Clean metal processing
With over 14,000 employees at 50 production sites worldwide, the privately owned Plansee Group generated sales of 1.5 billion euros in the 2018/2019 financial year, making it one of the global market leaders in the powder metallurgical processing of tungsten and molybdenum. The company’s headquarters and largest production site are located in Austria, where it was founded in 1921 as Metallwerk Plansee. If one initially thinks of a metal processing company as a production facility with chips, dust and dirt, the opposite is the case at Plansee. The company focuses on refractory metals such as tungsten and molybdenum, which have special properties such as high resistance and good conductivity. The metals are first processed into high-purity powder and then pressed, sintered and mechanically processed. The semi-finished products and components are used in the electronics industry, in semiconductor production and in medical technology. Absolute cleanliness in production is therefore a top priority. For the current production of components for semiconductor manufacturing, the process even takes place within an ISO class 6 clean room. In the modern Cleanroom CleanCell4.0, which was installed in 2019, parts and components made of molybdenum and other materials are assembled, the function of which is impaired by even the smallest impurities. Contamination of the sensitive components by particles must be absolutely ruled out. More than half of the 400 m² production area therefore meets the strict cleanliness requirements of ISO cleanroom class 6.
Cleanroom technology with energy-efficient air recirculation
Clean air is fed into the Cleanroom with the help of laminar flow units integrated into the ceiling, which are equipped with ULPA15 high-performance filters. The particle-free air flows displace airborne particles downwards and are then discharged from the Cleanroom into the recirculation duct. This air exchange process is carried out up to 60 times per hour. Recirculated air and return air are routed inside the cleanroom walls. The already cooled and filtered air is circulated, which contributes to very efficient operation of the cleanroom. In addition, the air flow within the walls ensures optimum use of space. Plansee opted for a cleanroom system from Schilling Engineering. Mario Kuisle, project engineer at Plansee, explains the advantages of the system: “The air circulation of the CleanCell4.0 cleanroom system convinced us right from the start. We can save high energy costs here in the long term. It was also important that the air routing within the walls ensures optimum use of space. The Cleanroom was adapted precisely to our circumstances.” The special conditions of the on-site location required a Cleanroom that was tailored to the customer’s needs in several respects. The project engineer recalls some of the challenges that the planning cleanroom company faced: “The on-site ceiling of the Plansee hall is not structurally suitable for suspension due to the expected snow loads, among other things. The cleanroom ceiling was then constructed with a self-supporting truss made of aluminum profiles. The ceiling can be walked on and was designed with stable walkways. A huge advantage of the construction is that the Cleanroom was designed without supports and columns.”
Modular design
Another challenge was the desired height of the cleanroom, which was designed to be four meters higher than standard cleanrooms. The height, required due to the installation of measuring machines, could be achieved with removable wall elements. The ceiling, equipped with 67 clean air units, is also modular and can be flexibly reconfigured. The modular system of the CleanCell4.0® cleanroom enables flexible planning of future capacity utilization, as Mario Kuisle explains: “The modular structure of the cleanroom system helped us enormously in our investment decision. We wanted to be able to quickly and flexibly convert the Cleanroom to other production processes. At the moment, we are producing for semiconductor manufacturing and have integrated the production machines into the cleanroom walls to suit. Thanks to the modular wall and ceiling elements, we will be able to convert to different occupancy concepts in the future.”
Intelligent control
Dimmable LED light strips are homogeneously integrated into the aluminum strips of the ceiling, which achieve uniform lighting with little shadowing at 1000 lux and contribute to energy savings. Doors and material airlocks are also illuminated with LEDs and use different colors to indicate whether a door can be opened or must remain closed for pressure equalization and active rinsing. Intelligent control is provided by the connected CR-Control® control and monitoring system, which is used to control and monitor individual filter units, production-relevant room data such as temperature and humidity and the air conditioning technology. The air conditioning system is characterized by extremely energy-efficient air treatment. In addition to the high proportion of recirculated air already mentioned, the use of an air pre-treatment unit and an air-cooled chiller achieve significant savings. Mario Kuisle is very satisfied with the first few months that the Cleanroom has been in operation: “The Cleanroom is running perfectly. The technology is very complex, but perfectly coordinated and well thought out. The energy optimization of the clean room was very important to us. By using a heat pump, we can save high ancillary costs in the long term. We also have the option of programming a night-time setback. The quiet filters and good lighting are also very positive, which makes daily work in the Cleanroom easier.
This article was published: Cleanroom online 01/2020
