As with any mining process, high accuracy is important, as the ore is weighed to determine mine production rates. In particular, Apatit sought to reduce maintenance time, requirements for spare parts, and modernise its production processes.
Conveyor belt-scales are designed to continuously calculate bulk material flow rate by measuring belt load and speed. They can be installed in many locations throughout a mine or mineral processing operation for rate control, production, and inventory monitoring. Proper selection is important because with increased accuracy comes greater cost.
In addition to high accuracy and reliability, Apatit had two specific requirements for the modernisation and expansion of production at its Russian operations: first, calibration of the belt scale must take place without stopping the process, and second, safety of staff was paramount.
Apatit invited Siemens to test its Milltronics belt scale systems at two mines on the vacuum filters and load mills. Tests were conducted over several months using a variety of calibration methods. Apatit needed to ensure accuracy and reliability even with uneven, heavy or light loading.
Belt scales work by responding to vertical forces, both desired and undesired. Many issues are a result of problems with the conveyor or improper commissioning. Careful evaluation of the application, proper installation, calibration, and routine maintenance will yield years of continuous and reliable service.
A typical belt-scale system is made up of a weighbridge structure supported on load cells, electronic integrator, and a belt speed sensor.
Siemens offered the Milltronics MSI belt scale and the Milltronics MMI belt scale (a combination of two or more MSI belt scales working in tandem). The compact design of the single idler model allowed for quick and easy installation, and reduced the total weighing space required. This allowed for a more suitable area in the conveyor to be selected.
A Sitrans WS300 speed sensor mounted on a self-cleaning bend pulley, or a Milltronics RBSS return belt speed sensor, a calibration test chain and a Milltronics BW500 integrator completed the belt scale system solution. Installation, initial configuration and commissioning of the system was carried out by JSC ROITECH, an authorised Siemens service partner.
After testing a variety of systems from different suppliers, Apatit chose the Siemens Milltronics package. The two belt-scale systems were installed on belts carrying nepheline ore before and after the secondary crusher. The first belt width is 1,600mm with a heavy-duty feed rate of 3,200t/h. The second belt is 1,400mm wide and the feed rate is 500t/h.
Following installation of the belt scales at the material dosing portion of the mill, Apatit noticed improved performance and higher quality of material components in the finished product.
Apatit’s inventories are now measured in real-time, preventing costly inventory adjustments. The company was able to improve capacities and production infrastructure, while increasing output and keeping safety at the forefront.