welding hazards.pdf

7/28/2019 welding hazards.pdf

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Welding Hazards


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TABLE OF CONTENTS

INTRODUCTION...........................................................................................................................5

WHATS IN THIS MODULE?.......................................................................................................5

WELDING PROCESSES...............................................................................................................6

ELECTRIC ARC WELDING AND CUTTING ...........................................................................6

Shielded Metal Arc Welding ..................................................................................................6

Gas Tungsten Arc Welding ....................................................................................................6

Submerged Arc Welding........................................................................................................7

Flux-Cored Arc Welding........................................................................................................7

Gas Metal Arc Welding .........................................................................................................7

Inert Gas Welding..................................................................................................................7Plasma Arc Welding ..............................................................................................................7

Arc Cutting............................................................................................................................8

GAS WELDING AND CUTTING ..............................................................................................8

Brazing..................................................................................................................................8

Soldering ...............................................................................................................................8

Gas Cutting ...........................................................................................................................8

RESISTANCE WELDING..........................................................................................................8

SPOT WELDING ......................................................................................................................9

ELECTRON, LASER AND THERMIC PROCESSES................................................................9

Laser Beam Welding and Cutting...........................................................................................9

Electron Beam Welding .........................................................................................................9

Thermic Welding ...................................................................................................................9

UNDERWATER WELDING AND CUTTING ..........................................................................10

One Atmosphere Welding....................................................................................................10

Habitat Welding...................................................................................................................10

Dry Chamber Welding .........................................................................................................10

Dry Spot Welding................................................................................................................10Wet Welding........................................................................................................................10

Lance Oxygen Cutting .........................................................................................................10

ROBOTIC WELDING .............................................................................................................11


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WELDING HAZARDS.................................................................................................................11

AIRBORNE SUBSTANCES.....................................................................................................11

By-product Gases................................................................................................................

12

Ozone..............................................................................................................................12

Nitrogen Oxides...............................................................................................................12

Carbon Monoxide ............................................................................................................12

Carbon Dioxide................................................................................................................13

Hydrogen Chloride ..........................................................................................................13

Phosgene .........................................................................................................................13

Asphyxiants .........................................................................................................................14

Fumes..................................................................................................................................14

Dusts ...................................................................................................................................17

ELECTRICAL HAZARDS.......................................................................................................17

MATERIAL HANDLING HAZARDS.......................................................................................18

RADIATION............................................................................................................................18

HEAT STRESS........................................................................................................................19

ASSESSMENT..............................................................................................................................19

Fume Measurement.................................................................................................................21

Gas Measurement....................................................................................................................21

LEGISLATION SPECIFIC TO WELDING HAZARDS............................................................22

Mining Regulations (Specific to Welding) ............................................................................22

Industrial Regulation............................................................................................................23

Breathing Equipment ...........................................................................................................23

CONTROL....................................................................................................................................24

CONTROL AT THE SOURCE.................................................................................................24

CONTROL ALONG THE PATH..............................................................................................24

Air Quality...........................................................................................................................24

General Ventilation ..........................................................................................................25

Local Ventilation .............................................................................................................25

Air Cleaners.....................................................................................................................26


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Radiation .........................................................................................................................26

Electrical Systems................................................................................................................26

Compressed Gas..................................................................................................................27

CONTROL AT THE WORKER................................................................................................27

Respiratory Protection .........................................................................................................28

Eye Protection.....................................................................................................................28

Protective Clothing..............................................................................................................28

Medical Monitoring .............................................................................................................29

Safe Work Practices ............................................................................................................29

Posture............................................................................................................................30

Manual Material Handling..............................................................................................30

WORKPLACE STRATEGIES ....................................................................................................31

REVIEW .......................................................................................................................................32

REFERENCES..............................................................................................................................32


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INTRODUCTION

Welding is a technique for joining metals through the application of large amounts of heat, usually sufficientto melt the materials being welded. There are a variety of health and safety hazards associated with this

process. Safety hazards include the potential for fire or explosion and injuries from radiation, electrical

shock, or material handling. Health hazards include exposure to fumes released from the work or from

materials used in the process.

Welding hazards can cause both acute and chronic health effects. These include toxic effects from

chemical agents and damage to the respiratory system as well as injury from physical agents such as noise,

heat and radiation. Controlling these hazards requires that they first be recognized and assessed. To carry

out these functions effectively, joint health and safety committee members need a basic understanding of

welding processes and the nature of the welding environment.

WHATS IN THI S MODULE?

This module is intended to provide certified members with an understanding of the hazards associated

with welding and the means for assessing and controlling those hazards. It stresses the need for

systematic inspections of the workplace by members of the Joint Health and Safety Committee and the

development of a welding and cutting control program. The module is divided into six main sections:

types of welding

welding hazards

assessment

legislation review

control

workplace strategies

The module concludes with a brief review and a list of references for further reading.


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WELDING PROCESSES

The American Welding Association recognizes more than 100 different types of welding, cutting andrelated processes. For simplicity, they will be discussed here simply as welding processes. The welding

methods most commonly used in Ontario workplaces are discussed separately in the following sections.

All welding process require that metals be melted. In most types of welding, the material to be jointed

(hereafter the work) becomes molten so that the pieces fuse together. In brazing and soldering, only the

filler metal is melted and it bonds to the pieces to be joined, creating the weld. Either way, large amounts of

heat are created, leading to the vapourization of metal to form fumes and gases.

