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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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