Hannes Potgieter, specialist ventilation consultant at BBE, describes some of the issues impeding the widespread adoption of ventilation-on-demand in South African mines.
Click here to download and read pdf
If correctly implemented and maintained, VoD can provide significant benefits such as improved safety, enhanced air quality and reduced energy consumption.
Ventilation on Demand (VoD) is an innovative technology designed to optimise airflow within underground mining operations. While this strategy can help reduce operating costs in existing mines, it holds even greater potential for new mines. Moving air through a mine is expensive, and insufficient air quantities can constrain mining activities and reduce a mine's ability to extract ore and generate revenue.
Production losses alone, however, are insignificant when considering the overall impact of an inadequate ventilation system. The primary purpose of ventilating mines is to supply oxygen and protect thousands of miners from inhaling airborne pollutants. Short-term, high-level exposures can be fatal within minutes, while long-term exposures over a career can lead to lung disease, cancer, or a reduced quality of life in retirement. Mining companies that value their workers understand that a healthy workforce is a productive one. Health-related litigation claims have far-reaching consequences beyond occasional production losses, including reputational damage, reduced worker productivity, and legal repercussions that can jeopardise the license to mine.
So, what’s the big deal - can’t you just send in more air if needed? Ideally, yes, but it is not always that simple. Planning a mine and its ventilation system requires careful consideration. Although larger fans are an option and their initial costs are manageable, their operating expenses can be significant. In addition, increasing the volume of air circulated through a mine does not always ensure the desired outcome.
In today’s world where sophisticated technology is available to measure anything in real-time accurately, the mining world largely still relies on production personnel to “choke” a flexible ventilation duct or to set a damper to an approximate position and measure velocities without considering the actual area of the tunnel. Since miners are primarily production-orientated, they often assume everything is fine as long as temperatures remain within acceptable limits.
The ideal ventilation system is one where technology identifies requirements and responds accordingly, with humans overseeing operations and identifying abnormalities. However, implementing such a system is easier said than done. It is often perceived as expensive, shifts the responsibility from production personnel to maintenance personnel, and can be viewed by production personnel as restrictive.
So, where are the savings for new mines? By minimising airflow, the number of shafts needed to carry air is reduced, making the operating costs of fans more manageable and decreasing the overall cost of mining. Shafts are expensive and take a long time to establish. VoD offers a convenient solution to minimise airflow and, by extension, the required number of shafts. Depending on the orebody and mining method, vertically equipped shafts are used to convey personnel and materials, with their primary purpose being to provide sufficient air to the mine to support mining activities.
From a design perspective, VoD has been widely accepted, and many mines using massive mining techniques assume VoD will be implemented. It seems like a great technique to reduce costs and ensure the right amount of air. So, where are we going with this? Well, VoD is often perceived as a fully automated system that adjusts airflow as needed, similar to lights coming on when you enter a room. The assumption is that when a Load-Haul-Dump vehicle (LHD) enters a development end, the fans automatically activate. While this is possible, there are complexities to this assumption. To begin with, we have to ensure the conditions in the development end are suitable for both personnel and machinery. Mining equipment is not designed to operate under extreme conditions, so they have operational limits.
When driving an LHD into a development end, it is possible to achieve similar conditions as with an automated VoD system by manually switching on a fan or opening a damper a little more. However, this approach has its limitations and challenges compared to an automated VoD system. Manually adjusting ventilation can be effective in achieving the desired conditions, but it requires significant effort and time. The human factor plays a crucial role in this method, and is often the reason for its downfall. Manual VoD systems in comparison are set up once, usually at the beginning of a shift, and cannot react to system changes, like other fans being started or fan trips. Implementing remote monitoring of ventilation flows within secondary ventilation systems would be a significant initial step in ensuring that miners are working in healthy environments.
Suffice to say, automation has a lot to offer when it comes to VoD. If correctly implemented and maintained, VoD can provide significant benefits such as improved safety, enhanced air quality and reduced energy consumption. But, despite these advantages, several factors contribute to the slow adoption of VoD in the mining sector:
- High Initial Costs: The implementation of VoD requires substantial upfront investment in sensors, control systems, and integration with existing infrastructure. For many mining companies, particularly those operating on tight budgets, this capital expenditure can be a significant deterrent.
- Complexity and Reliability: Mining environments are notoriously harsh, with dust, moisture, and vibrations posing challenges to the reliability of electronic systems. The complexity of VoD systems requires robust and resilient components, which can be difficult to ensure consistency.
- Integration with Existing Systems: Many mines rely on legacy ventilation systems that may not be compatible with modern VoD technology. Retrofitting these systems can be complex and costly, creating additional barriers to adoption.
- Skills and Training: Effective implementation and maintenance of VoD requires specialised skills. The shortage of trained personnel familiar with VoD technology can impede adoption, as mining companies may be reluctant to invest in extensive training programmes.
- Safety Concerns: VoD systems have to be used with care, especially if the mine is at risk of rock strata gas ingress into the mine’s ventilation system. Stagnant air must be avoided to prevent a build-up of harmful gases like sulphur dioxide, hydrogen sulphide, methane or radon, for example. Navigating regulations and best practice for managing these gases can be a challenging process.
It is important to note that VoD is not universally suitable for all mining methods. VoD is particularly well-suited to massive mining techniques such as sub-level caving, blast hole stoping, or long hole open stoping. These methods benefit significantly from VoD due to their large, open spaces and extensive ventilation requirements. In these environments, VoD can efficiently regulate airflow to match the dynamic needs of different sections of the mine, thereby maximising energy savings and improving air quality.
Conversely, for smaller-scale or more intricate mining methods, the complexity and cost of implementing VoD may outweigh the potential benefits, making traditional ventilation methods more practical.
Despite these challenges, some mining operations have successfully implemented fully automated VoD systems, demonstrating their feasibility and benefits.
VoD holds great potential for transforming ventilation practices in mining. However, overcoming the barriers to its adoption requires a concerted effort from industry stakeholders, government bodies, and technology providers to fully realise the benefits of this innovative technology and pave the way for safer and more efficient mining techniques. The saying, “You can only manage what you can measure” forms the basis for VoD, but it is also important to remember that “Rome was not built in a day”. Mines with successful VoD systems generally start small and then build on them.
