mine safety appliances

With many successful employments of lost persons detection systems in deep mines across the world, the implementation of industrial wireless networks in both surface and underground mines is a noteworthy technological advancement.

The Infrastructure that Enables WiFi in Mine Safety Applications

The successful installation and implementation of mine safety appliances such as Lost Persons Detection Systems (LPDS) in underground mining, depends on the availability of a stable and reliable Industrial Ethernet Network.

By making use of Industrial Ethernet switches from leading brands such as Hirschmann, a robust Ethernet backbone is created as infrastructure for Access Points. These Access Points in the OpenBAT family offer an optimum degree of flexibility, while maximizing cost effectiveness.

Through the use of Clear Space® technology  problems with competing radio frequencies can be avoided, guaranteeing stable WLAN connections at all times. Robust hardware and integrated ESD protection (capable of withstanding electrostatic discharges of up to 25 kV) make the OpenBAT family a dependable model, ideal for mining applications.

OpenBAT hardware by German company Hirschmann have several unique features, which makes it the preferred platform for this application:

  • IEEE802.11a/b/g/h/n WLAN interface as per IEEE802.11n, up to 450MBit/s gross bandwidth
  • Supports Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC)
  • Interference-proof MIMO antenna technology
  • Versions with an extended operating temperature range (-40°C to +70°C) and conformal coating
  • Ideal for use with all Industrial Ethernet switches and routers from Hirschmann™
  • IEEE 802.11i / WPA2 with passphrase or 802.1x and hardware-accelerated AES, closed network, WEP64, WEP128, WEP152, user authentication, 802.1x /EAP, LEPS, WPA1/TKIP
  • QoS according to IEEE 802.11e.  This standard is an important basis for the use of voice applications in WLANs (Voice over WLAN, VoWLAN)
  • Multiple SSID’s supported
  • Supports Wireless MESH based on IEEE 802 11s for dynamic mobile applications and Infrastructure mode for hotspots

Forward Moves of Mine Safety with Wireless Network 

A crucial part of the success of an underground WiFi network with room and pillar layout, is the planning and execution of continuous forward moves.

Industrial Communications Specialist, Profitek’s Minelert, shares their experience in implementing forward moves in terms of Wifi coverage, in shafts with a room and pillar layout such as Anglo Platinum’s Bathopele shaft:

“It is a process that requires utmost accuracy and speed in execution to ensure minimum downtime. Every mine has its own criteria on the frequency of the forward moves. This is dependent on the signal strengths (RSSI values) from the last row of Access Points to the face of the mine.”

Forward moves in Underground WiFi

Profitek’s Minelert recommends following these 6 steps in the execution of forward moves:

1.  Monitor the signal strength over time to see when the forward should be executed.

2.  Forward moves should start once the signal strength reaches -70dBm for voice applications and -80dBm for data applications.

3.  Access Points 5-8 is removed in Figure 4 and re-installed as per Figure 5

4.  The fiber optic cable extension is not spliced with every move. It is installed as needed and the remainder left on the reel as per Figure 6

5.  Every second or third forward move will require an Industrial Ethernet switch as part of the Infrastructure where fiber termination (splicing) will be done.

6.  Enclosures, antennas and the fiber optic cable reel should be installed away from movement of vehicles and should be protected.

Underground Mine Safety