INTRODUCTORY SAFE WELDING PROCEDURES FOR NON-CRITICAL APPLICATIONS: MEL02INF21907 Page 1 of 21 HEALTH & SAFETY REQUIREMENTS:

RECORDING REQUIREMENTS: Record your result on the Welding Process and Application Task Worksheets MEL02TWS08 & MEL02TWS12. REFERENCES: This document relates in part to the requirements of Unit Standard 21907.

© Competenz - N Z Engineering Food & Manufacturing Industry Training Organization Inc.

In this booklet you will find information about; • Welding principles, terminology and applications • Welding hazards and safe working practices • Health risks and personal protective equipment

• Welding processes, techniques and practices • Welding quality assurance, test and inspection • Visual identification of defective welds

Version 1.1 March 31st 2009

Brazing is a non-fusion type of jointing, similar to soldering. It uses a flame created by burning a mixture of oxygen and acetylene gases. When brazing, the melting point of the filler wire material is much lower than the melting temperature of the metals being joined. The molten filler wire and flux adhere to the heated base metals, then cool to form the brazed joint.

Neutral Flame

Oxidising Flame

Carburising Flame

Thoroughly cleaning the surfaces to be joined dramatically improves both the ease of brazing the two surfaces, and the quality of the finished joint. Some material may require a flux paste or powder to create a clean joint. Most faults which occur during brazing can be rectified by using a neutral oxygen-acetylene flame and adjusting the motion, rate of travel and the angle of the torch and filler wire.

To create a good quality brazed joint, the different variables need to be balanced correctly. They are;

• Tip size • Gas pressures • Gas mixture ratio • Type and size of filler wire used • Frequency of feeding the filler wire • Rate of travel of the torch travelling across the material.

Soldering is a non-fusion type of jointing. The soldering process bonds the parent metals through capillary action, unlike welding which melts the two metals. The edges to be joined are cleaned with flux, then heated and solder wire added. The two surfaces are wetted (often called tinning) by the solder, which creates a joint by bonding to the two surfaces.

To create a strong joint, the different variables need to be balanced. These are;

• Correct type of solder for the metals used • Correct type of flux for the metals used • Sufficient heat from the iron is applied to the joint • The surface condition of the material.

Thoroughly cleaning the surfaces to be joined dramatically improves both ease of soldering the two surfaces, and the quality of the finish. A number of faults can occur during soldering, all of which can be rectified by using the correct types of solder, flux, and iron temperature.

Electric Soldering Iron

Typical applications where brazing is an advantage include; • Thin metal plate and pipe • Repairing cast iron • Where appearance is vital such as jewelry, art, architecture etc. • Where corrosion resistant joints are required for items such as bicycle

and motorcycle frames, and pipes on submarines.

Typical applications where soldering is used include; • Car radiators and small mechanical parts • Cans and other containers (including food) • Roof flashings, roof gutters and plumbing applications • Where appearance is vital, jewelry, art, architecture etc • Electrical work.

Spot Welding is the most common type of resistance welding and is used to join sheet metal up to 3.2 mm thick. Two copper electrodes are used to clamp the sheets together and carry the welding current to a small “spot” where the sheet metal fuses together. The amount of heat energy delivered to the “spot” is determined by the amount of current selected, the duration of the current and the resistance between the electrodes. Too little heat energy will create weak fusion at the “spots”. Too much heat energy will melt away the metal and leave a hole instead of a weld.

HANDY HINT; Clean and correctly formed electrodes are essential for creating spot welds that are strong, flat, even and clean.

HANDY HINT; The “divot test” can be used to check the spot weld is being formed at maximum strength.

Oxy-Acetylene Welding produces a fusion joint using a flame created by burning a mixture of oxygen and acetylene gases. When welding, the edges of the metals being joined are melted until they fuse together to form a weld pool. A filler wire of a similar material is often added to the weld pool, providing additional mass and increasing joint strength.

Typical applications where oxy-acetylene welding is an advantage include; • Pipes and tubes for bicycle and motorcycle frames • Plate and sheet metal up to 5mm • Vertical or overhead applications.

Typical applications where resistance welding is an advantage include; • Sheet metal car or boat bodies where a waterproof seal is not required • Automated production line assembly • Attaching studs, nuts or other machine parts to metal plate • Creating continuous seams on sheet metal and thin plate sections.

Resistance Welding is the simplest, cleanest and quietest welding process.

The most common type of resistance welding is spot welding. Other types of resistance welding include;

• Seam welding where the electrodes take the form of a set of disks • Projection welding which uses integrated components or raised sections of

the workpieces to create localized heat.

Typical Projection Welding Set-ups

Typical Seam Welder Set-up

Thermal Cutting

Typical applications where plasma cutting is an advantage include;

• Aerospace and boat building industries where electric-plasma is used for cutting precision workpieces

• Manufacturing of heavy machinery, agricultural equipment and aircraft components where plasma cutting produces comparatively clean edges and a tidy cut profile • High-end production manufacturing where electric-plasma cutting is used on

production line CNC type machines as a substitute for drilling, machining, punching and cutting.

Oxy-acetylene gas mixtures is ideal for cutting a wide range of carbon steels and plate thicknesses. The plate is not melted but heated to its oxidisation point and then additional oxygen is blown into the heated area. This causes the metal to oxidize and blows a hole through the metal. The metal plate is not required to be heated to its melting point, which makes the cutting rate fast and efficient.

The thermal cutting of metal can be done using either gas or electricity. Thermal cutting has significant advantages over mechanical cutting such as grinders and hacksaws. Thermal cutting is very fast, especially with thicker material, is quieter in operation and reduces operator fatigue.

HANDY HINT; When setting up, lighting and switching off the oxy-acetylene

torch, be careful not to cause backfires and flash-back.

HANDY HINT; Regular cleaning of the gas nozzle will help

to prevent backfires and flash-back.

Typical applications where oxy-acetylene gas cutting is an advantage include; • Civil construction and shipbuilding when electricity is not available at the cutting site • One-off jobbing, engineering repair shops and blacksmithing where it is used for

cutting low to medium carbon steel and wrought iron • Heavy machine shops and scrap yards where it is necessary to cut plate sections up to 200 mm thick.

