MEM05008C Perform Advanced Manual Thermal Cutting, Gouging and Shaping - Learner Guide

8/10/2019 MEM05008C Perform Advanced Manual Thermal Cutting, Gouging and Shaping - Learner Guide

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MEM05 Metal and Engineering

Training Package

Learner guideVersion 1

Training and Education Support

Industry Skills Unit

Meadowbank

MEM05008CPerform advanced manual

thermal cutting, gouging andshaping

Product Code: 5207


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Developed by Training & Education Support Industry Skills Unit, Meadowbank

TAFE NSW 2010

MEM 0 5 0 0 8 C Pe f o r m a d v a n c ed m a n u a l t h e r m a l cu t t i n g , g o u g i n g a n d s h a p i n g

AcknowledgmentsThe TAFE NSW Training and Education Support Industry Skills Unit, Meadowbankwould like to acknowledge the support and assistance of the following people in theproduction of this learner resource guide:

Air LiquideBOCLincoln Electric CompanyLinde gas

Writer:Ed Harkness

Reviewers:John Anderson (Hunter Institute)John Myers (North Coast Institute)

Neil Smith (Illawara Institute)Ted Armstrong (Western Sydney Institute)Vince Aranda (South Western Sydney 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

The State of New South Wales, Department of Education and Training,TAFE NSW, Training and Education Support Industry Skills Unit,

Meadowbank, 2010.

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

ISBN 978-1-74236-203-8


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Developed by Training & Education Support Industry Skills Unit, Meadowbank

TAFE NSW 2010

MEM 0 5 0 0 8 C Pe f o r m a d v a n c ed m a n u a l t h e r m a l cu t t i n g , g o u g i n g a n d s h a p i n g

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

5. Assessment ....................................................................................... 12

Topic 1: Oxy-fuel gas cutting ........................................................ 21

Equipment ............................................................................................ 22

Care of equipment .................................................................................. 31

Personal safety ...................................................................................... 32

Manual flame cutting techniques and accessories ........................................ 35

Cutting faults and corrective measures ...................................................... 41

Review questions ................................................................................... 44

Topic 2: Flame gouging ................................................................ 49

Care of equipment .................................................................................. 51

Operating techniques .............................................................................. 52


Topic 3: Plasma arc cutting and gouging ...................................... 57

Basic plasma arc cutting equipment .......................................................... 59


Topic 4: Carbon arc gouging ......................................................... 71

Principles and applications ....................................................................... 71

Equipment and accessories ...................................................................... 71

Operating techniques .............................................................................. 73

Carbon arc safety ................................................................................... 74


Practical exercises ....................................................................... 81

JOB 1 - Flame cutting using cutting guides - circles and holes ...................... 85


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MEM 0 5 0 0 8 C Pe r f o r m a d v a n c ed m a n u a l t h e r m a l cu t t i n g , g o u g i n g a n d s h a p in g

Topic 1: Oxy-fuel gas cutting

P r in c i p l e s a n d a p p l i ca t i o n s

Flame cutting, or oxy-fuel gas cutting as it is sometimes termed, is the most widelyused thermal cutting process in metal fabrication industries for cutting steel sectionsto size and shape. The operational principles of flame cutting were described inMEM05007C Perform manual heating and thermal cuttingand stated that theprocess is reliant upon a chemical reaction taking place between heated iron andoxygen to form iron oxide; the iron oxide formed is then melted by the heat of thereaction and blown away by the oxygen jet.

The flame cutting process uses a carefully controlled high-velocity oxygen streamto sever heated steel sections (cutting); or as in flame gouging, large volumes ofoxygen at low velocity to remove defective welds or unwanted material.

Cutting means the oxygen cutting jet is used on the part at 90 to produce a

straight cut. Whereas for bevelling, the cutting jet is used at an angle other than90 to produce a chamfered or slanted face on the edge of the part. This is done tocreate a groove for a weld preparation or to remove a defective weld.

Parts for a steel structure can be cut from plates, structural sections and pipesdepending on the type of work required.

Manual cutting is done where; a small number of parts are required; when theaccuracy of the cut part does not have to meet restrictive tolerances or whenflame cutting is performed on site

Skilled operators can manually cut parts to a high level of accuracy, by freehandor guided cutting, if strict flame cutting skills are learned and attention is paid to

detail

when the accuracy of the cut point does not have to meet restrictive tolerance

Where flame cutting is performed on site.

