PPS for Pneumatic Actuators
The Bürkert factories in Ingelfingen, Germany, produce products for process automation, such as for filling systems, processing plants, applications in the food and beverage industry and hot steam in which liquid and gaseous media with various chemical compositions are conveyed. Particularly high resistance to the media and temperatures as well as a long service life are required here.
For the development of the “CLASSIC” valve series into the new “ELEMENT” valve series, the specifications stipulated an ambient temperature of up to 100 °C. Resistance to cleaning agents and disinfectants as well as autoclavability had to be ensured, along with a high-quality surface and high tolerance requirements for the cylinder friction surface. Based on the positive experience already gained with the plastic used in the previous Classic range, plastic was selected again for the new ELEMENT series of process valves for pneumatic actuator systems.
The design freedom afforded by a plastic construction offers a considerable cost advantage due to functional integration. The new valve series integrates significantly more functions than the previous generation, resulting in considerably more complex geometries and a multifaceted tool concept. Working with Hamburg-based plastics distributor K.D. Feddersen, PPS was identified as the material of choice once again. During the first tests, there were initial problems with the strength of the weld line, tolerance adjustments and burr formation, and not all of the impact tests were successful either.
The Bürkert ELEMENT valve system with decentralised automation – pneumatic actuator and automation components made of Fortron® PPS.
After component, process and tool optimisation, the material finally selected for this application was Fortron® 1140L4 SD3002 black, a PPS compound with 40 % glass fibre reinforcement produced by Celanese. The existing UL746C classification of f1 for outdoor use also proved helpful in the area of certification. This material is also used successfully in other products in the Bürkert portfolio. It meets the V0, CTI and RTI electrical and fire protection requirements.
“The feedback from the market, especially with regard to resistance properties, is very positive”, says Joachim Götzelmann, from R&D at Bürkert.