Shield Gas

(―ve) Electrode

Workpiece (+ve)

Plasma Gas

Typical applications for electric-arc cutting include; • Repair workshops and rework in manufacturing where it is used for gouging to remove

welds and excess material • Remote location cutting where gas supply and cylinder refills are not immediately available, but there is a plentiful supply of compressed air • Scrap yards where rough edges and uneven cuts are acceptable.

Electric-arc cutting (or carbon-arc cutting) forms an electric arc between a consumable carbon or graphite electrode at the handset and the metal workpiece. The workpiece is melted by the electric arc and the molten metal is blown away with a continuous blast of compressed air.

Plasma cutting and gouging uses a flow of plasma which is produced at around 16,000°C. The plasma melts the metal workpiece and removes the molten pool in the same operation.

Plasma cutting is used across all types of manufacturing industry and is best suited to cutting curved and angled shapes in fabrication materials ranging from 1 mm to 300 mm thick.

Plasma cutting and gouging is ideal for use on a wide range of ferrous and non-ferrous alloys and is particularly suited to cutting aluminum and stainless steel. This process tends to be noisy, creates high levels of radiation and can generate a considerable amount of fumes.

15°

Tungsten Inert Gas (TIG) Welding (also known as Gas Tungsten Arc Welding, GTAW) is a process in which the workpiece is melted by the arc from a pointed tungsten electrode. The molten pool is protected with an inert gas. Unlike other forms of arc welding the electrode doesn’t melt. TIG is used mainly to weld sheet metal and can be used to weld most commonly available metals. TIG is slower than both MIG and ARC, but produces very high quality welds. With a direct current (DC) TIG set, the handset is normally negative (-ve) and the workpiece positive (+ve). Engineers prefer TIG welds because of its low-hydrogen (higher strength) properties and the match of mechanical and chemical properties with the base material.

Metal Inert Gas (MIG) Welding uses an inert gas, usually an argon mix, to shield the arc as it melts the two edges together and automatically feeds a wire filler to the weld pool. A direct current (DC) arc is produced, normally with positive (+ve) at the handset and negative (-ve) at the workpiece.

Typical applications where MIG welding is an advantage include;

• Fabrication and structural steelwork where quick production of high quality slag-free weld is required

• Small run production workshops where only minimal weld spatter is produced which allows high production output

• Ship building and bridge construction as it is extremely versatile for large projects.

Arc Welding uses a flux coated welding rod. An electric current is passed through the rod, jumps the small gap to the workpiece, forming an arc. As the current crosses the gap, it generates enough heat to melt the metal rod and the workpiece, the two metals then mix together forming a weld bead. During the welding process the flux on the rod melts and protects the weld from oxidation.

Typical applications where manual metal arc welding (MMAW) is an advantage include;

• Construction of steel structures and industrial fabrications where thicker section heavy-fabrication materials require higher welding temperatures

• Outdoor use in rural and civil construction applications where shielding gas is not practical

• Repair and maintenance workshops where quick, simple and versatile welding processes are required.

MMAW is commonly used for general engineering, mechanical repairs and construction site work. With no shielding gas requirements or continuous wire feed mechanisms to maintain, this simple process requires less operator skill and training, making it the most common welding process.

Typical applications where TIG welding is an advantage include; • Repair of aluminum and magnesium tools and dies • Specialized high quality welding on medical and aerospace projects • Critical welding operations such as sealing spent nuclear fuel canisters • Precision welding of small-diameter, thin wall tubing on mountain bike

frames and race car roll cages.

Welding Terminology

Weld leg length is a measure of the amount of weld fused the workpieces being joined. Weld throat is a measure of the thickness of the weld connecting the two workpieces.

Identification of the weld profile is helpful during visual inspection, as it helps to indicate faults which may be present in the weld. Concave - a weld viewed from the side, that curves inwards like a cave. Convex - a weld viewed from the side, that looks like an overfilled container or a bubble. True-mitre - a weld that looks like a regular triangle from the side.

Penetration - the depth that the weld fuses or melts into the workpieces. This is the fusion zone of the weld. Welds without sufficient penetration won’t hold together and will fail when the joint becomes loaded or stressed.

Fillet weld - two plates are joined by welding in a T-configuration. The welding bead is approximately triangular in shape and is placed in the inner corners of the T. Fillet welds are typically used for structural bracing and lifting lugs.

Butt weld - two plates welded together using an edge-to-edge joint. The workpieces are laid (or clamped) with the welding-edges facing each other. This type of joint is typically used for welding the seams of pressure vessels, stor-age tanks and pipework, or to join structural sections on construction sites. The weld bead is approximately half-round and is placed evenly across the joint.

Fusion - the melting and mixing together of two metals. During welding, these two metals are typically the filler rod (or wire) and the workpiece. When the two workpieces are connected with a fusion joint (welded, not soldered or brazed), the workpieces and the filler material become one continuous piece of metal.

• Use Only if Trained and Authorized to do so • Follow Directions and Comply with Instructions • Check for and Report Damage or Deterioration • Use Adequate Extraction, Ventilation and Lighting • Never Leave Live or Moving Machinery Unattended • Use Correct Personal Protective Equipment ( PPE) • Select and Use the Correct Tools and Equipment for the Job • Fit and Use Fall Restraint Systems if Working Above Three (3) Meters • Isolate and Lock-Out Before Opening, Disconnecting or Disassembling.

• If In doubt– ASK! • Do Not Work Alone • Don’t Do Work that is Unsafe • Check and Clean Before Using • Tidy-up and Clean-up as you Work • Fit and use Guards and Safety Devices • Remove Sources of Ignition • Use Storage Systems Provided • Tidy-up and Clean-up when Done • Report Incidents, Accidents or Injuries.

Guidelines for Safe Working Practices Welding workshop procedures will be specific to the scope and complexity of the work and will require appropriate employee training. The following basic safety guidelines can be incorporated into the workshop procedures to avoid accidents or incidents;

When performing welding operations, always follow safe working practice. To enable a welder to work safely, a set of safe working procedures and specifications must be published and be available in the workplace. Company Welding Procedures and Specifications (WPS) should reflect industry safe working practices and standards.

