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.
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.
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.
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 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.
We advocate that all stair treads be painted white (leading edge plate) to further improve visibility and cut down on falling accidents.
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.