Adequate lighting of factories is of vital importance, as it provides improved amenities for the employees, increased production and has a definite economic value in reducing accidents with their consequent loss of time and compensation payments.
General Requirements and Types of Installations for Factory Lighting:
A factory lighting installation, in common with other indoor equipments should provide an adequate illumination on the working plane and give a good distribution of light, employ simple and easily cleaned fittings and avoid glare. It is essential not only to avoid glare from the lamp itself but also reflected glare from any polished surface, which may be within the line of vision.
i. General Lighting:
The usual scheme in factories and workshops is to mount a number of lamps at a sufficient height so that uniform distribution of light over the working plane is obtained. In large machine shops the height is governed by the necessity of keeping the lamps above the travelling crane. In such cases it is often desirable to supplement the main lighting by side lighting in order to give additional illumination on a vertical plane. Since light coloured walls and ceiling add to the effectiveness of an installation, therefore; it is necessary to get whitewashing or painting done.
ADVERTISEMENTS:
ii. Local Lighting:
On some points fairly intense illumination is required. For this purpose local lighting can be provided by means of adjustable fittings attached to the machine or bench in question or mounted on portable floor standards. Such lamps should be mounted in deep reflectors so that glare is avoided.
Portable hand lamps attached to wall plugs by means of trailing leads are used for maintenance work and emergency lighting. Low voltage lamps of not more than 50 volts are recommended for use as portable hand lamps because such lamps have thicker filament and are, therefore, more robust than those for normal voltage and danger of shock is also avoided in these few volt lamps. The supply for such lamps can be obtained from a special low voltage distribution system running throughout the factory or by means of a small transformer for each individual lamp.
Local lighting should never be employed alone, good general lighting is essential so that the dark places between the local lighting units are avoided. Dark places between the local lighting units cause fatigue to the eyes on account of its continually having to adjust itself to new conditions.
ADVERTISEMENTS:
iii. Emergency Lighting:
Some lights, such as for:
(i) Internal pilot lighting required for safe and speedy evacuation of personnel after main lighting circuit is off
(ii) External pilot lighting, provided with careful shades leading to shelters required for evacuation of personnel
ADVERTISEMENTS:
(iii) For control posts, first aid centres etc.
(iv) Dials and gauges in important plants required to be watched regularly are required during an air raid when all the factory lights are off as a matter of air-raid precaution.
The circuit supplying the above emergency lights should be independently controlled. It is very desirable to provide auxiliary lighting from the source other than the main electric supply preferably from batteries or from small petrol driven generator set. If, however, emergency lighting circuits are operated from main electric supply, these should be completely separated from main lighting circuit.
Types of Lamps:
ADVERTISEMENTS:
The discharge lamps have been used in where colour rendering is not important. The fluorescent lamps are widely employed on account of its natural day—light colour, its even illumination and absence of glare and in some cases, the fact that it gives rise to considerably less heat than filament lamps of the same light output.
Industrial Lighting Fittings:
Reflectors for industrial purposes must be simple in design and easily cleaned.
The requirements of most of the installations can be met by one of the following types of fittings:
i. Standard Reflectors:
ADVERTISEMENTS:
These reflectors are made to accommodate lamps of ratings from 40 to 1,500 watts and designed so that they give adequate and uniform illumination when they are mounted at a spacing equal to about 1.5 times their mounting height above the working plane.
ii. Diffusing Fittings:
When more diffused light is required than that given by the standard reflector a diffusing glass screen may be fixed across a standard type of reflector. Such fittings are used where highly polished articles are dealt with.
iii. Concentrating Reflectors:
A reflector with a concentrated beam is employed in large machine shops and foundries, where the fittings are to be mounted on a considerable height above the working plane. In such places an ordinary reflector would have too wide angle of divergence and would waste a great deal of light on the walls.
iv. Enclosed Diffusing Fittings:
An opal globe completely enclosing the lamp giving a very even and well diffused light is used when light coloured walls and ceiling are there.
v. Angle Reflectors:
Angle reflectors are used to provide illumination in a vertical plane where concentrating type reflectors are used. These can be mounted on suitable stanchions or the walls.
Maintenance of Factory Lighting:
In order to maintain the fittings in a condition of reasonable efficiency it is necessary to clean the light fittings periodically. The frequency of cleaning depends on the conditions in the particular factory under consideration and varies from once or twice a week for very dirty surroundings to every four or six weeks under the best conditions.