The heat sources used for welding include gas flames and electrical arcs as well as laser and

electromagnetic systems.

ELECTRIC ARC WELDING AND CUTTING

In electric arc welding, heat is created when current flows between an electrode held by the welder and the

work, which is connected to the opposite side of the electrical source. In many types of arc welding a

shieldis provided around the arc to prevent oxidization of the molten metal. This shield can come from

substances contained in the electrode or from gases supplied from an external torch. In some types of arc

welding, the electrode is coated with a flux, which among other things, cleans the joint and helps the

molten metals to fuse. The electrode, orrod, may be consumed in the process, in which case it may be a

source offillermetal. Many types of arc welding use non-consumable electrodes.

Shielded Metal Arc Welding

In shielded metal arc welding, electrical current flows between a flux-coated electrode

and the work. A shield is provided by the breakdown of the flux. Filler metal is

obtained from the metal core of the electrode, and/or metallic particles in the flux. The

arc creates intense heat and ultra violet radiation. Metal fumes are released from the

base metal, the filler metal and the flux.

Gas Tungsten Arc Welding

In gas tungsten arc welding, the metal is heated by an electrical arc flowing between a

tungsten electrode and the work. The electrode is not consumed and does not


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contribute fumes. A shield is provided by a gas such as helium, argon or nitrogen. This

process is used for welding stainless steel, copper, copper-nickel alloys, bronze, brass,

titanium, titanium alloys and zirconium.

Submerged Arc Welding

Submerged arc welding creates a weld by heating the metal with an arc established

between a base metal electrode and the work. A shield is provided by a granular flux

material. It is calledsubmergedarc welding because the arc is not visible. Metal fumes

are produced in lower quantities than other welding processes, and sparks and splatter

are eliminated.

Flux-Cored Arc Welding

Flux cored arc welding uses an arc between a continuous consumable electrode and

the work. A shield is provided by flux contained in a core inside the electrode.

Gas Metal Arc Welding

Gas metal arc welding is a process in which the weld is created by heating the metal

with an arc between a consumable electrode and the work. Shielding is provided by a

gas.

Inert Gas Welding

Inert gas welding heats the metal with an arc established between a consumable

electrode and the base metal. Shielding is provided by an inert gas.

Plasma Arc Welding

Plasma arc welding involves the use of gas from a torch as well as an electrical arc. It

may use either a transferredornon-transferredarc. A transferred arc joins metals byheating them with an arc between an electrode and the work, while gas is supplied

from a torch. A nontransferred arc is created between the electrode and the nozzle of

the torch. Shielding is from hot gas flowing from the torch, which may be

supplemented by additional shielding gases..


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Arc Cutting

Air-carbon arc cutting employs an electrode to strike an electrical arc at the work. Astream of compressed air from the torch oxidizes the metal and projects it away from

the work, thereby cutting the metal. Other types of arc cutting use a jet of oxygen.

GAS WELDING AND CUTTING

Gas welding typically uses an oxy-acetylene gas flame as a source of heat. Some types of gas welding,

such as soldering, use propane or other fuel gasses.

L. [Ed note - arent there other types of gas welding where the metal parts to be

joined are melted? If so, these should be added]

Brazing

Brazing applies heat to the metal, usually from an oxy-acetylene gas flame. The metal

does not reach its melting point. Instead, filler material and flux from a welding rod

melt to form the weld.

Soldering

Soldering, like brazing, is accomplished without melting the metal parts that will be

joined. The temperatures needed are lower than for brazing. Toxic fumes are

generated by the solder, or filler metal, but not by the work pieces themselves. Fluxes

and other cleaning agents used to ensure a good joint may also emit fumes.

Gas Cutting

Cutting creates a molten pool of metal using heat from a gas torch. A jet of oxygen is

injected into pool to accelerate the oxidation of the material.

RESISTANCE WELDING


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Resistance welding is accomplished by passing a very high current through two pieces of metal causing

melting at the interface. High magnetic fields may be created in the process causing hazards for workers

wearing metal objects or pacemakers.

SPOT WELDING

A spot weld is made on overlapping metal surfaces by applying heat and pressure at a particular spot on the

work. Electrical current typically provides the heat source.

ELECTRON, LASER AND THERMIC PROCESSES

In recent years, new technologies have advanced the use of more sophisticated welding and cutting

systems based on laser beams, electron beams or liquid metal heat sources. These are used mainly for

specialized applications.

Laser Beam Welding and Cutting

Laser beam welding joins metals using heat from a concentrated beam of coherent

light. Laser beam cutting works with or without the application of jets of gas to

augment the removal of metal.

Electron Beam Welding

In electron beam welding, metals are joined by heat from a concentrated beam of

electrons, travelling at high velocity.

Thermic Welding

Thermic, also known as thermite welding, joins metals by heating them with

superheated liquid metal. This is created by a chemical reaction between a metal oxide

and aluminum, with or without the application of pressure.


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UNDERWATER WELDING AND CUTTING

Underwater welding operations require the use of a variety of specialized techniques. Most of them workby enclosing either the arc or the entire process in a dry chamber. One process allows welding to be done in

water.

One Atmosphere Welding

One atmosphere welding and cutting is performed underwater in a pressure vessel

maintained at approximately one atmosphere, regardless of depth.

