| Written by Mark Buzinkay
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The Mine Improvement and New Emergency Response (MINER) Act of 2006 amended the Federal Mine Safety and Health Act of 1977 to allow greater protection for underground (coal) miners and enhance emergency preparedness.
It mandated mine operators to develop emergency response plans, guarantee that rescue teams were nearby, and maintain communications and tracking systems for use in a crisis. In addition, it also boosted mine safety training and research.
Radio Frequency Identification (RFID) transponders attached to miners' clothing transmit location information to readers strategically throughout the mine for tracking purposes. Personnel in above-ground control rooms can then identify the location of any miner belowground.
Legal safety rules are binding and must be followed. However, most companies do more and understand that protecting miners while they perform their hazardous work is a number one priority in the mining business.
Many mines worldwide use manual tracking to monitor the position of miners underground. Typically, a foreman provides a list of people's names to the dispatcher at the beginning of each shift. This list includes the assigned location within the mine.
Once inside, every move from one site to another must be communicated to the dispatcher via a dial phone in the mine. The dispatcher then edits the list of miners' current spots.
But as with many manual procedures, this type of tracking has several disadvantages. For instance, a miner's location may be within too large a working section to pinpoint their location. Or a worker could forget to inform the dispatcher when transferring to another work location.
Several electronic tracking technologies that overcome the limitations of manual tracking are currently available. One of them uses a reader-based approach based on radio frequency identification (RFID) technology. One typical implementation of RFID technology can be found in retail stores to prevent merchandise from being stolen. A small electronic circuit called a tag (or transponder) is attached to the inventory in this type of system. Two standing gates periodically emit a radio frequency signal at the store's exit. The signal is then received by the tag attached to the merchandise, and the circuit emits a return RF signal if the tag has not been deactivated at the cash register. These RFID systems use ultralow-cost and short read-range (passive) tags. There are many tag-and-reader systems, but active RFID solutions are preferred in industrial surroundings. Each design is optimized to trade-off read range, cost, reliability, and robustness parameters.
In addition to defining the location, tracking systems have other critical characteristics. For example, the system must have the capacity to track the maximum number of people in a coverage area. It must also be able to differentiate each individual in a group of workers travelling in an area of the mine at differing speeds, e.g. walking or riding in a vehicle. In addition, there may be a necessity as to how often the tracking system needs to update each miner's location. These features should be discussed when considering the acquisition of a tracking system.
One of the most common scenarios for miner tracking solutions is visibility. Visibility is the knowledge about the presence and location of individuals in the mine. It is not about knowing the exact position of a person, but knowing in which area she currently is. Zone-based tracking is applied to make the set-up easy, affordable and fail-proof.
Maybe the essential task for miner tracking safety is to register everyone who enters and exits the mine. Readers are mounted at each entry/exit point of the point and must be capable of reading many tags at once at high speed. Big mines transfer their staff each shift with busses to their work stations underground, sometimes 50 people at once. Everyone on board must be registered. WiFi-based miner tracking systems show difficulties to deliver such performance.
Zone-based RFID runs on readers positioned in known locations within the entries, and each miner wears an RFID tag. A tag transmits a unique identifier that has been assigned to that miner. The transponder is read whenever the miner passes within the RF range, and the reader sends an RF signal to which the tag answers. Upon receiving the return signal from the tag, the reader must forward the detection information to a central location, usually the mine operations centre (MOC). The data can be sent in many ways, e.g., over a pair of wires, through fibre-optic cable, via wireless communication, or through an interface to the communications system.
Each RFID reader has a unique identification, and a location associated with that identification so that when a tag is read by a given reader and the information is forwarded to the MOC, personnel at the MOC know that the miner is within a certain radius (the RF range) of that reader's location. Because the miner's location is determined to be within the RF range of the reader, this is referred to as zone-based RFID.
The Operations Manager not only wants to know who is in the mine but also where. From a production point of view, this information is necessary: working in the mine is hazardous, and you want to keep your workforce out of harm's way. All you have to know is the position of your personnel and the actual hazards. Imagine a scheduled blast in zone A/12 at 01:00 am, and as the responsible officer, you first have to evacuate the dangerous area before pushing the button. You must be 100% sure that everyone left the zone. If you can't, you have to postpone the blast and get all your personnel accounted for.
Other examples of location-awareness helping to increase operational efficiency are locating specific personnel within the mine (electrician, first-aid, engineer), moving maintenance crews from machine to machine and analyzing movements for work path optimization.
A third scenario is access control to specific areas of the mine - with or without a vehicle. For security reasons, access should be controlled and monitored. The main principle is to ensure that only assigned workers can access their designated areas. Besides security, there are also safety arguments about closed-off areas: to avoid hazards, some places should be accessible only to trained or authorized personnel. Old and not functional shafts, shop floors with dangerous machinery, and even storage for explosives should be off-limits for most miners. The main functionality of location access controls should be proper and fast identification of personnel.
An RFID tag works as the key for access management, identifying the owner and checking access rights with a database. It can also be used as an entrance opener for buildings or the mine area in general. As RFID doesn't need visual contact with the reader, it is comfortable placing it in your shirt pocket.
An RFID transponder for miner tracking can achieve a high level of safety and security in mines. Being a proven technology, RFID is ideal for the safety needs of underground operations. Miners can be tracked for safety, higher productivity and security reasons. Typical scenarios include knowing who is the mine, where and when to avoid, mitigate or warn of hazards and, therefore, reduce the risks of an accident.
If you want to learn more about miner tracking solutions, read more about Crew Companion and its genuine approach to better mine safety.