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Screen Changers for Filtration of Plastic Melts
In every plastic extrusion line, melt streams carry contaminants – particles that can impair granulate quality and destabilise production processes. Screen changers filter these contaminants directly out of the melt before they reach the granulating head or the production extruder.
SIKOPLAST supplies single- and double-piston screen changers for melt filtration in extrusion systems for plastics recycling. The screen changers are designed as continuous filters: a screen change during ongoing operation is possible without production interruption.
The component is available both as part of SIKOPLAST extrusion systems and individually for retrofitting existing systems.
Operating Principle: Continuous Filtration without Production Stop
The screen changer sits in the melt stream between the extruder and the granulating head or production extruder. The filtration principle:
- The plastic melt passes through a screen that retains contaminants and particles
- When the pressure drop across the screen increases – a sign of increasing contamination – the screen change is initiated
- The pistons are moved hydraulically: the contaminated screen carrier is moved out, a clean one moved in
- The melt stream is not completely interrupted during this process – with the double-piston screen changer, production runs fully through
- Continuous pressure monitoring shows the filter status in real time
- Depending on the equipment variant, position switches and visualisation are supplied
Single-Piston vs. Double-Piston Screen Changer: Choosing the Right Version
| Parameter | Single-piston screen changer | Double-piston screen changer |
|---|---|---|
Number of pistons | 1 piston | 2 pistons |
Operation during screen change | Brief interruption possible | Continuous – no production stop |
Screen diameter | 58 mm to 250 mm | 58 mm to 250 mm |
Max. material throughput | Up to 2,000 kg/h | Up to 2,000 kg/h |
Piston actuation | Hydraulic | Hydraulic |
Pressure monitoring | Continuous | Continuous |
Position switches / visualisation | Depending on equipment variant | Depending on equipment variant |
Typical application | Systems with plannable maintenance windows | High-throughput production lines without interruption tolerance |
Versions: Single- and double-piston screen changers
Screen diameter: 58 mm to 250 mm
Material throughput capacity: up to 2,000 kg/h
Piston actuation: hydraulic
Operation: continuous – screen change without production interruption
Pressure monitoring: continuous
Equipment variants: available with position switches and visualisation
Adapter flanges: available for adaptation to all common extruders
Integration and Compatibility
The SIKOPLAST screen changers are designed to be integrated into any existing extrusion line. Corresponding adapter flanges allow adaptation to all common extruders – regardless of manufacturer.
In SIKOPLAST systems, the screen changer is positioned as a downstream unit after the extruder:
- In the offline regranulation system, it sits between the extruder and the granulating head and increases the material purity level of the regranulate
- In the SIKOREX in-line return extruder, it can optionally be retrofitted and serves for melt filtration before feeding into the production extruder
- In the HYBRID system, an integrated screen changer is provided for the removal of contaminations in the melt
In addition to integration into SIKOPLAST systems, the screen changers are also supplied individually for completing third-party systems.
Typical Applications
- Recycling extruders for films, nonwovens, profiles, regrind and fibres
- Offline regranulation systems for improving the granulate purity level
- Inline return systems (SIKOREX, HYBRID) for melt filtration before production feed
- Retrofitting of existing extrusion lines – including third-party systems
- Systems with high throughput and high requirements for production continuity
FAQ
What is a screen changer and what is it used for?
A screen changer is a melt filter used in plastic extrusion systems to remove contaminants and particles from the melt stream. It sits between the extruder and the granulating head or production extruder and protects downstream units as well as product quality.
What is the difference between single- and double-piston screen changers?
With the single-piston screen changer, there is a brief interruption of the melt stream during the screen change. The double-piston screen changer works with two offset pistons, so that one screen always remains engaged during the change – production runs fully through without pressure fluctuations or production stop.
What throughput capacities are possible?
The SIKOPLAST screen changers are available for material throughput capacities of up to 2,000 kg/h, with screen diameters from 58 mm to 250 mm.
Can a screen changer be retrofitted into an existing system?
Yes. The screen changers are available with adapter flanges for all common extruders and can be integrated both into SIKOPLAST systems and into third-party systems.
How do I know when the screen change is due?
The screen changer has continuous pressure monitoring. When the pressure drop across the screen increases, this is the indicator of increasing contamination and the impending need for a change. Depending on the equipment variant, position switches and visualisation are supplied that show the status directly.