ACCORDING to Eximo, the Australian mining industry can help assure the safety of employees by developing significant work practices and technologies in areas like mine ventilation.
Eximo says when designing a mine auxiliary ventilation system, the basic objectives are to provide sufficient clean air for workers and equipment, and provide adequate ventilation for the removal or dilution of hazardous gases or dust.
Various factors should be considered, including the quantity of air required, and physical constraints.
Eximo claims air quantity must be considered in terms of both velocity and volume: the air velocity in the entry or tunnel; and the volume of air required for workers, the operation of diesel equipment, the dilution or removal of gases and dust, cooling, and other needs.
Physical constraints can include head room over haulage, or material transport equipment, ducting length and associated handling and hanging problems, potential for damage from operations, and correct sizing.
Other considerations include the legal and contractual requirements for fans and duct, the preferred directional airflow, be it suction or blowing, and acceptable levels of leakage.
Four categories of ducting are available: steel, fibreglass, flexible suction, and lay-flat.
Steel is cheap, non-flammable, holds high positive and negative pressure, allows medium leakage, is low friction, and is best suited for moderate length ventilation runs and single use applications.
Eximo says fibreglass is the most durable of suction ducting materials. It is flame resistant, holds up well under abuse, is light-weight, gives high positive and negative pressure, has a low friction factor, and is best suited for short-length ventilation runs of less than 500m.
Flexible suction is expandable and contractible, allowing storage. This sort of ducting is also flame resistant and best suited for starter tunnels, short ventilation runs, and flexible connections with other types of duct.
The cheap lay-flat type of ducting has a medium friction factor and low leakage in long lengths, but requires an additional fan for reversing airflow.
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