Without proper engineering, abrasive materials can cause havoc in pneumatic conveying systems. HammerTek has engineered a solution to this problem that reduces labour, downtime and material degradation.
Moving glass-fibre-reinforced resin pellets through dilute-phase pneumatic conveying lines can be a challenging process. Plant engineers must not only design conveying systems that minimise pellet damage, which affects product quality, but also reduce damage to the lines themselves from the reinforced polymer.
Assuring line integrity is especially critical at bends, where material impacts elbow walls when changing direction, often causing blowouts and related downtime.
RheTech Inc., a supplier of proprietary thermoplastic polyolefin alloys and compounds, has found a way to pre-empt such damage.
The company’s production facilities at Whitmore Lake and Fowlerville in Michigan, United States, run 24 hours per day, five days a week. Its pneumatic lines, which transport pellets from extruders to storage silos to trucks, were previously blowing out conventional stainless-steel long-sweep elbows at a rate of once a month per elbow.
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Steve Mosher, Maintenance Manager at the RheTech Whitmore Lake plant, says polypropylene pellets with glass reinforcement impacted sweep elbows at high speed. They wore through elbow walls as if they were sand blasted. The impact also created dust and frictional heat that caused pellets to melt as they skidded along hot elbow walls, forming streamers.
It took one hour to replace each elbow, at a cost of $169 to $212 per elbow, and $39 per hour for labour – plus interruption of production, Mosher adds.
To address these issues, RheTech began specifying 90º deflection elbows, which prevent the pellets from impacting the elbow wall. It has since installed 140 of them at both plants, preventing blowouts and associated costs of parts, labour, downtime and pellet degradation.
Manufactured by HammerTek, the Smart Elbow design features a spherical vortex chamber protruding from the elbow. When material transitions 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 flow, gently deflecting incoming pellets around the bend.
The phenomenon prevents abrasion, degradation, frictional heat and streamers, while causing pellets to exit evenly across the elbow outflow in a laminar state, maintaining the dilute-phase distribution of particles required to maximise conveying efficiency.
RheTech installed around 100 deflection elbows on 11-centimetre diameter pneumatic lines from the extruders to 70 silos and truck stations at the Whitmore Lake plant. It also installed 40 elbows on 13-centimetre diameter lines running to 30 silos and truck stations in Fowlerville.
“We’ve replaced only six elbows since installing the original units years ago,” Mosher says. “We are more likely to replace the straight sections of pneumatic lines than we are the HammerTek elbows. Blowouts and replacements haven’t been an issue for years.”
He adds that the elbows, along with adjustments to flow, pressure, and heat throughout the conveying system, have also eliminated streamers.