A filter from Nordson Polymer Processing Systems approaches the task of removing contaminants from a melt stream in a unique way, reducing melt loss and extending the filter life.

Instead of sending a stream of melted plastic straight through a screen to remove contaminants, the BKG HiCon R-Type 250 tackles highly contaminated PE, PP and PS streams with a rotating cylindrical “separating head” and a strainer tube, according to the company.

Nordson Polymer Processing Systems (Nordson PPS) described the equipment’s operation:

It involves the use of a cylindrical “separating head” with knives arranged on its surface in a helical pattern designed to move contaminant particles forward as the head rotates. Enclosing the head is a stationary filter element called a “strainer tube.”

When contaminated melt from an entry port flows into the cylindrical space between the rotating head and the strainer tube, the knives capture the contaminant while the contaminant-free melt moves through the strainer into flow channels that lead to an exit port. At the same time, the rotating head turns a screw, which guides the contaminated material through cooling sections and finally to where it is discharged into collecting bins.

The special design results in a constant melt pressure on the strainer tube during the cleaning process, giving the filter and scrapers a longer life and reducing melt loss, Sven Conrad, Nordson PPS business unit director, stated in a press release.

“Nordson’s newest development cleans much more efficiently than commercially available filtration systems for highly contaminated polymers,” Conrad stated.

The HiCon R-Type 250 operates at a maximum pressure of 350 bars and maximum temperature of 320 celsius (608 degrees Fahrenheit). Throughput can range from 500 kilograms per hour to 1,500 kilograms per hour (1,102-3,307 pounds per hour), depending on polymer viscosity, filtration fineness, contamination levels and other factors.

The holes in the steel strainer tubes are available in sizes ranging from 120 microns to 750 microns, and they’re conical in shape to prevent blockage by contaminants.