6.3 Airflow Control Devices
233
6.3 Airflow Control Devices
Flow control elements are primarily used to block air passage, direct air to the points
where it is most needed or reduce air short circuits. The use of these devices results
in an increase in the resistance of the ventilation circuits and therefore in an increase
in power requirements.
6.3.1 Deflector Brattices
Brattice is a general category that includes different types of air control devices used
for the partition of airflow in underground mining. Their mission can be to direct
the air into a dead-end gallery or a working place above or below the main airway.
They are also extensively used in emergency events such as fires or landslides. If
they have a permanent mission, they are usually made up of wood, brick, metal
or concrete whether their character is temporary or they are made of cloth of fireproofed canvas. Temporary brattices also receive the name of cloths, brattice curtains
or simply curtains. Airtightness offered by temporary brattices is usually very low.
6.3.2 Overcasts and Undercasts
It is common for intake and return air currents to cross within the mine, especially in
mines with horizontal or sub-horizontal seams. In these cases, overcasts and undercasts are used to prevent short circuits. Overcasts are bridge-type works that allow
two airways excavated at the same level to pass over one another without contact
between them while maintain the cross-sectional area (Fig. 6.32). Undercasts, also
called underpasses, are inverted overcasts, that is to say, one airway descends to pass
beneath the other. Undercasts are not usually used in mining due to their tendency
to fill up with water and debris.
Intake
Exhaust
Fig. 6.32 Air overcast. Exhaust air usually flows through the overcast, as it is warmer and has a
natural draught
233
6.3 Airflow Control Devices
Flow control elements are primarily used to block air passage, direct air to the points
where it is most needed or reduce air short circuits. The use of these devices results
in an increase in the resistance of the ventilation circuits and therefore in an increase
in power requirements.
6.3.1 Deflector Brattices
Brattice is a general category that includes different types of air control devices used
for the partition of airflow in underground mining. Their mission can be to direct
the air into a dead-end gallery or a working place above or below the main airway.
They are also extensively used in emergency events such as fires or landslides. If
they have a permanent mission, they are usually made up of wood, brick, metal
or concrete whether their character is temporary or they are made of cloth of fireproofed canvas. Temporary brattices also receive the name of cloths, brattice curtains
or simply curtains. Airtightness offered by temporary brattices is usually very low.
6.3.2 Overcasts and Undercasts
It is common for intake and return air currents to cross within the mine, especially in
mines with horizontal or sub-horizontal seams. In these cases, overcasts and undercasts are used to prevent short circuits. Overcasts are bridge-type works that allow
two airways excavated at the same level to pass over one another without contact
between them while maintain the cross-sectional area (Fig. 6.32). Undercasts, also
called underpasses, are inverted overcasts, that is to say, one airway descends to pass
beneath the other. Undercasts are not usually used in mining due to their tendency
to fill up with water and debris.
Intake
Exhaust
Fig. 6.32 Air overcast. Exhaust air usually flows through the overcast, as it is warmer and has a
natural draught