PSI-Polymer Systems

PSI-Polymer Systems, Inc. Introduces New Continuous Backflush Screen Changer Hickory, NC (December 7, 2004)

PSI-Polymer Systems Inc. has introduced a new Continuous Backflush Screen Changer (CSC/BF), designed for highly reliable polymer filtration in a wide variety of extrusion applications.

Featuring a unique design, the new CSC/BF allows for increased filtration screen life, by at least 25 times over typical continuous screen changer designs.  Increased screen life means less frequent screen changes due to clogging from contaminants in the plastic melt.  This translates into much less downtime, meaning higher reliability and higher productivity for processors.  Another key benefit of the CSC/BF is that it reduces the back pressure on the extruder to a much lower pressure, thereby allowing for increased output – as much as a 50% increase on some materials and processes.

“The idea behind any continuous screen changer design is to allow constant production with absolute minimum downtime,” said Glenn Woodcock, President of PSI.  “By splitting the polymer flow into two streams, processors can change a clogged screen without interrupting production.”

“This new backflush unit takes this concept to a new level.  By automatically purging contaminants from clogged screens, it dramatically extends screen life.  This product will operate much longer without the need for maintenance than any conventional screen changer.”

How It Works

Like PSI’s existing Continuous Screen Changer, the new CSC/BF divides the incoming polymer into two streams, both being filtered in the top and bottom pistons.  Unlike the CSC design, however, the CSC/BF has two filtration cavities in each piston, allowing for twice the filtration of the comparable-sized CSC design. 

The most unique aspect of the CSC/BF is the capability of “recycling”, or maximizing screen life automatically.  When upstream pressure rises due to a high contaminant level in the polymer, the PLC control automatically actuates each piston to its backflush position, allowing pressure to push contaminants off of the dirty screen.  Contaminants are purged out of ports in the housing.  Once the backflush sequence occurs, the “recycled” screens are returned to the home position until the sequence takes place again.

CSC/BF Features and Benefits

Like PSI’s line of CSC’s, the new CSC/BF is guaranteed to operate leak-free at pressures up to 10,000 psi, and temperatures up to 650°F.  All parts are manufactured to ISO-9002 standards.  Its rugged design provides excellent resilience to wear, and with no seals or contact parts, there is virtually no maintenance required other than the occasional screen change. 

Typical applications for the new CSC/BF screen changer include recycling, sheet, blown film and cast film, compounding, underwater pelletizing and strand pelletizing, extrusion coating, pipe and profile, wire and cable, and others.  Five standard sizes of backflush screen changers are offered by PSI, with outputs ranging from 1,000 to 10,000 lbs/hr.