8.2 Types of Secondary Ventilation
289
exhausting fan, which must extract a greater flow to reduce recirculation, is placed
furthest away. Normally the recommended configuration for the case of coal mines
is (e.g. ASM-51):
• Distance between the face and air inlet of exhaust duct <10
√
S.
• Distance between the face and the forcing duct <5
√
S.
• The zone of overlap between the exhaust and forcing systems should be between
√
S and 5
√
S.
• With the additional requirement that the flow circulating through the main gallery
must be at least 1.3 times greater than that circulating through the exhaust duct.
With regard to the height at which the ducts are to be laid, the exhausting duct is
usually located on the roof of the gallery, as the gases in the gallery tend to be hot
and will, therefore, rise.
8.3 Required Airflow Rate at the Face
8.3.1 Minimum Airflow Rate to Ensure Miners Can Breathe
(Q op )
The minimum airflow rate required for each independent development heading must
be a function of the number of persons present in the largest shift and assuming a
consumption rate of 40 litres per person per second (e.g. ITC 04.7.01 [MITC 2000]).
Therefore (Eq. 8.1):
Q op [l s
−1
] = 40n
(8.1)
where n is the maximum number of workers that are in the face at a time.
8.3.2 Minimum Airflow Rate Required for Gases to Return
at the Regulatory Minimum Speed (Q r )
This is calculated as:
Q r = A v
where A is the cross sectional area of the gallery (m
2 ).
For works using explosives, international regulations generally require that this
minimum speed should be 0.2 m s
−1 . Thus, the flow will be (e.g. ITC 05.0.01 [MITC
2000]) (Eq. 8.2):
289
exhausting fan, which must extract a greater flow to reduce recirculation, is placed
furthest away. Normally the recommended configuration for the case of coal mines
is (e.g. ASM-51):
• Distance between the face and air inlet of exhaust duct <10
√
S.
• Distance between the face and the forcing duct <5
√
S.
• The zone of overlap between the exhaust and forcing systems should be between
√
S and 5
√
S.
• With the additional requirement that the flow circulating through the main gallery
must be at least 1.3 times greater than that circulating through the exhaust duct.
With regard to the height at which the ducts are to be laid, the exhausting duct is
usually located on the roof of the gallery, as the gases in the gallery tend to be hot
and will, therefore, rise.
8.3 Required Airflow Rate at the Face
8.3.1 Minimum Airflow Rate to Ensure Miners Can Breathe
(Q op )
The minimum airflow rate required for each independent development heading must
be a function of the number of persons present in the largest shift and assuming a
consumption rate of 40 litres per person per second (e.g. ITC 04.7.01 [MITC 2000]).
Therefore (Eq. 8.1):
Q op [l s
−1
] = 40n
(8.1)
where n is the maximum number of workers that are in the face at a time.
8.3.2 Minimum Airflow Rate Required for Gases to Return
at the Regulatory Minimum Speed (Q r )
This is calculated as:
Q r = A v
where A is the cross sectional area of the gallery (m
2 ).
For works using explosives, international regulations generally require that this
minimum speed should be 0.2 m s
−1 . Thus, the flow will be (e.g. ITC 05.0.01 [MITC
2000]) (Eq. 8.2):