Formerly, an operator dumped 50-lb bags of titanium dioxide, calcium carbonate and two types of talc into the 54- to 72-in diameter high-speed disperser tanks. The process was slow. The powders and granules would often clump, taking a long time to migrate to the center blade’s vortex to fully break down into the desired mix.
Now, the 10-ft-long, 45-degree-angle portable flexible conveyor deposits the dry material directly from the hopper into the vortex. The material disperses uniformly and quickly, ready to flow to the next step, milling.
Bags Dumped Dust-Free
The 4 1/2-in diameter flexible screw conveyor rides on a 6-ft-long cart along with the 36-in square, 9-cu ft capacity hopper. The operator wheels the cart to each mixer to deposit the various dry materials. As the bags are emptied into the hopper, drop-lines from the plant dust collection system connect to the hopper’s dust collection port to siphon off dust. The enclosed flexible conveyor tube minimizes dust to the atmosphere.For power, an electric cord from the cart connects to the nearest outlet in an electric raceway in the ceiling. The conveyor’s electrics are explosion proof, and the conveyor screw is made of non-sparking stainless steel, due to the presence of VOCs used in the paint-making process.
The flexible screw conveyor moves the materials through its polyethylene outer tube enclosing a rugged, flexible stainless steel screw, driven by a 3-hp electric motor. Only the inner screw contacts the material. As the screw rotates in the tube, it self-centers to provide clearance between the screw and tube wall.
Materials Pose a Challenge
Collectively, the five materials are difficult to move using one conveyor due to varying bulk densities and the tendency of several to pack, cake, bridge and otherwise resist flow. They include a free-flowing granular flake resin, a non-free-flowing titanium dioxide powder, two forms of light density semi-free-flowing talc, and a non-free-flowing calcium carbonate.Flexicon applied its Bevcon style flexible screw, which reduces compression of the material on all screw surfaces except the top surface, to propel material in the desired direction, thus promoting flow of the most difficult-to-handle products.
The hopper configuration is also engineered to prevent non-free-flowing materials from bridging. It uses a steep backwall and diametrically opposed sidewalls having panel sections that are skewed outward on a horizontal axis, forming a trapezoidal area. The divergent angles reduce the ability of non-free-flowing materials to establish a bridge between the hopper sidewalls, instead causing material to topple and flow toward and down the steep backwall.
The hopper walls converge to form a trapezoidal inlet to the conveyor interface adapter, which also uses shear planes and vertical walls, to direct material into a rotating flexible screw more positively than with previous rectangular interface adapters. After conveying the materials to the mixers, the operator cleans the tube by reversing the screw rotation and unscrewing the bottom clean-out cap to remove the remaining material.
Robert Wyrobek, Transtar operations manager, says he considered other flexible conveyors and a continuous tubular disk conveyor, which he concluded was a high maintenance item. He chose Flexicon after its local representative, Michael Lorr, of McKay Process Systems, Stanwood, MI, and Flexicon ran tests on the materials and found a workable solution.
Plant to Expand
Transtar plans to retool its plant to meet increasing demand. “Our four-year plan looks to double the sales we have today,” Wyrobek says. Flexicon conveyors, having proven their mettle, will figure importantly in realizing that growth. cFor more information on conveyors, contact Flexicon Corp., 1375 Strykers Road, PO Box 5269, Phillipsburg, NJ 08865-5269; phone 888/FLEXICON; fax 908/859.4820; e-mail sales@flexicon.com.