Habitat Welding

Habitat welding is done in a pressurized underwater chamber big enough to

accommodate both the welder and the work. Diving gear is not required.

Dry Chamber Welding

Dry chamber welding uses a dry chamber fitted over the joint. The chamber may be of

any size, but does not enclose the welder, and diving gear is required.

Dry Spot Welding

Dry spot welding encloses only the arc is in a dry environment. Shielding gases are

maintained at the arc by a mechanical barrier.

Wet Welding

Wet welding and cutting are accomplished at ambient pressure with the welder diver in

the water and with no physical barrier around the arc.

Lance Oxygen Cutting

Lance oxygen cutting is a form of cutting is used on concrete and cast iron. It can also

be used in underwater operations. This type of cutting produces high fume


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concentrations.

ROBOTIC WELDING

Robotic welding allows the welder to work at a safe distance from hazardous processes by using a variety

of remote-controlled devices. Because of their automated operation, robots can create their own hazards.

WELDING HAZARDS

The health effects of welding hazards are caused by both chemical and physical agents. Chemical agents are

found in the gases that are used for fuel or shielding and also in the fumes created when metal vapourizes.

Physical agents involved in welding include heat, noise, electricity and radiation.

AIRBORNE SUBSTANCES

Airborne hazards from welding include fumes, gases and dusts. The amount and type of substance

produced depends on the type of welding involved, the metals to be welded, the filler and flux materials,

and the shielding gas, if one is used.

Gases are used in welding for two purposes: energy sources and shielding. These gases are not generallyconsidered a major source of toxic contaminants, although some of them may be asphyxiants or may pose

fire and explosion hazards.

Toxic substances mostly come from gases and fumes that are produced as by-products of the welding

process. Gases and fumes can be created from metal parts, or from welding materials as well as paint,

coatings, cleaners and rust inhibitors that have been applied to the metal prior to welding.

Dusts are created by cleaning, grinding and chipping operations associated with welding.


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PRINCIPAL GASES ASSOCIATED WITH WELDING

Energy Sources Shielding

Gases

By-product Gases

oxygen Argon ozoneacetylene Helium nitrogen oxides

natural gas carbon dioxide carbon monoxide

hydrogen nitrogen carbon dioxide

propane hydrogen chloride

butane phosgene

By-product Gases

Ozone

Ozone is created by an interaction between ultraviolet light and

oxygen. It may be a problem when gas metal arc welding is

conducted in enclosed areas with inadequate ventilation. Excessive

ozone levels can produce headaches, chest pains and shortage of

breath. In high concentrations ozone can cause pulmonary edema

(fluid in the lungs) which can be fatal. A characteristic odour will

usually warn welders of the presence of ozone but prolonged

exposure can interfere with the sense of smell.

Nitrogen Oxides

Nitrogen dioxide and other oxides of nitrogen are formed in a

welding arc by ultraviolet light. They can irritate the eyes and

mucous membranes. High exposures can cause coughing and chest

pains. Pulmonary edema can occur within 24 hours.

Carbon Monoxide


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Carbon monoxide is created from carbon dioxide in certain welding

processes. It is a product of incomplete combustion. It can also be

produced from epoxy resin coatings on the work. Excessive

concentrations can often be detected near the arc. Concentrationlevels decrease quickly with the distance from the arc. Carbon

monoxide attacks the nervous system and affects the heart, blood,

lungs and kidneys. Exposure to high concentrations can be fatal.

Carbon Dioxide

Carbon dioxide is a colourless, odourless gas that is not usually

considered toxic. It is present in normal air at a concentration of

about 300 parts per million (ppm) The air in the lungs containsabout 55,000 ppm. Health effects include an increased heart rate.

Exposure to high concentrations, can cause coma and convulsion

within one minute of exposure. Carbon dioxide is heavier than air,

and may collect in pockets in confined spaces, where exposure can

be fatal.

Hydrogen Chloride

Hydrogen chloride is created when paints, dyes or coatings

containing chlorinated organic chemicals are vapourized by welding

heat. It is a strong irritant to the eyes, mucous membranes, and

skin. It can have delayed effects on the upper respiratory tract

causing cough, burning of the throat, and a choking sensation.

Excess fluid can collect in the lungs, causing pulmonary edema.

Phosgene


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Phosgene is produced by heating metals that have been cleaned or

treated with rust inhibitors with substances containing chlorinated

hydrocarbons. Inhalation of high concentrations of phosgene gas

can produce pulmonary edema, frequently after a delay of up to 72hours. Death may result from respiratory or cardiac arrest.

Phosgene also irritates the skin and the eyes.

Asphyxiants

Many gasses commonly used for welding fuel and shielding aresimple asphyxiants,

which means that they displace oxygen from the air. Normal air is made up of 21

percent oxygen and 78 percent nitrogen. When oxygen levels drop below 18 percent

dizziness and unconsciousness may result.

Shielding gases such as carbon dioxide, helium, and argon enter the air after

performing their function as a shielding around the arc. Other gases may enter the air

from leaks. As gases build up they displace the air. Argon is heavier than air and

helium is lighter than air. Thus, they can readily collect in pockets.

Chemical asphyxiants are substances that interfere with the bodys use of oxygen.

They are toxic in concentrations far below the level needed to displace the oxygen in

the air.

