Central Plains Cement — Raw Mill Duct

Since 1905, Central Plains Cement Company has provided Portland cement of varying grades for industrial, civil, and personal concrete projects throughout the Midwest. One step in this limestone extraction process involves blowing chunks of crushed limestone through a massive duct that is roughly 160 feet long and 7 feet 9 inches in diameter, mounted between three towers at a 63-degree angle.

Although the duct is made of resilient material, the over 20-year-old duct had reached the end of its design life and needed to be replaced. For the new duct, Central Plains wanted to install one with a larger diameter. However, the expanded diameter would require changes to its supports, transitions, and connection to the mill at its base. The new one would be fabricated off site and the crew had a limited window to complete the installation during the plant's scheduled maintenance shutdown.

Central Plains hired the Rogue Visual Design team to document the existing duct. Using a combination of our stationary laser scanner and UAS/drone, we were able to capture the exterior of the entire duct and its connections while the duct was still in operation. Considerable shaking caused by two 50-ton rolling mills at the base of the duct, and nearly 110 feet of vertical distance between two of the platforms presented significant challenges — but as always, the Rogue team was up to the task.

Once the drone and scan data sets were processed back at the office, our talented BIM team created an updated Revit model of the existing duct incorporating the original design from the PDF with the existing as-built conditions. The 3D model provided Central Plains the specific dimension information needed to determine if the new duct would fit properly prior to installation. The engineering team was able to ensure the new duct was fabricated to fit, and the installation at the plant went smoothly during the short maintenance shutdown.