By definition, ergonomics relates to the study of people
in the work environment although in practical terms it is more of a study
between working conditions and people.
In
terms of the Mine Health and Safety Act and the regulations, an emphasis is
placed on the minimisation of the negative impact of work conditions on the
“Health and Safety” of the worker.
Regulation & Policy
Many aspects of the Mining
Regulations have for years been totally inflexible, with the result that
operating concerns could rely on the gazetted provisions relating to the
responsibility of operators and their workers.
While the acts have not changed
appreciably the application of the legislated regulations and requirements have
changed and the replacement of the previously rigid requirements by a new system of
negotiation has largely meant that little is likely to remain ‘cut &
dried’.
Organised labour is likely to
continue pressing for concessions which operators view as undermining not only
safety and health standards, but also even the regulations, as acceptance of the
situation creates ambiguity.
To illustrate this point we
quote the following scenario:
In terms of the various
regulations, operators have to provide all safety and protective clothing and
equipment.
In terms of the negotiated
workers rights, enforcement of the wearing of devices is perceived as an
infringement of rights.
The operator has to carry the
full responsibility should an accident occur.
Compensation for loss of life
or injury could become a litigation issue, further loading the dice against the
operator.
The only tangible means of
enforcing the wearing of the protective devices or clothing appears to be
through the ‘company policy’ route, providing that the company policy
requirements echo the Act regulations.
Under
these provisions the Disciplinary Code can be applied, leading to dismissal of
habitual offenders. There is a good
indication from the DME Inspectorate that they support use of the Disciplinary
Code in this way.
Many concerns do not allow
operators on site without PPD’s and regard the regulation as having been met.
This unfortunately will not absolve the mine from having to accept the
responsibility of occupational exposure disease compensation responsibilities
under the present act and South African Law.
Every effort should be made to enforce the wearing of PPD’s.
A further and perhaps very
necessary requirement of the Mine Health and Safety Act is the continual
measurement of occupational hygiene conditions, and towards this end the
stipulation of the competence and acceptability of the auditors.
Audit Reports
While the Act requires that
physical conditions on the mine be reported on, we believe that our reports
should offer solutions rather than just report problems.
Noise
The concept of “white
noise” or low intensity soothing sounds can lead to minimization of the
psychological impact of higher noise levels.
For example, a high impact noise of 100 dBA will appear minimal outside
where wind or natural bird sounds prevail, while the same noise inside buildings
will be considered to be excessive and disturbing.
By contrast, in a recreational situation the opposite will be noted where
a daytime noise of 100 dBA will not be considered excessive, whereas a night
time noise at 80 dBA will be considered as excessive.
Neither in reality is likely to cause any lasting damage providing the
noise is not continuous to cause an exposure exceeding 85 dBA.
The white noise effect of wind around the noisy plant areas is likely to
have an effect on the levels although this is almost impossible to quantify.
Lighting
The amount
of illumination required to carry out a given task without eyestrain or fatigue
resulting will vary from person to person with younger persons requiring as
little as half the illuminance required by an older person.
The difference between
the computer screen and keyboard values should ideally be no more than 100 lux to 150 lux, as operators
scan continuously from the keyboard to the screen and back.
Any large difference in illuminance will lead to eyestrain and possible
headaches etc in operators who spend a considerable portion of each day at their
terminals.
Ideally the screen should also be located slightly above the
horizontal vision line for the same reasons.
This obviously applies more to typists, secretaries and CCR operators.
With modern VGA screens
offering low radiation emission levels it is still a good idea to maximise the
distance between the operator and the screen, but individual operators eyesight
requirements normally dictate the distance for each operator.
Ventilation
Ventilation or the adequate
changing of the air contents of several areas prevents these becoming filled
with respirable fumes, vapour or dust.
Some respirables are liberated in processes involving water spray
systems.
Dirty water atomised
through a high energy spray nozzle will liberate respirable particulate into the
air and thus the addition of dirty water into an atomising spray systems must not
be considered as a means of dust control.
Heat Stress & Temperature
There is a direct correlation
between the work output and the comfort of workers in addition to safe working
habits and comfort.