Chemical asphyxiants may be produced when cutting surfaces coated with paint, rust,

plaster and other substances. Examples of chemical asphyxiants encountered in

welding include: hydrogen cyanide, hydrogen sulphide, and carbon monoxide, all of

which are highly toxic. They can cause inflammation of the lungs, pulmonary edema,

emphysema and bronchitis as well as asphyxiation.

Fumes

Fumes consist of tiny metal particles suspended in the air. Metals are vapourized by

the high temperatures used in welding When circulated in the air, the vapour forms ametal oxide. This metal oxide quickly cools and condenses into particles that make up

metal fumes.

Each particle is less than 1/1000 of a millimetre in diameter. This means they are small

enough to enter the deep spaces of the lung. There, they can damage lung tissue, or


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dissolve into body fluids.

The fume and smoke that is typically seen rising from a welding operation is composed

of many different substances including gases and fumes released by the electrode, flux,

or metal being welded. The electrode is the greatest contributor of fumes.

Breathing the fumes can cause health effects ranging from discomfort to long term

illness. The major component of fumes from common structural steel is iron oxide in

relatively low concentration. When welding other metals, toxic substances can form a

large proportion of the fumes. For example, some copper alloys contain beryllium

which is highly toxic. Other toxic components can originate from consumable welding

materials and from coatings and residue on metal parts.

A common health effect from exposure to metal fumes is known as metal fume fever.Symptoms occur from 4 to 12 hours after exposure and usually last for 24 hours.

Recovery is complete with no permanent disability. The symptoms resemble influenza;

sweating, shivering, headache, thirst, muscle aches, nausea, and fatigue. A metallic or

sweet taste in the mouth, dryness or irritation of the throat, and coughing may occur at

the time of exposure.

Metal fume fever is frequently caused by exposure to zinc oxide fumes from

galvanized steel. The fumes of cadmium, copper, magnesium, manganese, nickel and

tin have also been implicated in some cases.


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METALS USED IN WELDING

Substance Uses Health Effects from

Exposure to Fumes or

DustsBeryllium hardening agent

found in copper,

magnesium and

aluminium alloys

metal fume fever; suspected

carcinogen

Cadmium* corrosion-resistant

coatings, solders

and brazes

pulmonary edema; suspected

carcinogen

Chromium* steel alloys irritant of skin, eyes and

mucous membranes; some

forms are carcinogens

Lead* paints and alloys anaemia; abdominal pains;kidney and nerve damage

Nickel steel alloys pneumonitis; cyanosis;

delirium; dermatitis;

carcinogenic.

Zinc aliminum and

magnesium alloys,

brass, corrosion-

resistant coatings

metal fume fever

Copper metal fume fever, damage to

livery, kidneys, nose and

spleenMagnesium metal fume fever, irritation

of eyes and nose

Manganese fatigue, nervous system

disorders, respiratory

disorders, liver damage

Mercury protective coatings

on metal

systemic poisoning

Molybdenum uncertain in humans

Titanium respiratory irritation, slight

fibrosis

Vanadium filler wire irritation of eyes and

respiratory tract, possibly

asthmatic reactions*Indicates designated substances under the OHSA


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Dusts

Dusts are fine solid particles which are larger than those in fumes and can remainsuspended in the air for a considerable period. Some cleaning operations associated

with welding generate dusts. They may also be produced by fluxes and filler metals.

During handling, for example, rod coatings may release phosphates, silicates and silica.

Tasks such as grinding and chipping of weld slag also generate dusts.

Prolonged exposure to silica can causesilicosis, a disease of the lungs marked by a

progressive shortening of breath. Silica is a designated substance. Metal dusts can

produce the same health effects as metal fumes.

Pneumoconiosis is another health effect caused by the inhalation of particles, such as

those in fumes and dusts. Specific conditions associated with welding include

aluminosis (aluminum), anthracosis (carbon),siderosis (iron), andstannosis (tin).

There is some debate about whether the pure forms of these substances cause

significant lung damage. Some authorities believe that most of the health effects are

actually caused by impurities such as silica, that are mixed with the metal oxides in the

workplace.

If welding or cutting involves asbestos, the Act requires that the agency having

authority must be consulted before beginning the job. Asbestos can produce fibrosis

and lung and other cancers. Asbestos is a designated substance.

ELECTRICAL HAZARDS

The electrical current used to power arc welding equipment varies from 110 to 575 volts. Even at the

lower end of this range, exposure to electricity can cause serious injury including shock, burns or paralysis.

Exposure to higher voltages can be fatal.

The voltage is reduced to approximately 80 volts at the welding machine output, and it drops further

during welding operations. Nonetheless, voltages as low as 25 volts can transmit enough current to causeinjury. For example, the involuntary muscle contraction resulting from such a shock may lead to a

dangerous fall and possible injury.


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MATERIAL HANDLING HAZARDS

Welders often perform tasks which include repetition, manual lifting and material handling. They mustadopt static postures such as sitting, crouching or kneeling for prolonged periods of time. As a result,

welders may suffer from body strain and fatigue.

Poor workplace design and the use of inappropriate tools and equipment contributes to these hazards. For

example, arrangements that require welders to work with their arms above shoulder height puts stress on

the muscles in the shoulders and arms. Maintaining fixed positions also forces the muscles to work harder.

Welders who repeat tasks which involve working in unnatural postures face an increased risk of

musculoskeletal injuries.

