The most specific and demanding applications are those for the filtration of Reticular Polyolefins.
Reticular Polyolefins are a peculiar and niche product. The filtration activity of reticular polyolefins is so exclusive, that it is a great success and a great satisfaction, for us, to know that a good number of special screen changers by Filtec is installed on major petrochemical plants in different parts of the world.
The filtration of Reticular Polyolefins is difficult, since they tend to easily develop viscous heat and they are sensitive to both high temperatures and pressures. Not to mention that the cylinders, screws and screen changers must be quickly and easily removed for periodic cleaning. The breakers (net-holding plates) installed on the sliding plate have several special and interesting features. First they are made of special Chrome-Molybdenum-Vanadium tempered steel to ensure a good resistance to thermal shock and thermal stress in general.
For the filtration of Reticular Polyolefins it is essential to design machinery without slowed flow and possible stagnation areas, because the plastic material would degrade definitively hardening there. The same effect would occur with exposure to air and light.
To avoid effects from exposure to air and light, the breakers are designed and developed to be easily removed and after every change they are extracted and sent to cleaning devices such as fluidized bed incinerators or pyrolysis heaters or the like.
To avoid stagnation, the drilling of holes of the breakers is performed with precision drilling machines so that the plastic material will flow within finding a surface with an accurate surface finish.
Last but not the least important characteristic relates to the shape of the breaker itself. Reticular Polyolefins are extruded with twin-screw extruders and for “simple” materials there is a transition fitting called 8-0 between the cylinder of the twin-screw extruder and the breaker on the sliding plate which is usually round. To totally avoid the 8-0 fitting, Filtec has developed breakers with holes arranged inside an “8” corresponding to the shape of the screws. In this way the whole system is shorter and more compact, the molten plastic material flow is smooth and the extruder screws come up to a few millimetres from the “8”-shaped breaker.