Problem solving

Clean and safe

Extraction plant at "Muskator" in Riesa

There are three good reasons why cleanness is of primary importance in the production of animal feedstuffs. First, feedstuffs be kept perfectly clean to prevent contamination by dirt of any kind. Second, the finely milled ingredients of animal feed are just like any other organic powder or dust. In the right conditions they can ignite and explode. In order to prevent the risk of a dust explosion, all dust deposits must be carefully and thoroughly removed. Third, dust makes an excellent breeding ground for micro-organisms and not surprisingly contains high concentrations of this type of contamination.

These are the reasons why Muskator-Werke in Riesa has installed a fixed dust extraction plant in its production facility. The Ruwac fixed extraction plant serves a production building with eight storeys and covers a height difference of fifty metres. Each storey of the building has suction connections. When the flap of a connection is opened, the extraction unit, located on the sixth storey, automatically switches on and the operator can proceed with vacuuming up any dust deposits.

It goes without saying that the entire extraction plant meets the requirements of ATEX directives regarding the use of equipment in potentially explosive atmospheres; this extraction plant is suitable for use in Zone 21 (Dust-Ex) as defined in the ATEX 100 directive. The directive specifies that only one type of product component can be stored on each storey of the production building. This facilitates recycling because it means that the vacuum equipment on each floor only picks up one type of product dust which can then be returned to the production process. This is done by a cell wheel sluice installed under the filter box of the extraction unit.

The PLC-controlled plant has a suction capacity of approximately 1,000 m³/h. Filter status is monitored by a differential pressure sensor which automatically triggers filter shake-out and dedusting when required. The dust collector bin has a level sensor which controls the emptying of the bin into the cell wheel sluice. Operator intervention is thus reduced to the minimum. Ruwac has developed and built many fixed extraction plants but this one is unique. Muskator's extraction system has 50 metres of vertical piping. The performance and design details of the extraction plant had to take this critical factor into consideration. Here's one example of how it was done. A PLC-controlled pinch valve on the bottom storey empties the pipeline in the overshoot time after the last suction valve has been closed.

Muskator is so satisfied with this extraction plant that it is about to entrust another project to Ruwac. This project will involve improving the system for cleaning and emptying residues from silo vehicles while they are at the loading station. At moment, cleaning tasks like removing deposits from silo struts are done by hand with ordinary brushes. Dusty deposits are simply swept out of the maintenance hatch. Besides being very time consuming, this method no longer meets the product purity requirements specified for the entire production and transport process for animal feedstuffs. Silo trucks must now be thoroughly cleaned before any changeover to new products. It should be added that feedstuff manufacturers and customers are now much more aware of issues surrounding product cleanness.

The new equipment is many more times efficient. The loading station has a steel framework supporting an extractor pipeline. The truck driver just connects up a suction hose to any one of the numerous connectors to commence thorough cleaning inside the silo. The vacuum is a 4 kW AC vacuum unit mounted on a small platform attached to the steel framework. The vacuumed material is collected in a large storage bin. When the level sensor signals that the bin is full, the contents are emptied into a wheelbarrow. The method is as simple as before but much more efficient. The plant is made up of standard Ruwac components, is highly efficient and ensures that silo vehicles are thoroughly cleaned to the high standard specified. The plant also contributes to making animal feed production safer and more hygienic - a topic very close to consumer hearts these days.