Plant operations – sources of ventilation


Proper and right ventilation not only prevent health hazards of personnel on shop floors but also considered by workmen as a good welfare measure or working atmosphere leading to one of the contributing factors for harmonious management worker relations.

Ventilation of any type may be provided through natural means or through artificial means.

Natural Ventilation

Natural Ventilation is effected by natural movement, by wind and temperature differences through walls and roof openings. It takes advantages of two natural forces, viz., the wind force and the stack effect. The wind force is naturally variable and depends on the geographical location and on the season. Advantage can be taken of such wind effect as is available in any given locality. As in mechanical ventilation, the first step is an assessment of heat gains of all kinds into the factory environment. The wind force data may be obtained from weather reports. The subsequent design of the scheme consists of sizing and locating openings like windows and openings in the monitors of roof trusses, with a view to ensuring the requisite air flow. The stack effect refers to the air flow caused by the temperatures differences between the interior and the exterior. If the factory interior is warmer, the air density which, in turn gives rise to a difference in pressure maintains the air flow. Natural ventilation through a building occurs because of the operating of both these effects; and a ventilation scheme based on natural ventilation should, therefore, be designed to take the maximum advantage of these effects.

Natural ventilation is the only feasible solution in Industries which release vast quantities of heat. Examples of the application of natural ventilation are blast furnaces, heat treatment shop, boiler houses, and engine rooms. Natural ventilation, moreover, is very cheap because it requires no installation and no power consumption.

Mechanical Ventilation

In mechanical ventilation, the mechanical means, chiefly fans, are employed to supply fresh air or to exhaust contaminated air. Fans of various types, such as centrifugal fans, axial fans, roof extractors and ducts are used to effect ventilation. The ducts are of various sizes and designs, and are allowed to run overhead, along walls or underground. This source of ventilation is highly suitable for local exhaust ventilation.

Provisions in the Building

In order to take advantage of natural ventilation, certain structural provisions have to be incorporated in the building design. These provisions are:

1. Height of the building: The greater the height, the more advantageous, it is to have natural ventilation.
2. Windows and Roof Openings: The larger the number of windows and roof openings, the easier it would be to allow fresh air inside.
3. Use of Pre-cast Slabs: Pre-cast cement slabs and hollow bricks may be used to construct walls.
4. Location: An elevated site, far from the maddening crowd, would be ideal for natural ventilation.

Certain provisions have to be made in civil and structural work for artificial ventilation. Schemes for the electrical work of the factory should include provisions for power, switch gear and wiring for the operation of the ventilation equipment. Care must be exercised in the choice of the location of the equipment, air intakes and the points at which the exhaust air should be located far from points at which the contaminant laden air is exhausted.

Care should also be taken to ensure that the contaminants thrown out do not become a nuisance to the public. Although dust control and pollution control do not form part of ventilation, they cannot be viewed separately from the latter. Thus, filters, dust collectors and scrubbers often become a part of the ventilation system and should be duly considered in any scheme of ventilation. Any industrial building should, therefore, include provisions for ventilation, dust control and pollution control.

Ventilation is directly related to the safety of shop floor personnel and engineers and the planners (top management) of operations must take into consideration the working environment as the prime factor for which effective ventilation system must be put in place. This not alone keeps workers healthy but also improves productivity and pre empts any accidents.

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