Emergency refuge forms an integral part of an underground mine’s wider Emergency Response Plan (ERP). Fires, explosions, rock-falls, flooding and the release of smoke and other forms of toxic gas are the types of incidents that occur all too frequently, despite the high levels of planning and the safety precautions in place.
In these types of emergencies, when evacuation is no-longer safe or practical, emergency refuge is designed to provide a safe and secure ‘go-to’ area for personnel to gather and await extraction. With the current mining environment, there is a growing industry need for large scale permanent refuge chambers and their requirement has been born out of multiple successful real life uses during underground emergencies such as fires and falls of ground (FOG).
Why use a permanent refuge chamber?
With Fresh Air Bays (FAB) and Portable Chambers commonly in use, it begs the question – why use a Permanent Refuge Chamber? Fresh Air Bays are only fitted with compressed air from the surface, meaning if the supply is compromised or fails then the Fresh Air Bay has no redundancies for life support and the miners are effectively stranded underground. A Portable Chamber’s maximum size will accommodate thirty people, and if the mine site has a large underground workforce then multiple chambers will be required. MineARC can and has supplied complete cost-effective Permanent Chamber projects with life support systems for up to 500 people.
MineARC is one of the few companies with the engineering capabilities to fully assess each individual customer’s site-specific requirements as well as provide hard engineering calculations to validate any equipment selection.
For any refuge chamber to be effective, it is essential that personnel can reach its location as quickly as possible, and can shelter from the immediate threat of fire, smoke and toxins.
The basic requirements for a self-sustaining environment include a respirable atmosphere, an uninterruptable power supply and the ability to thermally regulate conditions inside the refuge chamber to avoid heat stress. Aside from a direct supply of clean, compressed air into the chamber, a refuge should have an alternative, secondary source of breathable air as well as a system for scrubbing carbon dioxide and carbon monoxide from the atmosphere. On top of this, the miners should be supplied with gas detection equipment to verify the relative and continued safety of the refuge.
A secure steel cabinet outside the MineSAFE Permanent Refuge Shelter houses the refuge system’s battery backup UPS (Uninterruptible Power Supply). The UPS is a fail-safe system that can power the emergency refuge shelter’s internal life support systems for a minimum of 36 hours should mains (‘mine’) power become cut-off.
In the event of an emergency, during entry into the refuge shelter, the positive pressure created by Compressed Air Management System (CAMS) ensures contaminants do not pass into the refuge bay. Once all personnel have safely entered the refuge shelter, the CAMS allows filtered mine air into the main refuge bay providing continual, breathable compressed air flow for occupants for the duration of entrapment.
If mine air supply fails, permanent refuge shelters should be fitted with a reliable secondary source of oxygen supply (O2). MineARC Scrubbers operate in conjunction with breathing grade O2 cylinders and are supplied with primary and backup oxygen regulators.
An important factor to keep in mind is that Carbon dioxide (CO2) and carbon monoxide (CO) are expired by refuge shelter occupants as part of their normal breathing activity. Carbon monoxide can also enter the shelter via the compressed air intake if it becomes compromised, and as occupants enter and exit the refuge chamber. In high enough concentrations, carbon dioxide and carbon monoxide poisoning can lead to a loss of consciousness and eventually, death. The removal of these gases is therefore a vital necessity for any refuge shelter. MineARC’s patented Series IV electrical scrubbing system is designed to ‘scrub’ the build-up of harmful CO2 and CO from the air inside the permanent refuge shelter.
To ensure personnel safety once inside the permanent chamber, an airlock is designed to act as a secure staging area between the safety of the refuge shelter and the outside environment. This helps to significantly reduce the threat of contaminants being brought into the refuge chamber on entry. The front of the airlock is designed for easy identification and quick access during an emergency. The strobe lighting, warning siren and reflective signage alerts passers-by to the chamber’s location, while the interlocking rotating door handles provide simple, straight forward access to the safety of the interior. MineARC offers a choice of a normal entry or high flow entry airlock, with several optional add-ons to further improve the flushing efficiency during personnel entry.
The company manufactures a range of bulkhead doors to suit permanent refuge shelter specifications. All doors are constructed from solid steel plate, with double-locking rotating handles, rubber seals, porthole windows, and check valves to ensure a fully sealed emergency shelter. Doors can be configured either with a bulkhead mounting frame (allowing walls to be built around the door), or without a mounting frame, should a door cavity already exist.
For more information visit www.minearc.com or contact MineARC on info@minearc.co.za