perform advanced welding using manual metal arc welding ... · • basic-coated electrodes contain...

MEM05 Metal and Engineering Training Package

Learner guide

Version 2

Training and Education Support

Industry Skills Unit

Meadowbank

Product Code: 5754

MEM05016C Perform advanced welding

using manual metal arc welding process

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MEM05016C Perform advanced welding using manual metal arc welding process

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

Acknowledgments

The TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank would like to acknowledge the support and assistance of the following people in the production of this resource package:

Standards AustraliaAvesta PolaritCIGWELDFroniusLincoln AustraliaOneSteel AustraliaSilverwater Welding Supplies

Writers:

Updated from existing TAFE resources.

Reviewer:

John Anderson (Hunter Institute)TAFE NSW

Project Manager:

Education Programs ManagerTraining and Education Support, Industry Skills Unit, MeadowbankTAFE NSW

Enquiries

Enquiries 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 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 978-1-74236-464-3

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ContentsIntroduction .................................................................................. 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: MMAW safety ................................................................. 13

Review questions .................................................................................. 17

Topic 2: MMAW electrodes and storage ....................................... 19


Topic 3: Welding carbon and low alloy steels ............................. 31


Topic 4: High alloy steels, stainless steels ................................... 49


Topic 5: Welding symbols ............................................................ 57


Topic 6: Destructive weld tests ................................................... 63


Topic 7: Structural welding standard .......................................... 69


Practical work ............................................................................. 73

JOB 1: T-Fillet - Horizontal/vertical .......................................................... 78

JOB 2: T Fillet - Vertical ......................................................................... 80

JOB 3: T fillet - Overhead ....................................................................... 82

JOB 4: Fillet - Vertical (Pipe to plate) ....................................................... 84

JOB 5: Fillet - Overhead (Pipe to plate) .................................................... 86

JOB 6: Butt weld - Flat (hexagonal bar) ................................................... 88

JOB 7: Butt weld - Horizontal .................................................................. 90

JOB 8: Butt weld - Vertical ..................................................................... 92

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MEM05016C Perform advanced welding using manual metal arc process


JOB 9: Butt weld - Overhead .................................................................. 94

JOB 10: Butt weld - 2G pipe ................................................................... 96

JOB 11: Butt weld - 5G pipe ................................................................... 98

Resource Evaluation Form ......................................................... 101

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© TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2013 Page 13 of 104

Topic 1: MMAW safety

Electrical safetyWelding operators commencing this advanced welding unit must be familiar with the dangers and risks of working with electrical welding equipment. Summarising the causes and effects of electric shock:

Electric shock: low voltageElectric shocks are possible on the secondary (low voltage) side of the welding circuit. They may be caused by:

• Working on wet floors - a shock may be felt when inserting an electrode in the holder. Always stand on insulated mats or wooden boards to reduce the risk

• Always wear dry leather gloves or gauntlets

• Working in a very humid climate or rainy weather - a shock may be felt when changing electrodes. Keep electrodes and gloves dry at all times.

Electric shocks: high voltageHigh voltage shocks can be avoided if:

• Power sources are checked and tested on a regular basis by licensed electrical repairers

• Operators never interfere with the internal electrical components of welding power source.

Symptoms of electrical shockThe severity of an electric shock can range from a “tingling” sensation, muscle spasms, burns, or in extreme cases, death. When electricity passes through the body, particularly through the arms or legs it causes muscles to contract. When the heart is in this current path it can stop the heart beating.

Factors which affect the severity of a shock include:

• The open circuit voltage (OCV) of the power source• Whether the power source supply is alternating (a.c.) or direct current (d.c.)• The amount of moisture generated from perspiration, humidity or other sources• How well the operator is insulated from the electrode and the workpiece• The parts of the body in contact with the work and/or the electrode. Current flow

from hand to hand or hand to foot via the torso (heart) are the most dangerous • Susceptibility of the victim to shock which is dependent on general health and

wellbeing of the operator as well as other factors.

Safety investigations into several workplace fatalities associated with electric arc welding have resulted in a tightening of the safety requirements associated with on-site arc welding. Recent trends to arc welding safety on site include:

• All power sources to be d.c. welding circuits• All MMAW power sources are fitted with a voltage reduction unit (VRU).

Most modern welding power sources have these characteristics or facilities. Where existing machines do not it is recommended they be replaced or retrofitted to conform.

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Weld fumesWelding fumes consist of:

• Particulate fume, the part you can see, and• Gaseous fume, the invisible part which you usually smell.

Due to the close proximity of the operator to the welding arc, fume generated from the MMAW process presents an immediate danger to the health and safety of the operator. A summary of causes and effects of welding fumes include:

• The breakdown of constituents in flux coatings• Elements present in the parent metal• The production of oxides and nitrous gases produced• Ozone is formed during welding particularly when high currents by the action of

ultraviolet radiation on oxygen in the air

• Surface coatings on steel products, such as: - Galvanising - Cadmium plating - Chrome plating - Paints and solvents (eg red oxide, coated parts and degreasing solvents).

