resistant material the number of supports 4 to be deployed will depend on the available length of the furnace 1 and the diameter of the radiation exchange tubes 10 due to its unusual configuration the lower supports 6 and upper guide 8 make it possible to use high strength supports 4 of relatively slender dimensions without any height restrictions and whose linear expansion will not cause any excessive stress on the ceiling 11 or the base 12 of the furnace 1 when in operation by using the support system of the present invention in which the main supports 4 rest upon lower supports 6 the greater part of the burden is transmitted to the base 12 as already mentioned furthermore since the transmission of stress from the supports 4 that rest upon lower supports 6 is made by pivoting in other words not rigidly there is no transmission of thermal stress by bending moment to the base 12 of the furnace 1 hence it is not necessary for the base structure 12 to be reinforced and as a result a base 12 can be provided with a far less robust construction than usual thus the upper guide 8 receive no vertical stress hence their function is essentially to serve as a lateral bearing for the supports 4 also to absorb thermal expansion of the supports 4 as a result the ceiling 11 and side walls 22 of the furnace 1 can also be less robust in this way additional expense on reinforcing the structure of these parts is avoided in addition due to the innovative features the main supports 4 lower supports 6.