Auxiliary Equipment

Polymer Diverter Valve (PoDV)

The start-up is an important phase of the entire pelletizing process. It has an influence on the stability of the process and quality of the pellets. This is particularly true for temperature sensitive products that tend to solidify or for which the timed start-up is critical. The polymer diverter valve guides the melt flow to the die plate within one second and ensures a stable and optimized volume flow per hole right from the start.

The polymer diverter valve is used to direct the polymer melt from the pump or extruder to the die plate or downward to the floor. This is an indispensible function during start-up for difficult products that are temperature sensitive. In underwater pelletizing, an optimized volume flow per die hole must be ensured right from the start. Most of the upstream equipment responds rather slowly, e.g. ramping up of the extruder. The polymer diverter permits a controlled start-up of these upstream components until the required throughput has been attained and allows a visual control of the compounding process by the operator. The option of diverting the melt is often used for online material or color changes.

The polymer diverter valve consists of a heated housing with an integrated bolt that can be moved hydraulically. This bolt allows the melt flow to be diverted from the start-up position to production position, i.e. toward the die plate, within one second. In many cases the inlet channel of the polymer diverter valve is adapted directly to the extruder outlet, screen changer or to the melt pump, eliminating the need for an additional intermediate adapter. The integration of a nose cone on the die plate at the outlet of the polymer diverter valve reduces the length of the flow channel and the volume of melt dead area before the die plate. This reduction of dead area prevents excessive melt flow through the die plate after extrusion has stopped so the system can be restarted with a generally clean die plate. This helps prevent the risk of polymer wrapping and increased agglomerate formation during start-up. A mobile support stand simplifies the removal or backing away of the polymer diverter valve pulling from the extruder screw.