New-generation double belt conveyors

At the beginning of 2009, the corrugated edge conveyor operated by ARBA, a company based in Altdorf, Switzerland, was replaced with a new-generation double belt conveyor supplied by VHV Anlagenbau GmbH (Fig.). Besides a lower cleaning and maintenance requirement, this ensures a consistent vertical delivery rate with a lower drive power.

As in the case of ARBA’s previously operated corrugated edge conveyor, first the horizontal part of the double belt conveyor is loaded with 90 t/h recycling material, which is then deflected into a vertical conveying direction by the patented flexi drum. The flexi drum, which also deflects the cover belt, draws the material in between the carrier and cover belts. Flat spiral springs in special receivers can dip the cover belt so far into the flexi drum that the stream of feed material remains in the centre even if the two belts are deflected by 90°.

Thanks to the lower required drive power compared to the old double belt system, the material clamped in the middle of the carrier and cover belts can be conveyed vertically over 30 m. ARBA required a vertical conveying height of 18 m.

The new clamping devices ensure the sealing of the belt edges of the VHV double belt conveyors. The belts between which the feed material is conveyed are pressed against each other by pneumatically actuated clamping idler stations. The applied pressure is adjusted depending on the material conveyed and ranges from around 0.5–2.0 bar. Different material behaviour with regard to flowability, moisture content, temperature, lump size and volume of material to be conveyed are the key criteria for selecting this setting.

For dry and free-flowing material, the new double belt conveyor can be equipped with material overflow shafts from which any small quantities of material that may escape from between the belts can be fed back to the material draw-in unit. The new double belt conveyor is suitable for conveying particle sizes from around 1–100 mm. Any isolated larger particles do not cause any damage thanks to the cut-out system.

The VHV double belt conveyor ensures conveying of purified materials, without residue or mixing, for a wide range of materials even when these are conveyed after each other. Equipped with effective scraper and cleaning systems, the double belt conveyor’s maintenance and cleaning requirement can be reduced considerably compared to that of corrugated edge, cleated and pocket conveyors, because conventional smooth belts are used in VHV double belt conveyors.

Compared to bucket elevators, additional belt connections for loading and further transport after discharge are not necessary. The biggest advantage compared to bucket elevators is the continuous and uniform material flow without additional transfers, bucket wear or other problems. A wide range of line systems is feasible and additional costs for expensive basement extensions are unnecessary. Problems with surge emptying, as experienced with pocket or bucket elevators, do not arise with double belt conveyors.

Installed older generation VHV double belt conveyors can be retrofitted with the new system for the bend stations and vertical transport. In this way a much higher cleaning and operating efficiency is achieved, as a result of which the drive power is reduced by around 30 %, with a commensurately positive effect on power consumption.

VHV Anlagenbau GmbH, Hörstel (D), +49 5459-9338-0, www.vhv-anlagenbau.de