Operating experience with the Gamma Metrics Cross Belt Analyzer

After a 15-month planning phase a Cross Belt Analyzer from the manufacturer s Gamma Metrics based in the USA was brought on stream in September 1997 in , the limestone quarry of the cement works of Buderus Guss GmbH in Wetzlar. The raw materials operations of the cement works include a total of three quarries. All three deposits contain Middle Devonian granular limestone whi ch varies considerably in quality. The main deposit is also heavily charact erized by ka, st topography. The existing cavities are filled with limeston e, quartz boulders and, in some cases, iron-rich clays. There are also dolo mite strata containing manganese, Fe-Mn ore veins, and their weathering pro ducts. Three independent loading positions in the quarry and a certain degr ee of pre-mixing of the different materials in the crusher hopper were ther efore essential for achieving the correct chemistry in the blending bads wi th a storage capacity of 14 000 to 21 000 t. In the past the blending bed h ad been controlled by a crushed stone sampling system followed by X-ray flu orescence analysis in the production laboratory of the cement works. Long w aiting times between sampling and transmission of the results to the crushe r cont,al room in the quarry, heavy maintenance and repair costs and inadeq uate representativeness of the samples were decisive factors in the decisio n in 1996 to buy the on-line analyzer. The entire raw material mass flow is now analyzed chemically by prompt gamma neutron activation as it passes th rough the analyzer and the result is displayed every minute at the crusher control room. The warranty values given for the Cross Belt Analyzer have be en safely reached in operation. The benefits of the Cross Belt Analyzer ran ge from the introduction of an active quarry management system through more uniform raw material quality up to a reduction in the quantity of limeston e from outside and of the overburden.