Welders who work with gas welding equipment face the added hazards of handling compressed gas

cylinders. In addition to the problems of manually moving these heavy objects, there is a risk of fire orexplosion of they hard not handled properly.

RADIATION

Electrical arcs and gas flames produce ultraviolet and infra-red radiation. Either type can damage the eyes

and skin if exposure is prolonged or repeated. The most common effect of ultraviolet is damage to the skin

or the surface of the eye, similar to sunburn. This is painful and disabling but usually temporary. The effects

of visible and near infrared radiation, on the other hand, may include permanent eye injury. Exposure to

infrared radiation may result in burns to the retina, and with repeated exposure, cataracts (clouding of thelenses or membranes of the eyes) may develop.

The generation of ultraviolet radiation is especially high in gas shielded arc welding. A shield of argon gas

around the arc doubles the intensity of the radiation. In addition, the higher current required (particularly

with a consumable electrode), can raise the amount of radiation to as much as thirty times the levels

associated with non-shielded welding.

Some welding operations also involve ionizing radiation. This radiation has a very short wavelength and

can damage living cells. It can cause serious health effects and can be fatal in large doses. X-rays and

gamma rays used to inspect welds are of the ionizing type. This type of equipment must be used only by

specially trained workers. X-rays can also be emitted by certain welding processes such as electron beamwelding.


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HEAT STRESS

Overexposure to heat can lead to heat stress. Heat stress occurs when the body is unable to regulate its

internal temperature effectively. The symptoms vary from mild discomfort, rashes, and dizziness to

cramps, exhaustion and heat stroke. Heat stroke is a potentially fatal condition in which the body's cooling

mechanism stops working altogether.

Welders are especially susceptible to heat stress because they are exposed to heat from welding

operations, and must wear heavy protective clothing. The problem is often compounded by heavy

physical work, carried out in cramped work spaces with poor ventilation.

ASSESSMENT

A variety of techniques are available to assess the severity of welding hazards. Most of them involve the

collection of air samples so they can be tested for the presence of toxic substances.

Typically, airborne contaminants are measured by a device which draws a known volume of air from the

work environment. The air is passed through a collection device which removes contaminants so they can

be tested for the presence of specific substances. The detection of the contaminant may take place in the

sampling instrument, or at a laboratory.

Levels of airborne contaminants that workers can be exposed to without suffering health effects have been

established by the American Conference of Governmental Industrial Hygienists (ACGIH). These

guidelines for allowable exposures are called Threshold Limit Values (TLVs) and are calculated as

milligrams per cubic metre of air (mg/m3). In most cases, exposure is measured over a full 8 hour work

shift, and is referred to as a time weighted average. The 8 hour daily exposures can also be averaged over

a 40 hour week. In addition, the ACGIH has published maximumshort term exposure levels that apply to

any 15-minute period, and ceiling levels which must never been exceeded.

Threshold Limit Values are considered the maximum levels that average worker can be exposed to

without adverse health effects. They should not be interpreted as goals when designing a work activity. Thereduction of all contaminants to the lowest possible level should always be the ultimate goal.


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TIMEWEIGHTED THRESHOLD LIMIT VALUES OF

COMMON GASSES AND FUMES ASSOCIATED WITH

WELDING

Substance mg/m3

Welding fume not otherwise classified

Welding fume (aluminum)

Barium, soluble compounds, as Ba

Beryllium and compounds

Cadmium oxide, fume as Cd

Calcium oxide

Carbon dioxide

Carbon monoxide

Chromium metal, Cr(II), Cr(III), Compoundsas Cr

Chromium (V1) Compounds, Chromates, as Cr

Copper fume

Fluoride, as F

Iron Oxide fume, as Fe

Magnesium oxide fume

Manganese, dust and compounds as Mn

Manganese, fume

Nickel, soluble compounds, as NiNitrogen dioxide

Ozone (Ceiling)

Phosgene (Carbonyl chloride)

Phosphine (hydrogen phosphite)

Silica, fused, respirable dust

Titanium dioxide

Zinc oxide, fume

5

5

0.5

0.002

0.02

2

9000

25

0.5

0.05

0.2

2.5

5

10

5

10.1

6

0.2

0.4

0.42

0.1

10

5


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Fume Measurement

Fumes are sometimes assessed using the fume generation rate. This measurement can be made using aspecial fume cabinet that collects all fumes emitted by the process. The fume produced is usually measured

in grams per minute. The fume generation rate is not directly related to worker exposure, since that will

depend on the nature of fume dispersion. Therefore, it is preferable to use samples of air from the workers

breathing zone, which can then be compared to the TLVs.

Fume concentrations will vary greatly over the work cycle. Typically, a 15-minute sample is taken to assess

whether a problem is likely to exist. If excessive levels are suspected, a full-shift sample is collected and a

time-weighted average exposure is calculated.

Fume sampling devices pass an air sample of known volume through a filter designed to trap particles of a

particular size. The filter is then analyzed in a laboratory. The trapped particles are weighed and theconcentration is calculated as milligrams per cubic metre. The most common filter material is cellulose

ester, but chromium reacts with this substance and must be collected on polyvinyl chloride filter medium.

Samples taken from the general workplace air establish the amount of fume accumulation in the area.