Cu t t i n g s t e e l p la t e m a n u a l l y


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MEM 0 5 0 0 8 C P e r f o r m a d v a n c ed m a n u a l t h e r m a l cu t t i n g , g o u g i n g a n d s h a p i n g

Fu e l g a s e s

It is common practice to use either acetylene or liquefied petroleum gas (LPG or LPGas) as the fuel gas.

Oxygen is the supporting gas, and as well as increasing the flame temperature itprovides the cutting stream necessary to rapidly oxidise the surface of the heatedmetal.

Natural gas can be easily used in existing equipment designed for LPG and someindustries will use high pressure natural gas piped from a reticulated supply.However, for the purposes of manual thermal cutting, gouging and shaping inworkshops and construction sites, acetylene or LPG are the fuel gases most used.

When fuel gas is burned with commercially pure oxygen, flame temperaturesmeasure:

Oxy-acetylene 3100C

Oxy-LP Gas 2700C

Equipment

Most manual flame cutting performed in metal fabrication industries use a compact,portable plant such as the one shown below. In general, a portable oxy-cutting plantwill consist of:

a pair of cylinders secured in a trolley;

gas regulators attached to the neck of

cylinders;

flashback arrestors

hoses and blowpipe

The complete plant is easily moved aroundthe workshop or site location as required, andimportantly the cylinders are secured safely.

Flashback arrestors are an essential pieceof safety equipment that must be used onall (fixed and portable) oxy-fuel gas cuttingplants.

A p o r t a b l e o x y a c e t y l e n e s e t


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Cu t t i n g a n d g o u g i n g t o r c h e s

A selection of cutting and gouging torches are commonly available for fuel gascutting and gouging applications.

For general workshop and construction site operations, the cutting torch assemblypictured below, is the most commonly used. It consist of a flame cutting attachmentwith a cutting nozzle which is connected to the blowpipe handle. This light dutytorch is quite safe for use where large quantities of parts are not being cut.Intermittent cutting allows the blowpipe to cool down and not ignite the gases.

Cu t t i n g t o r c h a s s e m b l y

As illustrated below, these torches mix flame gases in the handpiece inside a mixingchamber and take the mixed gases to the torch head and nozzle.

Heavy-duty torches used for continuous flame cutting are designed to mix the fuelgas and flame oxygen in the torch head. By mixing the flame gases very close tothe nozzle, the mixture has very little time to overheat and catch fire inside theblowpipe. This makes continuous flame cutting and gouging operations safer for theoperator.

H e a v y d u t y fla m e c u t t i n g t o r ch


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Cu t t i n g n o z z l e s

A number of manufacturers supply flamecutting equipment, which includes a range ofcutting nozzles for different metal thicknesses.

The most common nozzle used in todays steelconstruction industry is the "taper seat" type,pictured opposite. The name "taper seat"refers to the method of sealing the nozzle tothe blowpipe, creating a simple but effectivemethod of attaching the cutting nozzle to theblowpipe.

An industry-wide designation for nozzle sizes is the numerical system whichspecifies the cutting jet size in tenths of a millimetre. For instance, Number 15

cutting nozzle has a cutting orifice 1.5 mm in diameter; likewise a Number 8cutting nozzle has a cutting orifice of 0.8 mm.

Although this system is not universally used, it has become commonly acceptableamongst people working in metal fabrication industries.

Cutting nozzles are made differently to accommodate the type of fuel gas used.Nozzles are numerically stamped with a number to designate the fuel gas used.They are not interchangeable and the correct nozzle must be fitted to the cuttingtorch for the type of fuel used. For example:

Taper seat nozzles for use with acetylene fuel gas are stamped TYPE 41

Taper seat nozzles constructed for use with LPG are stamped TYPE 44

Cutting nozzles should be carefully stored to avoid taper seats being damaged byother tools.

A c e t y l e n e n o z z le s

Acetylene nozzles can be made from either brass or copper and are machined froma solid piece of material. Brass nozzles are normally used for low volume manualcutting; whereas copper nozzles are used forhigh production applications. Copper nozzles

normally don't require cleaning as frequently asthe brass type.

These nozzles have a number of holes (preheatports) to allow the preheat flame to surroundthe central cutting orifice or jet. Small nozzlesmay have only five pre-heat holes, whereaslarger nozzles have six holes.

T a p e r s e a t n o z z l e

A c e t y l e n e n o z z l e ( T y p e 4 1 )

MEM05008C Perform Advanced Manual Thermal Cutting, Gouging and Shaping - Learner Guide

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