Smart Elbows save money and downtime for RheTech

How often do you think about elbows? And no, Tennis Elbow doesn't count. Neither does your funny bone. This edition of Best Practices is about plastics operations, not Operation, the battery-powered board game.

Indeed, this month, Best Practices looks at the type of elbows in pipes for resin conveying systems. As the material zips along, the elbow can be a major wear point — especially when moving abrasive fiber-reinforced pellets. The bend of an elbow marks a sudden change of direction.

And blowouts aren't the only problem. Pellets themselves can get damaged, as material moving at a high speed creates dust, as well as frictional heat that can cause pellets to melt as they skid along the walls of the elbow, forming streamers.

Enter something called the Smart Elbow — and yes, the term is a registered trademark — from HammerTek Corp. of Bethlehem, Pa.

RheTech Inc., which makes polyolefin alloys and compounds, was plagued by blowouts once a month on its conventional stainless steel, long-sweep elbows. RheTech is based in Whitmore Lake, Mich., and also has a plant in Fowlerville, Mich. They run 24 hours a day, five days a week.

The conveying lines transport glass-reinforced pellets from extruders to storage silos and to trucks.

Steve Mosher, maintenance manager at RheTech's factory in Whitmore Lake, said polypropylene pellets with glass reinforcement impacted the sweep elbows at high speed, wearing through the elbow walls as if they were sandblasted.

When there was a failure, it took crews one hour to replace each elbow, at a cost of $120 to $150 per elbow, plus $27 an hour for labor. Not to mention downtime.

To address those issues, RheTech began specifying HammerTek's Smart Elbow — 90-degree deflection elbows that prevent pellets from impacting the elbow wall. The company has since installed 140 of them at both factories.

The Smart Elbow features a spherical vortex chamber that protrudes from the elbow. When material moves into the elbow, part of the flow is automatically diverted into the vortex chamber, where it forms a loosely packed mass that rotates slowly in the direction of the flow, gently deflecting incoming pellets around the bend, according to HammerTek.

Pellets exit evenly across the elbow outflow in a laminar state, and HammerTek said they maintain the dilute-phase distribution of particles needed to maximize efficiency of the conveying system. The design prevents abrasion, degradation, frictional heat and streamers.

At the Whitmore Lake plant, RheTech installed about 100 of the deflection elbows on 4.5-inch-diameter pneumatic lines running from the extruders to 70 silos and truck stations. At Fowlerville, the company installed 40 elbows on 5-inch-diameter lines running to 30 silos and truck stations.

"We've replaced only six elbows since installing the original units years ago," Mosher said. "We are more likely to replace the straight sections of pneumatic lines than we are the HammerTek elbows."

Mosher added that quality has improved, saying the elbows, along with adjustments to flow, pressure and heat throughout the conveying system, have also eliminated streamers.