The Mamba Cement plant is expected to be operational by mid-2016 and will boast the capacity to produce more than one-million tonnes per year, which will be sold to ready-mix and construction industries across South Africa.
This turnkey solution was made possible thanks to a synergistic partnership between SEW-Eurodrive’s South Africa and China branches. The girth gear was designed in China and commissioned before being installed locally to exact client specifications.
SEW-Eurodrive SA managing director, Raymond Obermeyer, explains that the girth gear will be used to transfer the drive torque from the gear motor to the rotary cylinder. “A major advantage of our girth gear is that it weighs less than half of conventional girth gears, while still maintaining the same safety factor.”
This is possible thanks to the fact that the gear is manufactured from first-generation Austempered Ductile Iron (ADI) – a family of heat treated cast irons. The austempering heat treatment converts ductile iron to ADI, resulting in excellent strength, toughness and fatigue characteristics.
The installation process
Once the kiln was installed onto its rollers, the girth gear was assembled and clamped onto the body using the clamp-on tooling. The gear was manufactured in 12 segments. The advantages of this are ease of transport and installation, as well as the possibility to replace only one segment, should a tooth fail. The kiln was rotated 360 degrees with the barring drive, while radial and axial readings were recorded at each of the positions.
Obermeyer indicates that minor adjustments were made, and measurements were well within tolerance. “At this stage, the girth gear was held in position with special adjusting jacks and clamps. The clamps pressed the spring plates against the kiln body. Welders were positioned on each side of the girth gear, and the first weld of 20 mm long was made on both sides of each spring plate.”
The kiln was then rotated 360 degrees, recording the radial and axial run-out in each of the 12 positions. This process continued on every run of weld until the welding was completed, to ensure the girth gear remained within the radial and axial tolerances.
After the final weld, the kiln was left to cool for 12 hours. Then, a final reading of the run-out was noted on the commission sheet before SEW-Eurodrive experts began to set up the pinion that drives the girth gear, after installers confirmed the specified tolerances.
The backlash of the gear teeth and tooth contacts were recorded in the same 12 positions. This was followed by aligning the main drive gear box output coupling to the pinion half coupling, and recording the radial and axial run-out. Obermeyer reveals that this process was repeated with the electric motor to input the coupling of the main drive gearbox.
“All final run-out readings were checked against the maximum and minimum tolerances provided by SEW-Eurodrive and recorded in the commissioning documents. The service technician was onsite to assist throughout the process and was available at any hour if needed,” he continues.
The field service team also checked and recorded the alignment of the whole gear train for commissioning purposes. The next stage will see the commissioning of the lubrication system, expected to take place in late-2015.
Despite the complexity of this project, Obermeyer notes that minimal challenges were encountered. “The largest obstacle was the language barrier with our Chinese colleagues; however, this was effectively overcome with the assistance of a translator.”
Obermeyer notes that a challenge is always welcomed. “Thanks to a global footprint, we are able to share and apply new technologies from other countries to ensure that we remain at the forefront of industry innovation.”
He adds that this project bears testament to the company’s commitment to customer satisfaction that goes beyond drive engineering solutions only.
“We have not only successfully installed our first girth gear, but offered a complete turnkey project solution which included installation, commissioning as well as after-sales service and maintenance when required,” he concludes.
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