The objective of the Health and Safety in Employment Act is to promote the prevention of harm to all persons at work and other persons in or around a place of work.

EMPLOYEE REQUIREMENTS

Duty to Avoid Causing Harm to Others The duty to avoid causing harm applies to employees in all industries and occupations, and as an employee you must take all practicable steps to;

• Comply with an employer’s instructions • Ensure your own safety at work • Ensure that no action or inaction by you while at work

causes harm to any other person, whether fellow employee, employer, visitor, or member of the public • Avoid interfering with any accident scene • Comply with notices, sampling or other requirements of

health and safety inspectors and/or medical practitioners.

RIGHTS OF EMPLOYEES The Right to Receive Information on Hazards The Act requires employers to provide employees with information on the hazards they may encounter or create in their work. Before an employee starts any kind of work, their employer must inform them of;

• Emergency procedures • Hazards they may be exposed to while at work • Hazards they may create while at work which could harm others • How to minimise the likelihood of these hazards becoming a

source of harm to themselves or others • The location of safety equipment.

This applies to an employee doing work of any kind, using plant, equip-ment or machinery of any kind, or dealing with a substance of any kind.

HANDY HINT; ASK FOR ASSISTANCE!

20 kg is a safe personal maximum load for a fit, medium-build adult to lift.

Workplace Safety

Employees have the right to refuse to do work that is likely to cause serious harm.

To keep yourself and others safe, you and your employer need to be able to identify potential and actual hazards in the workplace. Workplace hazards may exist in the following areas;

• Plant, machinery and equipment- e.g. Guards not fitted, worn or broken parts, or overdue maintenance. • People- Lifting, carrying, pushing or pulling loads. Stress and fatigue. • Location and Environment- Excessive noise, poor house-keeping, inadequate lighting, ventilation or extraction systems. • Chemicals and Substances- Poor storage or labelling, excessive quantities or types. Inappropriate handling. • Tasks- Repetitive actions, poor posture or straining. Working alone for long hours, driving or travelling away from base.

Identifying hazards is a learned skill, and usually requires some degree of training and experience. Hazards that have been identified in the workplace should be recorded on a hazard register for the purpose of action and reference. Actions required to eliminate, isolate or minimize hazards should be incorporated into technical information such as notices, signage, material safety data sheets, technical data sheets, operating procedures, work instructions, process documentation and manuals.

Welding Hazards Electric shock - Electrical equipment in a welding area is typically supplied by leads carrying up to 415V. Electrical shocks are capable of causing death and severe injuries such as external and internal burns, as well as organ and nervous system failure. Before starting work check for;

• Loose and exposed connections • Frayed, exposed, broken and burnt components or power cables • Damaged electrode holders, torches and hand-pieces.

Despite its obvious convenience, personal contact with electricity can be fatal.

Regularly check and maintain equipment, and replace damaged or defective components. Keep gloves and protective clothing clean and dry. Do not tamper with bare wires or exposed connectors.

Check welding equipment and power tools for current certification and tagging. Always use welding equipment and power tools with each of the following;

• Residual current device (RCD) protection, or an isolating transformer, or an monitored-earth circuit • Certified or test-tagged extension cords • Personal Protective Equipment (PPE).

Compressed gas cylinders pose a number of significant hazards and need to be treated with care. Cylinders must be secured against falls, kept away from electrical apparatus and sources of heat and regularly examined for signs of defects, rusting or leakage. Compressed gas cylinders must be clearly labeled and must be stored in separate locations. Material Safety Data Sheets (MSDS) must be available for all the gas cylinders in use or being stored on site.

Flammable and Explosive materials and containers must be removed from the vicinity of preparation, cleaning and welding operations. Contact between flammable or explosive materials and the welding flame, arc, sparks or spatter can have catastrophic results. Flame and spill-proof storage cabinets should be used in welding shops to minimise the risk of fire or explosions involving hazardous chemicals and materials. The local area around a welding site must be kept well ventilated to reduce the likelihood of gas, solvent vapours and dust accumulating and leading to an explosion or fire. Prior to welding, cutting or grinding operations, vessels, drums or cans which have been used to store explosive or flammable substances should be thoroughly steam-cleaned and then purged with a non-flammable gas such as nitrogen, or filled with water to prevent a build up of explosive fumes and gas mixtures.

IMPORTANT NOTE; The casings of double insulated

tools are identified with this symbol and do not require a safety connection

to an electrical earth.

Hard materials such as metal plate, if not handled with care, can cause bodily damage and/or damage to workshop equipment. Ensure the workpiece is securely clamped during grinding operations or other preparations. A disk grinder can propel loose items at great velocity for great distances. Remember you also have a responsibility for the safety of the people working around you. Hot particles created when welding, grinding, gouging or cutting are easily propelled or blown through the air. Molten metal will burn through normal street or office clothing. Ensure you wear personal protective equipment and safety clothing while welding.

Oxygen cylinders should never be substituted for an air cylinder. Acetylene is sensitive to the environment in which it is stored and used. Acetylene cylinders must be protected from excess pressure, temperature, static electricity and mechanical shock. Acetylene should always be drawn off at the rate recommended by the manufacturer.

Fumes and Gases used in or generated by welding processes range from nuisance fumes, to explosive and highly toxic. Negative side effects can occur very quickly after exposure. For example, exposure to cadmium fumes can be fatal within hours. Other side effects may not appear until many years after exposure to the toxic fumes. Toxic gases may be used as part of the welding process (e.g. acetylene or carbon-dioxide). Toxic fumes and gases can be generated by the welding process when surface coatings such as epoxy resins, degreasing agents or paint are heated, or when they react with the arc-flash (e.g. ozone, nitrogen oxides, carbon monoxide, phosgene or phosphine).

Asphyxiation can be caused during welding by the inhalation of fumes normally created by the welding process, or by fumes and gases present in the work environment. This can be reduced if the correct precautions are followed.

• Ensure workpieces are cleaned of dirt and contamination before use. • Sufficient natural and/or mechanical ventilation is essential at all times in a welding workspace. • Shielding gases are usually heavier than air. They can build-up in confined spaces and can cause suffocation.

