mem05007c perform manual heating and thermal cutting sample · mem05007c perform manual heating and...

MEM05 Metal and EngineeringTraining Package

Learner guideVersion 2

Training and Education SupportIndustry Skills Unit

Meadowbank

Product Code: 5752

MEM05007CPerform manual heating

and thermal cutting

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© TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2013

MEM05007C Perform manual heating and thermal cutting

AcknowledgmentsThe TAFE NSW Training and Education Support Industry Skills Unit, Meadowbank would like to acknowledge the support and assistance of the following organisations and people in the production of this learner guide.

CIGWELD BOC Gases AustraliaSilverwater Welding Supplies3M Australia

Writer:From existing TAFE resourcesTAFE NSW

Reviewers:John Anderson (Hunter Institute)

Project Manager:Stephen DaviesEducation Programs ManagerTAFE NSW

EnquiriesEnquiries about this and other publications can be made to:

Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE Level 3, Building J, See Street, MEADOWBANK NSW 2114

Tel: 02-9942 3200 Fax: 02-9942 3257

© TAFE NSW (Training and Education Support, Industry Skills Unit Meadowbank) 2013

Copyright of this material is reserved to TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. Reproduction or transmittal in whole or in part, other than for the purposes of private study or research, and subject to the provisions of the Copyright Act, is prohibited without the written authority of TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank.

ISBN: 978-1-74236-462-9

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© TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2013


Table of Contents

Introduction ................................................................................... 7

1. General introduction ............................................................................. 7

2. Using this learner guide ......................................................................... 7

3. Prior knowledge and experience ............................................................. 9

4. Unit of competency overview ................................................................. 9

Topic 1: Cutting, gouging and heating safety ............................... 15

Review questions ................................................................................... 19

Topic 2: Flame cutting process and equipment ............................. 21


Topic 3: Quality of flame cut surfaces ........................................... 31


Topic 4: Flame gouging and heating ............................................. 37


Setting up an oxy-fuel gas plant .................................................. 44

Practical work .............................................................................. 47

Job 1: Cut straight lines - Free hand (Plate) ............................................... 50

Job 2: Cut straight lines – Guided (Plate) .................................................. 52

Job 3: Cut rolled section .......................................................................... 54

Job 4: Cut outline of rolled section ............................................................ 56

Job 5: Flame cut circular flange - Guided ................................................... 58

Job 6: Cut bevelled edges ....................................................................... 60

Job 7: Flame cut and bevel composite component ...................................... 62

Job 8: Spot and continuous gouging ......................................................... 64

Job 9: Gouging (Weld defect and back gouging) ......................................... 66

Job 10: Flame heat material to shape ....................................................... 68

Resource Evaluation Form ............................................................ 71

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© TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2013 Page 15 of 74

Topic 1: Cutting, gouging and heating safetyFlame cutting, gouging and heating processes are safe to use provided equipment is assembled and used in a correct manner. Typical hazards associated with flame cutting, gouging and heating include:

• Burns• Hot metal • Fumes • Infrared rays and visible light• Heat stress.

Burns

Burns are typically caused by:

• Touching hot metal• Sparks or hot metal making contact with exposed skin• Flammable or frayed clothing ignited by the flame or sparks • Heat radiated from the flame.

Note: Severity of a burn can range from a slight discomfort to an agonising outcome that will require hospitalisation. Accidental burns are avoided by the use of proper work procedures and personal protective clothing and equipment (PPE).

Hot metalCutting, gouging and heating produces hot metal and heated surfaces which can cause burns. It is important not to leave heated work or offcuts unattended. Hot work should be marked as “HOT WORK” to warn others and when cool the message should be removed.

FumesThermal cutting, gouging and heating processes generate fumes which can create a serious hazard. Fumes are normally generated from:

• Metal coated surfaces exposed to heat from a cutting, gouging or heating flame. Examples include zinc, cadmium and painted surfaces etc.

• Surface contaminants, cleaning solvents.

A fume is a localised pollutant that invades the breathing zone of the operator and to a lesser extent those working in the vicinity.

Some general procedures include;

• Removing surface contaminants such as paint before you apply heat

• Ensure there is adequate ventilation around the work area at all times

• Minimise fume intake by adopting an upright posture to keep your head out of the concentrated fume plume.

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of 74 © TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2013


Ventilation

Methods used to improve air quality of in the vicinity of the operator include:

1. Natural ventilation: Workshops that have large doors and windows allow a natural movement of air to help dilute and remove fumes.

2. Forced fume extraction: When cutting, gouging or heating in a confined space or area where there is restricted air movement, a forced fume extraction system must be used. Forced fume extraction units can either be permanently fixed to a workshop ducting system or be transportable.

3. Using respirators: When natural or forced ventilation is not good enough operators should wear an Australian Standards-approved respirator.

