Steam generators, in particular high pressure steam generators and high-speed steam generators; thermal oil circulation heaters for heat transfer; boilers; waste heat boilers for utilizing waste gases; natural circulation boilers; all the above goods also for combusting in particular primary energy carriers; furnaces for solid, liquid and gaseous fuels, in particular for the above goods; facilities for converting primary energy into usable energy, substantially consisting of furnaces, conduits, heat exchangers, circulation heaters and waste heat vessels