Note: Depletion of oxygen in the welding workspace can cause asphyxiation. Oxygen enrichment dramatically increases the risk of fire.

Dust is typically created by from grinding and dressing operations and should be controlled at the source by regular collection, vacuum cleaning, duct extraction or exhaust ventilation. Dust can be ‘nuisance’ dust such as iron or aluminium oxides, which may be blown into eyes or inhaled. Harmful or toxic dusts can cause respiration illnesses or allergic symptoms. Flammable and explosive dusts can ignite, causing serious or fatal injuries.

• Supplementary training for access and emergency rescue, which requires a trained observer to be stationed outside the confined space for monitoring and rescue purposes • Compliance with Permit-to-Work documents which detail the type of work being done,

the risks and hazards that are present and the precautions that must be taken • Atmospheric testing before, during and after the welding process

to continuously monitor the atmosphere for inert, toxic or explosive gases and fumes which may build up and displace oxygen and contaminate the breathable atmosphere

• Continuous ventilation of the confined space and extraction of fumes, dust and gases created by the welding process

• Additional fire protection, first aid and emergency response.

Confined space welding also increases the risk of workplace incidents and accidents such as;

• Arc-flash due to light reflection in the confined space • Electric shock due to the close proximity of equipment • Heat stress from working in a confined environment.

Dilution ventilation can be created by setting up portable fans and ducting to supply fresh air and blow fumes away from the welding area. This can include large fans pointed in the direction of the welder or welding area, and may also include fresh air ducted in from a remote location. Battery powered, helmet mounted filtered air supply systems are also available.

Exhaust ventilation can be created by setting up fans, ducting and hoods to extract fumes and dust away from the welding area. Exhaust ventilation systems are typically large and form part of the fixed equipment in a welding bay. Smaller portable units can be attached in a position close to the welding handset. Capturing fumes in a localized welding area is difficult, but is required when exposure to toxic dust and fumes is a significant hazard.

Confined space welding includes working with a range of additional hazards. Personnel involved with confined space welding must follow a series of important safety, health and environmental procedures including;

Chemicals and agents for cleaning, pickling and passivating Some metals require aggressive chemical cleaning before welding. Passivation is done to remove iron deposits that have settled on the surface. Pickling is more aggressive than passivation and results in metal removal. Care must be taken when working with hazardous materials as they can cause chemical burns, poisoning asphyxiation and fire. The long term effects of inappropriate chemical handling can include dermatitis and cancer. Additional PPE such as rubber boots and gauntlet gloves, chemical aprons, full-face visors, area ventilation and respirators are required when preparing and working with pickling acids and passivation acids, and other hazardous and toxic chemicals.

Noise: Although welding and cutting processes are not particularly noisy, the preparation of components to be welded can create significantly elevated noise levels. Prolonged exposure to loud noises can cause permanent hearing damage. Long term exposure to noises above 80dB (decibels) can cause hearing deterioration. The damaging effects of loud noise can be prevented by using the correct type of properly fitted ear defenders.

Burns are the most obvious injury caused by poorly managed welding operations

Heat from the welding arc or flame from a torch can reach 1900°C. Care should be taken not to damage items in the close-working environment, such as hoses, cables, clothing metal jewelry and body parts. Welding causes items to become hot, creating a risk of burns and fires from hot metal and welding spatter. Radiation is generated during most types of welding and is emitted as infra-red and ultra-violet light. Exposure of arc-radiation to eyes can lead to temporary and permanent damage.

• Always check and select the correct shade of welding lens. Exposed body parts can become sunburned.

• Always cover up with the correct types of gloves and gauntlets.

SMART TIP!

Fuel, heat and oxygen

are all required to start

and maintain a fire.

Removing one of these

stops a fire dead.

Toxic materials Common toxins associated with welding include ozone, carbon monoxide, nitrogen oxides and fumes from highly toxic metals including cadmium, zinc, beryllium, lead, chromium, nickel, manganese and copper. Fumes, dust and particulates from these metals can cause poisoning and lead to cancer.

Decibels Noise source Time to hearing damage 130 Aircraft takeoff Instant 110 Disk grinder > 1 minute 105 Pedestal grinder 10 minutes 100 Power guillotine 15 minutes 95 Power tools 60 minutes 90 Average factory 120 minutes

81 City street Long term exposure may cause damage. Welding Filter Lens Guideline

Operation Welding Current

Shade Number

Manual metal Arc Welding

20 ~ 80 A 80 ~ 175 A 175 ~ 300 A

9 ~ 10 11 12

MIG Welding 40 ~ 80 A

80 ~ 175 A 175 ~ 300 A

10 11 ~ 12 12 ~ 13

TIG Welding

5 ~ 40 A 40 ~ 100 A 100 ~ 150 A 150 ~ 250 A

9 ~ 10 11 12 13

Plasma Cutting 60 ~ 150 A 150 ~ 250 A 250 ~ 400 A

11 12 13

O/A Gas welding

Heavy Medium

Light

6 ~8 5 ~ 6 4 ~ 5

Torch brazing — 3 ~ 4

Torch soldering — 2

HANDY HINT; Welding screens should be used to protect

people outside the welding area from arc-flash.

Welding workshops and engineering worksites are required to supply and maintain suitable equipment for the purpose of fighting fires. The equipment provided requires specialist training and will be specific to the nature of work carried out on a site. Fire-fighting equipment on site should include;

• Fixed sprinkler and automatic deluge systems • Hose reels, portable fire extinguishers and fire blankets.

HANDY HINT; Arc-flash or arc-eye can cause symptoms that feel like sand being poured into in your eyes!

WELDING SAFETY EQUIPMENT Welding in the fabrication workshop requires the use of good quality personal protective equipment as well as standard welding safety devices;

• Overalls, spats and steel-capped safety boots • Welding helmet, cap and gauntlet gloves • Safety glasses and hearing protection • Dust and fume extraction systems • Fire blanket and fire extinguisher • Leather jacket and apron • Filter mask or respirator • Filtered air supply • Welding curtains • Jigs and fixtures.

