New Granule Dosing System at Kreher Beton

Kreher Beton GmbH in Aschaffenburg Germany has a tradition as reputable, high-quality concrete product manufacturer. In the middle of 2017, the company made the decision of adding a new cutting-edge Würschum color dosing system to a rather outdated metering system for liquid colors.

For Mr. Theo Kreher, it was a matter of importance to change over to granule pigments with this new color dosing system. “Considerable contamination frequently occurs during malfunctions with liquid metering. The consistency of liquid color due to fluctuations in temperature and sedimentation is another reason for changing over to granules as well.”

Very high requirements

The requirements placed on the new granule system were high: additive dosing of eight basic colors, very high precision, cleanliness and frost protection. The Würschum system was able to fulfill all these specifications to the customer’s complete satisfaction. The basic concept is that the eight base colors are all positioned in a row and available for dosing at the same time so that changing color positions can be avoided. It also meant that the system was able to be installed in an optimum, space-saving layout along a conveyor belt in a hall. This also created sufficient room for a forklift to be able to manoeuvre easily.

The system functions with a stationary weighing hopper into which all eight pneumatic vibration feeders can dose. This accelerates dosing cycles since no travelling times of the weigh hopper are necessary. All connections are firmly joined and dust-free so that no dust can escape.

The vibration feeders can run at three speeds – coarse, fine and super-fine – with the purpose of functioning rapidly but very precisely as well. Quantities of pigment from 100 g up to 30 kg can be weighed with a precision of up to +/-5g in the extremely accurate weighing hopper of this COM 70-1 granule unit. It can all take place without restrictions on the dosing speed of max. 1 kg per second, which means that big batches can also be weighed rapidly and precisely. Its maximum accuracy of +/-5g is particularly important with color mixes to be able to maintain fine nuances with shades of yellow, for example. These pastel colors can also be mixed with shades of red and black according to customer wishes. This, again, is all controlled by recipe. The color system’s control unit was fully integrated into the Dorner control of the entire mixing and batching plant. Thanks to their many years of good cooperation with each other, Dorner and Würschum work seamlessly together in such cases.

Protection against frost specified by the management at Kreher Beton is another of the system’s special features. A frost monitor was integrated into the COM 70-1 dosing system, its housing was well insulated and sealed. The conveying hose was also thermally insulated to prevent condensation water forming through fluctuations in temperature.

High-class colored concrete products

The customer’s requirements in respect of cleanliness had also been clearly defined. Instead of open big-bags, rigid plastic containers are now utilized, which can be easily closed and better sealed off with the system. Before these containers are lifted after being emptied, the outlet is shut to prevent even the smallest amount of pigment from dribbling out.

The granule batch is conveyed pneumatically in two filter cyclones installed above both mixers. These cyclones also facilitate cleanliness as they filter off the conveying air. At the same time, a color batch can be held in intermediate storage in the cyclones, should work with a mixer be delayed.

This system has put Kreher Beton GmbH from Aschaffenburg in a very good position for manufacturing high-class colored concrete products in the future. Kreher’s product designers now have practically no limits in implementing their ideas. As Theo Kreher, managing director and owner, puts it: “The Würschum system has lived up very well to all our requirements and we have been very happy with how the installation, commissioning and training turned out as well as with how the color dosing system operates on a daily basis.”