Steam generator in horizontal design with exchangeable U-tube bundle. Steam, hot water or thermal oil are employed as heating media. This type is suitable for medium to high shellside steam pressures. The bundle tubes are attached by expanding or shrink-welding or both (depending on the operating conditions). The flow can be double- or multi-flow depending on the fluid throughput. If condensing steam is employed as heating medium, the heating tubes are installed at an angle in order to ensure that the condensate is properly drained. The condensate can be cooled down by an external heat exchanger. With a low steam space load good buffer conditions can be achieved if the steam is used irregularly. The steam generator has been designed for high performance but has a small fluid volume. An inspection opening for the shell side is possible due to which in many cases no bundle disassembly is required for a boiler revision. We recommend an inspection opening for the shell side if the vessel gasket is a weld ring gasket. As stainless steel version the RDEK 2002 type is suitable for pure steam generation.