Concrete Products

OCT 2016

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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36 • October 2016 www.concreteproducts.com San Antonio-based Robert Ober & Associates is a design/build firm serving an international client base for bulk material han- dling projects that range from $25,000 retrofit contracts to $25 million turnkey plant projects. Its early focus on pneumatic handling for concrete plants has grown to include a wide range of material transfer, weigh batching, and powder blending systems in other industries. About 60 percent of that focus is on new plant designs, the remainder on retrofits. The company began specifying HammerTek Corp. Smart Elbow deflection components in 2001 to reduce material line wear and related downtime, but now also relies on them to cut offload times; reduce degradation/dust; improve safety; and, reduce the space needed for conventional sweep elbow installations. Since initially specifying the deflection elbow—also called a "vortex chamber" or "non-impact" elbow—for wear resistance in concrete plant designs, company founder Bob Ober and colleagues have expanded the device's use to conveying of materials from fine, soft powders to larger, more abrasive particles such as silica sand in size ranges from 200 mesh (74 μ) to 20 mesh (840 μ). "I do not know of a single vortex-chamber elbow being taken out of service, among all that we have put in over these past 15 years," Ober affirms. "They have become an integral part of the fabric of our design any time we are dealing with dilute-phase material transport." His company specifies Smart Elbows as an alternative whenever a client's design calls for long-sweep models; such policy emanated after ongoing client complaints about prior uses of long-sweep elbows requiring excessive maintenance downtime for patching or replacing worn-through ells, or clogging of hygroscopic materials. Rober Ober & Associates has evolved its own installation procedures based on the historic longevity of the deflection elbow's wear resis- tance in client plants. "We will frequently hot-dip the flanged piping and paint the elbows with a zinc-metal cold galvanizing compound, because once they go up they're going to stay there for more than a decade," Ober explains. VORTEX CHAMBER A unique characteristic of HammerTek's Smart Elbow is a nearly spherical vortex chamber designed into the device's curve. Key parameters allow the chamber to capture a portion of the airflow traveling through the line and cause it to double back into the mate- rial stream, creating a deflection zone that minimizes both elbow wear and product degradation. The deflection zone also causes mate- rial to exit the elbow more uniformly across the airstream than in conventional sweep models, where material skids along the outside radius and the downstream conveying line. The airstream sweeps the vortex chamber clean after the material feed is shut off. The tight-radius Smart Elbow design requires roughly one-half to one-tenth the space needed to accommodate long-sweep elbows of equivalent diameter. This enables Robert Ober & Associates to reduce space requirements in new installations and reclaim space in retrofit applications. DUST CONTROL The firm initially specified the deflection elbow to reduce wear and downtime, but now also finds that the component reduces degrada- tion and dust by preventing material impact. By incorporating the Smart Elbow units into plant designs, Robert Ober & Associates has achieved targeted dust control while resolving the issues of wear and of bulk materials plugging pipelines. Bob Ober notes that Smart Elbow installations promote the material flow change from dilute- phase to what he describes as "slugging-phase" flow that deposits materials into storage silos with less aeration and dust. "Using these short-radius vortex chamber elbows provides a more controlled flow," he says, "and for dusty cement and fly ash applications, that's an important consideration." OFFLOAD TIME HALVED Because about 80 percent of Robert Ober & Associates' dilute-phase pneumatic transport installations involve offloading of bulk mate- rials from trucks or railcars into storage silos, transfer times are an important measure of design efficiency. The company optimizes the parameters of conveying systems on an individual basis by applying the performance characteristics of the Smart Elbow design to decrease aeration and increase density, thereby reducing the time a transport driver must wait for materials to settle as the silo fills up. Ober notes that some bulk transport drivers were initially reluc- tant to hook into his plant designs, for fear that the pneumatic INNOVATIONS REPORT MATERIAL HANDLING Pneumatic deflection elbows cut wear, dust, offload time for bulk handling The tight-radius Smart Elbow deflection component provides a con- trolled flow, which is especially advantageous when conveying dusty materials such as cement or fly ash.

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