Portable extraction unit Respirator

Infrared radiation (IR)

The bright cutting flame emits infra-red rays. These rays are dangerous and can cause eye strain or permanent injury through long term unprotected exposure. Excessive exposure to the heat from the flame can also cause fatigue to operators, especially when using large (high volume) cutting or heating flames.

Visible light

The intensity of visible light associated with cutting and heating may cause severe eye strain and other eye irritations. To avoid exposure to these harmful rays you must:

• Keep yourself covered at all times by wearing heavy drill cotton clothing.

• Always wear approved cutting goggles or face visor fitted with the correct shade filter. See table on next page for details.

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Filter shades

Shade Application

5 Used for general flame cutting, gouging and light heating applications.

6 Used for flame cutting thicker metal thicknesses. Flame gouging using large nozzles.Heating applications on thicker metal sections.

Filter shades

Heat stress

Cutting, gouging and heating activities can cause the body temperature to overheat resulting in a condition known as heat stress. It is generally agreed when working in hot conditions to keep the body temperature below 38°C. Strenuous physical activity is a major contributor and is aggravated by working in hot, humid conditions.

Overheating of the body temperature can cause discomfort; sweating, dehydration and exhaustion. When working in hot and humid conditions it is recommended to:

• Replace fluid loss (sweat) by taking frequent water drink breaks. Salt tablets or replacement electrolyte solutions are no longer recommended

• Stage frequent rest breaks

• If possible, plan to do the majority of cutting and/or heating work during the coolest part of the day.

Personal protective clothing and equipment

Protective clothing and personal protective equipment (PPE) must be worn at all times to protect the skin and eyes. Approved goggles, safety glasses, leather gauntlets/gloves and boots should all conform to the requirements of various Australian Standards.

Clothing should be made from industrial strength, heavy drill cotton and be in good repair. Shirts should be long-sleeved and made from heavy drill cotton. Clothing made from nylon or other flammable materials must not be worn.

PPE, where appropriate, must conform to Australian Standard specifications. Typical protective clothing and equipment operators are required to wear include:

• Cutting goggles with appropriate shade of filter lens (OW 5 or 6)• Clear safety glasses• Work boots or shoes with rubber soles and leather uppers • Ear muffs / plugs (where high noise levels are expected)• Leather gloves or gauntlets• Industrial-strength, heavy drill cotton overalls or pants and long-sleeved shirt • Leather spats (optional depending on type of work)• Leather or cotton skull cap (optional, depending on type of work)• Leather jacket or apron• Respirators (where surface coatings are present).

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Gogles Safety glasses Leather gloves

Boots Apron Overalls

Screening

When working in an open workshop or on-site, erect a screen made from flame-proof material. Screens help protect others working nearby from sparks and hot metal produced from cutting or gouging.

When cutting, gouging and heating is done on-site, a hazardous location or in a confined space it will be necessary to obtain a “safe work” or “hot work” permit from a Responsible Officer, or a person in a supervisory role.

Care should be taken when cutting and gouging around drain holes as they may have contained flammable or toxic material. It is good practice to cover drains and openings before commencing work. For more information on these safety issues refer to MEM05052A Apply safe welding practices.

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Review questionsThese questions have been included to help you revise what you have learnt in Topic 1: Cutting, gouging and heating safety.

1. List five (5) hazards associated with cutting, gouging or heating. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

2. List six (6) items of protective clothing and equipment operators are required to wear when cutting, gouging or heating. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

3. List two (2) examples where fumes are generated as a result of cutting, gouging or heating. _______________________________________________________________ _______________________________________________________________

4. Who in the workplace is responsible for issuing a “safe work” or “hot work” permit? _______________________________________________________________

5. Explain how hot metal is indicated as a danger to others working nearby. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

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True / false questions (circle the correct answer)

6. Salt tablets should be taken when working in hot, sweaty conditions. True False

7. Operators must wear clothing made from industrial strength, heavy drill cotton. True False

8. A shade 6 filter lens is recommended for general cutting, gouging and heating applications. True False

9. Flame cutting and gouging emits ultraviolet light rays. True False

10. Operators must wear a respirator when natural or forced ventilation is inadequate. True False

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Topic 2: Flame cutting process and equipmentFlame cutting uses a fuel gas such as acetylene or liquefied petroleum gas (LPG) and oxygen to support combustion. The flame cutting process is extensively used for cutting iron and steel as the process is highly dependent upon a chemical reaction taking place between heated iron and oxygen.

Principles of flame cutting

The key principle associated with flame cutting relies upon a chemical reaction taking place between iron and oxygen. When a piece of iron or steel is heated to its ignition point (a dull red) the material will readily burn to form a lower melting point constituent called iron oxide.

The ignition point or temperature for plain carbon steel is 815°C which is well below its melting point of approximately 1450°C. 815°C is the temperature at which point a chemical reaction takes place between iron and oxygen.

The chemical reaction, called an exothermic reaction, generates a great deal of heat to enable cutting to commence. Once the metal starts to burn, the surface of the workpiece rapidly oxidises and chemically transforms iron into an oxide.