• Welding Shields (or helmets) are designed to offer protection to your eyes and head from non-ionising radiation produced during welding processes. Use a shade selection chart to ensure protection. They also provide protection from impact caused by low velocity, low mass flying objects, such as welding spatter. Advanced light-sensitive welding helmets are fitted with a single fixed lens which features automatic shade adjustment from clear to shaded, in approxi-mately 1/25,000 seconds.

• Leather Gloves are used to provide hand protection from abrasion, minor impact injuries and variations in temperature. Available types include riggers gloves for handling sheet metal and heavy-duty long gauntlet types for protection during welding.

• Flameproof overalls are mandatory in most welding environments, and provide some flame protection to arms, legs and body areas as well as protection from dirt, dust and oil contamina-tion, and light abrasion.

• Safety Boots are mandatory in most engineering fabrication environments and usually offer toe protection from crushing or falling objects. Most safety boots have heavy-duty construction, and a choice of non-skid, chemical resistant and/or electrically insulated soles.

• Safety Glasses are mandatory in most engineering fabrication environments to protect the wearer from eye injury and impact caused by low velocity, low mass flying objects. Tinted safety glasses can be used to minimise arc-flash from nearby welding processes.

• Goggles are designed to offer additional eye protection from impact caused by low velocity, low mass flying objects in the fabrication environment, particularly when grinding or abrasive cutting. Goggle lenses are usually constructed from clear, light-weight, heavy-duty plastics and have optional flip-down shaded lenses for use during gas welding or brazing work.

• Hearing protection is required for workplace noise exposure above 85 decibels (dBA) over an eight hour working day.

As a general rule, hearing protection should be used where any discomfort is experienced. • Dust and particle masks are designed and rated to provide protection by filtering fine solids or

liquid particles from inhaled air (e.g. when grinding plate or cleaning welded surfaces). • Hard Hats are designed to prevent head injury due to impact from flying, falling or suspended

objects. Some types of hard hat can be modified by adding face-shields, visors, chin-straps and hearing protection.

To remain safe during welding processes, the correct personal protective equipment (PPE) must be worn. Some items of PPE are mandatory, while other types need to be used to ensure protection during specific activities.

Personal Protective Equipment

Setting up and Checking for Potential Worksite Hazards

Welding plant, equipment and materials must be checked and prepared before starting welding. • Regulator & Gauges - leaks, broken faces, corrosion and correct type for gas usage • Connections - suitability for purpose, cracks, contamination and tightness • Hoses - splits, perishing, kinks, burns, correct type and colour-coding • Torches - leaks, dents, correct gas hoses connected to the valves • Handsets - cracks, insulation, mechanical damage • Cables - as appropriate to the process • Cable insulation - amperage rating, frays, nicks, cuts and burns • Parent material and filler metal - Toxic or flammable contaminants.

IMPORTANT NOTE; The condition and suitability of gas

regulators, flash-back arrestors, hoses and torches must be checked.

Cylinders should be secured and checked for damage or deterioration, as well as the

correct gas type and pressure.

Specialised welding PPE, equipment and accessories must be checked carefully prior to use for the correct set-up and to ensure there is no equipment damage or deterioration. Welding area screens must be set up to protect other workers in the workshop. The main power switch for electric welding equipment must be isolated and locked-out when not in use.

HANDY HINT; Note the locations of the nearest fire

extinguishers and first aid kits, and the names of the workshop first aiders.

Welding operations require working with hazardous equipment and materials such as; • Compressed and explosive gases • Toxic fumes, smoke and dust • Electrical voltage and current.

Care must be taken to avoid electrocution, arc-flash, explosions, burns and respiratory damage.

Worksite hazards may include; • Confined space • Presence of flammable and/or explosive materials or containers • Defective equipment • Compressed gases • Toxic substances • Hot metal • Sources of fumes such as paint, oil and other contaminants • Hard and/or hot particles.

Hot Work Permit

• Confined Space

• Flammable & Explosive Materials

• Toxic materials & Chemicals

• Defective Equipment

• Compressed Gas & Electricity

• Machine & Equipment Noise

• Heavy Lifting & Height Work

• Fume & Dust Extraction

• Asphyxiation & Ventilation

• Hard and/or Hot Metal & Particles

• Specialized PPE & HSE Measures

Correct usage of gas equipment Know Don’t

The correct assembly procedures for attaching equipment to gas cylinders.

Don’t ‘crack’ a fuel gas cylinder valve near a source of ignition.

The correct procedures and materials Don’t use the oxygen to ‘sweeten’ the atmosphere.

The correct procedures for lighting gas torches and shutting them off.

Don’t use the oxygen cylinder to dust off clothing.

The signs of a flash-back, what to do in response, how to check if damage has occurred to equipment and the actions necessary if it has occurred.

Don’t forget to close the valve on a regulator and release any trapped gas from it before the regulator is removed.

HANDY HINT; A simple test for leaks from

gas or air connections; Brush soapy water on the connection

and inspect for bubbles.

IMPORTANT NOTE; Oxyacetylene welding equipment must be handled with care;. Never use grease, oil or Teflon tape on connectors and fittings

Never use homemade copper tube joiners to repair hoses

Neutral Flame

Oxidising Flame

Carburising Flame

To create a good weld, the different variables need to be balanced correctly. The key variables are;

• Tip size (see tip selection chart) • Gas pressures • Gas mixture ratio • Type and size of filler wire used • Frequency of feeding of the filler wire • Rate of travel of the torch moving across the material • Angles of torch and filler wire.

When preparing to weld, adjust the gas welding torch as below;

Step 1. Purge the torch by opening the acetylene knob a quarter turn for 3 seconds and then turn off.

Step 2. Purge the torch by opening the oxygen knob a quarter turn for 3 seconds and then turn off.

Step 3. Turn on the acetylene knob a quarter turn and ignite the gas at the tip.

Step 4. Quickly turn up the acetylene until no smoke is made by the flame.

Step 5. Open the oxygen knob to adjust the color of the flame from bright yellow to blue. The amount of oxygen must be varied until the light blue inner cone (about 10 mm long) merges with the main flame, without any grey outer cone between them.

This is a neutral O/A flame. See diagram at right.

