Page 45 - Advanced Mine Ventilation

28 Advanced Mine Ventilation

Table 2.6 Equivalent Lengths for Shock Losses a

Source Shock Loss in Feet
Acute bend, sharp 150
Acute bend, round 3
Right angle bend, round 1
Right angle bend, sharp 70
Obtuse angle bend, round 1
Obtuse angle bend, sharp 15
Doorway 70
Overcast 65
Inlet to a duct 20
Discharge from a duct 65
90 split in airway 200

Mine car (blocking 20% of airway) 100
Mine car (blocking 45% of airway) 500

a
Adapted from Mine Ventilation by Hartman et al. [14].

2.7 Mine Characteristics Curve

When the pressure and shock losses for an entire mine network is determined and
ventilation surveys (to be discussed later in the book) determine the air quantity needed
to properly ventilate the mine, it is necessary to create a “mine characteristic” to select
a matching fan. A plot of pressure requirements in the y-axis for different ventilation
quantities on the x-axis is known as “mine characteristic” (curve).
For derivation of this curve, we again use a modified Eq. (2.18). It can be rewritten
as

H ¼ RQ 2 (2.18)

where

KPL
R ¼ 3 .
5:2A
R is the sum total of all resistances to flow if we can use the analogy of the voltage
needed to make a current of Q to flow through a conductor of resistance, R. It is usually
the resistance of the split with the highest resistance called “free split.” Other splits
may be regulated.