8.18 Sizing the Auxiliary Fan
361
(a) Flow rate required to supply adequate fresh air for operators to breathe, (Q op ),
is set as a standard 40 l/s. In the case of five operators:
Q op =
40 l
s · operator
· 5 operators = 200
l
s
= 0.2
m
3
s
(b) Minimum airflow rate (Q r ) to return gases through the gallery at the specified
minimum speed of 1 m s
−1 :
Q r = A galllery v gallery = 30 m
2
· 1
m
s
= 30
m
3
s
It should be noted that this velocity is more usually within the range 0.1 m s
−1−6
m s
−1 .
(c) Airflow rate required to dilute the engine exhaust gases (Q m ) is defined above
and all that is required is to add up the powers of all the equipment that may be
in operation in the gallery at the same time (in this case 1 loader, 1 backhoe, 3
dumpers):
Q m = 0.06
m
3
s kW
· (150 + 100 + 3 · 90)kW = 31.2
m
3
s
(d) Airflow rate required to dilute the gases generated by the explosives used in
blasting (Q e ):
No data are provided on the quantities of explosive used in each cycle; however,
an estimate can be made using a rule of thumb:
Q e
m
3
s
= 0.28
m
s
A gallery
m
2
= 8.4
m
3
s
(e) Calculation of the total airflow required at the face (Q f ):
Selection of the highest flow rate between Q e and (Q op + Q m ):
Q e = 8.4
m
3
s
Q op + Q m = (0.2 + 31.2)
m
3
s
= 31.4
m
3
s
The largest is 31.4 m
3 s
−1 , which is in turn higher than 30 m
3 s
−1 (airflow rate
required for the gases to return at 1 m s
-1 ).
361
(a) Flow rate required to supply adequate fresh air for operators to breathe, (Q op ),
is set as a standard 40 l/s. In the case of five operators:
Q op =
40 l
s · operator
· 5 operators = 200
l
s
= 0.2
m
3
s
(b) Minimum airflow rate (Q r ) to return gases through the gallery at the specified
minimum speed of 1 m s
−1 :
Q r = A galllery v gallery = 30 m
2
· 1
m
s
= 30
m
3
s
It should be noted that this velocity is more usually within the range 0.1 m s
−1−6
m s
−1 .
(c) Airflow rate required to dilute the engine exhaust gases (Q m ) is defined above
and all that is required is to add up the powers of all the equipment that may be
in operation in the gallery at the same time (in this case 1 loader, 1 backhoe, 3
dumpers):
Q m = 0.06
m
3
s kW
· (150 + 100 + 3 · 90)kW = 31.2
m
3
s
(d) Airflow rate required to dilute the gases generated by the explosives used in
blasting (Q e ):
No data are provided on the quantities of explosive used in each cycle; however,
an estimate can be made using a rule of thumb:
Q e
m
3
s
= 0.28
m
s
A gallery
m
2
= 8.4
m
3
s
(e) Calculation of the total airflow required at the face (Q f ):
Selection of the highest flow rate between Q e and (Q op + Q m ):
Q e = 8.4
m
3
s
Q op + Q m = (0.2 + 31.2)
m
3
s
= 31.4
m
3
s
The largest is 31.4 m
3 s
−1 , which is in turn higher than 30 m
3 s
−1 (airflow rate
required for the gases to return at 1 m s
-1 ).