PROBLEM SOLUTION

Difficulty in forming a weld pool or slow rate of travel.

Tip too small. Torch angle too shallow. Filler wire too large.

Weld pool too large or difficult to control.

Tip too large. Moving torch too slow.

Lumpy weld beads. Filler wire too large.

Melted filler wire rolls away from weld pool.

Workpiece on too steep an angle. Wrong type of filler wire.

Oxy-Acetylene Welding Process

Thickness of mild steel

Tip size

Filler wire diameter

0.9 mm 1 1.2

1.2 mm 2 1.2

2.0 mm 3 1.6

2.6 mm 5 2.4

3.2 mm 7 3.0

HANDY HINT; Most faults which occur during oxy-acetylene welding, can be rectified by using a neutral oxygen-acetylene flame and adjusting the motion,

and the rate of travel or the angle of the torch and filler wire.

HANDY HINT; A flint-lighter is the safest and most efficient

way to light an oxy-acetylene torch.

Thoroughly cleaning the surfaces to be welded dramatically improves both the ease of welding, as well as the quality of the finished weld.

While welding;

Step 1. Hold the handset at approximately 60° and 5-12 mm above the surfaces to be welded.

Step 2. After about 5 seconds a weld pool should form.

Step 3. Add a little filler wire to the weld pool.

Step 4. After the weld pool has recovered, move the torch forward, away from the formed weld bead.

Step 5. Repeat until the complete joint is formed.

To create a good quality weld, different variables need to be balanced. These are;

• Output current and voltage • Welding rod size, type and condition • Angle and rate of the rod traveling across the material.

Step 1. Strike an arc by touching the electrode to the work, immediately lift the electrode so it doesn’t freeze to the workpiece. Step 2. After striking the arc, form an angle of about 70° between the electrode and the workpiece, leaning in the direction of travel. Step 3. Slowly move the electrode away from the forming weld bead, in the direction the weld needs to be formed. As the electrode is depleted, move it closer to the workpiece, keeping the arc length consistent. Step 4. Fill the crater at the end of the bead by raising the electrode tip

slightly and moving back over the crater area. Pause momentarily before withdrawing the electrode to break the arc.

Test and fine-tune the settings. You can check how well the equipment has been set up by welding a couple of pieces of scrap of about the same size and thickness as the workpiece. If the welding rod is too large or the current too high, then the weld pool can blow right through the metal or be uncontrollable. If the rod is too small or the amperage too low, the current through the rod may not create a sufficiently stable arc. A number of faults can occur during arc welding, all of which can be rectified by practice and adjusting the controls of the arc welding set.

PROBLEM SOLUTION

Can’t strike arc.

Welder not turned on. Return earth lead not connected. Wrong end of electrode in holder. Current or voltage too low for rod diameter or type. Flux coating chipped off electrode. Wrong type of rod for metal. Welding rods are damp.

High thin bead. Current or voltage too low.

Wide, low or rough bead. Current or voltage too high.

Manual Metal Arc Welding Process

HANDY HINT; Slow down, don't move the rod too fast!

By maintaining the correct arc length with a steady hand and constant feed rate, the pool of molten weld will be a constant size and shape.

Plate Thickness

Recommended Max Electrode Diameter

Current Range

1.2 ~ 2.0 mm 2.5 mm 60 ~ 95 Amps

2.0 ~ 5.0 mm 3.2 mm 110 ~ 130 Amps

5.0 ~ 8.0 mm 4.0 mm 140 ~ 165 Amps ≥ 8.0 mm 5.0 mm 170 ~ 260 Amps

70°

Thoroughly cleaning the surfaces to be welded, dramatically improves both the ease of welding, as well as the quality of the finished weld. Warm storage of rods in an oven helps to keep the rods dry, providing consistent rod characteristics and better weld quality. When preparing to weld, choose an appropriate welding rod for the material being welded. Adjust the settings as suggested by the manufacturer of the rods (this should be on the box the rods came in).

Method for striking an arc .

MIG Welding Process

To create a good quality weld the different controls need to be balanced. The variables are;

• Welding current and voltage • Wire quality and cleanliness • Shielding gas supply • Wire feed rate • Rate of travel of the torch across the material.

Thoroughly cleaning the surfaces to be welded dramatically improves both ease of welding as well as the quality of the finished weld.

Test and fine-tune the settings by welding a piece of scrap of about the same size and thickness as the workpiece. If the wire feed is too slow, the wire can fuse to the gas nozzle and tip, which will have to be cleared. A number of faults can occur during MIG welding, all of which can be rectified by adjusting controls of the MIG set or the travel rate and angle of the handset.

Step 1. Initial settings; wire feed rate - set for the thickness of material being welded. power setting - adjust the power settings to suit the thickness and type of materials being welded. Step 2. Hold the handset at approximately 80° with a gap of roughly 20 mm from the surfaces being welded. Step 3. Press the trigger on the handset to start the process. Step 4. Move the handset slowly over the pool of molten metal, travelling away from the new weld bead. Step 5. Listen to the noise the welding makes as you operate the handset. If it sounds like sizzling bacon, you are close to the correct feed rates and power settings.

Weld has holes all over it (porosity).

Not enough shielding gas. Windy conditions. Empty gas cylinder. Oil or dirt on the surface.

High bead. (Handset pushed back by wire).

Wire feed rate too high or Voltage too low.

Flat rough bead.

Wire feed rate too low, Voltage too high.

Weld pool rolls forward.

Moving handset too slow.

No wire from nozzle.

Empty wire spool. Wire rolls too tight. Fused tip.

PROBLEM SOLUTION

Steel Thickness

Wire Feed Rate (meters per minute)

0.6 mm wire 0.8 mm wire

0.8 mm 2.5 1.6

1.0 mm 3 1.9

1.2 mm 3.6 2.2

1.5 mm 4.3 2.6 2.0 mm 5.6 3.5 3.0 mm 7.9 4.9

HANDY HINT; Flux-core wire is also available for

use on MIG type welding equipment. The flux-core equipment requires a specialized setup and different operator techniques but does not require the use of shielding gas.

