Cost-effective Solution

Northern Ireland quarry operator demonstrates their belief in the benefits of in-pit crushing

Three Nordberg LT-series track-mounted mobile crushing plants have allowed family-owned aggregate producers Boville-McMullan to embark on an ambitious development programme at their 39ha basalt quarry in Ballymena, Northern Ireland.

Supplied by Metso Minerals (UK) Ltd, the Nordberg crushers are at the heart of a new in-pit crushing operation at Boville-McMullan’s Tully Quarry where high-quality aggregates are produced at a rate of almost 300,000 tonnes/year. The new crushers comprise an LT110 track-mounted primary jaw crusher that is equipped with a pedestal-mounted Rammer C285RC hydraulic hammer for reducing the size of oversize material; and two track-mounted cone crushers — an LT300GP and LT300HP — that perform secondary and tertiary crushing duties. All three machines feature fuel-efficient Caterpillar engines and a remote-control facility, removing the need for a full-time operator.

With blasting usually taking place twice a month, the LT110 is loaded directly from the face by a 50-tonne Hitachi Z-axis 500LCH excavator equipped with a 2m3 capacity rock bucket. When rock is loaded into the crusher’s feeder it undergoes a two-stage grizzly separation process that incorporates a TK screen to separate the natural fines. It then passes through the LT110’s Nordberg C110 jaw crusher from where it is either delivered to stockpiles ready for loading into on-highway trucks, or discharged into the LT300GP, which features a Nordberg 300GP gyratory cone crusher.

Once the rock has passed through the secondary crushing process it is placed in stockpiles from where it is either loaded into on-highway trucks or carried over to the LT300HP by one of the quarry’s 4–5m3 capacity Cat or Volvo wheel loaders. The LT300HP features a Nordberg 300HP cone crusher, another TK screen, and a recirculating conveyor that allows it to operate in a closed circuit for optimum crushing efficiency.

This crushing system, along with the quarry’s two 20 x 5 double-deck screens, produces 11 different products. These include: scalpings, a full range of aggregates for the production of concrete, high-quality sub-base and other building materials. Around 50% of these products are destined for Boville-McMullan’s sister company, Antrim Construction, one of Northern Ireland’s largest independent house builders. Other important customers include two local ready-mixed concrete plants, a pre-cast concrete plant, and a company in South Wales that use the high-quality basalt in the manufacture of insulation products and other building materials.

Since commissioning in July 2002 the LT110 and LT300HP have clocked up around 2,000h. They were joined by the LT300GP in July 2003 as the company responded to a significant growth in demand for sub-base and fines.

Boville-McMullan’s decision to purchase the three LT-series crushers has demonstrated their belief in the benefits of in-pit crushing. According to managing director Mark McMullan: ‘It required us to make a major investment in new equipment, but it was a decision that has already proved to be fully justified.’

Mr McMullan reports that the move to an in-pit crushing operation at Tully Quarry did not require a major re-organization of the quarry, which was only a very small operation before the company started their development programme in 2001.

He added: ‘It has also reduced the number of machines we need in the quarry. This has reduced the number of people working at Tully Quarry to less than half the number that worked in our old quarry at Ladyhill. That’s because we don’t need any off-highway trucks and the crushers are controlled by our excavator and loader operators.’

Mr McMullan also believes that another major benefit of the track-mounted crusher concept is the ease with which the machines can be relocated, particularly when they have to be moved away from the face during blasting.