In the aviation industry, the precision and quality of engine parts are of the utmost importance. Uniform drying is particularly crucial in the electroplating process of these components. The integration of heat pump drying technology offers a highly efficient solution that not only reduces drying times, but also optimizes temperatures and enables significant energy savings at the same time.
Future-oriented drying for engine production
In view of the high requirements in engine production, leading companies in the aviation industry rely on advanced and reliable technologies. MTU Aero Engines, Germany's leading engine manufacturer from Munich, is no exception. MTU specializes in the production of engine components for renowned manufacturers such as Pratt & Whitney and GE Aerospace. The company requires efficient and reliable drying for the production of engine parts. In the drying process for these complex geometries, however, the energy consumption, temperatures and heat load on the engine parts should be as low as possible. Sustainability is also a top priority at MTU. In order to meet all these requirements, MTU has been working with the drying system manufacturer Harter from Stiefenhofen in the Allgäu region for many years.
Heat pump drying as the key to increasing efficiency
Fig. 1: In the rack dryers, engine parts for aircraft are gently and completely dried at 50 °C within ten minutes - (Photos: Harter)Josef Linska, process engineer for chemical and galvanic processes at MTU, became aware of the innovative heat pump drying process at a lecture given by Reinhold Specht, managing partner at Harter, at the German Society for Electroplating and Surface Technology (DGO). Since then, MTU has relied exclusively on Harter's drying solutions.
Before the final implementation in production, Harter carried out extensive test series with the engine parts in the company's own technical center. This was followed by further tests in close cooperation with MTU at Harter's technical center. The purpose of these tests was to ensure that the drying parameters were optimally adjusted and to adapt the technology to MTU's specific requirements.
Harter's technical center has several dryers in which relevant parameters such as time, temperature, humidity, air speed and air flow are tested and determined. MTU's aim was to achieve gentle and uniform drying at a maximum temperature of 70 °C. In the tests, Harter was even able to exceed MTU's expectations. Even at 50 °C, the engine parts were completely dry after just ten minutes (Fig. 1).
These tests confirmed that Harter's heat pump technology not only optimizes temperatures and drastically reduces energy consumption, but also significantly shortens drying times.
Advanced heat pump drying for complex geometries
Harter has already installed several rack dryers in MTU's electroplating lines. Now another rack dryer has been added to further increase capacity. The rack dryers from Harter are equipped with an energy-saving heat pump. The drying process works without exhaust air. This means that the process air is not discharged to the outside. Instead, it circulates continuously in the system, which significantly reduces energy consumption and protects the environment at the same time. In addition, Harter's dryers offer a specially adapted air flow that is precisely tailored to the properties of the engine parts. "The geometry of our parts poses a particular challenge, as they have tight corners and undercuts," explains Linska. "The precise air flow ensures that even the most difficult parts are dried evenly and quickly, without any accumulation of moisture or uneven drying results," explains Specht. This technology meets the high standards that MTU demands for its engine parts and contributes significantly to efficiency and sustainability in production.
Fig. 2: Drying with a heat pump can save operating costs of 60 % and more
Sludge drying with heat pump technology
MTU has also opted for another innovative project in the field of wastewater treatment. Here too, the company is using heat pump drying from Harter to efficiently process the pre-dewatered sludge. This leads to considerable savings in disposal and transportation costs for the operators (Fig. 2). After mechanical dewatering, the sludge still has a water content of 60 - 70 %. By using heat pump technology from Harter, MTU is able to significantly reduce the water content of the sludge. In future, one ton of sludge will be dried at MTU. The concept developed by Harter provides for the sludge to be dried directly under the mechanical dewatering system. Special drying containers will be installed there, in which the sludge will be dried. Here too, the entire process takes place in a closed and exhaust-free system. The dried sludge is then transported via a screw conveyor to the filling station, where it is filled fully automatically and dust-free into big bags. This process not only ensures noticeable cost savings for MTU, but also a sustainable and efficient optimization of the entire sludge drying process (Fig. 3).
Fig. 3: The sludge falls from the two chamber filter presses into the drying containers below. From there, the dried sludge is automatically transported to the big bags of the emptying station via a conveyor system. On the right in the picture is the dehumidification module for preparing the required process air
Efficient component drying using heat pump technology
"The alternative physical approach that Harter pursues with its heat pump fascinated us right from the start," explained Linska. "This technology was something completely new for us at the time." The success of the system is based on two main pillars.
The first is air dehumidification. Harter uses highly dehumidified process air. This extremely dry and therefore unsaturated air is passed over the parts to be dried or through the sludge in the dryer. The heat pump module connected to the dryer treats the process air and is also responsible for the condensation process. The dryer and module are connected to each other via insulated pipes. The circuit is closed in terms of air and energy.
On the other hand, targeted air routing is just as important. Specht explains: "Air always moves along the path of least resistance. It must therefore be guided precisely to the components or homogeneously through the sludge so that it absorbs the moisture there quickly and effectively." For geometrically demanding components, Harter also uses compressed air-free blow-off technology in particularly difficult cases. This removes water even from areas that are difficult to access. Blowing off acts as a preparatory step or supporting measure for drying, but does not replace it.
Harter dryers with heat pump technology were recognized by the state as a sustainable technology back in 2017. Since then, customers have benefited from government subsidies for this energy-efficient solution. MTU also took advantage of these subsidies.
Long-standing successful partnership
"We are very satisfied with the solutions that Harter has always supplied us with," emphasized Linska. "The dryers have not only improved our production efficiency, but have also helped to reduce our energy costs. What's more, with our drying systems we now have an environmentally friendly solution that fits perfectly into our concept of sustainability." Specht also looks back positively on the long-standing partnership. "MTU is an important customer for us. We are proud to have developed customized solutions that meet both the technical requirements and the environmental specifications," he explained.
