Individual Crusher Drive-System Solutions made up of Standardized Gearing Elements

A jaw crusher in France for the comminution of ROM limestone has been replaced with a new Center Sizer solution in the context of a retrofit project. Not only the comminution rolls, but also, and above all, the gearing-system solution, are worthy of note. The reason: Flender combined standard technology with individual elements.

Comminution processes play a central role in the industrial scale preparation of primary and secondary mineral resources. Hazemag & EPR GmbH, based in Dülmen, to the south-west of Münster and possessing more than 170 years of corporate history, is one of the top addresses for high-quality comminution machines. Not only the comminution rolls, but also, and above all, the drive systems, are challenges, as is illustrated by the example of a retrofit project for limestone comminution in France. As the responsible for Center Sizer crushers at Hazemag affirms, “Whenever a new crusher project starts, the first thing we look at is gearing.”

The background to this is, on the one hand, the complexity of such a gearing-system solution and, on the other hand, the customary long delivery times. The project examined here was different, however: in the Center Sizer (HCS) crusher solution intended for France, in which two rolls contrarotate toward the center, Hazemag decided in favor of two FLENDER H3SH helical gear units. The benefits of these systems can be found in their compact size, standardized structure and the resultant short delivery times.

The Aim: Reduction of the Fines Fraction in the Crusher Product

The task of the Center Sizer crusher solution was that of replacing an ageing jaw crusher and, at the same time, increasing the overall system’s productivity. Also important was the optimization of the geometry of the limestone particles downstream the crusher, in terms of size and shape. Particles of a size of less than 40 mm are not suitable for the lime-burning process, and are screened out, causing extra costs for handling of the overall material. On the other hand, the so-called “oversize”, i.e. excessively large lumps, is also problematical for the burning process, since the chemical calcining reaction is not completed in the kiln. As the customer reports, “Our solution made it possible to cut fines content in the crushed product by 5 percent, and also to significantly reduce the oversize”.

Simplified Overall Construction

Flender for the first time supplied Hazemag a non-split housing for the H3SH15 gear unit size. This achieves greater overall stiffness and reduces the risk of leakage. The welded steel housing has a smaller structure than the split housing variant – a compact solution was necessary, in view of the restricted available space, in order that the HCS crusher system would fit into the existing configuration. What is more: the welded steel housing had its own shortened rear dimension, in order to permit positioning of the two helical gear units as close to each other as possible, and achieve the specified shaft spacing of 850 mm without difficulties. As Hazemag confirms, “We were thus able to position the helical gear units at a distance of a few centimeters from each other, making the overall structure of the HCS noticeably simpler.”

Individual Solutions from Standard Elements

A decisive advantage of the gearing-system solution used here is the fact that standard components were individually adapted to the customer’s specifications. In this way, a modular system which can be adapted without great difficulty for a range of different crusher configurations has been created for Hazemag in recent years.

A transmission ratio of 1:40 means that the crusher rolls rotate at around 37 rpm, comminuting the ROM limestone in the process. The motors’ torque is transmitted via the FLUDEX FGD 565 fluid coupling to the helical gear unit. This is important, in view of the fact that brief blockages during the crushing operation would otherwise result in high current spikes in the electric motors. In addition, there would be a danger of damage to the drive train, due to the high kinetic energy in the motors. The hydraulic couplings damp such load peaks, without allowing torque – and thus crusher operation – to break off, in order to avoid both hazards. The breakdown torque of the motors, which in this specific case can for brief periods reach 4.4- fold the rated torque, is used for this purpose. As the customer explains, “This system structure saves us enormous flywheels, which other crushers need”.

All-in Crusher Gearing-System Solution with Potentials

The FLENDER H3SH helical gear unit offers a range of benefits as an overall solution. One decisive point is the fact that the gearing system is designed as a wall-mounted unit. It can thus be bolted to the side of the Center Sizer and needs no additional engineering effort in the form of a fixing frame, and therefore also saves weight and space.

The customer summarizes, and makes a note for the future: “Thanks to the standardized overall structure of this gearing system solution, we can now build even larger crushers without any enormous design changes.” In his estimation, Center Sizer crushers with roll diameters of 1.30 meters and roll lengths of 4 meters would be no problem. This, of course, puts the company in an excellent position to face the challenges of the future.

Author: Stefan Heyne