Personal exposures are determined by a battery-operated sampling device worn by the welder. Air is drawn

in through a collection tube placed in the worker's breathing zone. Since the welders protective faceshield

affects his or her exposure, it has become common practice to mount collection device inside the helmet.

Gas Measurement

Gas levels are commonly conduced in the workplace using colourimetric tubes attached to hand-operated

air collection devices. A known volume of gas is drawn through a glass tube containing a chemical reagent

that changes colour when exposed to a particular contaminant. The concentration of the substance in the

air is read from a scale in the tube. Readings are generally in parts per million, but colourimetric tubes are

not considered very accurate compared with other measuring techniques.

Another assessment method for gases is known as sorbing tube sampling. In this case a pump draws a

known volume of air through a tube containing a solid that absorbs the gas. The medium may be charcoal,

flourish, or silica-gel, depending on the gas to be sampled. The tube is sent to a laboratory for analysis. This

technique can be used for both area and personal sampling.

Passive dosimeterhas the advantage that it does not require pumps. They are small and light so they can be

easily carried by a worker. Some use tubes containing charcoal that require laboratory analysis. Others

employ tubes with colour indicators that can be interpreted with a special reader. They are used for both

personal and area sampling.


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Direct-reading instruments with electronic components can be used for sampling a limited number of

contaminants. They are effective in locating sources of contamination and are used to monitor work areas.

They typically include a built-in alarm system.

LEGISLATION SPECIFIC TO WELDING HAZARDS

Several regulations under the Act relate specifically to welding hazards. Certified members

in workplaces where welding is carried out should become familiar with any of them that

are relevant to their situation.

L. [Ed note - this section will have to be re-written. It should briefly explain what the various

regulations say specifically about welding. It should not repeat the regulations verbatim, but

should explain in plain English when the certified member might need them. Regulations not

directly specific to welding do not need to be mentioned. The reader understands that the entire

Act and its regulations are indirectly related.]

i. Industrial establishments - Regulation 851

ii. Designated substances

iii. Biological or chemical agents - Regulation 833

iv. Workplace Hazardous Materials Information System (WHMIS) -

Regulation 860

v. Mines and Mining Plants (Specific to Welding) March 1993 - Regulation

854

Mining Regulations (Specific to Welding)

Section 30-(5) to (6)


Section 194-(1) to (16)

Construction Regulations (Specific to Welding)


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Section 123-(1)

Section 124-(1)

Industrial Regulation

The Industrial Regulation does not have rules that are specific to welding, however several

sectors do apply indirectly. They include:

(i) Confined Space Section 71 to 75

(ii) Lockout Section 79, 80, 82

(iii) Protective Equipment Section 83 to 90

(iv) Ventilation/Air Supplied Section 143

Breathing Equipment

(v) Molten Metal Section 97

(vi) Industrial Hygiene Section 128 to 135

(vii) Noise Section 144

There are other pieces of legislation affecting welding and cutting operation. They include:

(i) The Ontario Fire Marhalls Act.

(ii) The Ontario Fire Code.

(iii) The Ontario Building Code.


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CONTROL

Welding hazards, like all health and safety hazards, can be controlled at three points: at the source of thehazard, along the path between the hazard and the worker, and at the worker. In general, the closer a

control is to the source, the more effective it will be.

CONTROL AT THE SOURCE

Welding hazards are most effectively controlled at their source. Substances that contain contaminants such

as coatings, cleaners and rust inhibitors can often be eliminated altogether. Alternatively, less hazardous

materials can be substituted. For example, metals that produce hazardous fumes and gases can sometimes

be replaced by less hazardous materials in the parts to be welded or in rods and fluxes.

Another approach is to cut down emissions of fumes and gases by using a welding process that works at

lower temperatures. For example, welding currents can sometimes be reduced.

Finally, hazardous processes can be isolated and enclosed to reduce worker exposure physical agents as

well as fumes and gases.

CONTROL ALONG THE PATH

If welding hazards cannot be eliminated, substituted or isolated, the next most effective point of control isalong the path to the worker. Airborne contaminants and electrical hazards can both be controlled along

the path. Barriers that protect non-welders from exposure to welding flash are also considered control

along the path.

Air Quality

The usually way to control airborne hazards along the path is by ventilation. There are

two types: general ventilation and local ventilation. The first type dilutes the general

workplace air to reduce contaminant levels. Local ventilation exhausts contaminated

before it has a chance to dissipate throughout the workplace environment.


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General Ventilation

General ventilation is acceptable for welding operations if steps are taken

to keep fumes and gases away from the workers breathing zone and tokeep flammable gases at safe levels. The concentrations of contaminants

must also fall below acceptable exposure limits and this must be

demonstrated with personal breathing zone samples. In addition,

combustible gases and vapours must be held at no more than 20 percent of

their lower explosive (flammable) limits. The workplace must also be free

of any areas of oxygen deficiency or enrichment.

Natural dilution ventilation should not be used as the only control for

welding in confined spaces, or in workplaces with barriers to natural air

movement. It is also inappropriate for welding of several types of the steel

alloys and non-ferrous metals.

Local Ventilation

Local ventilation systems capture contaminants at or near their source,

using hoods, ducts or vents. The contaminated air is then removed from

the workplace. Local ventilation is preferred over dilution ventilation

because it prevents airborne contaminants from entering the welders

breathing zone, or mixing with general workplace air where it could harm

other workers.

