Industrial Utility Efficiency

Riding the Waves to Resolve Common Issues with Dilute-phase Pneumatic Conveying

A long-held practice in the plastics industry is the use of high-speed, dilute-phase pneumatic conveying to deliver plastic resins to plant processes even if those same materials are the kind that can create problems ranging from excessive dust to damaged resins and more. All the while, slower-speed conveyance is normally unthinkable given production goals and the potential for plugged conveyor lines.

Yet, Conair Group, has developed a system that emphasizes the use of varied speeds –including slow-speed, dense-phase conveying – as way to avoid common pitfalls encountered with sensitive resins and other materials conveyed at high speeds, while also increasing throughput rates and saving energy.

Conair Group’s patent-pending Wave Conveying™ system uses controlled speed conveying to convey sensitive resins and other materials with higher throughput and over longer distances – while avoiding problems encountered with traditional dilute-phase pneumatic conveying systems.

Blower & Vacuum Best Practices Magazine visited with Doug Brewster, Conair Group’s Conveying Product Manager at the company’s plant in Cranberry Township, Pennsylvania, to learn how the company’s system breaks with conventional practices to overcome challenges with materials that don’t stand up to high-speed dilute-phase conveying.


Good morning! Tell us about Conair Group.

We’re a global supplier of auxiliary equipment and solutions for plastics processors. We manufacture 450 different products, including resin-drying systems, blenders, feeders and material-conveying systems, temperature-control equipment and granulators. We also offer a variety of extrusion solutions and we excel at plastics process integration, engineering and the installation of  complete manufacturing systems designed to help processors manage raw materials and manufactured parts, while improving process yield. 

In addition to our Pennsylvania plant, we have manufacturing, service and sales operations throughout the United States, China and India. We also have sales and service offices in Mexico, Singapore and Taiwan.


Describe conventional, dilute-phase vacuum conveying in use today.

Dilute-phase conveying commonly involves airflow velocities as high as 5,000 to 6,000 feet per minute (fpm) with corresponding vacuum pressures from five to 12 inches of mercury (Hg). 
With conventional dilute-phase conveying, materials usually enter the airstream of the system at around 3,000 fpm and then build up to velocities as high as 6,500 fpm. 

Conventional dilute-phase conveying like this is very useful and used throughout the world for a wide variety of materials. However, high-speed dilute phase conveying can be problematic with sensitive materials, including common plastics resins like Polyethylene (PE), Polyethylene Terephthalate (PET), Polypropylene (PP) and Polyethylene Terephthalate Glycol (PTEG), as well as well as Long Glass Fiber (LGF) and mineral-filled resins. 

Issues with dilute-phase conveying led us to develop a patented dense-phase conveying system we call Wave Conveying™ because it essentially pulls pellets through the conveying line in bursts of slow velocities versus a dilute-phase conveying system where the pellets travel individually through the line at consistently high speeds. It solves a lot of these issues. 


Why do problems occur with dilute-phase conveying and sensitive materials? What issues are typically encountered?

It all has to do with what’s happening with materials within a high-speed dilute-phase conveying line. 

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