Decades of drying know-how
Mesh belt dryer. Image: Sellacan
Evert van de Weg speaks to Dietmar Raupach, managing director of Germany-based Sellacan, about the company’s formation and its journey to becoming one of the most experienced partners in industrial heat treatment
We all know that tinplate (and aluminium as well) must undergo many treatments before it becomes a can. Even early-made tinplate was covered with a layer of paint, sometimes as protection and sometimes as decoration. Today, tinplate undergoes a protective coating (lining) to the interior, a layer of paint or varnish is applied to the exterior (the basecoat), if the can has to be printed, coloured inks decorate the exterior and then, to protect the ink, a layer of varnish (the topcoat) is applied. Every layer of paint, ink or varnish applied to a sheet of tinplate must be dried or cured in an oven at high temperature.
The development of coating and printing technology is very closely bound up with that of drying techniques. Originally, chamber ovens were used. These operated at temperatures of around 65°C. During the 19th century, these were heated using town gas. Varnish requires dry heat and the faster it can be dried, the better the results. The printed sheets of tinplate were originally placed in racks, which could be rolled into the oven on rack trolleys. Drying was a lengthy process.
Around the year 1900, gold varnish had to remain some two-and-a-half hours in the oven. By the 1920s, tunnel ovens had come onto the market. The wet sheets were drawn through these on metal stands, emerging dry from the other end. To dry paint and varnish, 30 to 40 minutes at a temperature of 180°C to 210°C was generally required. Such tunnel ovens thus shortened the time to dry a lining, e.g. of gold varnish, by some two hours, compared with chamber ovens. Over the many decades since then, capacity of drying ovens increased considerably. The use of new types of paints and inks reduced drying times often to just a few seconds.
Along with the development of industry in the 20th century, in many different branches, industrial ovens were used for a variety of applications, including drying, curing or baking components, or parts of final products. Producers of industrial ovens were founded in Germany.
In the city of Detmold, the company Neitz became an important manufacturer of industrial ovens, and it built up a strong reputation in the metal packaging and automotive business, until it had to close in the early nineties due to economic changes. The knowledge and experience in oven construction, collected over decades, was at risk of being lost. However, the leading technical manager within Neitz, Dietmar Raupach, and some experienced alumni of Neitz, came together and reformed in 1996 to form the company Sellacan.
Coating lines for can making circa 1920. Image courtesy of Evert van de Weg
Sellacan Industrieofen GmbH
The company Sellacan, based in Lage, near Detmold, can thus look back on many years of experience in the construction of industrial furnaces based on its rich heritage of expertise. The company’s name is actually the translation of the German phrase ‘verkauf eine Dose’ which translates into ‘sell a can.’
Sellacan’s managing director, Dietmar Raupach, divulges more about the company and its highlights: “I founded Sellacan in 1996, together with three fellow campaigners. The inner circle of the founding community were former employees of Neitz. The furnace sector lost a supplier through the closure of Neitz, and we wanted to preserve know-how and continue developing our capabilties. Sellacan started in the metal packaging market with ends drying ovens, and we have found much success since then.”
Did Sellacan begin with the production of drying ovens for metal can production, and later add on ovens for other products?
“At that time, there had been only a few really independent suppliers of drying ovens in the metal packing industry. From the very beginning, Sellacan has focused on drying ovens for the twistoff sector. We have also solidified our market position with the advantages of our well-known furnace concept: individually adjustable heating zones and temperature ranges. The fact that we have managed to achieve this position, especially in the twist-off area, was retrospectively, on the one hand, so that we could establish Sellacan after minor initial problems as an eligible partner.
“The second reason is that we have also been able to build up a market position in other product areas, in which we have brought appropriate proficiency. Today, we are a supplier of tempering furnaces for the automotive industry and of brazing furnaces for industrial applications. The story would not have been successful just with the metal packaging business alone.”
Is the production of drying ovens for the metal packaging industry the most important part of your sales?
“The development of equipment with high-speed lines in the lid area in competition with low-cost suppliers has asked us to look for other product areas. We have broadened our activities to new markets and supply our individually optimised designs in industrial furnace construction to the automotive industry, namely heat treatment and brazing lines.”
How did Sellacan learn about the importance of stable temperatures for the various types of can coatings?
“Back then, only relatively expensive oven concepts containing a temperature range, or low-cost providers were known. We have developed and strengthened our knowledge, together with our experienced engineers – to provide the appropriate temperature setup for the different applications of our valued customers. Our mission: listen to customers, gain own experience by running trials, and never give up satisfying customer needs – that is the short answer. Sellacan’s mesh belt drying ovens for twist-off, for example, are delivered to six continents. The design allows a reliable and condensation-free operation of our dryers.”
Omega dryer. Image: Sellacan
Your list of credentials names many international can makers; are the conditions in your ovens for can and closure coatings still subject to further developments?
“With respect to the development of the PVC-free sealing for twist-off lids, there was meanwhile a noticeable drop in demand for us. The market has since consolidated, and we’ve gone back to previous numbers. As there are generally, both in the metal packaging industry and at our other customers, continuous evolutions or requirements to be considered, Sellacan’s ovens are subject to ongoing development. The most important things for Sellacan are quality and precision in manufacturing – from design to implementation. We build long-term relationships with our customers and intend to be a partner.”
What would you consider the most important innovations in your drying ovens for metal cans/closures in the last few years?
“We have set up small improvements, especially for the control and industry 4.0 – to keep our products always up to state-of-the-art status, the reliable process of drying itself is not affected.”
Are you working on a transition to lower energy use of your ovens? Are you thinking about replacing the use of natural gas by electricity, or even other sources of energy?
“The impact of the war and climate crisis is challenging all industries. Regarding our gas-powered drying ovens, we offered our customers conversion packages, from gas to conventional electric heating. But, after initial euphoria, only low orders were placed. The discussion about higher admixtures of hydrogen into natural gas is certainly interesting. The keyword here is H2-ready. However, there is still a lot to be done on the supplier side.”
Has your company ever considered UV curing ovens?
“We have carried out corresponding test series in the past. It turned out that the use of UV devices leads to rapid heating. This means skin formation on the compound and thus blistering, but no uniform drying.
“I would like to mention an important development we undertook. This was the special individual development of our Repair coating machine. The high-speed machines are equipped with electro-mechanical spraying guns, with the ends running on a rotating vertical table. The R12S works reliably and has the advantage of little overspray on the device. A magnetic belt system feeds the ends after application into our horizontal pocket dryer. Two Repair Coaters can be connected to a dual-line dryer to increase output. The system is equipped with an exhaust system to extract emerging lacquer mist.”
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