Plant utilities-lighting

Lighting is one of the physical facilities most required in a factory. It is the most important single environment factor contributing to worker satisfaction, comfort and productivity. Adequate and good lighting is necessary for a worker so that, he may see minute details of his job with ease and accuracy.

Lighting is said to be good when it is free from glare and is properly diffused, its color pleasant and its flow direct and steady. An excess of lighting or its inadequacy is harmful to the eyes of the workmen and should, therefore, be avoided. Illumination between 14 and 18 lumens will be ideal in any industrial establishment. Adequate and good lighting in a factory is a legal requirement.

Sources of Lighting

There are two major sources of lighting: day-light, which is often referred to as natural lighting, and artificial lighting


Day-light is that light which is received from the sun through apertures in the building .It is the main , and sometimes the only lighting used during the greater part of the working period ./Compared to artificial lighting , day-light has the following advantages:

(a)It is available in abundance, particularly in tropical regions.
(b)It is available free of cost and has all the attributes of good lighting.
(c)It requires no maintenance.
(d)It is free from problems like load-shedding, power failure, etc.
(e)It is particularly suitable for general lighting purposes.

Natural lighting has, however, certain limitations. These are:

(a)Though it is free of cost, being gifted by Nature, day-lighting is expensive in an indirect way. Windows and roofs have to be specially constructed to admit natural lighting freely. They have to be kept clean and are likely to increases heat losses, and so lead to increase in heating costs.
(b)It is available only during the day time and the intensity of light varies with the season, weather and hour of the day.
(c)It is difficult to provide uniform lighting throughout the building with day-light only.
(d)Its intensity cannot be changed or controlled to suit the different requirements at different places and times.

Two factors have to be borne in mind in order to take advantage of natural lighting:

(a)Facilities should be provided in the building to admit natural lighting without any obstacles; and
(b)An effective utilization or uniform distribution of the light admitted inside the plant should be made.

Admission of Light

The following provisions should be incorporated in the buildings so as to admit enough daylight inside:

(a)The provision of a sufficient number of windows on all the sides of the building .In the past, buildings with as many as a thousand windows were constructed .Attempts were made to build factories that were described as factories with one thousand windows.

Such buildings are no longer constructed More windows certainly help in the admission of more natural light; but they also make air-conditioning and heating difficult and expensive Therefore, the windows may be so constructed as to leave a ratio of not more than 6 to 1 between floor space and window space.
(b)Roofs play an important role in admitting natural illumination .Illumination admitted through the roofs eliminates the glare which is at times formed ,if light is admitted only through the windows .Different roof models are in existence , each capable in a particular way, of taking advantage of natural illumination.

Artificial Illustration

Artificial lighting refers to the illumination secured through artificial means, such as the use of bulbs and tubes .The term illumination, strictly speaking, involves the use of artificial sources of light .In the best conditions, natural day-light is available only during a few months of the year and artificial lighting has to be made use of either for a part of the day or for the whole day. As soon as natural light becomes inadequate, artificial light should be switched on before workers begin to grumble. Other wise, poor lighting, as indicated earlier, would inflict strain and fatigue on the eyes .Compared to natural lighting, artificial lighting has certain advantages. These are:

(a)The illumination provided is constant. There are no variations in the illumination during the day or night.
(b)The intensity of the illumination can be controlled to suit the requirements of specific operations.
(c)It is the only method of lighting available during the night shifts and for over timework.
(d)It is well suited to provide supplementary lighting.
(e)There is no need for a large number of windows to admit illumination .The larger the number of windows, the more difficult it is to clean them .There is also the loss of heat if there are many windows.

But artificial lighting has certain disadvantages which are worth noting:

(a)It is quite an expensive method of lighting because of high investment on luminaries, power consumption and expenses incurred on the maintenance of a department to look after the system.
(b)Power cut imposed by State Government or power failures often create problems unless generators are maintained which again, are expensive.

Artificial illumination may be necessary during 10 to 40% of the working period, depending on the latitude, the season of the year, the weather and the natural lighting conditions in the shop .The details of types of artificial lighting is not within the scope of this article. It will be detailed in another article,