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Installation and Repair: Pulling
and Feeding Wire
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Electrical
employees run or pull wire throughout a worksite. This involves
pulling at one end of the run and feeding at the other.
Wire is pulled through chases, conduit, or knockouts
to get from the electrical supply to the final destination.
This path is usually under the floor or in the ceiling,
which forces employees to reach up or bend down.
When these tasks are performed manually,
they often require employees to exert significant force, assume awkward postures,
perform repetitive motions, and be exposed to vibration and contact stress.
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| Pulling Force |
Potential
Hazards:
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Figure 1
Heavy spools.
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Figure
2
Large mechanical wire puller.
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Figure
3
Portable pulley in an open ceiling panel. |
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Due to increased weight and stiffness, pulling larger gauge wire requires greater
effort than pulling smaller gauge. This increased
effort can stress the hands, arms, shoulders, and back.
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Running wire through small diameter conduit
increases the contact points between the conduit
and wire. This increases the resistance,
requiring employees to exert more force while
pulling.
- Unwinding wire from spools may be strenuous
when wire spools are large and heavy (Figure
1).
- Pulling wire through bends in conduit creates
restriction points, which increases the force required to perform the
task.
- Running wire while standing on
ladders results in twisting torso and
awkward posture of the upper extremities.
Possible Solutions:
- Use a
mechanical wire puller (Figure 2). Pullers provide the force
of several employees, eliminating the manual effort needed to pull
therefore increasing
productivity and
reducing risk of
overexertion.
- Appropriately positioned
portable
pulleys (Figure 3)
allow employees to exert larger forces when in proper postures.
Employees
standing on the ground or other stable surfaces and working with the elbows
close to the body and the torso upright can increase
effectiveness of the task.
- Use spool rollers (Figure 4) that allow spools
to rotate in place and release wire smoothly
without twisting.
- Install inspection boxes at appropriate
intervals so that employees do not have to pull wire
through repeated bends or long lengths of
conduit.
- Employees should be
provided with platforms,
scaffolds, or lifts so
that they can raise
themselves to
do pulling tasks within
easy reach and minimize
overhead or low-location
pulls. Pulling should be done in the
power
zone.
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When manual pulling
is required:
- take regular breaks from manual pulling,
allowing muscles
to rest.
-
rotate
employees
between pulling and feeding,
installation
and
repair
tasks.
- use gloves that improve
coupling and protect the hands from contact stress and cuts.
- Lubricate wire as it enters chases, conduits or knockouts to reduce friction
and force requirement of
pulling task.
- Use platform ladders which
provide a work surface where employees may stand
and turn to face the direction of work when
pulling. This allows employees to exert force in
ergonomically correct postures improving
efficiency and reduces fatigue. A regular ladder
is generally not as desirable since it restricts
repositioning, forcing employees to reach and
twist the torso when performing pulling tasks.
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| Frequency of Pulling
and Feeding |
Potential Hazards:
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Figure
4
Spool roller.
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Figure
5
Mechanical wire puller.
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Manually pulling or
feeding wire through long
runs of conduit may take a
great deal of time,
requiring
highly repetitive forceful exertions
involving muscles of the hands,
arms and back.
Possible Solutions:
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Use spool rollers (Figure
4) that allow spools to rotate in place, releasing wire smoothly with less effort
thus reducing force
requirement of the task.
- Use a
mechanical wire puller (Figure 5).
This can reduce force
requirements of the task, thereby reducing the risk and preventing
cumulative trauma disorders in the workplace.
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When
manual
pulling
is
required:
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rotate employees
between pulling and feeding
and
installation and
repair
tasks.
-
use
gloves
that
improve coupling and protect
the
hands
from
contact
stress
and
cuts.
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| Overhead Reaching |
Potential
Hazards:
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Figure
6
Overhead reaching.
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Figure
7
Pulling in the power zone.
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Figure
8
Using a pulley in the ceiling overhead allows employees to pull or guide wire without overhead arm positions.
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Working on overhead tasks
in
awkward
posture with the hands
raised above the shoulder may
restrict blood flow and result in nerve compression
that
affects the
upper extremities and shoulders causing numbness,
tingling, discomfort and
fatigue when these postures
are maintained for long
periods of time.
Common overhead tasks may include attaching parts, completing
circuits, and pulling or feeding wire. (Figure 6)
- Awkward postures while pulling with the hands above the shoulder
cause an increased load imposed on the shoulders, neck and back.
When performed repeatedly, these tasks may result in
overexertion of
the back and upper extremities.
Possible Solutions:
- Conduct pre-planning to ensure that employees are
provided with appropriate height ladders.
- Use platform ladders, lifts
or other devices
to get closer to the work area. Remove
impediments such as work tables, bins or power
equipment
to improve access.
- Adjust height of the work pieces to allow
elbows to stay close to the body within the power
zone
(Figure 7).
- Use of a
portable pulley (Figure 8) combined with
mechanical pullers may
significantly reduce overhead reaches
and force requirements of the
task.
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