A French subsidiary of the HeidelbergCement Group, Unibéton is producing specific ready-mixed concrete for the Grand Paris Express project. In order to optimise the production process, the company replaced a planetary mixer with a twin-shaft mixer from BHS-Sonthofen (BHS). For the first time in France, the mixer was installed with frequency converters to enhance operations.
The Grand Paris Express is said to be the largest public transport and infrastructure project in Europe. It comprises four new transit lines and the extension of a further three existing lines. In the suburban area of Paris Issy-les-Moulineaux, Unibéton is using new concrete recipes that require longer mixing times. In order to ensure reliable and homogenous mixtures between batches, the Unibéton management team decided to replace one planetary mixer with the more powerful DKXS 4.50 twin-shaft batch mixer from BHS.
BHS invented the twin-shaft mixer more than 130 years ago and has continuously developed the technology. Unlike the circular motion of other mixing systems, the twin-shaft batch mixer offers a 3D mixing concept that results in an intensive exchange of materials. This happens in the turbulent overlap area of the two mixing circles.
The mixer rapidly produces mixtures with consistently high levels of homogeneity. In the case of ready-mixed concrete, cement and admixtures undergo optimal integration. Admixtures are rapidly and evenly distributed throughout the entire mixture. The 3D mixing concept also leads to shorter mixing cycles and reduced energy consumption.
The mixer is designed with a drive comprising of two 80 kW motors that are coupled with frequency converters. It is further equipped with a fully automatic central lubrication system, high-pressure cleaning, and a moisture probe. The discharging gate opens reliably using hydraulic cylinders.
Frequency converters regulate the mixing speed
For Unibéton, BHS installed a twin-shaft batch mixer type DKX with two frequency converters for the first time in France. The converters have a key role in processing specific concrete recipes. The frequency converters made by Danfoss are designed to control speed. They slow down the rotation speed at the end of each mixing cycle and, as a result, air becomes less likely to be trapped in the concrete and passes at the surface of the mix.
BHS delivered the mixer on time in August 2017. BHS cooperated with the renowned French industrial boiler specialist, Taillefer, to put the new mixer into operation quickly. From the disassembly of the old machine and the assembly of the new mixer, to installing new steel structures and platforms, the company took care of the entire replacement process. Taillefer also supplied the special discharge cone of the mixer, which was designed by BHS.
“The civil works companies in the Grand Paris Express project work with concrete recipes that feature a lot of binders, additives, and plasticisers,” said Alexandre Bernabé, Technical Engineer for the French Market at BHS. “Our technology delivers highly dynamic movement during the mixing processes and is a perfect long-term solution for these new concrete recipes. With two parallel production lines, the replacement was quite a change. Thanks to close cooperation with Unibéton and suppliers like Taillefer, we are fully on schedule.”
“With this mixing line we are producing close to 750 m3/day of concrete and around 15 000 m3/month,” said Stéphane Haffreingue, who is responsible for operations in the Paris area and the Issy-les-Moulineaux site of Unibéton. “Since the twin-shaft mixer has been installed, we have considerable boosted our quality.”
Read the article online at: https://www.worldcement.com/europe-cis/18032019/new-bhs-mixer-for-grand-paris-express/