Underground mining operations are fraught with dangers as tunneling through earth presents miners with unfamiliar environments and a host of problems that affect the health and safety of workers. Lack of ventilation is one of the biggest obstacles.
In strip mining where miners work on the surface of the earth, oxygen is plentiful despite the air being clouded by dust. Underground mining churns up toxic gases, little breathable air and newly introduced particulates from machinery. Ventilation solutions to create a safe working environment are, therefore, needed to prevent health hazards.
Ventilation systems designed for underground mining reduce the amount of goaf gas like methane and carbon dioxide released from mines. The systems work alongside ventilation shafts excavated to draw in oxygen from the surface. These shafts are created after careful planning to determine size, shape, airflow and location of control devices.
Mining methods vary according to requirement and ventilation systems must adhere to the different techniques. For example, drift mining where horizontal tunnels are excavated will not benefit from systems designed for slope mining and vice versa. A meticulously detailed ventilation plan understands this.
In all ventilation systems, two circuits exist to ensure proper air flow and removal of gas. Flow-through ventilation is the main circuit while auxiliary circuits distribute air to various mine workings. The use of fans, brattices, overcasts and regulators helps facilitate airflow where needed and controls its volume.
Mines located in areas that witness extreme weather like the Arctic regions have even more use for ventilation systems. Aside from filtering gas and bringing in clean air, the shafts invite warm or cold air to maintain temperatures not only for the comfort of miners but for the equipments as well. When planned correctly, cold air prevents melting of permafrost which can prove dangerous to mining operations when liquefied.
Common ventilation control devices
Ventilation control devices direct airflow where needed. Certain devices are standard and are used in most underground mining operations.
Stoppings: Stopping’s are walls set up to channel airflow in a direction. They may be permanent or temporary. Since the risk of fire hazards is high in mines, the materials must be fire retardant and fire resistant.
Man doors and air locks: Man doors are doorways mounted in stopping’s to provide passage to workers. Air locks are a set of two doors built to maintain air pressure as workers go through man doors.
Brattices: Brattices are partitions made of wood or cloth to control and direct the entry of fresh air and the exit of gas. They’re installed between columns of mines.
Overcasts: Overcasts guide air across intake and return airways if the air is required to cross but not come into contact with either intake or return air. Prefabricated steel and concrete blocks are generally used for overcasts.
Regulators: Regulators control airflow and pressure in a section of a mine by keeping them to desired levels.
Booster fans: Booster fans adjust airflow by enhancing it and directing it to a section of a mine. Some countries have regulations regarding them because they can cause undesirable recirculation of air. If used, they must be integrated into the ventilation system without interfering with airflow. Auxiliary fans are smaller and less powerful than booster fans and are used more frequently.