Vision protection and protection from heat and
electricity, or the arc itself, are obvious precautions for welding. Less
obvious is how to prevent exposure to the fumes and gases inherent with many
welding projects—and keeping the shop door open for ventilation isn’t always
enough.
This is particularly true in hardfacing, work with
stainless steel, and other arc welding projects that may feature high arc-on
time.
Hardfacing also involves heavier flux-cored wire.
“Hardfacing is an application that has higher fume-generation rates than just
joining two pieces of metal together,” says Allan Hilbert, product manager for
Filtair equipment at Miller Electric. “When you’re doing overlays and
rebuilding surfaces on larger pieces of earthmoving equipment, there’s a lot of
welding at any given time. And during that time a worker could be overexposed
very easily.”
What’s in welding
fumes?
The most common compounds in arc welding fume mild steel
are iron, manganese, and silicon, although other compounds in the electrode or
base metal may be in the welding fume.
Fumes from the use of stainless steel and hardfacing
products are likely to contain chromium or nickel, which have their own
potential health effects, such as asthma. Also, some forms of the two metals
have been known or suspected to cause lung cancer in nonwelding processes,
according to information published by Lincoln Electric.
Overexposure to manganese may affect the central nervous
system, resulting in irreversible coordination problems, difficulty speaking,
and tremors in the arms and legs. There’s also possible overexposure to zinc
from welding on galvanized steel that can cause “fume fever,” featuring
symptoms that mimic the common flu.
In addition, pay attention to the surface being welded.
If a base metal that’s plated or painted cannot be cleaned before welding, the
composition of the coating should be evaluated.
There are also the shielding gases used in arc welding.
Most of the shielding gases used in arc welding—argon, helium and carbon
dioxide—are nontoxic, but they can displace oxygen in breathing air, causing
dizziness, unconsciousness and possible death. Carbon monoxide can also be
present and pose a hazard if levels are excessive.
OSHA has published a ceiling limit definition regarding
how much fume it takes to impact a welder:
“Ceiling is the employee’s exposure which shall not be
exceeded during any part of the work day. If instantaneous monitoring is not
feasible, then the ceiling shall be assessed as a 15-minute time-weighted
average exposure which shall not be exceeded at any time over a working day.”
If a welder feels symptoms of being overexposed, he or
she should stop welding and go outdoors for fresh air immediately. If they
continue to feel the symptoms, consult a doctor. Back in the shop, be sure the
supervisor and any co-workers are aware of the situation and can avoid the
hazard. Suspend welding until the situation is resolved.
Measurement and prevention
A welder’s exposure can only be determined by taking a
sample of the welder’s breathing air during the workday, essential when
hardfacing, welding with stainless steel, or with other special ventilation
products.
The two most common exposure limits are established by
OSHA in the form of permissible exposure limits or PEL and by the ACGIH in the
form of Threshold Limit Values or TLV.
The best way to
attack potential problems with welding fumes, according to Hilbert, is to enact
OSHA guidelines known as the Hierarchy of Controls. The first two steps deal
with changes to the workplace; the latter two require worker participation.
A first step in the Hierarchy is establishing work
practice controls for fume reduction, which can include a process or material
change, and substitution, eliminating the problem before it can happen.
“This could mean changing consumables away from heavier
wire,” Hilbert says. “Take a close look at your process and what you’re using;
there may be another way to accomplish your goal with less fume generation.”
Another example would be shifting from stick welding to
MIG welding with a solid or metal-cored wire, or using low-manganese filler
materials.
The next step in the Hierarchy deals with engineering
controls, or physical changes to the workplace. These would include isolation,
or ventilation, perhaps enclosing the welding process, capturing material at
the source (local exhaust ventilation), and/or ambient collection.
Types of ventilation for welding
“Ventilation is the most common precaution,” Hilbert
says. “There are a number of ways to achieve this.”
Keep fumes and gases from the breathing zone and general
area using natural or mechanical ventilation, fixed/moveable exhaust hoods, or
exhaust at the arc.
Fume extraction guns are another type of source capture.
In the past, these guns have been heavy and somewhat unwieldy, but now there
are redesigned guns that come close to the weight, handle size and reliability
of traditional MIG guns.
There’s also something more basic. Teach workers to keep
fumes and gases from the breathing zone by keeping their heads out of the
fumes.
“There are some companies that have gone to vision tests
to make sure their welders could see well, because guys had their heads too
close to the weld,” Hilbert says.
Welders can also change their body position so that
airflow moves from back to front. Air movement in the work area should be
designed to push fumes away from the breathing zone, as well.
Finally, there is personal protection equipment (PPE) and
respiratory protection.
If ventilation can’t be provided, it may be necessary to
wear a NIOSH-approved respirator. OSHA requires that engineering and workplace
controls be installed first, and if the controls alone do not keep exposures
below applicable limits, use respirators.
This step includes implementing respiratory protection
such as disposable masks, half masks, powered air- purifying respirators, or
supplied-air respirators.
Respirators: the last frontier
Respirators should be used if engineering controls are
not feasible or do not reduce fume levels enough, or in maintenance or
emergency situations. Whenever respirator use is either mandatory or voluntary,
companies must establish and maintain a written respiratory protection program
as stated by OSHA 29 CFR 1910.134.
Each type of respirator is given an assigned protection
factor (APF), which is the level of protection it will provide when used
properly, in conjunction with a written respiratory protection program.
Companies must consider the respirator’s APF, air sampling results within the
facility, and OSHA’s PELs for those contaminants in the environment to
determine which respirator is suitable.
To get the most out of the respiratory protection, it is
also important to ensure each employee has selected a respirator that provides
a comfortable fit and does not negatively impact productivity. Respirator
inspection is an important step that can help ensure the welding operator is
fully protected. Train employees on proper inspection procedures before any
respirator is used. This information can be found in the user instructions.
Miller’s website stresses that employee training also
should cover topics including proper selection of respirators; the consequences
of improper fit, usage or maintenance; proper maintenance and storage
procedures; and how to use respirators in emergency situations. Having proper
documentation when respirators are used also is a critical part of maintaining
OSHA compliance. Requirements vary between mandatory and voluntary respirator
use, though both do require a written respiratory protection program.
The written program must include information on
respirator selection; medical evaluations; fit testing for tight-fitting
respirators; use in routine and emergency situations; established schedules for
cleaning; procedures to ensure air quality and flow for atmosphere-supplying
respirators; employee training; and evaluation of the respiratory program.
Source: ConstructionEquipment.com
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