PSI-Polymer Systems Inc.’s New 3-Way Divert Valve Technology Ideal for Numerous Extrusion Processing Functions Conover, NC (October 16, 2013)
PSI-Polymer Systems has recently introduced two new polymer Divert Valve designs. The first design is a new combination filter I divert valve (DIV-F), intended primarily for lab applications but suitable for larger scale operations as well. The second is a combination A-B die I divert valve (DIV-3X) used to direct material either to multiple dies or directly to the floor to purge.
In most divert valves there are two standard positions machined into a vertical bolt (piston). In the divert position, the polymer is directed to the floor. In the on-line position, polymer flows straight through the bolt into the die. When in divert mode, to protect against the degradation and cooling of the polymer, the through bore is normally encapsulated within the divert valve housing.
PSI’s combination filter I divert valve (DIV-F) introduces a breaker plate with a filter pack into the normal through bore position. This cost effective design eliminates the need for a screen changer and adapters and is ideal for applications such as underwater pelletizing, where instant flow to the die is required and space is too limited to accommodate a screen changer for die protection. The DIV-F is also well suited for batch processes like hot melt applications, where the filter is typically exchanged at the end of a run.
To allow for screen changes, PSI extended the length of the bolt and added a longer cylinder. In the on-line mode, the through bore and filter are directly in the melt stream. In divert mode, the unit operates similarly to other divert valves, encapsulating the through bore and the filter within the body. When exchanging the screen pack, the through bore shifts into an offline mode where it and the breaker plate move up and out of the housing. In this position, a vent, machined into the bolt, communicates with the divert port to allow any pressurized polymer in the head to escape to the floor. The screen change position allows polymer divert at full rate, however, most processors would generally prefer to slow the line or change the filter with the process offline while the extruder is at rest or idling.
PSI’s other new development, the versatile A-B Divert Valve (DIV-3X), provides improved control and functionality for lines dedicated to multiple processes, for example, an HMA application where a single line is used to alternate between pelletizing and producing glue pillows. Processes like extruded profile also would find this product extremely valuable, as it can instantly switch between two profile dies that are fed by a single extruder that feeds independent cooling and cutting equipment.
The DIV-3X is supplied with a 3-way valve that directs the flow either to one of two process flow bores or to a divert position that directs the polymer through a discharge port.
Both divert valve designs use a bolt in lieu of a slide plate and utilize a leak-free bolt design without a mechanical seal.
The new 3-way valve can be particularly useful for applications where the timing needed for coordinating the sequence of material flow needs to be perfect. The 3-way divert valve is easily customizable and enables operators to control the optimum timing sequence.
“Our divert valves are one of the more innovative and universally useful auxiliaries we’ve developed here at PSI,” said Don Macnamara, General Manager of PSI-Polymer Systems. “The advantages of both designs are apparent to anyone who has used one of these devices before, and we recommend them to any compounder, pelletizer, or resin producer that we sell equipment to.”