Conair rethinks materials conveying with vacuum power
For one plastics processor, conventional conveying approaches were falling short. That’s when the company turned to Wave Conveying — a patented technology from Conair that makes it possible to move any type of resin at a constant velocity over long distances with minimal damage to material or equipment.
Among its other benefits, the Wave Conveying system can be retrofitted to existing systems, said Doug Brewster, conveying product manager at Conair. Once it completed the retrofit, Conair’s customer saw some dramatic results.
“We recently visited a customer and installed seven automatic flush valves, one on each receiver in the system,” Brewster recalled. “The customer’s load times dropped from 20 seconds to 7 seconds. He picked up 13 seconds per receiver. This allowed him to serve additional receivers using the same system, just because of the valve.”
What makes Wave Conveying unique is that the air volume and material flow volume are independent of each other, and Conair’s FLX-128 Plus control automatically changes recipes based on which receiver is calling for material.
“It is the first vacuum-powered material handling system able to precisely control both the material speed and volume. It presents molders with an opportunity to automatically move different materials through a vacuum system at a speed that is ideal for that resin,” Brewster said.
Wave Conveying systems have a variety of modes, including Wave Flow and Pulse Wave Flow; users also can run the system as a traditional dilute-phase conveyor. Suited for conveying materials that are prone to smearing or shattering, Wave Flow delivers speeds from about 1,000 feet per minute to 1,800 feet per minute. Pulse Wave, which carries materials at speeds ranging from about 300 feet per minute to 900 feet per minute, is ideal for moving abrasive resins.
For less sensitive materials or less critical applications, users can run the Wave Conveying system at conventional dilute-phase speeds.
PROBLEMS WITH CONVENTIONAL CONVEYING
The gentleness of Wave Conveying is in contrast with other common conveying approaches, such as dilute-phase conveying, which can damage pellets.
The pulling power of the vacuum pump in a dilute-phase line is a central concern. The speed of the resin is constantly increasing as it travels through the conveying line, and that increasing speed can cause damage to the resin or the conveying system. It is not uncommon for material in a dilute-phase system to start at a velocity of 2,800 feet per minute and arrive at a receiver or blending unit at speeds of 6,000 feet per minute or faster. There is no easy way to slow the resin down in a standard dilute-phase system.
“The material at these speeds scrapes against the inner wall of the conveying tube, especially in the elbows or bends,” Brewster said. This friction can cause the pellets to degenerate. Soft resins like LDPE and PP can smear and deform against the sides of the pipe, creating streamers of material, also known as angel hair. Sometimes, the friction creates flakes that agglomerate into thin strips of resin called snake skins, Brewster said. Brittle materials can crash into each other or the walls of the system and shatter, forming dust and fines, while more abrasive materials can wear through the conveying tube itself.
Once formed, angel hair, snake skins, dust and fines can clog the conveying system, Brewster said. A processor typically must purchase angel-hair traps, dust filters, snake skin screens or pipe elbows made from a low-friction material to mitigate the issue. However, more frequent maintenance may be required, impinging on machine uptime.
Another common approach, dense-phase conveying, uses lower speeds and higher pressures. Batches of resin move through the pipe a few feet at a time, pausing, then surging forward. Generally, a dense-phase conveying system moves pellets at rates from about 300 feet per minute to 900 feet per minute. This approach may reduce the risk of material degradation when compared to a dilute-phase system, but the dense-phase approach tends to require expensive, more specialized components.
A NEW WAVE
According to Conair, the Wave Conveying system can deliver throughputs as much as 1.5 to 3 times greater than those of a dilute-phase system, especially over longer distances. It can move resin up to 1,000 feet horizontally and 250 feet vertically — distances that easily best typical dilute-phase systems, which are capable of moving material 600 feet horizontally and 70 feet vertically. In all, it can handle throughputs of as much as 15,000 pounds per hour.
Wave Conveying’s lower speeds mean it can deliver the material with negligible dust and absolutely no angel hair or snake skin.
“The gentle style of the Wave Conveyor system generates no angel hair,” Brewster said.
The Wave Conveying system maintains material speed and tailors it to the resin that it’s carrying. Unlike with other technologies, the material’s speed doesn’t increase as it moves through the system, so the material moves at nearly the same speed near the receiver as it does upon start-up.
“The pump can operate at 60 Hertz and I can have material moving at 300 feet per minute, or I can have the pump running a lower 40 Hertz, yet have the material moving at 1,000 feet per minute, or anywhere in between. The air volume and the material flow are not dependent on one another. This makes the system versatile,” Brewster said.
The Wave Conveying system comprises several specific pieces of equipment that can be incorporated into a standard conveying line that uses standard pipe, receivers and loaders. It can be used with any Conair receiver model, including the DL, FL and AL series.
It includes the FLX-128 Plus control, its long-distance pump (LDP) operated with a variable-frequency drive (VFD) and patented valve technology
The FLX-128 Plus control can control up to 128 vacuum receivers, 40 vacuum pumps — plus two backup pumps — and up to 256 source valves. The motors, pumps, receivers and valves are tied into the control system using a combination of centralized I/O and expansion modules that are interconnected through an industrial Ethernet connection.
An 8-inch color touch screen displays icons that represent different components and change appearance to indicate operating status. The control automatically tracks and logs equipment run times, which can be used to plan maintenance schedules.
The FLX-128 Plus can coordinate the loading and unloading of vessels, hoppers and machines, Brewster said. In this use, a level sensor in the bin can signal for unloading, either from one or multiple vessels to a common receiver or to a dedicated receiver.
The software required to perform Wave Conveying is a standard feature of the FLX-128 Plus. A user simply presses an icon on the controller screen to activate Wave Conveying.
Other patented components in the Wave system include valve technology. Conair recently developed an automatic flush valve that eliminates sealing problems that can occur with some material types or during certain conveying applications. In common-line distribution systems, which use a single conveying tube to carry material to multiple destinations, the improved sealing capability of the valve prevents vacuum leaks and improves conveying performance. The automatic flush valves can improve material loading times dramatically.
More than 40 Wave Conveying systems are in operation in the field, with all but four or five operating in the U.S., Brewster said. Medical molders, wire and cable coaters and pipe makers, which use materials that are particularly sensitive to issues like dust and angel hair, are showing increased interest in the technology, he said.
Mikell Knights, senior staff reporter
Cranberry Township, Pa.,724-584-5500,