Blades on a large heavy metal circular ball spin at a high speed crushing rock and, possibly, releasing dangerous levels of invisible methane gas. Pressure and speed are adjusted by the operator controlling the machine with joysticks and buttons, but this is not your next-generation gaming console.
This is reality 61 metres below ground in a coal mine. The machine: a roadheader.
The roadheader is equipped with tools that grab the rocks and place them on a conveyor before they are sent out of the mine for processing, ultimately to be burned to produce electricity, cement or even steel.
The danger of methane
Although the cliché ‘safety first’ is used in just about every work environment, it has to be the standard in a coal mine where people are working hundreds of metres underground in a hazardous environment.
KFG Electric Systems in Poland is a company that knows this. KFG recently engineered and installed a modern underground coal mining control system that is designed to be used anywhere in Europe with the latest safety features desired by the major mining companies, including protection against methane.
Methane is a big concern for coal miners as it releases naturally during coal extraction. For years, canaries were used in mines to detect high methane levels as they could not survive in slightly lower than the dangerous levels for humans. When the bird stopped chirping, the miners knew to flee. For the last four decades, thanks to modern detectors worn by every miner, methane is detected without killing any birds.
The problem
The controls enclosure that is on the rear of the roadheader measures 1700x700x600 mm with a weight of 1200 kg, making it rock-solid for underground mining applications. It is equipped with a safety Rockwell Automation Compact GuardLogix 43S, a Point IO safety adaptor and a regular Point IO adaptor. A safety PAC is used for safety specific instructions, security and safety I/O.
KFG needed to communicate from the Rockwell Automation system that natively speaks EtherNet/IP to protection relays, EX IOs and other devices that communicate using Modbus.
The solution
The system uses several specialised Modbus devices from different vendors and because of this, it needed a gateway with multiple ports. ProSoft Technology’s gateway has four Modbus ports and is fast with up to 4000 words in 5 ms.
KFG chose ProSoft Technology’s EtherNet/IP to Modbus Gateway to communicate from the controller to the protection relays and other remote Modbus devices. “We didn’t want to be beta testers and use a device made by a one-person company,” Marcin Ptaszny CEO of KFG Electric Systems said. “It was key to have long term support and availability of the device.”
A proven solution was required and hence ProSoft Technology was chosen. A protection relay senses when there could be trouble and transmits the information to the PAC which shuts off the system.
Port 1 of the gateway is connected to an RTU master and communicates with over current protectors. Port 2 is connected to a RTU slave which is used for the remote radio control system that allows the miner to control the roadheader from a safe distance. Port 3 is connected to an RTU master and explosion safe distributed I/O system. Port 4 is connected to an RTU slave and communicates to a surface scada system.
The ProSoft Technology EtherNet/IP to Modbus gateway was easy to configure, diagnose and implement. “This is why the customer loves the add-on profile and add-on instruction we delivered,” said Ptaszny. “They are pleased with the implementation of EtherNet/IP to Modbus gateway, specifically the I/O connection allowing really fast data exchange with the I/Os and the remote joystick in the roadheader.”
Mining is the kind of market which does not implement technological changes quickly. KFG is one of the first companies in the world designing new mining systems this way, using safety I/O and a GuardLogix safety controller communicating with numerous protection relays and EX IOs.
For more information contact Bob Petrie, Throughput Technologies, +27 (0)11 705 2497, [email protected], www.throughput.co.za
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