When the metal is at its ignition point, a pressurised stream of oxygen is directed on to the surface of the workpiece to sever the material. The concentrated spread of oxidisation through the full thickness of the workpiece allows cuts to be made in varying thicknesses of material.

The most common gas combinations used for flame cutting use oxygen with either acetylene or oxygen + LPG. A neutral flame setting should be used for cutting steel components.

oxygen/fuelgas flame

direction of cut

oxygencutting jet

cuttingnozzle

kerf width

Section across cutSection along cut

cuttingoxygen

Nozzle end

pre-heatingflame holes

Flame cutting operation

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KerfKerf refers to the width of the flame cut. Factors influencing the width of kerf include the type of tip used, the size of the oxygen orifice, gas flow rates and travel speed. It is important to account for the width of the cutting kerf in order to achieve dimensional accuracy of the finished work. For example, depending on the type and size of nozzle, the width of the cutting kerf will vary from 1.3 to 3 mm.

This cutting width needs to be taken into account when marking dimensions on the workpiece and adjusting cutting aids. When cutting external and internal circles or radii the width of the kerf needs to be added (+) or subtracted (-) to give the required dimension.

Uses

Flame cutting is extensively used in the fabrication industry to cut plate and structural sections to construct:

• Building frames • Earth moving, mining and transport equipment • Boilers, pressure vessels, steam pipes• Ships and containers • Tanks, silos and storage vessels.

Limitations

Because flame cutting relies upon an oxidising or chemical reaction taking place between heated iron and oxygen, the process can only be used on metals predominately made of iron. For this reason its application is limited to plain carbon and some low alloy steels. Nonferrous metals such as copper, brass and aluminium cannot be flame cut because their chemistries are vastly different to that of steel. For a metal to be readily flame cut it needs to have:

• An ignition temperature below its melting point so the metal can be cut without being melted by the flame

• A higher melting point than the oxide formed as a result of the cutting action.

Cutting equipment

Portable flame cutting plants are identical to those used for oxyacetylene welding except they are fitted with a specially designed blowpipe and nozzle. An oxyacetylene cutting plant consists of the following components:

• Oxygen cylinder• Acetylene cylinder• Gas regulators• Flashback arrestors• Hoses• Cutting blowpipe or torch• Cutting nozzle• Tip cleaners • Cylinder trolley or cart (fitted with safety chain).

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Gas cylinders

Oxygen cylinders and regulators are coloured coded black and all fittings have right-hand threaded connections. Oxygen cylinders can be compressed upto a pressure of 17500 kPa. The pressure in the cylinder is directly related to the quantity of gas stored inside. Oxygen is odourless and is primarily used to support and accelerate combustion. Cylinders are available in G, E, D and C sizes for different industrial applications.

As previously mentioned, oxygen by itself is not flammable or explosive; however it will support combustion and cause material to burn freely. When using and handling oxygen, never use it for:

• Operating pneumatic tools, spray painting or compressed air equipment • Purging or blowing out pipelines, vessels or containers• Freshening air or remove fumes in a confined space • Cooling yourself or blowing dust from clothing.

Acetylene cylinders and regulators are coloured coded claret, although they are sometimes referred to as maroon or crimson. Acetylene is a combustible fuel gas that gives off a distinctive garlic smell. All acetylene gas fittings have a left-hand threaded connection which are identified by a “notch” or grooved appearance on the outside of the fitting. Similar to oxygen, acetylene cylinders are available in G, E, D and C sizes to accommodate increased volumes of gas.

Cylinders are filled with a porous substance and acetone. Acetylene is dissolved in acetone to stabilise the gas allowing it to be stored safely up to I800 kPa. When combined with oxygen it will produce a flame temperature of approximately 3100°C which is higher than that achievable by LPG.

When handling and using acetylene it is important to:

• Keep cylinders in an upright position at all times• Never transfer the gas from one cylinder to another• Store cylinders in a cool, well ventilated location• Never withdraw more than 1/5th or 20% of the cylinders contents over a 1 hour

period. If this is likely to occur use gas supplied from a manifold or pack.

LPG cylinders are colour coded silver, grey or galvanised and have left-hand threaded connections. LPG is a highly flammable fuel gas that is given an artificial odour to indicate its presence and often used as an economic alternative to acetylene. Although LPG burns more efficiently than acetylene, the temperature of the flame, when combined with oxygen is lower (2800 - 2900°C) than that produced by acetylene and oxygen. For this reason LPG is limited to cutting and heating not welding applications.

Cylinder safety features

• Never attempt to interchange left-hand threaded pressure regulators between gases. Each regulator is designed for use with a specific gas, and to interchange them could be hazardous. Gas cylinder pressures and properties are different

• Acetylene should not be pressurised above 170 kPa as a free gas due to the possibility of an explosion

• Oxygen cylinders have bursting disc in its value assembly to avoid over pressurisation of the cylinder

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mem05007c perform manual heating and thermal cutting sample · mem05007c perform manual heating and...

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