Three types of local exhaust systems are suitable for welding operations:

1. fixed hoods over a welding bench;

2. portable hoods equipped with flexible ducting; and

3. fume extraction guns or devices with flexible ducting.

To be effective, local exhaust ventilation must have a collection hood

located above and to the side and as close as possible to the source. Thevelocity of the air should be at least 0.5 metres per second or 100 feet per

minute.


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Air Cleaners

Exhaust air from workplace ventilation systems is typically exhausted

outside the workplace. In some cases it is acceptable to clean andrecirculate a portion of air that would otherwise be exhausted. This has the

advantage that contaminants are not vented into the outside environment.

Recirculation is acceptable only under strictly controlled conditions. First,

the air must first be passed through a high efficiency filter system. This

must be done in compliance with regulations, and regular monitoring is

needed to make sure that harmful gases remain below allowable limits.

The system must be designed to stop recirculation of contaminated air if

the filer fails. Recirculated air is not acceptable for some materials used inwelding.

Radiation

Whenever possible, arc-welding operations should be isolated so that

other workers will not be exposed to either direct or reflected radiation.

Arc-welding stations for regular production work can be enclosed in

booths with non-reflecting surfaces. Portable screens or curtains should

also be provided. Such enclosures should be designed to allow adequate

air circulation.

Electrical Systems

The electrical hazards of welding can be controlled by a variety of measures that

prevent worker contact with energized components.

Electrical cables must be protected from damage. Cables on the floor should be

covered or arranged so they will not come into contact with falling sparks.

Alternatively, cables can be suspended overhead. They should never be coiled around

the body.

Cables should be kept free of moisture, oil and grease to prevent deterioration. Worn


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or defective cables should be replaced immediately.

Welding units must be properly grounded. The plugs and receptacles for portable units

should be designed to prevent disconnection while the circuit is turned on. Special

connectors approved for disconnection under powered-up conditions are also

available.

Compressed Gas

Compressed gas cylinders pose a number of hazards which are discussed in detail in a

separate module.

In general, controls for this hazard involve proper labelling of gas cylinders, as well asprotecting them from damage or deterioration during handling and use.

Gas cylinders must be clearly identified when they enter the workplace and the labels

or marks must not be tampered with. Never use unmarked cylinders.

Cylinders weighing more than 40 pounds should be moved by a hand truck or by

mechanized equipment. If cylinders must be moved by hand, they can be rolled on their

bottom edges, but should not be dragged.

Cylinders must be stored in clearly identified storage areas, where their fittings cannotbe contaminated by oil or grease. They must be stored in an upright position, and

secured from falling over. They should also be protected from ice, snow or direct

sunlight. Different types of gases should be separated. In particular, Oxygen cylinders

must be no less than 6 metres away from flammable gases, or they must be separated

by an approved barrier.

CONTROL AT THE WORKER

Control at the worker is usually considered the least effective form of control because they do nothing to

eliminate the hazard. But in many situations it is the only type that is practical. Control at the workerincludes a variety of personal protective devices as well as administrative controls such as medical

monitoring. In addition, a variety of safe work practices and procedures are also considered control at the

worker. The use of personal protective equipment (PPE) is treated in greater detail in a separate module.


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Respiratory Protection

If gases, fumes and dusts cannot be reduced to acceptable levels by other types ofcontrol, welders should wear respiratory protection. It is recommended that such

equipment should comply with CSA Standard Z94.9. Where oxygen is deficient,

welders should use self-contained breathing apparatus. Special precautions are needed

for workers performing inert-gas welding.

Eye Protection

Goggles, helmets, and shields are an essential part of a welders equipment. They

should also be worn both by any other workers exposed to welding radiation. These

devices must give specific protection for the type of welding or cutting involved. Theworkers eyes must be protected from exposure to ultraviolet, infrared and visible

radiation.

Protective eye equipment is classified according toshade rating. The shade number

required depends on the type of welding as well as electrode size, arc current and plate

thickness. CSA standard W117.s-94 lists the minimum protective shade number

required and the suggested shade number for comfort.

Arc welders must also wear standard safety glasses with side shields to protect their

eyes from flying objects entering through the rear of the helmet.

Protective Clothing

Welders require a variety of protective clothing, made for leather or other flame

resistant material. They must protect the worker from radiated heat, sparks and

splatters. The main categories include the following:

gauntlet gloves;

aprons;

for heavy work, fire-resistant leggings and high boots;

high top safety boots;

safety hats or other head protection; and

for overhead work, capes or shoulder covers, skull caps


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worn under safety hats and possibly ear protectors.

People working with inert-gas-shielded arc-welding machines should cover all parts ofthe body that could be exposed to ultraviolet and infrared radiation, to protect against

burns. Dark clothing, particularly a dark shirt, is preferable because it reduces

reflection on the operator's face.

Wool clothing is preferable to cotton because it is more resistant to deterioration, it

protects the worker from temperature changes and is not readily ignited. Cotton

clothing, if used, should be chemically treated to reduce flammability. In either case,

clothing should be thick enough to keep radiation from penetrating it.

Aprons and overalls should not incorporate front pockets that can trap sparks. For thesame reason, trousers or overalls should not have turned-up cuffs.

Thermal-insulated underwear is designed only to be worn under other clothing and

should not be exposed to open flames, sparks, or other sources of ignition.

