Quarry gets a new blast of life

A quarry in North Yorkshire has solved the problem of limestone dust ‘rat-holing’ in its main silo by using two powerful air cannons supplied by H&H Services.

"Limestone dust, in damp and freezing conditions, adheres to the sides of mild-steel silos and can also bridge across the bin, reducing capacity. Hanson Aggregates’ quarry at Pateley Bridge experienced a reduction in effective bin capacity from 220 tonnes to 150–170 tonnes in their 10m high silo which feeds an asphalt plant and a lorry load-out system."

The main problem Hanson encountered was that the interior surface of the silos was so rough the limestone dust clung to it. Hanson decided vibrating motors were not an option as they would have been both costly and detrimental to the longevity of the silo. Initially the company tried using stainless steel liners 2.5m up the sloping section of the silo to help solve the problem but this was only partly successful. Following a suggestion by one of the quarry staff air cannons were tried.

"The Vibco air cannon consists of a high-pressure tank storing compressed air (80–125 lb/in2) and a quick-release piston valve which instantaneously releases the compressed air into the silo. Operating almost noiselessly, the maintenance-free air cannon works efficiently from any position. Its double-piston design prevents clogging and sticking even if foreign matter enters the valve."