Electrode Diameter

Amperage Range for ≥99.5% Pure Tungsten Electrodes

1.6 mm 60 ~ 90 Amps

2.4 mm 125 ~ 160 Amps

3.2 mm 190 ~ 240

4.8 mm 260 ~ 320

HANDY HINT; The current carrying capacity of high

purity tungsten electrodes is diminished, but they maintain a clean, ball-end which provides good arc stability.

TIG Welding Process

HANDY HINT; Hold the TIG handset like a pen.

Practice sliding your hand smoothly along the workpiece.

Set the welder to the appropriate voltage and amperage settings required for the type and thickness of the material. To make a weld on cleaned mild steel (1.8 mm thick) or stainless steel (1.4 mm thick), set the welder to about 80 Amps.

Step 1. Hold the torch at about 80° from horizontal, facing in the direction of travel. Keep the tip of the electrode at about 2.5 mm from the surface of the workpiece. Step 2. Hold the filler rod touching the surface at 15° from horizontal. Keep the rod at about 10 mm from the electrode tip. Step 3. Flick down the welding mask. Step 4. Press the arc switch to initiate the arc. Step 5. A weld pool will form in just a few seconds. Step 6. When the weld pool is at the desired size, start feeding the filler rod into the pool. Step 7. Build up the weld bead size by adding the filler rod. Step 8. When the desired bead size has been achieved, withdraw the filler rod but do not take it out of the gas shield. Step 9. Move forward along the joint and allow the pool to grow. Repeat from step 5 above. Step 10. At the end of the run of weld bead, build up the pool crater with filler rod. This will prevent weakness or cracking of the workpiece.

Difficult to keep up with filler rod. Need to move handset too quickly.

Current set too high, turn down.

Lack of penetration. Lack of fusion.

Current too low or arc too long. Turn current up or hold tip closer.

Inconsistent, weak or wandering arc.

Not holding the handset correctly, use the ‘pen’ grip.

PROBLEM SOLUTION To create a good quality weld, the different variables need to be balanced correctly. They are;

• Power settings • Gas pressures • Type and size of filler wire used • Frequency of feeding of the filler wire • Rate of travel of the torch across the material • Dirty joint faces or clamps • Angles of torch and filler wire.

Test and fine-tune the settings by welding a couple of test pieces using scrap of about the same size and thickness as the workpiece.

Step 4. Clean the two plates around the joint area to remove moisture, oil, grease, oxides or any protective coatings, with the exception of weldable primers. Note: The cleaned zone should be approximately 30 mm wide along the edges that will be joined. Clean the area with an angle grinder or wire brush and file. Use a solvent to clean the weld area if oil or organic contaminants have penetrated the metal surface.

Step 1. Ensure your work area is safe to work in and check for hazards.

Step 2. Use all the required safety equipment (especially eye protection and gloves) for the type of welding process being performed.

Step 3. Cut two plates, both approximately 150 mm in length from 75 x 3.2 mm thick flat bar.

Butt Welding 3.2 mm Thick Mild Steel Flat Section

Step 10. Inspect the joint for compliance to the required quality standard. If the joint is not to the required standard, you can also use the visual inspection sheet to diagnose the problem before the exercise is attempted again.

HANDY HINT; Tack welding is achieved by holding the two plates in place

while a number of short welds are made. On 3mm plate these welds should be about 75mm apart or at each end.

Step 6. Position the cut plates as shown at right. Align the two plates with no gaps between them. Note: Clamp the cut plates in position using vice-grips, g-clamps,

long-backs or hold in place by pre-tacking the plates at each end.

Step 7. To ensure a constant travel rate and distance can be maintained during the weld, find a comfortable position and practice doing the weld without the handset turned on.

Step 8. Weld along the centre of the joint using a minimal weave pattern. Note: Try to create a weld with consistent width and height, without it being overly convex .

Step 9. Clean the finished joint with a wire brush. This is especially important if you have arc welded the workpieces,

as remains of the slag may still be stuck to the surface of the weld.

Step 5. Place the plates over spacers on a suitable heat resistant work surface. The spacers ensure that the weld will not become contaminated with inclusions from the work surface.

Handy hint!

Before you start welding,

use some scrap pieces of

the same thickness material

to set up the equipment.

Step 8. Remove the clamps (if used) and run another weld on the other side of the joint, with approximately the same dimensions as the first weld.

Fillet Welding 3.2 mm thick Mild Steel Flat Section

Step 10. Inspect the joint for compliance to the required quality standard. If the joint is not to the required standard, you can also use the visual inspection sheet to diagnose the problem before the exercise is attempted again.

Step 9. Clean the finished joint with a wire brush. This is especially important if you have arc welded the workpieces,

as remains of the slag may still be stuck to the surface of the weld.

Step 7. Weld along the centre of the joint using a minimal weave pattern. Try to create a weld with a leg length of approximately 2x the plate thickness and a weld throat thickness of approximately 1x the plate thickness.

Step 6. Clamp the two plates using corner clamps or magnetic angle clamps as shown at right.

Note: The clamped plates should look similar to the diagram at right, with one of the plates aligned along the centreline of the other. Check the angle between the clamped

plates with an engineers square.

Step 5. Place the plates over spacers on a suitable heat resistant work surface. The spacers ensure that the weld will not become contaminated with inclusions

from the work surface.

Step 4. Clean the two plates around the joint area to remove moisture, oil, grease, oxides or any protective coatings, with the exception of weldable primers.

Step 1. Ensure your work-area is safe to work in and check for hazards.

Step 2. Use all the required safety equipment (especially eye protection and gloves) for the type of welding process being performed.

Step 3. Cut two plates, both approximately 150 mm in length from 75 x 3.2 mm thick flat bar.

Note: The cleaned zone should be approximately 30 mm wide along the edges that will be joined. Clean the area with an angle grinder or wire brush and file. Use a solvent to clean the weld area if oil or organic contaminants have penetrated the metal surface.

Welding Quality Assurance

Welding inspection and test ensures the weld is compliant to specification. This can involve both non-destructive and destructive testing and inspection of samples. The cosmetic condition and appearance of a weld often indicates internal defects and anomalies. There are many forms of non-destructive inspection and test, including;

• Visual inspection for surface defects • Liquid dye penetrant inspection • X-ray and ultrasound • AC field and magnetic measurement.