Medical Monitoring

In some workplaces, medical examinations, including a chest X-ray and lung

examination, are performed when individuals are first employed as welders and

thereafter at regular intervals. This is sometimes controversial because of the intrusionon personal rights and the difficulty of protecting confidentiality of medical

information. Medical monitoring is required under the designated substance

regulations, but in that case, individual examinations are voluntary and the use of

medical information is strictly regulated. If the health and safety committee

recommends medical monitoring, it will usually include provisions for the preservation

of confidentiality of medical information, and the rights of individuals.

Safe Work Practices

Welding often involves adopting awkward positions. In addition, welders typicallyhave to move heavy tools and materials as part of their work. Both of these factors can

result in direct injury or lead to fatigue that can contribute to accidents. Permanent

welding workstations can be designed to minimize these hazards. But welding is often

performed in temporary situations, where the use of safe work practices by the welder


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are often the only effective control.

Posture

Wherever feasible, welding should be done at a comfortable height, so that

it is not necessary to maintain awkward postures. Ideally, the arms should

be supported by a chair or a bench. Arm motions should be limited to the

normal work area, with materials and tools within easy reach. If it is

necessary to stand for long periods, a foot rest should be available.

Manual Material Handling

Safe material handling procedures for welders are very similar to the

general principles that are discussed in detail in a separate module.

Safe work procedures include protecting the hands and feet from sharp

edges or falling loads, and using safe lifting techniques. Heavy or awkward

loads should be moved either by mechanized equipment or by a group of

workers.

Welders using gas cylinders should understand the proper way to move

them. Manual handling of cylinders should be avoided where possible. If

they must be moved by hand, the Industrial Accident PreventionAssociation recommends the following procedure:

1. Place forward foot around the cylinder.

2. Lower cylinder across the thigh by pressing down with

the rear hand while holding the cylinder underneath and

slightly beyond the centre point.

3. Raise the end to the desired height.

4. Push the cylinder forward with the rear hand .


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WORKPLACE STRATEGIES

Under the OHSA, employers are required to maintain a written health and safety policy and program. Thejoint health and safety committee is the main forum for discussion of health and safety issues by all

workplace parties. Ideally, it will play a key role in the development and operation of the employers

program. At a minimum, members of the committee have the right to conduct regular inspections of the

workplace and to make recommendations to the employer. Worker members also have the right to be

present at the beginning of workplace testing and to be involved in training programs.

If welding is a significant part of the work process, the employer and the committee will probably consider

a special welding and cutting control program, to form part of the overall health and safety program. In

some workplaces, a sub-committee or working group of the JHSC may be designated to develop a welding

program. This will normally involve the systematic inspection of the workplace, the identification of all

welding and cutting hazards, and the specification of detailed work procedures. The committee may alsorecommend changes in processes or materials, or the use of engineering controls.

Whether or not there is a separate welding and cutting control program, the procedures for assessing and

controlling welding hazards should be reviewed regularly, perhaps annually. The review will include input

and recommendations from the joint health and safety committee. It might include the following main

components.

_. Are-evaluation of all hazards associated with welding, including both chemical agents and

physical hazards.

_. An assessment of the adequacy of all controls, with reference to relevant legislation, accepted

guidelines and an overriding goal of continuous improvement.

_. An examination of personal protective equipment to make sure that it continues to meet all

requirements for effective hazard protection, comfort and safe communication.

_. An inspection of all welding and cutting areas to consider if monitoring is required.

_. A look at new and improved control systems which have become available since the previous

review.

_. A review of worker education and training to ensure that all workers understand established

safe work procedures and that welding workers have received specialized training.

The CSA standard W117.2-94 "Safety in Welding, Cutting and Allied Processes" sets out a complete

health and safety program for welding in much greater detail. It is an excellent reference for joint health and

safety committees in any workplace where welding is performed.


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REVIEW

More than 100 different types of welding and cutting operations have been recognized. All of them involvehealth and safety hazards, which vary according to the type and setting of the welding process. Safety

hazards include the potential for fire or explosion and injuries from radiation, electrical shock, or materials

handling. Health hazards include exposure to fumes released from the metal parts being joined or from

other materials used in the process.

Controlling these hazards requires that they first be recognized and assessed. To carry out these functions

effectively, joint health and safety committee members need a basic understanding of welding processes

and the nature of the welding environment.

Regular inspections of the workplace are the principal means of recognizing welding hazards. Assessment

is often assisted by a variety of air monitoring tools, than can measure concentrations of gases, fumes ordusts in the workplace air.

Control of welding hazards can sometimes be accomplished at the source though the elimination,

substitution or isolation of hazardous materials. More commonly, it involves ventilation systems, radiation

barriers, electrical protection devices and other systems that control hazards along the patch from the

source to the worker.

In many cases, especially for the welders themselves, the only effective means of control is personal

protective equipment or individual safe work practices. As a result, training and evaluation of the training

effectiveness are essential components of a welding and cutting control program. Ideally the joint health

and safety committee will play a key role in developing and operating such a program.

REFERENCES

Author or publisher?] Accident Prevention Manual for Business and Industry, Engineering and

Technology 10th edition.

Canadian Standards Association, Safety in Welding, Cutting, and Allied Processes. (CAN/CSA - W117.2

94).

Industrial Accident Prevention Association, Safety and Health in Welding.

Welding Institute of Canada, Welding Health and Safety.

Documents

welding hazards.pdf