By: James Snodgrass
EUROPEAN PLASTICS NEWS
October 29, 2013
DÜSSELDORF, GERMANY — Being invisible is something of a compliment for Don Macnamara, general manager of PSI-Polymer Systems Inc.
The Conover, N.C.-based firm sees its role as "from the extruder to the die," and its innovations as practical solutions for reducing downtime and mechanical failure.
"They're innovations but they're within the heart of the machine so it's difficult to actually see them," Macnamara said. "The products that we make fit that envelope. That's where the melt pumps and the screen changers and the mixers all come in. Then we stop at the die so we're not stepping into an underwater system or something else that somebody's making."
PSI is showing several innovations at K 2013. One is a lip seal for gear pumps, seals being at the heart of PSI's business, since its formation 13 years ago.
PSI sought to address the leakage from gear pumps of low and very-low viscosity melts. Macnamara explained: "The closer the polymer gets to water, the less likely the machine is to be able to prevent that fluid from escaping past the seal. A seal ultimately wants to form against a viscous material."
Lip seals traditionally use packing seals, typically TPFE, which wear and require maintenance. The PSI innovation is the addition of a u-ring. Anything that passes the packing gland forms up into the u-ring. If it pressurizes the u-ring, it pushes the u-ring up. So the ID pushes against the spinning shaft and the OD pushes against whatever constraint it's sitting in.
It's a simple solution, but an effective one.
"To a degree it's become an OEM product because the OEMs like it so much they're putting it in their equipment and sending them out," Macnamara said.
Another seal developed by PSI is a low viscosity seal for bolt-type screen changers. The seal technology works with polymers with extremely low viscosities and has been tested on viscosities as low as 1cP (e.g. toluene) to 300,000 cP and, PSI claims, it is capable of sealing nitrogen at over 3,000 psi.
The seal can be used in any PSI piston-type screen changer unit or divert valve and, the company claims it is idea for processing high melt materials, adhesives and solvents.
A third innovation on display at PSI is a three-way divert valve allowing an automatic changeover of the melt stream from extruding to a pelletizer to extruding adhesive pillows, from the same extruder.
"Our customer wanted two through-bores. So they wanted a through-bore they could go over to feed the pelletizer and they wanted one through-bore that could go over and feed the pillow line," Macnamara explained. "So, depending on the position that they shift to, and they could fly through one, they can actually shift it over and divert the material this way, or shift it this way and the material just goes to the ground."
Macnamara said that the divert valve could be used for other extrusion applications that require a quick change-over, including profile extrusion.