Thirty years of reliable operation set to continue as Cauldon upgrades its ATOX® mill with an FLSmidth MAAG bevel-helical gear unit
Located in Staffordshire in the UK, Cauldon cement plant is today owned by Lafarge Tarmac. Its first generation ATOX® vertical roller mill was commissioned in the early 1980s. The raw mill was driven by a conventional bevel-helical gear unit, the TTVL-A 3080A, which consisted of one bevel and two adjustable helical stages. Although Cauldon’s ATOX raw mill was upgraded in 1991, the gear unit had undergone only one design update in its entire 30 years of operation and it was decided that now was the time to replace the gear box.
1st generation ATOX mill with static separator and TTVL-A gear unit
The task was to find the best, most economical solution offering maximum reliability. In particular, Cauldon was looking for a high level of quality in design, materials, and heat treatment gear teeth – all key features of FLSmidth MAAG Gear products.
Different solutions were considered, all requiring a complete replacement of the lubrication unit. The most obvious solution appeared to be to install FLSmidth’s planetary gear unit of type WPU-72C, which is today’s standard solution for new FLSmidth ATOX and OK™ mills and a popular retrofit solution for other brands. But it became apparent that fitting the WPU-72C between the foundation and the grinding table wasn’t the most cost-effective solution in this case.
The final choice fell on a one-to-one replacement of the bevel-helical gear. This unit would fit the existing foundation without the need for major modifications, meaning it was cheaper and faster to erect.
Mark Powling explains Cauldon cement plant’s decision: “A number of different options were considered to provide a reliable long-term solution. These included bringing to condition the existing gearbox; an alternative design, such as an FLSmidth MAAG Gear equivalent; and a new TTVL gearbox as a direct replacement with improved lubrication system.
“We required a long-term solution, and as such, a new gearbox was favoured. Whilst the FLSmidth MAAG gearbox was considered, we chose to opt for a direct replacement based upon the TTVL’s proven reliability, simplicity and robustness. The option of a direct replacement was also beneficial as we already had a compatible spares package, and as a direct replacement, the TTVL gearbox did not require civil foundation or bed-plate modification.” - Mark Powling
TTVL 3080A on trial run in workshop
FLSmidth needed to demonstrate that it could supply a viable solution for the one-to-one TTVL gearbox replacement, meeting Cauldon’s high expectations for reliable mill operation. Several design features were in focus:
• As the original unit was still operational after 3 decades, the general bevel-helical design was approved
• The new TTVL-3080A gear design today features semi-hydrostatic thrust bearing shoes, which is state-of-the-art for vertical roller mills and flexible torque ring connections
• All the pinions and wheels in the helical gearings are ground on the same manufacturing equipment as the planetary units and meet the same high level of quality
• The HPG bevel gear is machined on FLSmidth MAAG Gear’s own Klingelnberg GMC 160 cyclo-palloid cutting system
• The new lubrication system should fit into the existing pit with just minor modifications
• The old unit could still be used as an emergency gear unit
After careful evaluation, it was determined that these design features could be met, and the decision fell on FLSmidth.
Flexible Torque Ring for TTVL-A gear unit
During the design phase, ongoing dialogue ensured that the system would be an optimal fit to the location. The local control unit (LCU) was replaced with an I/O box, as Cauldon wanted to integrate the control system into their PLC. Mutual cooperation and flexibility ensured a smooth change.
The gear unit was successfully tested at the FLSmidth MAAG Gear workshop in Elblag, Poland in September 2014, witnessed by Cauldon inspectors. Tests showed that the gearings were delivering a very low level of vibrations, an essential requirement for the entire setup.
Assembly drawing of new TTVL 3080A at Cauldon
Erection of the unit commenced in January 2015 under the supervision of FLSmidth’s gear specialist and an electrical supervisor. After minor corrections and adjustments, the mill started up again in the middle of February, operating at the desired level of 240 tph at 1600 kW and 150 bar grinding pressure. Mark Powling looks ahead with confidence and says,
“Lafarge Cauldon is very satisfied with the overall project to date. This includes the pre-engineering stage, for which the Cauldon plant received regular updates of the build progress and an option of a site visit during the manufacturing stage. The final installation was supported by FLSmidth with both mechanical and electrical engineers and with in-depth written documentation for future reference. Lafarge Cauldon looks forward to continuing its working relationship with FLSmidth.” - Mark Powling
TTVL 3080A erected under the ATOX 40 raw mill
The gear installation is subject to the coming 1000 hours inspection check in April 2015, where the complete performance will be evaluated and the first reference for the forthcoming vibration analysis will be taken.
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