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Welding Safety
Document Number: 109
Welding is the most common method of joining metals in industry
today. When welded, two pieces of similar metals are fused (melted)
together. Once completed, the welded joint is as strong or stronger
than the pieces from which the joint is formed. General hazards of
welding include impact, penetration, harmful dust, smoke, fumes, heat
and light radiation. The proper personal protective equipment can
protect you from these hazards.
Types of Welding --
Gas Welding,
Arc Welding,
Oxygen and Arc Cutting
Gas
Welding -- In gas welding, two metals are joined by melting or
fusing their adjoining surfaces. This is done by directing a gas flame
over the metals until a molten puddle is formed. The energy for gas welding
comes from the combustion of a fuel with oxygen or air. A few of the most
popular fuels are acetylene, Mapp gas and hydrogen. Since gas welding
is slower and easier to control than electric arc welding, it is often
used in applications such as general maintenance work, brazing and soldering.
Arc
Welding -- Arc welding involves a different process - two metals
are joined by generating an electric arc between a covered metal electrode
and the base metals. Heat is produced by the arc which in turn melts the
metal and mixes the molten deposits of the coated electrode. The arc energy
is provided by a power supply unit that furnishes direct or alternating
current. The electrodes carry the current to form the arc, producing a
gas that shields the arc from the atmosphere, and add metal to control
the weld shape.
When an arc is struck using a coated electrode, the intense heat
melts the top of the electrode. The drops of metal from the electrode
enter the arc stream and are deposited on the base metal.
The equipment needed for electric arc welding is a power supply,
electrode holder, ground clamp, protective shield, and welder's
protective clothing.
Oxygen
and Arc Cutting -- Metal cutting in welding is the severing or
removal of metal by a flame or arc. The most common cutting processes
are:
- Oxygen Cutting: Metal is heated by gas flame and an oxygen jet
does the cutting.
- Arc Cutting: Intense heat of electric arc melts away the metal.
Personal Protective Equipment
Eye and Face Protection
-- Proper eye and face protection varies depending on the particular task
being performed. Helmet, hand shield, goggles and safety glasses or combination
of these are acceptable protection in various applications. All filter
lenses and plates must meet the test for transmission of radiant energy
prescribed in the ANSI standard Z87.1968, Practice for Occupational and
Educational Eye and Face Protection.
According to OSHA 29
CFR 1910.252, "Helmets and hand shields shall protect the face,
forehead, neck and ears to a vertical line in back of the ears, from the
arc direct radiant energy, and weld splatter."
Welding helmets with filter plates are intended to protect users
from arc rays and from weld sparks and spatters which strike directly
against the helmet. They are not intended to protect against slag
chips, grinding fragments, wire wheel bristles, and similar hazards
which can ricochet under the helmet. Spectacles, goggles or other
appropriate eye protection must also be worn to protect against these
impact hazards.
OSHA requires that when arc cutting and arc welding with open arcs, helmets
or hand shields with filter lenses and cover plates shall be used by operators
and nearby personnel viewing the arc also subject to wear proper protection.
Spectacles
with a shade 2 lens are recommended for general purpose protection
for viewers. When resistance welding or brazing: operators of resistance
welding must use face shields, spectacles, or goggles depending on the
particular job to protect their faces and eyes from welding hazards.
| Filter Shade Selection for Type
of Welding |
| Operation |
Electrode
Size (mm) |
Arc
Current (A) |
Min
Shade |
Suggested
Shade |
| Shielded Metal |
< 2.5 mm |
< 60 |
7 |
* |
| Arc Welding |
2.5 - 4mm
4 - 6.4mm
> 6.4mm |
60 - 160
160 - 250
250 - 550 |
8
10
11 |
10
12
14 |
| Gas Metal Welding and Flux Cored Arc Welding |
< 60
60 - 160
160 - 250
250 - 500 |
7
10
10
10 |
*
11
12
14 |
| Gas Tungsten Arc Welding |
< 50
50 - 150 |
8
8 |
10
12 |
| Air Carbon Arc Cutting |
150 - 500
< 500
500 - 1000 |
10
10
11 |
14
12
14 |
| Torch Brazing |
3 or 4 |
| Torch Soldering |
2 |
| Carbon Arc Welding |
14 |
Gas Welding
(plate under 1/8" thick, light) |
4 or 5 |
Gas Welding
(plate 1/8" to 1/2" thick, medium) |
5 or 6 |
Gas Welding
(plate over 1/2" thick, heavy) |
6 or 8 |
Oxygen Cutting
(plate under 1" thick, light) |
3 or 4 |
Oxygen Cutting
(plate 1" to 6" thick, medium) |
4 or 5 |
Oxygen Cutting
(plate over 6" thick, heavy) |
5 or 6 |
|
|
|
|
|
| *As a rule of thumb, start with a shade that is too
dark to see the weld zone. Then go to a lighter shade which gives
sufficient view of the weld zone without going below the minimum. In
Oxyfuel Gas Welding or Cutting where the torch produces a high
yellow light, it is desirable to use a filter lens that absorbs the
yellow or sodium line in the visible light of the operation. |
| **This applies to where the actual arc is clearly
seen. Experience has shown that lighter filters may be used when the
arc is hidden by the workpiece. |
| Note: Workers with prescription lenses are
not exempt from wearing proper eye protection. |
Protective
Clothing -- According to ANSI Z49.1.88-Welding and Cutting (4.3),
appropriate protective clothing for any welding and cutting operation
will vary with the size nature and location of the work to be performed.
Clothing shall provide sufficient coverage and be made of suitable materials
to minimize skin burns caused by sparks, spatter or radiation. covering
all parts of the body is recommended to protect against ultraviolet and
infrared ray flash burn.
Dark clothing works best to reduce reflection under the face shield.
