VENTILATION- Mechanical ventilation, Natural ventilation: MiningSYNC

VENTILATION

Ventilation of mines is a form of air conditioning by the distribution of air currents in U/G opening in quantity sufficient to maintain working places in safe and healthful conditions.

NOTE :

· Its primary function is to dilute and carry away dangerous accumulation of gas and dust.

· It controls quality, quantity and temperature/humidity of mine air.

Production of ventilation-

Airflow from a region of a high pressure to a region of a low pressure . The difference in pressure may be caused by-

1) By purely natural means:- it is then called natural ventilation.

2) By fan:- it is called mechanical ventilation or artificial ventilation.

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The ventilation in a mine using a fan is a combination of natural and mechanical means.

Natural Ventilation :

1. Pressure difference required to cause airflow in a mine, may be produced by natural or mechanical forces.

2. Airflow caused by unequal densities or weight of air column in mines opening and without the aid of any mechanical contrivances is called natural ventilation.

In order to start and maintain purely natural ventilation, two conditions must normally be satisfied-

1) The inlet and outlet of the mines must be at different surface levels.

2) There must be a difference in temperature and density between the two air columns.

Mechanical ventilation-

Fan ventilation- It means artificial ventilation is produced in a mine by fans.

A fan may force the air in mine (forcing fan) or it may suck up the air from it (exhaust fan).

Types of fans-

1) Centrifugal fan

2) Air screw or axial flow fan.

Air screw fan vs Centrifugal fan-

a) An air screw fan requires less space in installation compared to a centrifugal fan.

b) Air screw fans as well as centrifugal fans have an overall efficiency varying from 70% to 85% but the manometric efficiency of axial flow is low only 20% to 30%.

c) The air screw fan is noisy at the high speeds of the blades.

d) An air screw is more suited for low water gauge (pressure) and high volume.

But centrifugal fans are more suited for high-pressure low volume.