In the last few articles we have discussed ventilation in mining. Today we will focus on Ventilation-On-Demand in underground mines.
This is a technology that was adopted from building heating ventilating and air-conditioning (HVAC) systems where the use of louver dampers coupled with variable frequency drives provide the right amount of ventilation at each part of the mine currently being occupied.
One of the central components in a ventilation-on-demand system, or VOD system, are the large louver dampers that open to ventilate an area being occupied, and are closed when that area is not being worked.
When there is no mobile equipment or personnel in an area, then there is no requirement for ventilation in those areas, typically after a blast while the dust is settling.
The VOD louver dampers must be of a very special design. In addition to the regular demands of the louver damper, such as good sealing, it also must be able to handle the dust loading in the air that can get into the actuator and bearing mechanism and could cause early failure if the design is not robust enough.
Moreover, the louver must be designed to be able to handle the percussive force of a dynamite blast.
A couple of manufacturers of dampers that pioneered the early work with mining ventilation companies is Effox in the USA and the Flextor brand in Canada. Both of these companies had the required specific expertise in corrosive and erosive environments developed specifically for industrial applications.
However the added demand of percussive blasts was a new twist on traditional custom heavy duty louver dampers. Working with innovative mining companies, the VOD technology was able to be trialed and is now beginning to become more of an established operating strategy.
By positioning the many louver dampers in the mine for ventilation (or non-ventilation) at each location, the correct amount of ventilation is provided for the occupied areas. The large centrifugal or axial primary ventilation fans are then ramped up or ramped down, based on the demand of all the areas being occupied.
VOD can save significant energy costs for a mine. In addition, as the fan will be slowed down, it can reduce the number of cycles of rotation, which has the potential to extend the life of the rotating assembly and thereby reducing maintenance costs on these large fans.
Both the Effox and Flextor brands have delivered a robust, reliable damper for VOD applications and have proven themselves in these demanding applications providing trouble-free operation with only minimal maintenance requirements.