All
concerns should look to upgrade the ergonomic conditions as an
ongoing priority and while its easy to just add another air conditioning unit,
it may be more beneficial to actually rather increase air changes in a given
situation.
A well-placed louvre can
be considerably cheaper than just another air conditioner.
General Safety
We advocate that all stair
treads be painted white (leading edge plate) to further improve visibility and
cut down on falling accidents.
Design Criteria
Modern design associated with
everything from earthmoving machinery to computer keyboards is continually being
improved from an ergonomic viewpoint, while in-house’ plant design tends to
muddle along with a minimal consideration for personal comfort or ergonomics.
It is inevitable that older
plants that are built with minimal ergonomic consideration have non-standard
areas like very high stair treads and minimal cost access ways and platforms.
Control valves at uncomfortable
dangerous heights. In this instance
we note that if any effort has to be applied to control valves that are not at
an optimal height, injury can occur apart from the safety issue of the
possibility of falls.
Most fire extinguishers are at
a good height for use by men. Where
there is a possibility of ladies having to use the units, there is a possibility
of injury as the units are a little high.
As mentioned previously, we
advocate the painting of the leading edge of each stair tread (outside only) in
white to make these more visible at night illumination levels.
Stairways on open plants have
high glare factors which can result in trip incidents and we comment as follows:
On proceeding down a stair many
lower landings have a light fitting that almost blinds you just as you step off
the upper landing. The same can be
said when emerging along a walkway inside the building directly onto a stair
immediately outside the building. Under
such circumstances a sign indicating stairs should be positioned on the door.
Stairway direction changes and
narrow landings subject to wet conditions could result in slippages and hand
railing is not sufficient to prevent injury. a mesh or plate catch fence should
be located opposite the stairs, especially if there is any possibility of the
stairs being wet. Slip accidents are more common at these intersections.
Refer to the attached cartoon sketches for some tips.
The sketches are part of our
awareness training programme that has been developed for smaller mining
operations and plants that do not have established awareness campaigns.
Signage should be appropriate
for the hazard and located suitably to warn of the hazard.
To mark off hazard areas with a
painted line does not offer a barrier to entry and the trend towards the use of
chains offers perhaps a better solution, especially if signage is attached to
the chain. This is especially true
of noise area, which should be barricaded off with chains even if it means that
persons have to step over or remove the chains to gain entry.
As the enforcement of the use of HPD’s becomes a legal requirement such
a barrier becomes a necessity, especially if workers have to remove or step over
the chain in order to gain entry to the area.
Positioning of Computer Screens
Most computer operators accept
that there are only 2 heights that the computer screen can be position at:
These are either (A) on the
desk or work surface or (B) on top of the computer casing (providing this is not
a tower type casing).
In the first incidence the
screen is too low and has to be tilted up to see the screen adequately.
This results in light reflections off the screen from windows or lights,
which adds to the eye strain and lower back or lumbar region stress as the
operators move their heads in order to see what they are trying to read on the
screen.
In the second case the screen
is possibly more optimally positioned but in theory is still a little low.
To improve posture the screen should be lifted even further and located
at a height permitting near horizontal viewing or slightly elevated viewing.
This will move the screen slightly further away (decreasing the ionising
radiated absorbed off the screen.) This
will also throw the reflection of windows behind the operator downwards away
from the line of vision.
The forearms should lie almost
horizontal with the palm of each hand resting at the base of the keyboard.
To achieve this, lift or lower the chair seat and adjust the backrest to
fit against the back firmly while in an upright position.
Driving Seat Positions
Most drivers have no idea of
the ideal adjustment of the seat position.
All seats should be adjusted
for leg length first. The seat is
adjusted with the brake pedal firmly depressed and the clutch pedal at the fully
depressed position. There should be
sufficient comfort to the driver, whose knee must be slightly bent to prevent
long operator hours causing cramps of the calf muscles.
The height of the seat must
then be adjusted to permit the driver to view the road at a reasonable sighting
distance of 60 to 80m without having to lift or tilt his head back.
Hand positions on the wheel
should be at a theoretical ‘ten past ten’ time position. Arms should be either horizontal for optimum comfort but may
be up or down depending on personal choice.
Drawings and illustrations
Below are some sketches used to
increase awareness in certain areas.
Electricity
is a real risk
