Anyone who follows daily life in a crushing plant can see that there is a lot of movement, heavy machines drive around transporting rock and the crushing process itself may move towards the blasted quarry face as needed. It is easy to see what a problem cabling can be in such an environment. Sometimes cables can be dug into the ground, but often they hang precariously in the air between machines and over roads, or are a tripping hazard on the ground. In an environment where everything moves, it is not just the cables but also the connectors that must withstand harsh treatment.
Wireless systems used at quarries
Wireless technologies are already present in crushing plants in many ways. Wireless remote controls for crushers are common, as are Bluetooth links for transmitting system bus messages and showing crusher data in tablets and wireless links for camera feed transmission.
For remote data collection, cellular (GPRS and 3G technologies) or satellite communications can be utilised. Not forgetting portable radios (walkie talkie) and mobile phone, it is safe to say that radio silence has been lifted in quarries.
Many modern industrial wireless technologies take the presumption that devices are immobile and radios must be battery-operated. Neither of these is true in a crushing plant. Everything moves and electrical power is plentiful. Since the technologies are designed to be efficient for battery operation, using them with wired power makes them very powerful radios for difficult environments.
Lokotracks are already connected wirelessly
One such wireless technology is Zigbee, which shares the licence-free 2,4 GHz band with WLAN and Bluetooth, among others. A recent application for Zigbee is connecting Lokotrack mobile crushing plants wirelessly. The existing interlink capabilities can be utilised, so enabling wireless connectivity is an easy upgrade.
Wireless local area networks or WLANs are an established technology that has become ubiquitous. However, quarry environments with large metal objects and structures have been problematic for WLANs because of reflections that interfere with the transmission of radio waves.
This has changed since the introduction of the new 802.11n wireless standard, which utilises multiple input multiple output (MIMO) technology. This means that multiple aerials are used simultaneously for transmitting and receiving data. Reflections and multiple propagation paths that used to hamper WLAN reception are now useful carriers of data. This ‘wireless-N’ capability is present in modern WLAN capable devices and is a standard feature in all Metso deliveries that utilise WLAN technologies. For modernisation projects, client devices like tablets need to be updated, but the increased range and performance of WLAN 802.11n is well worth the upgrade.
Reliability and security are important
When considering a quarry-wide wireless network, reliability and security should be of the utmost importance. WLAN transmissions can be protected using strong encryption and redundant networks can be built. It is also possible to use WLAN technology for point-to-point links, but not use the normal frequencies allocated as WLAN channels. This makes the wireless link impossible to access with normal consumer equipment, making it safe against attackers or eavesdroppers.
It is also important to separate process data from other data in the network. There can be separate networks for process control and generic data, like video feeds. Access to the process network must be very restricted to ensure availability and integrity, wireless process network components should be duplicated for critical links.
Metso has also deployed WLAN equipment to provide long-distance links, up to 5 km. This is possible using directional aerials, but better technologies exist for very long distances, and sometimes even cellular data can be used. Usually these kinds of links are used to connect remote equipment to the main office, where there is a broadband Internet connection available. This link can then be used to replace a more expensive cellular or satellite data connection.
Wireless applications made possible in quarries
Wireless technologies are just a means to transport data between locations; the most important aspect is the applications they make possible. Rock crushers contain a lot of information that is not very easily accessed, such as logs. Sometimes the only means to view this information is by using a small screen right next to the crusher itself. But, it is possible to show this information anywhere in the quarry after a wireless infrastructure has been built.
The excavator operator can see operating data from the crushers and the quarry manager can see production data and possible error logs, in other words, everyone has a better view to what is happening at the site. This improves productivity and communication.
Another important application is video cameras, which can be installed freely around the plant since cabling is not an issue. Power must still be provided, of course. Video feeds can be transported wirelessly around the quarry, storage and use is easy when digital video feeds are used.
Safety is improved
Safety is also improved. Any time a quarry worker needs to exit the cabin to address a problem, it is a safety hazard. For example, the excavator operator needs to exit the cabin, climb to the tracks and down to the pile of rocks the excavator is on. From there, he needs to go right next to the crusher, in the midst of the dust and noise, in order to use the small screen to see what is wrong with the crusher. Bringing this information to the excavator cabin is an immediate improvement in work safety. The quarry manager who can check crusher logs and production data from his tablet or mobile computer while sitting a safe distance away from the machines is also a lot safer than if he has to go through the machines one by one while the process is running.
In conclusion, modern wireless technologies enable industrial-scale automation solutions in crushing plants, and when designing a quarry, wireless networking should be considered. Metso has the expertise to provide industry-leading wireless solutions to quarries.
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