Visual inspection considers the appearance of the weld to identify actual and potential faults. Physical measurements can also be taken and compared to the sizes specified for the job in the WPS.

Welding procedures and instructions are designed to ensure the resulting weld is strong enough to do the job. If incorrect processes or materials (i.e. parent metal, welding gas or filler rods) are used, the quality and strength of the finished weld may be compromised.

Welder skill is key to producing good quality welds. Highly skilled welders are able to understand and follow complex technical instructions, and can repeatedly produce top-quality, code-compliant welds. Suitable plant and equipment is essential to the quality of the weld. If you choose a machine that cannot produce the correct current or voltage or a machine that is a different type to the machine requested on the WPS, the resulting weld may be defective. Filler materials need to be carefully selected and must be compatible to the parent metals being joined. Condition and compatibility of the parent metals must be accurately identified and assessed. The material must be in suitable condition. Dissimilar parent metals can be joined if the correct process and filler materials are used i.e. aluminium can be welded to stainless steel using an electron-beam welder and a silver transition metal.

How to ensure welds are sound and without obvious defects? • Select the correct materials for the job. • Ensure the work area and materials are clean, free of defects and prepared correctly. • Securely clamp the workpieces in the correct orientation, with the required gap or angles. • Set up the welding equipment correctly and install the correct size electrode, wire or tip. • Use the correct gas types and suitable filler rod or wire. • Perform the weld in the approved sequence, using the correct techniques. • Clean the finished weld, if required.

Quality Assurance (QA) is required to ensure a welded component can be repeatedly manufactured to the required specifications to meet industry standards and customer requirements. To achieve quality assured welding, engineering workshops use three key tools:

• Welding specifications and procedures • Welder qualification • Welding inspection and test.

Welder qualifications exist to assure that a welder is capable of performing the required work. This requires the welder to complete a recognized training program, work for a certain amount of time under the supervision of a qualified welder and then sit practical exams to show competency. There are three critical parts in the process of gaining a welder qualification;

• Welding Procedure Specification (WPS) outlines all of the technical requirements of the weld • Welding Procedure Qualification Record (WPQR) qualifies the welding procedure specification • Welder Performance Qualification (WPQ) provides a record of the capabilities of the person doing the welding.

When a welder has achieved these qualifications, they are competent at welding to recognised ‘code’ such as ASME-IX, MIL-STD-248, ASNZ-4711 or BS-4870.

Identification of Defective Welds by Visual Inspection:

Undercut appears as a groove in the parent metal. Undercut reduces the thickness of the metal being joined and therefore it’s strength. Undercut introduces a stress concentration site and the potential for fatigue cracking when the welded component is in service. Causes of undercut include excessive amperage, arc length too long, travel-rate too fast or incorrect electrode angle.

CORRECT SIZE WELD

Undersized welds do not have the required throat thickness or width across the face of the weld. This fault produces a weld of inadequate strength and can cause complete failure of the joint. Causes of undersize welds include; amperage too low, tip size too small, incorrect filler rod or wire size.

UNDERSIZE WELD

Non-metallic inclusions are often seen as dark, non-metallic spots or particles embedded in the weld. Inclusions reduce the cross-sectional area of the weld and can induce cracking or cause weld failure. Non-metallic inclusions can occur due to surface contamination (from paint, grease or rust) or when several runs are made along the welded joint. Non-metallic inclusions can also occur when the slag covering a completed weld is not completely removed.

Porosity occurs when gases are trapped in the solidifying weld. Porosity may occur due to damp consumables, damp metal workpieces or from dirt, particularly oil or grease on the parent metal in the vicinity of the weld. Porosity can be avoided by ensuring all consumables are stored in clean, dust-free, warm and dry conditions and the workpiece is carefully cleaned and degreased prior to welding.

Cracks and Cracking can include;

• Longitudinal cracks that can be seen running the length of the weld. • Transverse cracks that can be seen running across the width of the weld. • Crater cracks that can be seen at the end of a weld where the arc has been broken.

Cracks normally occur due to incorrect welding procedure or the use of an incorrect type or poorly maintained welding electrode, filler rod or wire. Cracking often occurs due to a com-bination of mechanical strain which accompanies thermal shrinkage as the weld cools.

Identification of Defective Welds by Visual Inspection:(cont)

Blow through appears as holes along the length of the weld, often with large blobs of weld at one end. Causes include amperage too high, incorrect thickness of parent metals or incorrect filler rod or wire size.

Incomplete penetration occurs when fusion of the filler metal does not continue deep enough into the parent metal. The welded joint is weakened and can fail under stress. Causes include oversize electrodes, current set too low or insufficient root gap.

Incomplete fusion is caused by a lack of fusion between the molten pool of filler material and the parent metal. This can be viewed from the end of the weld or from underneath the joined plates. Causes of incomplete fusion include using small electrodes on thick plate or cold plate, current set too low, incorrect electrode angle, travel rate too high or contaminated parent metal surfaces.

Excessive Concavity creates an undersize throat and can cause the weld to crack and fail. If a significant degree of concavity is noted when inspecting a weld, the weld throat should be measured and compared to the specification. The weld should also be inspected for other defects. Causes of excess concavity include; amperage too low, gas tip too small or incorrect filler/wire size.

Edge-melt appears as a scallop shaped pattern at the end of the weld. The edge of the plate is melted due to the edge material being less able to absorb the heat of the arc. Causes of edge-melt include incorrect technique at the end of a weld, amperage too high or wrong size plate being used.

Overlap appears as an imperfection along the toe of the weld and is caused by metal flowing onto, but not fusing with, the surface of the parent metal. This has a similar effect to ‘undercut’ and creates stress in the workpiece. Causes of overlap include incorrect welding angle, too low an amperage, too large an electrode or an incorrect rate of travel.

Joint misalignment occurs when the plates being welded become misaligned. The joint may fail under load due to insufficient weld thickness or stress build up in the joint. Causes of joint misalignment include; incorrect assembly, inadequate clamping or tack welding, or incorrect welding sequence.