Gas monitors for tunnelling refuge chambers allow occupants to inspect gas levels inside and outside the chamber closely. Also, when needed, take corrective actions to maintain a safe and inhabitable environment during an emergency.
Due to certain conditions, some gases can occur in a chamber. During entrapment, occupants consume oxygen and exhale carbon dioxide and carbon monoxide as part of their normal respiration. CO and other gases can also enter the chamber during occupant entry and if the compressed air intake is compromised. As a result, internal and external gases need to be monitored by reliable monitoring systems.
Digital Gas Monitoring in Tunnelling
Portable or fixed Digital Gas Monitors (DGMs) automatically detect the presence of gases within an area. The monitors contain specific sensors used to identify hazardous levels of combustible, flammable and toxic gases as we as oxygen depletion within the confines of a refuge chamber.
DGM’s must be calibrated, with portable devices requiring more frequent scheduling. Calibration involves measuring the readable output of the sensor against a known standard to determine accuracy.
Bump tests allow for more frequent examination. These tests expose the gas sensor to a known concentration of the gas, ensuring any audible or visual alerts are activated.
Manual Gas Monitoring in Tunnelling
As a fail-safe, manual gas sampling tube should be in every refuge chamber, along with tracking equipment. Manual Gas Sampling uses single-use, pre-filled chemical tubes that react to air being drawn through the hand-held pump device to test the levels of O2, CO and CO2. A calibrated scale printed on the tubes indicates gas concentrations.
Occupants within a chamber are required to take a sample of air, every hour, and measure gas levels using the instruction on the sampling pump.
External Gas Monitors for a Refuge Chamber
In some circumstances, it may be beneficial to place gas monitors of the exterior of the chamber to notify occupants of external hazards. Customised manifolds enable the measurement of external gases while maintaining a seal against the outside environment. The manifold is placed over a pair of display board modules, sealing directly over the intended sensors. A switch is mounted on the front face to turn on a sampling pump to pull external air over the sensors; the pump then exhausts to the exterior.
Methane Shut Off Systems for Tunnelling
In the event of a methane gas leak, a refuge chamber is no longer safe for operation due to its electrical componentry being at risk of causing an explosion. MineARC’s Methane Shut Off Systems for tunnelling is a manually activated electromechanical system that will isolate all electrical components and will prevent the UPS back up from restarting them. The MSOS unit will fundamentally shut down the refuge chamber and automatically seal the battery box.
Before evacuation from the tunnel, the MSOS is activated by pressing one of the shut-off switches located adjacent to the chamber door (externally) and adjacent to the ELV Scrubber (internally). Personnel will be notified of the chambers state visually with intrinsically safe amber flashing lights and audibly via a different siren. Once activated, the refuge chamber is rendered uninhabitable and is not to be occupied.
Utilising a closed-loop compressed air system, once MSOS is activated, compressed air flows from the cylinders inside the chamber through an actuating cylinder. This cylinder, mounted on the interior face of the battery box cover plate, closes a knife gate valve that seals the battery box. Once the battery box is cleared of any potentially explosive gases such as methane from the local atmosphere and hydrogen from charging batteries, a separate airline supplied from the same cylinders purges air through a gland in the rear bulkhead; pressurising the battery box to a level higher than the surroundings and reducing the risk of contamination ingress.
Once the traces of methane have cleared, and re-entry into the tunnel is safe, the refuge chambers can be returned to service by ensuring that both emergency MSOS buttons have been reset.
Aura-FX Sensor Technology
MineARC Systems utilise a fixed gas detector, specially designed for use in refuge chambers and safe havens, called the Aura-FX Digital Gas Monitoring System (Aura-FX).
Aura-FX provides a more advanced solution to internal and external gas monitors for a refuge chamber. Capable of individually monitor anywhere up to 11 gases, plus ambient temperature, via a series of user-friendly, digital screens. Available in fixed, compact, and external designs Aura-FX can be retrofitted onto existing chambers and is included in all new models.
Audible voice alarms will prompt occupants to replace scrubbing chemicals or adjust oxygen supply levels into the refuge chamber as required.
When utilised as a part of the GuardIAN Intelligence Network, Aura-FX provides real-time gas monitoring data and analysis to the surface. Several MineARC products feature Aura-FX sensor technology to detect, alert, and transmit information on particular gas levels within a mine. Currently, the range includes:
- Aura-FX Digital Gas Monitoring System: A fixed or compact digital gas monitor observes gas levels within a MineARC Refuge Chamber. It is also capable of sending information to the surface via the GuardIAN Refuge Chamber Monitoring dashboard.
- Aura-FX External Gas Monitor: Designed to measure gas levels outside of the refuge chamber, the external Aura-FX sensors will detect gases while maintaining a seal against the outside environment.
- GuardIAN Nodes: Monitor gas levels in surrounding areas, through an expandable network, allowing increased coverage and accuracy of data transmitted between MineARC Refuge Chambers, underground personnel, and above-ground control.
- Aura-PT: A handheld gas detector has been designed to provide underground personnel with the ability to monitor up to six gases within their immediate surroundings. Aura-PT automatically communicates dangerous gas levels back to the GuardIAN Server via the GuardIAN Nodes.