATION Substance. COMPONENTS / IMPURITIES Contains no other components or impurities which will influence the classification of the product. CAS NR. 00074-86-2. EEC Nr (from EINECS) 200-816-9. 3. HAZARDS IDENTIFICATION HAZARDS IDENTIFICATION

o Dissolved gas. o Extremely flammable.

4. FIRST AID MEASURES INHALATION

o In high concentrations may cause asphyxiation. Symptoms may include loss of mobility / consciousness. Victim may not be aware of asphyxiation.

o In low concentrations may cause narcotic effects. Symptoms may include dizziness, headache, nausea and loss of co-ordination.

Acetylene (dissolved) 001


o Remove victim to uncontaminated area wearing self contained breathing apparatus. Keep victim warm and rested. Call a doctor. Apply artificial respiration if breathing stopped.

INGESTION Ingestion is not considered a potential route of exposure. 5. FIRE FIGHTING MEASURES SPECIFIC HAZARDS Exposure to fire may cause containers to rupture/explode. HAZARDOUS COMBUSTION PRODUCTS Incomplete combustion may form carbon monoxide. SUITABLE EXTINGUISHING MEDIA All known extinguishants can be used. SPECIFIC METHODS

o If possible, stop flow of product. o Continue water spray from protected position until container stays cool. o Move container away or cool with water from a protected position. o Do not extinguish a leaking gas flame unless absolutely necessary. o Spontaneous / explosive re-ignition may occur. Extinguish any other fire.

SPECIAL PROTECTIVE EQUIPMENT FOR FIRE FIGHTERS In confined space use self-contained breathing apparatus. 6. ACCIDENTAL RELEASE MEASURES PERSONAL PRECAUTIONS

o Wear self-contained breathing apparatus when entering area unless atmosphere is proved to be safe.

o Evacuate area. o Ensure adequate air ventilation. o Eliminate ignition sources.

ENVIRONMENTAL PRECAUTIONS Try to stop release. CLEAN UP METHODS Ventilate area. 7. HANDLING AND STORAGE HANDLING AND STORAGE

o Ensure equipment is adequately earthed. o Avoid contact with pure copper, mercury, silver and brass with greater than

70% copper. o Suck back of water into the container must be prevented. o Purge air from system before introducing gas. o Do not allow back feed into the container. o Use only properly specified equipment which is suitable for this product, its

supply pressure and temperature. Contact your gas supplier if in doubt. o Keep away from ignition sources (including static discharges).


o Segregate from oxidant gases and other oxidants in store. o Refer to supplier's container handling instructions. o Keep container below 50°C in a well ventilated place.

8 EXPOSURE CONTROLS/PERSONAL PROTECTION PERSONAL PROTECTION

o Ensure adequate ventilation. o Wear suitable hand, body and head protection. Wear goggles with suitable

filter lenses when use is cutting / welding. o Do not smoke while handling product.

9. PHYSICAL AND CHEMICAL PROPERTIES MOLECULAR WEIGHT 26. MELTING POINT -80.8 ⁰C. BOILING POINT -84(s) ⁰C. CRITICAL TEMPERATURE 35 ⁰C. RELATIVE DENSITY, GAS 0.9 (air = 1.) RELATIVE DENSITY, LIQUID Not applicable. VAPOUR PRESSURE 20⁰C 44 bar. SOLUBILITY MG / L WATER 1185 mg/l. APPEARANCE / COLOUR Colourless gas. ODOUR

o Garlic like. o Poor warning properties at low concentrations.

AUTO IGNITION TEMPERATURE 325 ⁰C. FLAMMABILITY RANGE 2.4-83 vol. % in air. 10. STABILITY AND REACTIVITY STABILITY AND REACTIVITY

o Can form explosive mixture with air. o May decompose violently at high temperature and/or pressure or in the

presence of a catalyst o Forms explosive acetylides with copper, silver and mercury. o Do not use alloys containing more than 70% copper.


o Dissolved in a solvent supported in a porous mass. o May react violently with oxidants.

11. TOXICOLOGICAL INFORMATION GENERAL No known toxicological effects from this product. 12. ECOLOGICAL INFORMATION GENERAL No known ecological damage caused by this product. 13. DISPOSAL CONSIDERATIONS GENERAL

o Do not discharge into areas where there is a risk of forming an explosive mixture with air.

o Waste gas should be flared through a suitable burner with flash back arrestor.

o Do not discharge into any place where its accumulation could be dangerous. o Contact supplier if guidance is required.

