Screen Changers for Polymer Melt Filtration -- Overview

From High-Technology Corp.

 

High-Technology Corp. has been a leader in the field of continuous automatic screen changers since 1969. Built in the USA and serviced world-wide, HITECH™ screen changers are offered in eleven sizes, ranging from 1.0" (25 mm) to 8.0" (200 mm). (Click here for a list of HITECH™ screen changer sizes.)

HITECH™ screen changers are unconditionally guaranteed for a period of 10 years not to wear, and therefore, not to leak. We also guarantee our machines and their controls against defects, parts and labor for a whole year after start-up.

Our highly experienced engineers have backgrounds with the world’s leading manufacturers of extrusion equipment, and are capable of handling every phase of a project, from initial testing in our lab to installation and start-up in the field.

Our screen changers are handed over “on stream” by process engineers, who also provide operator training and who can, if called upon, trouble shoot the entire extrusion line.

Constant Head Pressure + Uniform Melt Temperature = Better Product




The operating mode of hydraulic and manual screen changers represents a source of disruption to the otherwise continuous nature of the extrusion process. As a result of their intermittent operation, these types of screen changers become a cause of head pressure and melt temperature fluctuations (Fig. 1)

extruder head pressure of hydraulic and manual screen changers fluctuations


By contrast, HITECH™ screen changers operate on a principle that works in harmony with the rest of the extrusion process. The filter screen, in the form of a long, 120’ (36 m) ribbon, moves at a slow, barely perceptible rate through the screen changer body to blend smoothly with the polymer flow (Fig. 2)

continuous extruder screen changers filter in harmony with extrusion process


The slow, steady incremental rate of screen travel in a HITECH™ screen changer, together with the capability to automatically accelerate the rate of travel, when needed, to adjust to fluctuations in the levels of contamination. With a consistently moving screen, the extruder head pressure stays steady, and, in turn, melt temperatures and flow rates remain perfectly uniform, throughout months of non-stop operation. (Fig. 3)

HITECH screen changers keep extrusion pressure and temperature constant

NO DOWNTIME

No Moving Parts. The force of the extruder head pressure is used to move the screen. No driving mechanism (air cylinder or hydraulic power package) to maintain.

No Hot Breaker Plates to handle; no screen packs to change. The screen belt moves automatically through the screen changer flow canal.

No operator attention required for day-to-day operation. The controls can be interlocked to follow the status of the extruder’s functioning.

No wear, no leaks: no metal-to-metal seals to wear out. Leak proof polymer seals maintained indefinitely by the continuously circulating cold water.

BETTER PRODUCT

Constant extruder head pressure is maintained indefinitely: uniform melt temperature; steady pumping rates.

Precision gauge control: scrap & reject rates significantly reduced.

Color changes: no extra steps are needed to handle color changes. By the time the screw and barrel are purged, the screen changer body is free of any color residue.

Polymers: HITECH™ screen changers can handle all commonly used families of thermoplastics, including flexible PVC and most engineering resins.

Technical Specifications

For a list of HITECH™ screen changer sizes, click here.

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HITECH™ The Leaders in Continuous Melt Filtration since 1969