Extrusion International 2-2024

62 Extrusion International 2/2024 MATERIAL HANDLING Gear Pumps Enable Extrusion Industry to Meet Growing Sustainability Demands Gear pumps are a proven off-the-shelf technology that can bring significant sustainability benefits, helping processors reduce their carbon footprint while improving efficiency and productivity, according to PSI-Polymer Systems. A company’s carbon footprint runs deep and includes everything from the production and transportation of the raw materials to in-plant storage and material conveying, to energy used to convert the raw materials to an end-product. In many cases, processors seeking to reduce their carbon footprint can use readily available technologies to reduce energy and material consumption. "As processors struggle to meet to- day's sustainability demands, the gear pump has emerged as an eco-friendly, go-to solution proven to reduce over- all energy load for the ex- trusion line while simul- taneously minimizing the amount of material required for the prod- uct,” said Don Macnamara, general manager of PSI-Polymer Systems Inc. “This allows for 100% use of regrind without compromising output consis- tency and minimizing scrap from start-up or off-spec dimensions. Plastics are not going to go away, and it falls to us as industry participants to produce more responsibly. The gear pump helps get us there." By taking over the pressure-generating function for the die, the gear pump allows the extruder to process the same, or often more volume at a lower RPM. This translates to less energy required to produce a specific volume of output. While this energy amount is arguably small, it adds up, says Macnamara. Consider an extrud- er running at 100 RPM, 24 hours/day, 5 days/week, 50 weeks/year. That equates to 36 million RPM/year and a gain in yield of 10% to 25% at a lower RPM and a drop in corresponding extruder amps which significantly helps the product's energy footprint. Another eco-benefit of lowering the head pressure is reducing the extruder motor load, leading to significant long-term energy savings. Lower head pressure also minimizes wear and tear on the screw and barrel. Also reduced is the load on the thrust bearing and drivetrain, which boosts the B10 life of the bearing and reduces the need for gearbox rebuilds. Lower wear leads to fewer rebuilds, each with its additive carbon footprint. For this reason, PSI says many OEMs specify large gear pumps for high-pressure applications to take the load off the extruder. Today’s focus on sustain- ability also involves the inclu- sion of reclaim, according to PSI. Many processors limit the percentage of regrind in the extruder due to pressure surge which results from vari- able feed and melt rates of the differing feedstock bulk densi- ties. The tight clearances in the gear pump effectively dampen the extruder surge at the pump inlet by up to 50:1. In many cases, this results in die pressure control of +/- .25%. Consistent die pressure holds wall/gauge varia- tion within a tight tolerance. Running true to the lower end of the dimensional specification elimi - nates scrap caused by out-of-spec production (over/un- der). Cutting scrap saves energy by producing the prod- uct once and avoiding the energy impact of reprocess- ing. Running a tighter tolerance also means using less polymer per product length. For example, one conduit producer extruding 1.5” SDR 13.5 pipe had an average weight of 151 grams per length. Adding a gear pump minimized the overage and resulted in a constant weight per length of 145 grams. At 65 ft/min, 20 hours/ day, 5 days/week and 50 days/year, the 6-gram savings eliminated 257,940 lb from the product footprint. That is roughly one million pounds taken out of production in four years while consistently making high-quality pipe. PSI also notes that a gear pump can reduce the de- mand for additional cooling during the extrusion pro- cess by reducing backpressure-induced shear heating. This can lead to further energy savings by reducing the load on the cooling system. PSI-Polymer Systems Inc. www.psi-polymersystems.com