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Unique Features for Rotary Rock Scrubber - Design modifications solve problems.

Rotary Rock Scrubber for Texas Aggregate Plant
Unique Features for Rotary Drum Design

Phillips Kiln Services Ltd. recently supplied and installed a new rotary rock scrubber at the TXI aggregate plant in Bridgeport, Texas. The existing scrubber had a history of problems; cracked welds between the tire sections and screen sections, drive problems, and problems with erosion of the liner and screen bolts. Because Phillips had performed various maintenance projects on this equipment over the past few years, we had first hand experience with these problems. A decision was made to replace the scrubber based on the desire to increase production rates as well as minimize the operational problems experienced with the existing system.

The project began with a design review with TXI engineers and Phillips. This approach utilized the operating and maintenance experience of TXI, and the rotary equipment knowledge and project experience of Phillips. The design modifications that were jointly agreed upon included: 1.) an improved tire mounting system, 2.) an improved shell design with better rigidity to minimize bending and torsional stresses, 3.) switching from a chain drive to a gear and pinion drive arrangement, and 4.) incorporating a simple shielding system to help protect the liner and screen bolts from the abrasive action of the water as it passes through the screens.

Based upon these modifications, Phillips supplied a complete new rotary scrubber that would utilize the existing screen design. The supply portion of the project included new forged riding rings with a "fixed mounting arrangement", the new shell, new thrust rollers and support rollers, and a new flange-mounted gear and pinion. TXI supplied a new motor and gear box arrangement utilizing a fluid coupling for a "soft" start arrangement.

Responsibilities were divided during the replacement portion of the project, with TXI handling the tear-out of the existing drum and replacement of the drum’s water shroud. Phillips supervised this work so that the actual installation of the new drum could be properly coordinated. Phillips’ crews performed the drum installation, beginning with alignment of the new support rollers and thrust rollers. The screens were field-mounted and a lesson was learned about the importance of the proper sequence of installation. The new gear and flange were designed to be field- mounted to allow setting the final run-outs to the drum’s actual operating position. The installation was completed in a seven day outage. TXI project engineer, Joel Dahlin, commented, "I’ve never seen any of our scrubbers run so smooth.

"A second unit is already under way. Based upon the experiences of the first project some minor improvements have been made. The unique features of this application for a rotary drum design continues to make this a very interesting and challenging project.

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