Mining & Quarrying
The quarry's first two years of operation found the plant to be far from the 'dream machine' first envisaged by its designers. The plant's original control system was built around a third-party PC-based control system and human machine interface (HMI) that was plagued with problems. The most essential problem stemmed from the PC control engine's basic inability to reliably monitor operation of the plant's heavy equipment.
2) China's Da Liu Ta Coal Mine (pdf)
Both Da Liu Ta and Huo Ji Tu were designed around the traditional laborintensive mining processes used throughout China's coal industry. Control and monitoring systems on both mine sites were generally disparate and not fully integrated. As a result, Da Liu Ta and Huo Ji Tu comprised a myriad of manual operations — such as the synchronization of multi-stage conveyors via telephone-linked manual operator stations dotted along the length of conveyors.
3) Fujian Zijin Gold Mining (pdf)
From its inception, Fujian Zijin faced great commercial challenges in the turbulent global gold market. Intermittently peaking during 1987 at US$450/ounce, world gold prices have fallen steadily throughout the life of Fujian Zijin mine (at mid-2002, it had fallen to US$325/ounce). This has placed great pressure on Fujian Zijin management to continuously assess and improve the mine's efficiency and throughput. The mine's falling re grade has also added to this pressure.
To help achieve these improvements, the mine has carried out three separate upgrades of the separating plant since 1988, increasing its raw ore processing capacity from 7,000 tons/day to 10,000 tons/day. In the late 1990s it became clear that the separating plant had reached maximum capacity and had become the mine's process 'bottleneck.'
According to UCC Energy senior project engineer, Graeme Lothringer, unlimited flexibility of the overall plant design was essential. "This is completely new technology," he says. "It's important that we have the ability to move equipment around—and add it in, where necessary." Flexibility was also required for ease of scaling up the plant in the future.
5) Vattenfall Europe Coal Mining (pdf)
The traditional slip ring (or wound rotor) motor solution was characterized by high maintenance, a load dependent acceleration with some limitations and no continuous conveyor speed control. The new, variable speed solution had to start and accelerate smoothly independent of load without slipping the belt on the drums, even with overload. The load has to be equally shared on all attached motors at all times, but particularly during acceleration.
As weight and cost are key issues, re-use of existing components and lightweight new equipment is essential. Line side harmonic standards EN 6100-2-4 and power factor (cos (phi)) greater than 0.9 for the operating speed range of 50 to 120 per cent of nominal speed had to be met.