Laser ranging beats dust problems at power station

The sensor - an LM80 from ABB - helps operators to track the position of rail-mounted coal cars, or paddle feeders, which ferry coal from the station’s receiving hopper to the main conveyor into the combustion process itself.

The ABB units are replacing existing range sensors that kept failing because they could not withstand the tough, dusty environment around the hopper, and were more difficult to set up, requiring the use of a laptop, proprietary software and an RS232 link. Andy Jones, EC&I engineer with Aberthaw operator, RWE Npower, takes up the story:

“The trial unit hasn’t failed once in the six months since it was installed. That’s already a big improvement on the existing sensors. It’s hard to say how much the old units were costing us because a failure didn’t actually stop coals being loaded, but the operators were accustomed to being able to use them, and had developed ways of operating the plant that required knowledge of the position of the paddle feeder.

"Every time they broke down it was another defect for the maintenance department to resolve. In a way the situation is similar to having rear parking sensors on the car – we all managed without them for years, but now we’re used to having positioning sensors and they make everything run more efficiently."

With reliability at the top of RWE’s wish list, Mr Jones acknowledges that the rugged LM80 has delivered the performance the company is looking for: “We haven’t needed any support from ABB following the set-up of the device because it’s never broken down. We literally have had no reason to call them!”

The paddle feeders around the 60m-long receiving hopper were originally driven manually, requiring operators to work in a dusty, inhospitable area. The system was initially automated with the help of CCTV cameras, but these did not enable controllers to pinpoint the location of the cars with any accuracy. In 2009 the company added laser range sensors offer a non-contact alternative for far greater accuracy, enabling the cars to navigate safely and more efficiently.

The LM80 from ABB is a high-performance laser transmitter that accurately measures level, distance and position over long ranges in extreme environments. It features advanced timing and sophisticated signal processing for pinpoint accuracy at up to 100m for level applications and up to 150m for positioning applications. Contained within a rugged, aluminium enclosure, the sensors are non-contact and maintenance-free.