Motive column :
Ø The natural ventilation air current flow around the mine simply because the downcast air column is heavier than the upcast air column of the same vertical height the force causing the motive is the excess weight of the downcast air column 1 m2 in section, an upcast column of similar section.
Ø A column of downcast air having such excess weight is called the motive column.
Measurement of ventilation pressure –
The ventilating pressure ordinary used in a mine are relatively small pressure as compared to with the atmospheric pressure.
Ø The term pressure as used in mine ventilation has precise meaning as follows-
1) Static pressure(RQ2 ) :This is the pressure exerted by a moving fluid on a surface parallel with the direction of movement.
2) Velocity pressure (1/2pv2 ) :This is the pressure exerted by the fluid in virtue of its motion and it varies with square of the velocity.
3) Total pressure : The algebraic sum of static pressure and velocity pressure is called the total pressure.
4) Fan pressure or ventilating pressure : This is the difference between the mean total pressure of the air entering the fan.
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