Fumes in the breathing zone of operators

Effects of gases, dusts and vapours given off during weldingDepending on the exposure time and volume of fume, breathing in gases and vapours may cause:

• Ailments from irritation of the respiratory tract, to serious lung disorders• Acute flu-like illness sometimes referred to as “metal fume fever”• Asphyxiation due to oxygen depletion in a work area such as a confined space • A build up of poisonous metals in the body, such as lead, cadmium, zinc,

beryllium or mercury.

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Fume controlFume exposure levels and measurements are normally determined by the Work, Health and Safety (WHS) Act 2011 and the WHS Regulations, authorities and other government statutory bodies. Their purpose is to advise and ensure industries limit the concentration of welding fumes in the breathing zone of the operator.

On completion of a measured period of time, a number is calculated to reflect an 8-hour time weighted average (TWA) of the fume concentration in the operator’s breathing zone, measured in milligrams of particulates per cubic metre of air.

Other terms used to measure and tabulate fume concentrations include:

• Threshold limit value (TLV)• Permissible exposure limits (PEL)• Short-term exposure limits (STEL).

Analysis of fume content, concentrations and exposure levels are used by welding manufacturers of consumables to produce safety information, known as Material Safety Data Sheets (MSDS).

As well as providing details of consumables MSDS’s provide Responsible officers and operators with advice on exposure limits and suggested safety measures to limit inhalation of fumes.

Operator wearing a respirator system

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Emissions from electrode flux coatingsParticulate fume is commonly formed from vaporisation of welding consumables. The level of fumes produced will depend upon the composition of the electrode consumable and compounds in the flux coating. To a lesser extent, production of fume will depend on the composition of the material being welded. The flux-covered electrodes used in this resource study include:

• Basic-coated electrodes contain a high proportion of calcium carbonate (limestone) and calcium fluoride (fluorspar) and one bonded with sodium or potassium silicate

• Cellulose electrodes contain a high proportion of cellulose in the coating with titanium oxide to provide arc stability and one bonded with sodium or potassium silicate.

These electrodes produce a range of particulate and gaseous fumes not found in general purpose (GP) electrodes. Basic coated electrodes produce fluorides and carbon dioxide gas in the weld fume. Cellulose electrodes produce hydrogen and carbon dioxide gases but with adequate ventilation, they are unlikely to present a significant hazard.

Deep penetrating arc and rapid burn-off rates associated with cellulose electrodes produce greater volumes of weld fume than those produced by GP rutile electrodes. Accordingly, when cellulose electrodes are used it may be necessary to use a portable fume extraction unit or respirator. In summary, methods used to ensure air quality is safe to inhale during welding include:

• Keeping your head out of the fumes rising from the weld zone

• Using forced ventilation and respirators when welding harmful fume producing metals such as stainless steel, nickel, nickel alloys and copper or coated metal surfaces including galvanised or cadmium coated steel. This also applies to high fume producing consumables.

• Using a forced fume extraction system if welding is to be done in a confined space or area where there is restricted air movement

• Respirators must be worn to filter out toxins if natural or forced ventilation is inadequate or the material being welded and/or consumables are able to generate dangerous fumes

• Limit exposure times to weld fumes (PEL and STEL), such as those documented on material safety data sheet (MSDS) for the welding electrode

• In workshops that have high roofs, large doorways and windows, natural movement of air helps to dilute and remove welding fumes making them suitable for general welding work.

Note: Respirators must be suitable for welding applications and manufactured in accordance with Australian Standard guidelines.

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Review questionsThese questions have been included to help you revise what you have learnt in Topic 1: MMAW safety.

Q1. List two (2) possible causes of electric shock from the secondary (low voltage) side of the welding circuit. _____________________________________________________________

_____________________________________________________________ Q2. State four (4) factors which affect the severity of electric shocks.

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Q3. Name the unit incorporated in MMAW power sources to prevent the possibility of electric shocks.

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Q4. List four (4) causes of weld fumes.

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Q5. What are the potential effects of fumes on welding operators.

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Q6 State four (4) precautions welding operators can take to ensure air is safe to breathe during welding:

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_____________________________________________________________

_____________________________________________________________

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Introduction1.General introduction2.Using this learner guide 3.Prior knowledge and experience4.Unit of competency overview

Topic 1: MMAW safetyReview questions

Topic 2: MMAW electrodes and storageReview questions

Topic 3: Welding carbon and low alloy steels Review questions

Topic 4: High alloy steels, stainless steelsReview questions

Topic 5: Welding symbolsReview questions

Topic 6: Destructive weld testsReview questions

Topic 7: Structural welding standard Review questions

Practical workJOB 1: T-Fillet - Horizontal/verticalJOB 2: T Fillet - VerticalJOB 3: T fillet - OverheadJOB 4: Fillet - Vertical (Pipe to plate)JOB 5: Fillet - Overhead (Pipe to plate)JOB 6: Butt weld - Flat (hexagonal bar)JOB 7: Butt weld - HorizontalJOB 8: Butt weld - VerticalJOB 9: Butt weld - OverheadJOB 10: Butt weld - 2G pipeJOB 11: Butt weld - 5G pipe

Resource Evaluation Form

perform advanced welding using manual metal arc welding ... · • basic-coated electrodes contain...

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