In contrast to frequently used temperature control systems based on oil or water, this extrusion equipment maker relies, as a standard, on air to cool the barrels of its single- and twin-screw extruders. The Air Power Cooling (APC) system is said to be maintenance free since no exchange of cooling agents is required, nor is there any need for additional units such as temperature regulators. Dieter Reisenhofer, product manager at the company, says the APC system offers higher efficiency than competitive systems since these require the cooling liquid to cover all barrel zones. "As soon as two or even all three zones of the barrel need cooling, the efficiency is reduced by half," he says. The APC is designed to provide consistent performance throughout all cooling zones. Reisenhofer claims it has been successful even in high-temperature countries such as Saudi Arabia.
In comparative tests using an Argos 93 model, parallel twin-screw extruder and the three cooling agents-air, water, and silicone oil-the manufacturer recently examined the different properties of each media. At an external temperature of 20ºC (68ºC), silicone oil is a slow energy transport medium and took the longest to heat up or cool down a barrel element to a given temperature, he said.
The heating elements of the air temperature-controlled system were able to heat the barrel to 180ºC (356ºF) within two-thirds of the time taken by temperature-control systems based on either water or oil. In the latter case, a larger tempering jacket mass needed to be heated in addition to the barrel. In tests to cool down to 30ºC (86ºF), similar results were obtained, says Reisenhofer. For air cooling, times were reduced by almost 80% compared to oil. Cincinnati Extrusion GmbH, Vienna, Austria. +43 1 610060; www.cet-austria.com