Anyone who follows daily life in a crushing plant can see a lot of movement; heavy machines transport 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 IN
VOGUE IN QUARRIES
Wireless technologies are already present in crushing plants in many ways. Wireless remote controls for crushers are common. There are Bluetooth links for transmitting system bus messages and showing crusher data in tablets and wireless links for camera transmission.
For remote data collection, cellular data is used (GPRS and 3G technologies), and in remote locations, satellite communications can be utilised. And let?s not forget portable radios, technologies in use at the office or the mobile phone. It is thus safe to say that the 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. This does not prevent us from using these technologies in quarries. Since the technologies are designed to be very efficient in battery operation, using them with wired power makes them very powerful radios for difficult environments.
MOBILES 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 (WLANs) are an established technology that has become ubiquitous. Quarry environments with large metal objects and structures have been problematic for WLANs because of reflections that interfere with radio wave transmissions.
This has changed now 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 utilising 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.
IMPORTANCE OF RELIABILITY, SECURITY
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 network data. 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, and wireless process network components can be duplicated for critical links.
Metso has also deployed WLAN equipment to provide long-distance links, up to five kilometres. This is possible using directional aerials but for very long distances, better technologies exist, 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 a means of transporting data between places. The most important aspects are the applications they make possible. Rock crushers contain a lot of information that is not 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. 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, of course, improves productivity and communication at the site.
Another application is video cameras that 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 to many devices in the quarry and their storage and use is easy when digital video feeds are used.
Analogue video cameras and systems are cheaper, but they are not easily extended and long cabling reduces video quality. Storing the video can also be costly; when using digital video cameras and a central video server, the storage of video feeds comes with no additional costs.
Safety is also improved; workers are quite safe when they are in their cabins. They are protected from the weather, dust and noise, and most importantly, other work machines. Anytime 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, 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 in his car a safe distance away from the machines is also a lot safer and happier 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.?
Antti Jaatinen is the project manager of minerals processing applications at Metso Automation, Tampere, Finland.