hour must be provided. When welding is performed
are described in NSTM, chapter 074, volume 3.
on galvanized metals, brass, bronze, and some other
Keep in mind that welding MUST NOT be
metals, the ventilation requirements increase by at
performed in any location outside the shop unless
least 10 percent. For welding performed in a
the necessary precautions have been taken and
confined space, positive steps are necessary to
approval has been obtained. Any compartment,
ensure the elimination of health hazards. In
room, tank, or space adjacent there to which
addition, some conditions, like welding inside a
contains or which has contained flammable or
tank, make it necessary for the welder to wear an
explosive materials, liquids, or vapors must be made
air-line mask.
safe, tested, and proclaimed safe before you can
weld in such a space. These restrictions also apply
As a welder, you must consider as unsafe every
to closed drums, tanks, and similar containers.
closed compartment or poorly ventilated space, all
tanks, cofferdams, voids, and similar spaces, until
When welding is being done, a fire watch must
the gas-free engineer has inspected the space and
be posted in the vicinity, particularly when
has indicated that adequate precautions have been
flammable or explosive materials are exposed. If a
taken. When the condition of the space has been
fire hazard exists on both sides of a bulkhead or
determined, the gas-free engineer posts a tag
deck, fire watches must be stationed on both sides
describing the condition of the space. The tag
with appropriate types of fire extinguishers. For
posted includes complete information as to whether
example, if the only combustible material within
or not the space is safe for persons and whether or
range of the sparks or heat from welding or cutting
not it is safe for hot work. The information on the
operations is bitumastic waterproofing, a CO2
tag is expressed in one of the following ways,
extinguisher may be adequate. In a small space with
depending on the condition of the space:
a very small access opening, however, the operator
might not be able to get out quickly in the event of
fire. The use of CO2 would be dangerous in this
NOT safe for persons--NOT safe for hot
case; the use of water from a 1 1/2-inch waterline or
work
water pump tank would be preferable. If the
insulation on some electrical equipment is the only
Safe for persons--NOT safe for hot work
combustible material present, the use of water
would be more dangerous than the fire itself. In
Safe for persons--Safe for hot work
this situation, CO2 would be used. In each case, it
is necessary to consider what kind of fire might
INERTED--NOT safe for persons
occur and to provide the appropriate equipment to
INSIDE--Safe for persons and hot work OUTSIDE
combat it. The fire watch must remain on station at
least 30 minutes after a job has been completed to
PRESSED UP (with water or oil)--Safe for
make sure that there is no smoldering fire.
persons and hot work OUTSIDE
Adequate ventilation must be provided in all
The term inerted means that a nonflammable gas
spaces in which welding is being done and to
(usually CO2) has been introduced into the space
eliminate health hazards such as gases, fumes, and
and that the concentration of the gas is sufficient to
dust caused by the welding operation. Any welding
reduce the oxygen content of the space to a level
operation requires that the operator, helper, or fire
that will not support combustion. The term pressed
watch wear approved respirators regardless of the
up means that the space has been entirely filled with
amount of ventilation provided. When welding or
water or oil.
cutting operations are performed on lead-bearing
steels, lead-coated or cadmium-coated metals, or
When it is necessary for welding or cutting to be
metal covered with paint containing lead or
performed in any confined space that has a small
cadmium, an air-line mask should be worn even if
exit, all heavy equipment, such as gas cylinders and
the work is done in the open air or in a
welding generators, must be left on the outside. An
well-ventilated space.
attendant who can observe the welder at all times
must also be stationed on the outside of the space
When welding is performed on uncoated ferrous
so that in an emergency the attendant can shut off
metals, a minimum space allowance of 10,000 cubic
the gas or the electric current and provide such
feet per operator or three complete air changes per
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