Screen changers help filter plastic melt during the extrusion process, and efficient screen changers are crucial in plastic extrusion lines.

Plunger screen changers Enhance filtration operations

Mag Corporation, a manufacturer of gear pumps, granulation systems, filtration systems and shredders, recently announced the market availability of its new screen changer technology.

The plunger type screen changer is characterized by Mag's modularity. Its double plunger design can be customized to adjust the filter unit according to the user's unique process requirements.

The design allows the use of five different filter chamber shapes within the same screen changer housing: round, for a simple round filter; Oval, for twice the size of the filter area; Arched crushing plates and screens for four times the filtration area; Leaf disc design to expand the filtration area to 12 times; Candlewick filter element increases the filtration area to 60 times.

Although there are many available filter chamber shapes, screen changers still allow users to individually select specific design and operating characteristics, such as electrical or thermal medium heating, nitrification or stainless steel construction, specific flow channel coatings, and high temperature or high pressure operation.

Screen changers range in size from CSC-30 to CSC-520 with a filter area of 2× 7cm2 to 2× 12.5m2. Its robust construction and highly precision engineering ensure reliable, leak-free filtration of all polymer types in extrusion applications.

Among them, the CSC-116/R screen changer is an extension of the MaG CSC screen changer family and is designed for use in all polymer extrusion applications. It features a unique, patented arched screen design with double plungers that quadruple the filtration area.

This model uses 75% of the plunger surface for filtration, providing additional operational advantages such as increased residence time of the filter screen, increased yield, improved filtration accuracy, reduced pressure on the melt, reduced flux rate, and more.

In addition, the design minimizes the size, weight, heating power and hydraulic power requirements of the filter surface, which can significantly reduce operating costs.

CSC-R screen changers are designed with a filter area of 2x877cm2 to 2x0.86m2. The CSC-R technology's robust construction and high precision engineering structure require no additional seals for reliable, leak-free filtration of all polymer types in extrusion applications.

Fully automatic operation improves mesh changing speed

High-tech, an American mesh changer manufacturer, presented its new generation Model DP-XL fully automatic mesh changer at NPE 2018. These net changers offer better performance and are easy to use in a variety of applications.

The DP-XL changes the net twice as fast as previous models and can filter a higher percentage of contaminants. The new design is capable of filtering at up to 650° Leak-free operation at temperatures of up to 650 & deg, and the formation of a polymer seal, resulting in a smooth, uninterrupted filter change cycle.

In addition, the new high-strength filter media enables the unit to operate reliably under constant filter pressure differential of up to 2000 psi. The multi-layer filter media combination can filter as small as 50 microns and is suitable for a wide variety of polymers, including high and low viscosity polymers.

Screen changers can be fully customized integrated into complex production lines with PLC color touch screen controls and descriptive graphics. Operating parameters and hardware conditions, such as heaters and sensors, can be continuously monitored for fast response features. The

control (including 20 distributed alarms) detects immediate process conditions and automatically adjusts the screen change rate at intervals of 5 minutes to 8 hours, allowing for a high degree of continuous production, even under conditions of unstable contamination levels.

Screen changer for rigid PVC

Another screen changer highlight at NPE 2018 was PSI-Polymer Systems' screen changer and gear pump for rigid PVC. The company is a leading supplier of mesh changers, extruder gear pumps and static mixers in the United States for the extrusion, polymer processing and recycling industries.

The target application areas for both new products include sheet and profile extrusion. The system is also suitable for PVC formulations, which can withstand 10-15° F melt temperature variation.

Screen changers are not usually used in hard PVC processing because of the flow transition in the sealed area exposed to the melt flow. When rigid PVC flows through these flow transition zones and steps, shear heat generation can occur, which in turn triggers local scorching of the material.

However, PSI has developed the Expansion Plate Screen Changer(ESC, Expansion plate screen changer) solution, which addresses chemical issues related to heat, flow and thermal conductivity, enabling it to be used in PVC processing processes that can withstand 10-15° F's melt temperature fluctuations. Now the technology is patent-pending.

When replacing the filter on the ESC, the PLC rapidly heats the expansion spacer bar to separate the two halves of the structure above and below the skateboard between the two halves of the main body. In this design, an instant increase in melt temperature can be avoided. The spacer bar expands to separate the body, thus allowing the skateboard to move freely without hindrance.

After installing the new mesh bag and moving the old mesh to the outside of the main body, the factory compressed air or cooling medium is passed into the partition to cool and shrink the steel body. This effectively retracts the two halves of the main body back onto the skateboard, re-forming a seal through tight steel-steel contact.

ESC uses chrome-plated runner holes that pass directly through the net changer and there is no hanging area. The unit has no mechanical seal and therefore does not wear out. Moreover, the upstream and downstream bodies are the same.

These interchangeable two-half structures can be repaired on site. If the surface is scratched as a result of the main body coming into contact with the skateboard, the surface can be ground in a local machining shop before being put back into use. Parts are made of corrosion-resistant stainless steel.

For temperature control, ESC can be electrically heated and air - or liquid-cooled expansion spacers. The body comes standard with electric heating and can be fitted with a jacket for more even heat transfer.

Compact design of rotary filtration system

Several models of the patented compact rotary filtration system of Gneuss Kunststofftechnik, headquartered in Germany, are quite advanced in technology. These models have improved mesh changer housings to work at higher pressures in a wider range of applications, while providing a larger effective filtration area. Because components and modules have been standardized, lead times are reduced and costs are reduced. The

SFXmagnus filtration system operates automatically, keeping the process and pressure constant. The series features a large effective filter area, a compact design and ease of operation. It is said that the replacement of the filter will not affect the product quality.

As for the RSFgenius filtration system is a fully automatic, constant pressure filtration system, can be used in almost any occasion, can realize the automation of the production process, the manufacture of high quality end products. Due to its compact structure and the use of high quality insulation materials, the energy consumption is extremely low.

The RSFgenius filtration system is particularly suitable for ultra-fine filtration, heat sensitive melt filtration and filtration of highly contaminated materials. Its integrated self-cleaning system is suitable for extremely demanding applications and high quality requirements. The filter screen can be automatically reused up to 400 times, and the filtration accuracy is up to 1 micron.

The company's KF screen changer series features a small and compact design that enables simple, cost-effective integration even in very confined Spaces. Another advantage is that the rheological properties of the melt flow path and the internal components of the mesh changer can be individually adjusted according to specific requirements. These mesh changers are also very suitable for heat sensitive polymers. In addition, the mesh changing process can be triggered automatically without stopping production.

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