One of the four tube bending machines, belonging to the German manufacturer Reimann und Kahl: A machine of type PR8-12CMC can process tubes with a diameter of 8, 10, 12 mm. The standard size of serpentines is 2.5 x 2.5 m2, but the machine can be adjusted to produce parts with an area up to 6 x 2 m2. Photo: Reimann und Kahl
The Reimann und Kahl GbR has increased its production capacity lately. The German manufacturer of serpentine tubes (also called meanders) for collector manufacturers has just started operating its fourth tube bending machine in Teistungen, Germany. “We are now able to produce 1.2 million m2 of serpentine tube area,” Peter Reimann says. He is one of the managing directors of the German company, which has been in the business of tube bending since the 1990's. There are also plans for a fifth production unit for serpentine tubes, which will be set up soon.
It was in 2003 that the company delivered to its first customers in the solar thermal industry. Since then, Reimann und Kahl has most probably become the biggest supplier of serpentines for solar applications in Europe. In 2008, the German company shipped around 600,000 m2 to ten different countries in Europe. And Reimann und Kahl is continuously improving its machinery for tube bending. Last year, it patented the bending head. “We are now focusing on improving the tube infeed and straightening. “The new technology is no longer producing an oval-shaped tube during processing,” the company explained in a letter to customers in July this year.
The German manufacturer will follow two objectives in the future: selling costumer made serpentines to collector manufacturers, as well as shipping machinery units to big producers of the sector. “If one produces 150,000 to 200,000 m2 of collector area per year with serpentine tubes, purchasing its own serpentine tube bending machine is worth it,” Reimann analyses. One requirement: The machinery needs a large space in the production hall of the collector manufacturers – 300 to 400 m2, depending on the collector size. Reimann experiences a growing interest in meander tubing, especially in Central European countries - thanks to cheaper production costs than soldered harp-type tubing.
A market survey among international collector manufacturers by the international magazine Sun & Wind Energy found harp absorbers to be more common than meander absorbers. Only ten of the 61 collector manufacturers, which took part in the market overview, favour serpentine absorbers. There are two reasons for this trend: Collectors for thermosiphon systems – the dominating solar thermal technology on the world markets – have to be equipped with harp-type tubing. And secondly, the decrease in pressure of serpentines in larger collector fields is too high, that´s why harp absorbers are chosen here as well.
Reimann und Kahl offers custom-made harp absorbers, too. The company runs an automated punching machine, a tube straightening unit and a semi-automated array brazing machine.