New precision metering systems
for the Czech Republic

Best AG is one of the leading suppliers of products for the garden and landscape construction industry in the Czech Republic. As usual in this market segment, the product portfolio includes, among others, a large number of colored products. For the employees of Best the coloring of concrete - and hence handling and use of color pigments - has become a common practice in day-to-day operations since the beginning of their activities in 1990.

Advantages and disadvantages of liquid colors

Already in the early years of the business activities, Best took a decision in favor of automated pigment metering, because the manual addition of pigments can be quite elaborate depending on the quantity and number of concrete color shades required. The company used ready-made pigment suspensions which were metered automatically and afterwards fed into the concrete mixer by means of appropriate liquid metering systems. At first, on the one hand, using liquid colors obviously offered the advantage that handling and use of the pigments needed became simple and clean.

The advantages certainly provided by the application of liquid colors, on the other hand, are also coupled with some disadvantages. First of all, the increased freight charges owing to the large water content are to be mentioned. In addition to that, liquid colors have a limited shelf life contrary to powder pigments. Furthermore, special measures - in particular during winter months - have to be taken in order to keep the liquid color workable.

Switching to iron oxide granules

In view of the specific local conditions and the economic interests, the company finally decided to switch from the so far used liquid colors to purchasing Bayerrox granules in future. This is a dry material with 100 % color strength that does not agglomerate, is easy to meter and suitable for pneumatic conveying. Once the fundamental decision was taken in favor of the Bayferrox G grades, another very important point had to be clarified: It was not possible to obtain the deep blue-black shades desired by Best with the iron oxide black pigments available so far - not even by adding an extremely high proportion of pigments.

The solution for this problem was found by Bayferrox TP LXS 5255 brought to the market recently; this is a free-flowing and low-dusting iron oxide black granule providing a very good price-performance ratio. In comparison with common iron oxide black granules well-known in the market, Bayferrox TP LXS 5255, featuring a significantly higher tinting strength, allows far more bluish colorations. In this way, it was possible to replace the suspension used so far, consisting of iron oxide black and carbon black pigment. Bayferrox TP LXS 5255 now enables colorations being similar in color shade and features a long-lasting weather stability that is typical for iron oxide pigments.

The change to Bayferrox G grades facilitates handling by using metering systems that are pneumatically conveying the pigments metered.

Within just a few months 18 systems supplied

Würschum GmbH was awarded a contract to convert the plants with the appropriate equipment and was able to supply Best AG with the 18 systems requested just within three months. In a two-week cycle four systems each were delivered and installed in close coordination with the staff of Best. In this process, it was necessary to adapt the metering systems to the conditions respectively prevailing on side which was easily possible owing to the modular design of the granule metering system type COM 70. This system is able to serve one or more mixers in a flexible way. The number of basic colors is also variable; Best mostly used four basic colors. It was moreover part of the contract to equip all plants with at least one additional unit in order to allow the company to expand the range optionally by new color shades at minimum effort.

System COM 70 provides highest metering accuracy, which is of vital importance, in particular, as far as color blends are concerned. Because in this case sometimes even minor quantities matter, above all regarding black colors, which have to be added accurately to the gram. For this purpose, the systems are furnished with flexible vibration systems allowing to be set very fast for large quantities or alternatively very precisely for smaller quantities. Stop valves for shutting down in a force-controlled way increase the metering accuracy as well as the system safety, as this prevents granules from falling down inadvertently.

COM 70 integrated in the existing plant control system

The granule solution of Würschum was furthermore characterized by the fact that the control system of the COM 70 can totally be integrated in the existing control system of the plant, thus providing the operator an optimum ease of use. Statistics concerning consumption and metering accuracy are contained in the overall evaluations. All this leads to an increased operating safety and error avoidance, as signal exchange and a change of the recipe are no more necessary. Best AG was able to make a lot of the welded and frame components, being used several times, in their own factory. In this way, the delivery time could be accelerated once more and the price reduced.

Detailed manufacturing documents and the close collaboration between Würschum and the final customer resulted perfectly in a total package enabling the future production of high-quality products in line with the market by means of up-to-date precision metering systems and high-performance granulated pigments.