The world’s largest vertical belt reeler has been manufactured for the Sasol Impumelelo mine in Secunda where it will be used to store and unspool 2 195 m of conveyor belting when the mine’s main decline shaft becomes operational.
Upon delivery the 9 m diameter reel weighing more than 185 t (when full) will be installed on top of the shaft and will enable the 150 t belt to be unspooled in a single operation. Thereafter the reeler will be respooled with spare belting to be used for critical repairs, as well as general maintenance of the conveyor when required
Designed by conveyor fastening and accessory specialist, Flexco, the break-through design overcomes previous barriers that had prevented the use of vertical reelers on large-scale projects and has allowed Flexco to manufacture a smaller and simpler mechanical structure. The uncomplicated nature of the design also ensures it has improved reliability over horizontal equivalents and a price tag that is considerably less.
Meeting the challenge
According to Flexco project engineer, Simon Curry, the main challenge of the project was the sheer scale of the task to store more than 2 000 m of 1 800 mm wide conveyor belting, 22 mm thick and weighing in at 70 kg per meter.
In addition, with limited space to work in and a tight budget to boot, the reeler had to overcome the pitfalls of vertical storage and possible compression damage caused by the sheer mass of the belt compressing and overstressing the belt at the core of the reel.
“We also needed to ensure the reeler is able to operate at the highest possible availability as the Impumelelo decline shaft is aligned with the mines’ requirement to employ a single arterial conveyor rather than the usual double system that was previously required on its mines. This means that any belt damage or problems need to be addressed quickly and may require the reeler to spool and unspool replacement belt in order to keep production flowing.
“Although it’s primary job is initially to spool the new belt onto the conveyor, it then has the very important role of storing replacement belt that can be quickly utilised to replace damaged areas or even the whole belt if required. This means that it has to be always available and ready to perform when needed,” explains Simon.
Flexco engineering manager, Neil Cochran, says after much deliberation it was decided that the most versatile option would be for a vertical belt reeler with a large enough drum diameter to prevent compression damage. “Our calculations showed that it was possible and feasible to build a vertical reeler and after confirming with belt supplier, Veyance, that the belt would not be damaged and would still be covered by the full guarantee during storage, we were satisfied to go ahead.
“The operation of the machine is straight forward using a PLC controlled variable speed drive motor to wind the belt on and to rotate the drum from time to time to alleviate compression on any one given part of the belt for prolonged periods. The full weight of the belt is fastened to the base of the drum with a specially designed 1.8 m fastener designed by Flexco to withstand the substantial forces that will be exerted by the pull of the 150 t belt.
“In operation the reeler makes use of a pair of functional brakes that allows the belt to be released down the shaft in a controlled manner even as the full length begins to weigh down the system as it extends down the shaft. The system has an additional pair of fail safe brakes to stop the reel in case of an emergency or failure of the main brakes. The PLC has a system of sensors that controls the torque of the motor in the initial phases to unspool the belt until its weight takes over and gravity pulls the rest of the belt out under braking,” says Cochran.
The project forms a part of Sasol’s Impumelelo project and required close cooperation between Sasol staff along with ELB Engineering Services and Flexco technical teams. In addition, materials and design criteria had to be closely met by the fabricators Bosworth, who built the reeler where after they will provide accurate schematics to the final installers, ELBCON, ELB’s in-house construction company.
“Thanks to the combined efforts of our teams, as well as independent engineering experts Deon Niemann (structural engineer) and Roland Friesenecker (mechanical engineer), the winder was constructed and pre-assembled successfully at the Bosworth factory recently.