Tata Steel RFID Case Study
In a project to implement an effective anti-collision system, Tata looked at a number of technologies.
Shaft encoders would not work reliably, as coke production is a harsh and highly abrasive environment resulting in wheel slippage and wear so locomotive wheel rotations would not give accurate positioning. Laser and sonar positioning were also unreliable and satellite positioning did not prove effective, as the cooling towers are a brick structure the locomotives disappeared from satellite tracking when inside.
According to Cross-Check Systems, was to implement an RFID installation that would effectively correct the real position of the locomotive shaft encoder in the event of wheel slippage. RFID tags are positioned on a wall alongside the locomotive track at 1.2m intervals, equivalent to the distance between coke oven door centres. Each of the three locomotives, two of which are in service at any one time with one held for maintenance, is fitted with a sealed RFID antenna which is directional. This locates each locomotive to within 30cm and the location is presented in the cab on a monitor.
This location data is transmitted in real time to the central coke plant control room so that the precise location of each locomotive is shown.
Safety – a priority
However, safety controls are automated. The control system measures the distance between the locomotive units, which weigh 110 tonnes each when fully loaded and travel at up to 125m per minute. At 90m apart, each driver gets an audible warning in the cab. At 80m apart, the locomotives are automatically restricted to ‘creep mode’ of a maximum of 25m/min and there is another audible warning. If locomotives should approach within 15m, they are stopped automatically.
A Tata Steel spokesperson said;
“We have tested this system every day for ten months and it is working perfectly. Mechanical equipment tends to wear out very quickly here so radio frequency is ideal.”
The anti-collision system can also be used to ensure workers safety.
“We have the ability to create a ghost locomotive on the track – it’s not physically there but the control system treats it as there. We use this facility as a safety measure when we are on the track to protect the workers.”
There are a total of 309 RFID tags spread along 370m of track. The system employed the use of LRP250 Passive Read/Write RFID tags and LRP820-02 Long Range Passive Reader/Writer. Each tag has an individual identification number so reading a tag reveals the exact location of the locomotive.
The Cross-Check RFID system has already proved so successful that RF tag implementation is planned in other areas.
“We are now looking at replacing the old, unreliable induction loop system on the pusher machines,” concludes Tata Steel. “Each machine weighs 230 tonnes and the induction loops are expensive to maintain and change. The RFID tag system has proved far better.”