BG Europa complete project for Aggregate Industries-West Drayton under difficult weather conditions.

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  • BG Europa complete project for Aggregate Industries-West Drayton under difficult weather conditions.

15th February 2011 - Despite some of the worst weather in recent years BG Europa (UK) Ltd (BGE) installed a 3.1m x 15.0m drum mixer replacement over the Christmas period at Aggregate Industries West Drayton plant.

Site works commenced in the week before Christmas with removal of the old drum which BGE transported from site for disposal. Over Christmas and New Year the drum, airplate, exhaust base, trunnion rollers and thrust rollers were all replaced with new components.

The drum drive was then modified, and in addition an existing conveyor mounted under the drum (to catch spillage from the previous recycle breaching) was removed as it was no longer required. The project, despite the extreme weather was completed safely within the prescribed time frame.

Phil Coupland, Area Operations Manager, Yeoman Asphalt (part of Aggregate Industries UK) explained: "We wanted to convert our drum mix asphalt plant to enable an increased level of recycled asphalt to be added to our materials. However, we needed to achieve this without increasing the overall amount of equipment we already had on site.

"The dryer drum at our West Drayton plant had come to the end of its economic life and therefore needed replacing. BG Europa offered us a solution that would provide an increase of recycled asphalt from 20 to 50 per cent."

Utilising their extensive experience and working knowledge BG Europa designed and manufactured a new dryer drum mixer shell which was fabricated from 15mm thick 50D boiler plate to offer resistance to flaking under temperature cycling. All flights were manufactured from 10mm EN8 plate bolted to cleats which were then welded to the shell to facilitate replacement. In total the new drum weighed 40 tons and required a 200 ton capacity crane to install within a difficult location over the bitumen tank farm.

Insulated in two sections with 75mm thick rockwool the drying section of the drum is covered with 1.0mm galvanised sheet fixed with plated self-tapping bolts. The two trunnion support rings are forged from a solid billet of EN8 steel, normalised and machined to tolerance to provide a trunnion path free from joints.

Historically the old dryer had suffered from difficulties with tracking and the over slung chain drive arrangement had been problematic. In response to this BGE offered and installed their own design of trunnion roller and pivoting supports which also included drive modifications to provide an under slung chain drive arrangement.

BGE also replaced the existing pillow block bearings with taper roller bearings mounted within the trunnion support roller, as taper roller bearings offer superior performance when handling the thrust forces associated with tracking inclined rotary dryer drums. The rollers are machined from a billet of EN8 steel, before the running face is spin hardened and tempered back to 440 - 500 BHN to ensure long life. The BGE trunnion roller pivot mounting assembly ensures accurate tracking adjustment can be performed to maintain the drum's position on the chassis during operation. Additionally, by adjusting tangentially the design maintains full face contact between the roller and ring eliminating the point contact associated with tracking by other designs. In addition to aiding tracking this also ensures maximum roller and ring life is achieved.

The existing 160 kW overslung chain drive was also modified by the installation of idler and tensioner arrangements. The underslung chain drive is well suited to large heavy rotary drum operation as additional forces are not transmitted to the running rollers. As the drum loading increases the pull on the drive chain it cradles the drum and does not pull the drum down onto the support rollers as occurs with overslung designs. The positive drive provided by the chain is not affected by atmospheric conditions which also blight trunnion roller drive start up.

BG Europa installed their recycle breaching design at the interface between the drying and mixing sections of the drum. Recycled Asphalt Pavement (RAP) is introduced to the dried aggregate prior to mixing with a bitumen/fines slurry. At commissioning RAP additions of 30% were being easily achieved and modifications to the mix design have targeted higher inclusion rates.

BG Europa (UK) Ltd manufacture all equipment and provide full installation services with their sister company Hill and Webster Ltd. Their policy not to sub contract installation ensures customers timely, high quality and safe site services.

Aggregate Industries quarries, manufactures and supplies a wide range of materials to the construction industry. Through continued innovation and investment it has been certified The Responsible Source offering a diverse portfolio of sustainable solutions to complement its traditional product offering. Operating across the UK, Channel Islands and northern Europe, Aggregate Industries is a member of the Holcim Group.
www.aggregate-uk.com