EQUIPMENT | MELT FILTERS
Right: This CSC piston screen- changer from Maag is fitted with its high surface area ‘R’ type curved screen
“In the past the next size up was the size 150, with a jump of more than 50% in active filtration area,” according to a company spokesperson. “The new intermediate size will ensure an optimised and cost-efficient filtration solution for every application.” Automatic Rotary Filtration Systems operate continuously, so are able to provide constant process pressure. Screen cavities are located in a ring pattern on a disc, which means that screens can be changed on the part of the filter disk that is not active in the melt channel. This avoids any interruption or disturbance to the production process. The various models differ mostly in terms of drive design, encapsulation and whether they offer integrated back-flushing. Around three years ago, Cofit International
Right: Cofit says its low cost, self- cleaning AP screenchanger is proving a popular option
introduced the Gorillabelt T, a sophisticated automatic and continuous screenchanger intended for heavy recycling and featuring a “zero polymer loss cleaning cycle.” That project is on hold at the moment, with the company instead highlighting its AP manual, continuous, self- cleaning screenchanger, which is suitable for materials with low levels of contamina- tion such as polymers for production of films and filaments. “The screenchanger re- moves the impurities that come with the raw material and disrupts any coagulates formed during extrusion. Besides this, its usage prevents damage to downstream equipment. Furthermore, an efficient extrusion process can be achieved by using a continuous screenchanger, since it does not require frequent change of filter
IMAGE: MAAG GROUP
which is time-consuming and costly,” says Cofit General Manager Alessandro Fabbri.
Parallel filters The AP screenchanger, which has been on the market for some time but the company says is proving very popular, features two parallel filtering cartridges that are cleaned one at a time without the need for removal from the extrusion equipment. As the flow of melt through the second filter continues while the first is being cleaned the extrusion process can continue uninterrupted. “The self-cleaning feature of AP screenchangers extends the service life of screens, thus
reducing maintenance activities such as filter replacement to a
minimum,” says Fabbri. He also highlights the unit’s solidity and reliabil-
ity. “It is also cheap and does not require expensive parts such as hydraulic units and control panels to operate. Apart from that, it is made of steel with nickel plating that serves as superior protection against wear and tear, thus ensuring its long-lasting service,” he says. Comparing the AP unit with hydraulic slide-plate
screenchangers, which can also be operated without stopping the extrusion process, Fabbri says that with the latter design some off-spec melt may be produced during the change-out since contami- nants may pass through because of temporary stops and air entrainment. “Furthermore, manual work is still needed to
Above: Gneuss has introduced a 110 model to fill out its RSFgenius, SFXmagnus, SFneos and CSFprimus lines
54 COMPOUNDING WORLD | July 2021
clean or replace the soiled screens while produc- tion continues,” he claims. “Contrarily, AP screen- changers maintain a high-quality melt because heavy build-up dirt on the screen that may affect filtering performance is prevented by the self-clean- ing action. Moreover, occasional screen replace- ment does not negatively affect product quality.”
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IMAGE: GENUSS
IMAGE: COFIT INTERNATIONAL
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