Extrusion equipment manufacturers think BIG

As the markets for high-output and large extrusion applications grow across the globe, increased output and size needs are driving extrusion machinery manufacturers to think ?big.? Pipe, sheet, and foam applications are all part of the push to improve machinery capabilities to accommodate processors? efficiency and output needs.

Dana Hanson, president of extruder manufacturer PTi (Aurora, IL), says that the requests for high-output sheet extrusion systems are increasing as processors are forced to improve their operating costs. PTi manufactures sheet extrusion lines ranging from 1000-10,000 lb/hr.

?Each application presents its own challenge,? he says. ?The biggest challenge in high-capacity sheet extrusion processing is managing the thermal aspects of the process.?

However, some applications are more conducive to high production rates than others. Inline thermoforming for packaging applications is well suited for higher output rates due to the thermal benefit of delivering hot, stable sheet downstream to the thermoformer, versus having to cool it for winding or shearing and stacking.

Traditionally, PTi has seen requests for high-output sheet extrusion systems for both polystyrene and polypropylene, but recently PET sheet extrusion has entered into the realm of high production capacities (5000-6000 lb/hr).

Challenges to High Output

Hanson outlines five challenges that present themselves when trying to achieve high rates of sheet extrusion production:

1. Proper tension control. Because the line is running faster, balancing tension becomes increasingly critical.
2. Managing the process from a thermal perspective. High heat rates are characteristic of high output rates.
3. Finding suitably powered drive systems. Extruder, gear pump, and roll drives all have to be properly sized in order to accommodate the upper range of production.
4. Internal flow passages. Feed pipes, feed blocks, and die manifolds must be properly sized.
5. Achieving dimensional stability. End usage drives this requirement with regards to lay flatness, squareness, gauge tolerance, appearance uniformity, physical properties, orientation concerns, and exit temperatures.

When working with high-capacity sheet extrusion, the die manifold is critical. Auxiliary equipment must be suitably sized to accommodate the increase in production capacity, including material handling systems, feed and blending equipment, edge trim handling, chilled water supply, and stable electricity at the required power levels.

In response to the need for auxiliary equipment that accommodates high-output extrusion, Davis-Standard LLC is displaying its XP Express roll stand system at NPE 2006. The company says the roll stand system is well-equipped for high-output applications and offers high-speed features for thin-gauge applications, thermal cooling, and the capacity to operate at temperatures up to 800°F.

Maximizing Output

Hanson is shocked at the number of low- production (typically less than 2500 lb/hr) sheet extrusion systems that have been installed in the last two decades. ?There are many low producing sheet systems operating every day. Consider examining the efficiency differences between the small output lines of the 1980s and 1990s and put them against the high-output systems that operate at production rates of more than twice the output. The results are staggering,? says Hanson. ?Limiting a line?s output drives up the labor and overhead burden factors for every pound of sheet produced. Take the same labor with the same overhead and apply it to twice or three times the output rate and results are eye opening.?

Large-diameter Pipe

Although the primary markets for large-diameter pipe extrusion lines are in Europe, China, and the Middle East, sales of the technology are increasing in North America as the benefits of using plastic pipe become apparent.

Battenfeld Extrusionstechnik GmbH (Bad Oeynhausen, Germany) says it holds 70% of the market share for equipment used to produce large-diameter pipes from PVC and polyolefin. In the last two years, the company has shipped 15 large-diameter pipe extrusion lines to produce pipe with diameters ranging from 800-1600 mm.

These are all smooth-pipe lines, but the company has also delivered equipment for large-diameter corrugated pipes and wrapped tubes.

?The use of plastics pipes is on the increase worldwide because they are easy to lay, weigh less, and are free of deposits and corrosion. Moreover, they offer a long service life with high quality standards and only minimal environmental risk from leakages,? says P.J. Buriak, sales manager for the PE Pipe Div. at American Maplan.

In November 2005 American Maplan Corp. (AMC; McPherson, KS) teamed with Battenfeld Extrusionstechnik GmbH to engineer the biggest HDPE line in the U.S., according to Buriak. The line was 63 inches and purchased by three undisclosed North American companies. Buriak says the ?industry acceptance of large-diameter HDPE pipe is growing in the U.S. and elsewhere in North America, spurred in part by the success of such lines in Europe and by new grades of resin formulated for the market.? He says that the fact that the U.S. is adopting this technology after it became fairly common in Europe is no surprise. ?Plastics technology usually emanates from Europe and trickles into the U.S. five or six years later. The U.S. processors are not as apt to quickly adopt new technologies because they?re averse to change?they?d rather stick pins in their eyes.?

Although Buriak can?t disclose the companies that have purchased the machines, he says the primary use of the large-diameter pipe being produced on the machines is for mining applications.

AMC also has a 78-inch-diameter line on the drawing board, with some potential buyers knocking on the door but no takers, as of yet. Buriak thinks it will take time for the technology to become cost-effective, but that it will happen. The 78-inch-diameter pipe uses a 220-mm extruder with a throughput of around 5000 lb/hr. Although designed for large-diameter applications (defined by AMC as 30 inches or more), the line can also be used to produce pipe down to 30 inches or smaller, with additional tooling and downstream equipment.

AMC recently launched its newest die in polyolefin pipe extrusion. The VSI die head incorporates 30% more holes than the previous model to reduce the total surface area needed, thus providing a more homogeneous melt and better wall-thickness control. Buriak says these improvements have enlarged the die?s processing window so it can accommodate a full range of pipe diameters?from 32-1600 mm?at outputs from 350-1200 kg/hr.

High-output Foam

Berstorff GmbH (Hannover, Germany) recently delivered two complete extrusion lines to Penoplex Holding (Kirishi, Russia), a manufacturer of XPS insulation boards in Russia. The lines were commissioned for the company?s new facility in Perm, Russia and offer a total throughput rate of more than 2000 kg/hr. The Schaumtandex ZE 60/KE 150 and the ZE 75/KE 250 extruders were delivered as well as inline board processing, recycling, and packaging units.

?The throughput rate of a foam extrusion line is not only determined by the plasticizing performance of the primary extruder but also by the cooling capacity of the secondary,? says Berstorff. The combination of the twin-screw and single-screw extruders maximizes this capability, according to the company.

Foam insulation boards are in high demand in Europe, where they are used primarily in insulation material for cellar walls and floor panels in the building. In extreme climates, the boards are used to insulate oil and gas pipelines.

In April, Krauss-Maffei (Florence, KY) announced that it had supplied a Russian processor with a polyurethane (PU) metering system capable of output at around 6.6 kg/s, which, according to the company, sets a new record in PU processing. The system is designed for foam insulation of large-diameter heating pipe shipped to Russia. The newest machine is part of a system that produces pipe sections up to 12m long, with a diameter of the outer layer up to 1200 mm for heating networks. The reactive PU system fills the space between the inner pipe and the PE outer layer with foam. ?Applying foam insulation effective in pipe of this size requires a PU machine capable of delivering extremely high output,? says Krauss-Maffei. The company engineered the system to minimize pressure losses, so that mixing performance stays constant even with the very high output.