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Drives for construction machinery: reliable raw material feed

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Mobile EUROMIX concrete mixing plants from SBM Mineral Processing (SBM) enable economical concrete production and processing directly on site. SBM consistently relies on drive systems from Watt Drive (part of the WEG Group) to drive a variety of conveyor belts in its mobile mixing plants. This includes the mobile EUROMIX 400C plant that processes waste products into storage-grade concrete for the Dutch company Van Gansewinkel. Robust, compact helical bevel geared motors and angle parallel shaft geared motors from Watt Drive are used in this application.

SBM specialises in the development and production of concrete mixing plants and in processing and conveying systems for the natural stone and recycling industries. The Austrian company is a full-service supplier in the ready-mixed and prefab concrete sector and has both mobile and stationary concrete mixing plants in its product line. In late August 2013, SBM acquired the concrete business of the Austrian company Doubrava and integrated their equipment portfolio into its own product line, thereby consolidating its position as a full-service supplier.

The supermobile EUROMIX 400C unit is one of the company’s special products, and boasts its own electrical generator for fully autonomous operation. It is compact, powerful and has approval to be transported via the public highway. SBM developed a microprocessor-based controller specifically for this application to allow the plant to be controlled by a laptop computer over a WLAN. A specially designed high-pressure cleaning system is integrated to reduce service and maintenance effort.

Dutch recycling company Van Gansewinkel uses the EUROMIX 400C to process materials such as excavated soil, bottom ash, sludge and sieved sand into concrete suitable for long-term storage. The plant operates in continuous operation with an effective production capacity of more than 400t/h. For the 400C model, as for other EUROMIX plants, SBM relies on geared motors from Watt Drive for the conveyor belt drives. They drive the dispensing and steep-angle conveyor belts and ensure reliable transport of the raw materials from the plant input to the double-shaft mixer.

Several conveyor belts with reliable drive systems are necessary for smooth operation of the concrete mixing plant. The aggregate is weighed and dispensed according to the desired concrete grade and fed to the steep-angle conveyor belt, which in turn transports the material to the double-shaft mixer. Cement, water and the necessary additives are fed directly into the mixer. The resulting concrete can be taken away by lorry or by ready-mix concrete trucks.

Extreme dust loading

Extreme operating and environmental conditions, high availability and optimal plant use impose high demands on the drive systems. The geared motors must be protected against humidity as well as extreme dust loading. Along with robustness, reliability is especially crucial for operation. Particularly for motorway or tunnel construction, a continuous supply of concrete is essential. The compact design and high mobility of the EUROMIX 400C also requires low-profile gear units with flexible mounting options. Due to the diversity of applications for the mobile concrete mixing plant, it requires a modular gear unit concept that can be adapted quickly to the needs of specific applications by means of optional additional functions.

Drive technology from Watt Drive used in the EUROMIX mixing plants includes various types of gear units from the K Series with torque ratings from 2700–20000Nm. The EUROMIX 400C has a pair of helical bevel geared motors (type KUA 85A 70 134M4) rated at 7.5kW for the two dispensing belts and an angle parallel shaft geared motor (type CSA 80A 70 161M4) rated at 11kW for the steep-angle conveyor belt.

The compact, structurally optimised housing of the helical bevel geared motors (efficiency class IE2, speed 22rpm at 50Hz, torque 3274Nm) features UNIBLOCK design with housings machined on all sides to provide flexible mounting options. The special motor orientation provides a nearly plane, easy-fitting ‘machine interface’. This also applies to the angle parallel shaft geared motors (efficiency class IE2, speed 80rpm at 50Hz, torque 1321Nm). The high rigidity of their housing block with minimal external dimensions also enables diverse mounting and use options. The geared motors are designed for use under severe conditions, such as on-site concrete mixing plants in the present case.

The K Series gear units used here are part of the modular MAS geared motor line of Watt Drive, which enables fast, flexible adaptation to customer-specific requirements. Together with SBM, Watt Drive designs drives optimised for each application according to specific environmental conditions and configures them flexibly for individual needs. Specifically for use in the EUROMIX 400C, Watt Drive configured the helical bevel geared motors and angle parallel shaft geared motors with the following special functions: humidity protection, condensation bores, temperature control (PTC), forced ventilation and protection covers. The angle parallel shaft geared motor is additionally protected by an easily fitted modular backstop. This prevents reverse motion of the steep-angle conveyor belt in the case of power failure. All three geared motors are controlled by energy-efficient frequency inverters.

The reliability and high quality of the geared motors reinforce the confidence of SBM’s customers in the availability and productivity of the EUROMIX concrete mixing plants. Low maintenance, robustness and long life are especially crucial attributes of drives for mobile use in job-site conveyor systems. The combination of high operational reliability and outstanding versatility makes the modular drive units from Watt Drive a good choice for flexible, demanding applications such as the EUROMIX 400C. For further information, please go to www.weg.net.

14 October 2013

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