Heavier materials such as wool clothing, heavy cotton or leather are
preferred as they resist deterioration. Materials that can melt or can
cause severe burn due to sparks that may lodge in rolled-up sleeves,
pockets of clothing or pant cuffs are not recommended.
The ANSI standard requires all welders and cutters to wear protective flame-resistant
gloves, such as leather
welder's gloves, which provide the heat resistance needed for welding.
A gauntlet cuff offers additional arm protection, and insulated linings
should be used to protect areas exposed to high radiant energy.
Other protective clothing would include durable, flame-resistant
aprons made of leather or other suitable materials to provide protection
to the front of the body when additional protection against sparks and
radiant energy is needed.
Ventilation
Ventilation refers to changes of room air as often as necessary to
prevent welders and other workers from breathing high levels of
airborne contaminants. Ventilation is a means of providing adequate
breathing air, and must be provided for all welding, cutting, brazing
and related operations. Adequate ventilation depends on the following
factors:
- Volume and configuration of the space where the welding
operations occur
- Number and type of operations that are generating contaminants
- Natural air flow rate where operations are taking place
- Locations of the welders' and other workers' breathing zones in
relation to the contaminants or sources
Proper ventilation can be obtained either naturally or mechanically.
Natural Ventilation -- Natural ventilation is considered
sufficient for welding and brazing operations if the present work area
meets these requirements:
- Space of more than 10,000 square feet is provided per welder;
- A ceiling height of more than 16 feet
- Welding is not done in a confined space
- Welding space does not contain partitions, balconies or
structured barriers that obstruct cross ventilation
If your specific operation does not fall within these guidelines,
mechanical ventilation will be required.
Mechanical Ventilation -- Mechanical ventilation options
generally fall into two basic categories. The first is the low vacuum
system which takes large volumes of air at low velocities. These
systems consist of hoods positioned at a distance from the work area.
The hood and housing may have to be repositioned by the worker to get
maximum benefit from this means of ventilation. Hoods generally remove
the fumes and contaminated air through ducting and exhaust the
contaminants to the outdoors. Hoods should be placed as near as
practical to the work, and should provide effective air flow with a
velocity of 100 linear feet (30m) per minute at its most remote
distance from the point of welding. Processes where low vacuum systems
work best are arc air gouging, taking afterburner, and arc cutting.
Another category of mechanical ventilation is the high vacuum
system. These are close-range extractors that are aimed at capturing
and extracting fumes as near to the work as possible. Fume extractors
often have an immediate area of welding. By removing a small volume of
air at a high velocity, the potentially hazardous materials are
effectively removed before reaching the welder's breathing zone. These
systems often are equipped with a fan that pulls the contaminants into
a filtration system, with a HEPA (High Efficiency Particulate
Absolute) filter or combination of HEPA filter and prefilter and then
recirculated the clean air back into the work area. Advantages of high
vacuum systems are greater flexibility for job adaptation, more
efficient means of fume removal, and greater visibility to the welder
due to reduced clouds of fumes and vapors being created.
Fumes and gases from welding and cutting cannot be easily
classified. The quantity of fumes and gases is relative to the metal
being worked and the processes and consumable material being used
(such as coatings, like paint, galvanizing and platings), along with
contaminants in the atmosphere (such as halogenated hydrocarbon vapors
from cleaning and degreasing activities).
Air sampling to verify the concentration levels of toxic fumes and
gases is necessary, and respiratory protection is required along with
mechanical ventilation in the cutting and/or welding of certain metals
and compounds. For more information, see OSHA 29 CFR 1910.252 on
welding regulations.
Commonly Asked Questions
| Q. |
What is a fume plume? |
| A. |
The fume plume is the clearly visible column of fume which
rises directly from the spot of welding or cutting. Welders and
cutters should take precautions to avoid breathing this area
directly. Ventilation can direct the plume away from the face. (Fume
removal is most effective when the air flow is directed across the
face of the welder, rather than from behind.) |
| Q. |
How do I know what hazardous materials I may be using? |
| A. |
Check the Material Safety Data Sheet (MSDS). The suppliers of
welding materials must provide an MSDS or equivalent documentation
which identifies the hazardous materials, if any, used in their
welding and cutting products. |
| Q. |
Where should oxygen not be used and why? |
| A. |
Oxygen should not be used as a substitute for compressed air.
It should not be used in pneumatic tools, in oil preheating burners,
to start internal combustion engines, to blow out pipelines, to dust
clothing or work, or to create pressure for ventilation or similar
applications. Oxygen should not be used as described due to the
possibility of a raging oxygen-fed fire occurring. Oxygen is not
flammable, but vigorously supports combustion. Oxygen can be
absorbed by clothing. A slight spark can result in severe burns. |
| Q. |
What is Mapp gas? |
| A. |
Mapp gas is a product that was developed as a fuel for welding,
brazing, cutting, flame hardening, and metallizing operations. It
has many of the physical properties of acetylene, but lacks its
shock sensitivity and therefore can be stored and shipped in lighter
containers. Mapp gas is the result of rearranging the molecular
structure of acetylene and propane. It also has a very distinct odor
so any leakage can readily be detected. |
Sources for More Information
ANSI Z49.1-88, American National Standards Institute-Safety in
Welding and Cutting.
29 CFR 1910.251-257, Welding.
Safety in Welding and Cutting, American Welding Society, 1988.
Workplace Safety in Action: Safe Welding Operations, J.J. Keller &
Associates, Inc., August, 1995.
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Please Note: The information contained in this
publication is intended for general information purposes only. This
publication is not a substitute for review of the applicable
government regulations and standards, and should not be construed as
legal advice or opinion. Readers with specific questions should refer
to the cited regulation or consult with an attorney.
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