Colasit Constructs Three Bio-washer Silos

In an otherwise empty industrial building, previously used by the Swiss army, big things are emerging: The company Colasit from the Berner Oberland region of Switzerland rented the building on a temporary basis to prefabricate 25 mm thick polyethylene panels that would subsequently be assembled in Spain. Three massive silos were built in the Basque Country, as commissioned by the German company m+w Zander Gebäudetechnik GmbH; these are now used in the biological washing process. They were integrated into a cellulose production plant. Using this technique, organic airborne pollutants are now extracted biologically in a multi-stage process. The waste gases flow through packed beds, are absorbed on the surface of substrate substances and are decomposed by micro-organisms. The bio-washer results in a considerable reduction in odor and pollutant emissions. The population of Torrelavega and the surrounding region therefore waited eagerly for the plant to be commissioned.

Each silo consists of four stacked arrays, each with ten wall elements. The panels of the three upper arrays are 3.8 m high, 2.67 m wide and weigh 300 kg, those in the lowest array are half the dimensions. In Thun, Switzerland, they were first mounted on a fixture device with a 4.25 m radius. In order to maintain the curvature, arch struts slot-milled on both sides were mounted of the upper edge of the panels and extrusion joined on the inside and outside. The 210° to 230° hot extruded material was delivered by powerful Weldplast EC4 and S4 hand extruders from Leister (EC4 with brushless motors for worm drive and hot air).

Three inspection hatches and a manhole were also welded on the curved PE panels. The Leister hand extruders also proved themselves equal to this awkward task. To ensure that the hatches did not deform while the extrusion material cooled, the covers were screwed on temporarily after welding. As a fixture aid for the insulation to be mounted later in Spain, four horizontal struts were also mounted on the outside of the individual elements. Here a simple welding seam was sufficient. The 4 mm thick welding seam was produced with the DIODE S hand tool from Leister.

Leister tools were also used in the final assembly phase in the Basque Country: Around 10 Colasit employees welded around the clock, 6 days a week using the Weldplast S4 and EC4 (brushless) extruders. With an output rate of up to 4 kg/h, joining of the parts proceeded apace. The individual panels were mounted in a ring structure and were screwed together on the sides. The vertical joints were then welded. Once the first array was finished, the panels for the second array were inserted into the slot of the lower array offset to the side and were extrusion joined on the inside and outside of the panels. The base and roof segments made of PE were also welded to the wall elements in Spain.

The three completed silos boast impressive dimensions: wall height 13.5 m, diameter 8.5 m, circumference 26.7 m. The plastics specialist from Colasit processed 45 tons of PE panels in total. The total welding seam length amounted to around 5 km!

When the production plant in Spain goes into operation, each of the three silos filled with 510 m3 wash packing and water weighs around 200 tons. No question that the strength of the joints is subject to extraordinary demands.

For Colasit, this contract was one of the biggest in its company’s over 60 year history. Besides the logistics challenge, the tight schedule also had to be observed: In just 5 1/2 months, all the prefabricated elements had to be ready, transported to Spain on nine trucks, the three silos built up and the complete system connected with the cellulose production plant.

For more information, contact LEISTER Process Technologies, Riedstrasse, CH-6060 Sarnen/Switzerland, 41 41 662 74 74, Fax: 41 41 662 74 16, E-mail: sales@leister.com, Web: www.leister.com.