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Installation and Repair: Connecting
and Fastening
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Connecting
and fastening tasks include splicing wires,
connecting wires to switches, outlets, control and service panels
as well as connecting to motors and appliances.
All of these tasks can expose employees to a number of hazards including forceful exertions,
awkward postures, repetitive motions and contact
stress.
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| Connecting |
Potential Hazards:
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Figure 1
Small tools
can press on the
palm of the hand.
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Figure 2
Connector that
needs no tools
and requires
little force or
awkward postures
or motions.
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Frequent bending
to
retrieve
materials
stored
below
knee
height.
-
Connecting wire to fixtures
may involve
using screwdrivers and other small hand tools.
This
process requires repetitive
bending of the wrists
while
exerting
finger
force
and
is
especially
hazardous
when
numerous
fixtures
are
mounted
within
a
short
period
of
time.
-
Using small tools (Figure 1) may result in
contact stress to the palms and fingers as
well as exertion of significant finger force using awkward hand positions.
- Application of the connectors
may
require the employee
to use
significant finger force with twisting.
-
Continuous
stripping
of
wires
requiring
pulling
force
and
pinch
grips.
Possible Solutions:
-
Conduct pre-planning to ensure that:
-
employees are provided with appropriate height
of work surfaces, such as using a saw horse with
plywood as a work table for materials, to reduce
bending.
-
tasks are managed to limit the time employees
perform similar tasks that affect the same
muscle-tendon groups. For example, intersperse
hand intensive tasks with lifting tasks.
- Use stab-in switches and outlets. For residential
work, use self-locking stab-ins. For larger
jobs, use stab-ins with a side-screw fastener.
- Use tool-less connectors, such as
low-voltage spring action screwless terminals
(Figure 2) where only a small amount of force is needed to insert
wire, and no twisting is
required. These connectors are easier and faster
to use, thereby increasing productivity and reducing
ergonomic risks.
- When stripping wires use proper size or spring-loaded strippers that are in good
condition (sharp teeth).
This reduces the amount of pulling force
required.
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| Hand Tools |
Potential Hazards:
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Figure
3
Tool with short handle.
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Figure
4
Power
drill.
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Figure 5
Padded-handle
tool.
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Figure 6
Spring-loaded
snips.
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- Using tools with short handles (Figure 3) may damage tendons and
nerves by compressing unprotected areas of the palm
and fingers.
- Using tools that are too large for the hand may result in fatigue of the hand and forearm.
- Using screwdrivers for highly
repetitive tightening or loosening tasks
may irritate the elbow tendons and their attachments, leading to inflammation
and epicondylitis (tennis or golfer's elbow).
- Wearing gloves that are too large or too thick may restrict movement
of the hands, leading to muscle fatigue and overexertion. Conversely,
gloves that are too tight may also restrict movement and blood flow.
Possible Solutions:
-
Select tools with handles
that are properly sized and shaped for the
employee. The handle
should be
padded and
made of
slip-resistant
material (rubber or
plastic).
- Use
powered (Figure 4) or
ratcheting tools whenever possible for repetitive tasks.
- Ensure that powered tools have variable speed, torque limiters
or stop bars to prevent over-tightening and wrenching of
employee's hands.
- Select tools that are light and fit well in
the hand. Tools such as pliers or punches that extend into the palm should be rounded and padded
(Figure 5).
- Use spring-loaded pliers, snips (Figure 6), and crimpers
for tasks that must be done frequently.
Caution:
Spring force should be just enough to open the
tool. Excessive spring force will increase the
grip force needed to use the tool.
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