14 TRANSPORT INFORMATION PROPER SHIPPING NAME Acetylene, dissolved. UN NR. 1001. CLASS / DIV 2.1. ADR / RID Item Nr 2,4°F. ADR / RID HAZARD NR. 230. LABELLING ADR Label 3: flammable gas. OTHER TRANSPORT INFORMATION

o Avoid transport on vehicles where the load space is not separated from the driver's compartment.

o Ensure vehicle driver is aware of the potential hazards of the load and knows what to do in the event of an accident or an emergency.

o Before transporting product containers ensure that they are firmly secured and:

Cylinder valve is closed and not leaking. Valve outlet cap nut or plug (where provided) is correctly

fitted. Valve protection device (where provided) is correctly fitted.


There is adequate ventilation. Compliance with applicable regulations.

15. REGULATORY INFORMATION Number in Annex I of Dir 671548 601-015-00-0. EC Classification R5IR6IF+;R12. SYMBOLS F+: Extremely flammable. RISK PHRASES

o R5 Heating may cause an explosion. o R6 Explosive with or without contact with air. o R12 Extremely flammable.

SAFETY PHRASES o S9 Keep container in well ventilated place. o S16 Keep away from ignition sources - No smoking. o S33 Take precautionary measures against static discharges.

16. OTHER INFORMATION

o Ensure all national/local regulations are observed. o Ensure operators understand the flammability hazard. o The hazard of asphyxiation is often overlooked and must be stressed during

operator training. o Before using this product in any new process or experiment, a thorough

material compatibility and safety study should be carried out. o Details given in this document are believed to be correct at the time of going

to press. o Whilst proper care has been taken in the preparation of this document, no

liability for injury or damage resulting from its use can be accepted.


Version: 2.01 Date: 29/06/1999 1. IDENTIFICATION OF THE SUBSTANCE/PREPARATION AND OF THE COMPANY MSDS NR. 097A. PRODUCT NAME Oxygen. CHEMICAL FORMULA 02. COMPANY IDENTIFICATION See heading and / or footer. EMERGENCY PHONE NUMBERS See heading and / or footer. 2. COMPOSITIONIINFORMATION ON INGREDIENTS SUBSTANCE / PREPARATION Substance. COMPONENTS / IMPURITIES Contains no other components or impurities which will influence the classification of the product. CAS NR 07782-44-7 EEC NR (FROM EINECS) 231-956-9. 3. HAZARDS IDENTIFICATION HAZARDS IDENTIFICATION

o Compressed gas o Oxidant. Strongly supports combustion. May react violently with combustible

materials. 4. FIRST AID MEASURES INHALATION Continuous inhalation of concentrations higher than 75% may cause nausea, dizziness, respiratory difficulty and convulsion. 5. FIRE FIGHTING MEASURES SPECIFIC HAZARDS

o Supports combustion. o Exposure to fire may cause containers to rupture / explode.

Safety Data Sheet Oxygen

097A


o Non flammable HAZARDOUS COMBUSTION PRODUCTS None. SUITABLE EXTINGUISHING MEDIA All known extinguishants can be used. SPECIFIC METHODS

o If possible, stop flow of product. o Move container away or cool with water from a protected position.

SPECIAL PROTECTIVE EQUIPMENT FOR FIRE FIGHTERS None. 6. ACCIDENTAL RELEASE MEASURES PERSONAL PRECAUTIONS

o Evacuate area. o Ensure adequate air ventilation. o Eliminate ignition sources.

ENVIRONMENTAL PRECAUTIONS o Try to stop release. o Prevent from entering sewers, basements and work pits, or any place where

its accumulation can be dangerous. CLEAN UP METHODS Ventilate area. 7. HANDLING AND STORAGE HANDLING AND STORAGE

o Use no oil or grease. o Open valve slowly to avoid pressure shock. o Segregate from flammable gases and other flammable materials in store. o Suck back of water into the container must be prevented. o Do not allow back feed into the container. o Use only properly specified equipment which is suitable for this product, its

supply pressure and temperature. Contact your gas supplier if in doubt. o Keep away from ignition sources (including static discharges). o Refer to supplier's container handling instructions. o Keep container below 50°C in a well ventilated place.

8. EXPOSURE CONTROLS/PERSONAL PROTECTION PERSONAL PROTECTION

o Do not smoke while handling product. o Wear suitable hand, body and head protection. Wear goggles with suitable

filter lenses when use is cutting/welding. o Avoid oxygen rich (>21 %) atmospheres. o Ensure adequate ventilation.


