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Compact, high-tech plastic valves ensure great-tasting coffee: A replacement for brass

The WMF name is known worldwide for high quality, functional and innovative products. These include the Presto!, Bistro! and Combination coffee machines.   Many Buschjost valves are at work inside these machines, guaranteeing a perfect Espresso, Café Crème or Latte Macchiato and ensuring the machines require very little maintenance, thanks to a sophisticated cleaning system.

Coffee machines have contributed significantly to the success of WMF in recent years. The range of innovative machines including the Presto!, Bistro! and WMF 1000 convince customers all over the world with their high quality, dependability and optimal ease of use.

The professional Bistro! single-cup machines for Espresso, Café Crème, Cappuccino, Latte Macchiato and coffee with milk, combine tried and tested systems with radical innovations.  The latter include the new milk foamer cleaning system and the optional integral chocolate reservoir. A high-quality stainless steel brewer and professional grinding discs made from specially hardened steel assure  long product life. The machine delivers speciality coffees in a matter of seconds. It also has high output reserves. The standard 6.3 kW model machine is able to produce 300 cups of Espresso, 220 cups of Cappuccino, 220 cups of Café Crème or 120 cups of hot chocolate per hour.

Performance such as this demands technical excellence at all levels, and of course this also applies to the valves. These hidden elements inside the machine ensure, among other things, that hot and cold water is supplied efficiently and the steamer operates correctly. Buschjost's superior quality high-tech plastic valves are used by WMF in their modern catering coffee machines (Presto!, Bistro!) and in their upmarket household machines (WMF 1000).   These replace the brass valves that have worked well in many machines, however, they do not represent the best solution.

For Frank Goeltenboth, Development Manager at WMF AG, there were a number of reasons for switching from brass to high-tech plastic valves. At the top of the critical list were the material properties of brass and the processing of the valves. Brass is not as resistant to hot water and steam as is required and, in particular, the lead components in brass alloys mean they are not ideal for use in coffee makers. In the production of hot water or steam, brass valves lose a lot of heat and this either must be simply accepted or minimised using costly insulation. In addition, much less calcium adheres to the surfaces of modern plastics. Another reason why Frank Goeltenboth decided to look for new solutions was the time-consuming assembly of brass valves, as the connections usually need to be screwed in and often require another seal.

Buschjost's valves are made from a high-tech plastic that was jointly developed and are far superior to brass valves and also to other plastic valves in applications such as coffee machines. The casing material is highly resistant to cold and hot water and steam. The plastic surface does not discharge any particles into the media flowing through the valves even after prolonged usage.

During the preliminary phase, Buschjost perfected all of the relevant features of the plastic valves using modern design simulation tools. These tools can detect unwanted turbulence and laminar and turbulent flow, analyse them and reduce them to an optimal level. In the injection moulding process, the determined contours were replicated exactly to a hundredth of a millimetre and the interior surface of the valve becomes much smoother than in mechanically processed products. During the optimisation process, the determined radii are transferred precisely on to the valves.

A special passivation process protects both the armature and the metal components in the body of the valve from the build-up of calcium and residues. The counterpressure design of the valves safely prevents the mixing of media. The valves are fitted with a hose clamp or push-in system to ensure a quick, airtight connection. The electric connections for the solenoid valves are a simple design similar to the hose connections. The magnets can be rotated in any direction and can be replaced without using tools. The compact design of the valves in sizes DN 2.5 and 3.5 means they are useful anywhere. They are optimised for use with water, purified water and steam and work safely in media temperatures up to 125°C and ambient temperatures up to 50°C.

"About four years ago, WMF and Buschjost began their successful working partnership," says Frank Goeltenboth. "I was pleasantly surprised by the competence, reliability and openness of the Buschjost employees with whom we worked cooperatively and effectively." The results were convincing and the valves have proved their worth in tough, everyday conditions. Last but not least, the WMF service data provides evidence of the product's superior quality. Using error descriptions and error codes, the company consistently checks the service team's duties and identifies what tasks the service staff on site are engaged in. All defective parts are accurately recorded. "And here," states Goeltenboth, "the new Buschjost valves have been completely convincing by their low failure rate."

Download picture coffee valve

Download picture coffee maker