PECM Issue 17 2015 | Page 114

Trommel Project Benefits From Brevini Expertise & Support Delivering robust and reliable machinery to the mining industry is a specialist task that requires components designed for the job, as well as experience in producing equipment for harsh environments. For one trommel manufacturer in the UK, this meant teaming up with Brevini in order to create a pair of 20 meter machines destined for an iron ore processing facility in Trinidad. esigned to separate materials by size, a trommel is a key piece of equipment within an ore processing facility, but dealing with hundreds of tonnes of rock every hour means that the design must be very robust. Designing and manufacturing a complete package requires several manufacturers to cooperate successfully in order to deliver a properly integrated solution that is both reliable and efficient. For this particular trommel, the power required for normal running would be 520 kW and this would be used to power four drives that would produce a gearbox output speed of 70 rpm. Due to the size and weight of the screens, the initial startup procedure would require 680 kW for around 15 seconds in order to accelerate the machine up to working speed. This additional power requirement would affect the specification of the drives and gearboxes being supplied by Brevini. The Holborne Group is a specialist engineering company that has considerable experience in designing and manufacturing trommels. Based in Shropshire, the engineering team has worked closely with its supply partners to design and construct the latest machine. Brevini was contracted to develop the complete drive package, which included the motors, gearboxes, couplings and electrical control system. The gearboxes were designed around the Posired 2 helical drive units that incorporate a two stage reduction, giving an output ratio of 16:1. All of the units were supplied with identical handling of the input and output shafts, which allowed the gearboxes to be installed in any of the drive positions on the rotary screen. This rationalisation of the design simplifies the installation and reduces the amount of essential spares required. D 114 PECM Issue 17 The reduction gears are housed in a bespoke, fabricated steel housing - as opposed to the more usual cast casing. This arrangement ensures that the gearboxes will fit easily into the restricted space of the trommel design and also eliminates the need for an angled base plate, which reduces the material costs and the manufacturing time for the components. The design of the couplings also posed a challenge to the Brevini engineers since the maximum diameter was limited to 280 mm. Considering the substantial torque that has to be transmitted, the designers created a coupling using a special hardened material that formed fully crowned and barrelled gear teeth giving ±2 degrees of misalignment per gear mesh. The hubs and flanged covers were manufactured from high tensile steel which provided a higher torque capacity and enabled standard couplings to be used for heavy shrink fit applications. All of the components were manufactured to extremely high standards using precision machines; the tight tolerances allowing complete interchangeability.