The new generation of impactors from German manufacturer Hazemag promise to increase throughput and crushing efficiency and at the same time reduce wear costs, says Stefan Koch of Hazemag.

The work at the Belgard quarry of Roadstone Dublin just shows how adept the crushers are in handling demanding projects, he says. The quarry wanted to fulfill the requirements of Irish Specification CI 804 and replace its rather dated impactor being used for the production of high-grade gravel.

Hazemag claims that during the first six months of operation with the new impactor, the production and sales of gravel as per CI 804 at the quarry have doubled, in no small way due to the 'intelligent' hard rock crusher from Hazemag'.

Koch explains: 'The parameters for the new machine were a capacity of up to 450 tonnes per hour (tph) and an availability rate of at least 97.5 per cent. The feed material, an abrasive limestone typical of this region, has a crushing resistance of 15 kN/sq cm and a chemical analysis provided by the Technical Institute at Aachen revealed an SiO2 content of up to 22 per cent.'

Low-level, variable-speed conveying equipment extracts pre-crushed material (0 to 25 mm, 25 to 50 mm and 50 to 120 mm) from three stockpiles to provide feed material for this impactor that conforms to the specifications of CI 804.

'The new impactor had to permit the integration into the existing control system, to be effected from the main control room located 100 m away and high demands were also made in respect of wear cost reduction and ease of maintenance,' he says.

'In order to satisfy all these requirements, the Hazemag engineers recommended one of the new generation of hard-rock impactors. On the basis of Hazemag's know-how and wide experience involving AP-K and AP-PH series impactors, a totally new concept for this impactor range was developed.'

'One of the main changes was the completely new design geometry of the crushing chamber. The combination of hydraulic impact apron mounting and optimised crushing chamber configuration resulted in the introduction of the AP-KH and AP-KMH series of impactors (A = Andreas-type impactor; P = Prallmپhle - which means impactor; K = Kies - hard rock; M = Mahlbahn - grinding path; H = Hydraulic impact apron mounting)
The impactor is based on a modular design, whereby the fitting-out of the impactor as well as the arrangement of the control system can be tailored to suit the customer's particular needs, right up to fully-automatic operation.

'The welded housing is lined with square cast plates of highly wear-resistant material, fixed in place by a well-proven wedge securing system,' he says.'Thanks to their uniform, symmetrical shape, the wear plates can be turned or interchanged to protect high-wear zones and minimise replacement costs.'
'The housing has three main sections. The front section, including the face wall, is hinged and can be opened hydraulically for maintenance purposes.'

'Mounted on the impactor rear wall with hydraulic support are two impact aprons. Together with the impact aprons and wear liners, the hinged rear wall can also be opened hydraulically. This arrangement provides excellent accessibility to wear plates, impact aprons and grinding path.'
'For this particular application, Hazemag has chosen the well-proven K-type rotor. The newly-developed double-groove blow bars for this open disk-type rotor have a high utilisation rate of 50 per cent and changing and turning it has also been greatly simplified.'

'The impactors of this range are equipped with two pendulum-mounted impact aprons located in the upper part of the housing. They are actuated by hydraulic cylinder, by means of which the gap settings can be adjusted at the touch of a button to suit the particular requirements. The impact plates are replaced with the help of a special changing device.'

'In addition to two impact aprons, the impactor for Roadstone was also fitted with a grinding path in the housing lower section. This grinding path similarly has a hydraulic mounting system, and is correspondingly easy to adjust,' he says.
The impactor has the 'Haztronic' automatic control system, which permits the integration with existing measuring and control systems as well as connection to visual control units.

Koch adds: 'As an option, the 'Haztronic' can also be used to incorporate the speed of the rotor drive on a frequency converter into the regulating system. The plant operator is then in a position to individually set all the parameters, which influence the impactor product, allowing him to react to the demands and requirements of his customers.

'Up to now, the Hazemag AP-KMH 1320 impactor has fully met - and in some cases greatly exceeded - all requirements. In fact, despite the varying composition of the feed material, the demands of CI 804 have been fulfilled satisfactorily. The guaranteed wear costs called for by the customer have also been undercut by about 30 per cent,' Koch points out.