Wireless technologies improve efficiency and safety at crushing plants

05 July 2011

Antti Jaatinen, project manager of Minerals Processing Applications at Metso Automation, explains how automation and wireless technologies can provide benefits for customers involved in aggregates production.

Wireless technologies can improve on-site safety. Operators are kept safe when they are in the cabins.
Wireless technologies can improve on-site safety. Operators are kept safe when they are in the cabins.

Wireless technologies are already well used in crushing plants in many areas. Wireless remote controls for crushers are common, for example. 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 utilized.

Many modern industrial wireless technologies assume that devices are stationery and radios must be battery-operated. However, neither of these are 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.

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 utilized, making wireless connectivity an easy upgrade.

Wireless local area networks or WLANs are an established technology that has become ubiquitous. Quarry environments with large metal objects and structures have, however, been problematic for WLANs because of reflections that interfere with the transmission of radio waves.

This has changed now, since the introduction of the new 802.11n wireless standard, which utilizes 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 utilize WLAN technologies. For modernization 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
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, and wireless process network components can be duplicated for critical links.

Metso has also deployed WLAN equipment to provide long-distance links, up to 5km. 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 just 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 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. 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 very important application is video cameras that can be installed quite 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 very 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 improved
Safety is also improved; although workers are safe when they are in their cabins as soon as they need 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.
In conclusion, modern wireless technologies enable industrial-scale automation solutions in crushing plants, and when designing a quarry, wireless networking should be considered.

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