Technology advances are giving coal mine operators a wider range of communication channels to choose from. By Peter Eaton*
With today’s monitoring equipment, it is possible to monitor and control just about anything, the only limitation being your budget and imagination. Advances in sensor, PLC and network technologies have given end users a system suitable to all needs and something to suit all budgets.
Most systems require a back bone of some description, the most popular being RS232, RS485/422, fibre optic, radio (both surface and underground options) or ethernet. Each type of system has its advantages and disadvantages, which are briefly outlined below:
— RS232. Requires three wires; cheap; only used for short distances; usually only good for one device in a system.
— RS422/485. Requires four wires; RS232 to RS422/485 converters are sometimes required; cheap; suited for long distances; supports multiple devices connected to the system.
— Fibre optic. The fastest speed of any network; expensive (advances in technology are reducing the costs); immune to electrical interference; fibres are fragile; converters are usually required to connect to equipment.
— Radio (surface). Used when long distances exist between sensor and controller; can be expensive; high speed data transfer is now possible; can be used to extend a computer network to remote locations.
— Radio (underground). Leaky feeder systems can now support a radio network to 9600 baud and eliminate the need to hardwire control cables; modems are cheap; proper set-up is required if the data is to be passed through a repeater.
— Ethernet. Newer devices on the market allow them to connect together in the same way as computers are networked; devices can be set up over this network; high speed control can be achieved; low cost installation.
Australia is the world leader in SCADA packages (System Control and Data Acquisition). When they are connected to the chosen system, it gives an operator a graphical view of the condition, and the option of control, of the plant and equipment. SCADA systems also allow the user to generate reports, raise alarms and develop history trends, to highlight just a few of its features.
* Peter Eaton is systems engineer with Mine Site Technologies.