9. PHYSICAL AND CHEMICAL PROPERTIES MOLECULAR WEIGHT 32. MELTING POINT -219 ⁰C. BOILING POINT -183 ⁰C. CRITICAL TEMPERATURE -118 ⁰C RELATIVE DENSITY, GAS 1.1 (air = 1). RELATIVE DENSITY, LIQUID 1.1 (water = 1). VAPOUR PRESSURE 20⁰C Not applicable. SOLUBILITY MG/L WATER 39 mg/l. APPEARANCE / COLOUR Colourless gas. ODOUR No odour warning properties. AUTO IGNITION TEMPERATURE Not applicable. FLAMMABILITY RANGE Oxidiser. OTHER DATA Gas / vapour heavier than air. May accumulate in confined spaces, particularly at or below ground level. 10. STABILITY AND REACTIVITY STABILITY AND REACTIVITY

o May react violently with combustible materials. o May react violently with reducing agents. o Violently oxidises organic material.

11. TOXICOLOGICAL INFORMATION GENERAL No toxicological effects from this product. 12. ECOLOGICAL INFORMATION GENERAL No ecological damage caused by this product.


13. DISPOSAL CONSIDERATIONS GENERAL

o To atmosphere in a well ventilated place. o Do not discharge into any place where its accumulation could be dangerous. o Contact supplier if guidance is required.

14. TRANSPORT INFORMATION PROPER SHIPPING NAME Oxygen, compressed. UN NR 1072. CLASS / DIV 2.2. SUBSIDIARY RISK 5.1. ADR / RID ITEM NR 2,1 ⁰O. ADR / RID HAZARD NR 25. LABELLING ADR

o Label 2: non flammable non toxic gas. o Label 05: fire intensifying risk.

OTHER TRANSPORT INFORMATION o Avoid transport on vehicles where the load space is not separated from the

driver's compartment. o Ensure vehicle driver is aware of the potential hazards of the load and knows

what to do in the event of an accident or an emergency. o Before transporting product containers ensure that they are firmly secured

and: Cylinder valve is closed and not leaking. Valve outlet cap nut or plug (where provided) is correctly fitted. Valve protection device (where provided) is correctly fitted. There is adequate ventilation. Compliance with applicable regulations.

15. REGULATORY INFORMATION NUMBER IN ANNEX I OF DIR 67/548 008-001-00-8. EC CLASSIFICATION O;R8. SYMBOLS O: Oxidising. RISK PHRASES R8 Contact with combustible material may cause fire. SAFETY PHRASES S17 Keep away from combustible material.


16. OTHER INFORMATION o Ensure all national / local regulations are observed. o Ensure operators understand the hazard of oxygen enrichment. o Before using this product in any new process or experiment, a thorough

material compatibility and safety study should be carried out. o Details given in this document are believed to be correct at the time of going

to press. o Whilst proper care has been taken in the preparation of this document, no

liability for injury or damage resulting from its use can be accepted.


APPENDIX 2 - USEFUL CONVERSIONS PRESSURE:

UNIT bar kPa psi 1 bar 1 100 14.503 1 kPa 0.01 1 0.145 1 psi 0.06895 6.895 1

VOLUME: (LIQUID AND GAS)

UNIT Litre Cubic Metre Cubic Feet 1 Ltr 1 0.001 0.0353

1 mtrᶟ 1000 1 35.31 1 ftᶟ 28.32 0.0283 1

FLOW RATES:

UNIT L/min L/hr Ftᶟ/min Ftᶟ/hr 1 L/min 1 60.001 0.035 2.119 1 L/hr 0.017 1 0.001 0.035

1 ftᶟ/min 28.317 1699.009 1 60.00 1 ftᶟ/hr 0.442 26.518 0.016 1

LINEAR MEASUREMENT Convert inches to millimetre - multiply (inch) by 25.4. Convert millimetre to inches - multiply (mm) by 0.03937.


APPENDIX 3 - INTERNATIONAL STANDARDS (relevant to oxyacetylene equipment)

ITEM ISO EN Regulators for cylinders (to 300 bar)

2503 EN ISO 2503

Hose connections 3253 560 Rubber Hose 3821 559 Safety Devices 5175 730 Quick action couplings (with shut off)

7289 561

Torches - Blowpipes (Hand Held)

5172 EN ISO 5172


NOTES

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