Screen changers | machinery feature Switching over: advances
in melt filtration and screen changers
The increased use of recyclate in polymer processing can raise problems. Processors must take care to remove impurities during processing – in order to raise product quality, and ensure that the materials process properly. This can be ensured through material testing, and by incorporating efficient melt filtration. At the recent K2016, several
exhibitors showed developments that help pipe and profile extruders process polymers more effectively.
Force reduction Nordson says that a new generation of manual screen changers halve the force needed to switch screens on the extrusion line – making life easier for machine operators. Like standard manual screen
changers from Nordson, the BKG NorCon EMR and XMR models are a less expensive alternative to stationary screen changer systems. The operator replaces a contaminated screen with a clean one by turning a handle or lever that activates an indexing system. Tests by Nordson showed that the NorCon EMR-35
unit required 25lbs (111N) of screen-switching force, compared to 50lbs (222N) for the EM-35. The new EMR and XMR screen changers contain a
ratchet mechanism that reduces the force required to turn the handle. This mechanism can also be retrofitted onto standard EM and XM models. While EMR and EM units are for use with extruders sized in inches, the XMR and XM units are for metric equipment. “By means of a simple swing of a handle during
routine shutdowns, NorCon manual screen changers quickly bring clean screens on-line, minimising costly downtime by avoiding need for line disconnection,” said Christian Schroeder, global product manager for melt delivery products. “The force reduction provided by the EMR and XMR models makes screen changes even
www.pipeandprofile.com Improvements to screen
changers and melt filtration equipment – such as higher
operating efficiency and faster changeover – have helped to boost product quality. Lou Reade reports
more efficient while improving the working
conditions of machine operators.” Available standard NorCon
manual screen changers range from 10 to 65 inches for EM units
and 30 to 120mm for XM units. EMR and
XMR models are available in most of these sizes. At the same time, the company has developed a new
melt filtration system for recycling highly contaminated plastics – saying it provides greater productivity than comparable machines while maintaining constant melt pressure and product consistency. The BKG HiCon R-Type 250 transforms contami-
nated polyolefin or styrenic plastics into clean, high- quality material, and exhibits less melt loss than traditional backflush systems, says Nordson PPS business unit director, Sven Conrad. The system uses a cylindrical ‘separating head’ – with
knives arranged on its surface in a helical pattern – to move contaminant particles forward as the head rotates. Enclosing the head is a stationary filter element called a ‘strainer tube’. When contaminated melt from an entry port flows into the cylindrical space between the rotating head and the strainer tube, the knives capture the contaminant while the contaminant-free melt moves through the strainer into flow channels that lead to an
January/February 2017 | PIPE & PROFILE EXTRUSION 21
Nordson’s NorCon EMR and XMR
manual screen changers
require less
force to switch screens
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