This system is used in almost all the annealing and decorating lehrs because it guarantees the best performance/consumption ratio. Based on the gas pressure available on site, the lehr may be fitted with burners for medium pressure, which are extremely simple in that no fan is required to create combustion air, or traditional low pressure burners with a fan.
Indirect heating system
The heating devices, radiant tubes, placed in the lehr areas, are used as heat exchangers. They are made up of a U-shaped, refractory steel tube with a feeding burner on one end and the flue gas exhaust chimney on the other end. Various types of fuels may be used for indirect heating, such as any type of gas or diesel oil. The chimneys release the flue gas from the upper part of the lehr, where they are gathered in two manifolds. Electric heating system
The photos show a high-efficiency triphase electric resistance panel and a section of a lehr with where these panels have been installed. The glow plugs are of the type with an exposed, air-wound wire for optimum heat exchange.
Mixed heating system
The photo shows a mixed heating system. The section on the right can function in a combined gas-electricity environment.
