PURPOSE: To enable a heat transfer pipe to be applied in a combustion gas passage having a wide width, restrict an increase in raws of soot blowers, prevent vibration of the heat transfer pipe from being applied without using any vibration restricting fitting and further to enable each of the heat transfer pipes to be connected to their operated states after bending at their manufacturing.

CONSTITUTION: This pipe assembly is provided with a plurality of heat transfer pipes 10 arranged within the same vertical plane, end supporting devices 20 for supporting both ends of the heat transfer pipes 10, and an intermediate supporting device 30 for supporting an intermediate part of the heat transfer pipe 10. Each of the heat transfer pipes 10 has a plurality of horizontal pipes 12 and a plurality of U-shaped pipes 14 connecting the adjoining ends of the horizontal pipes 12 from each other. The end part supporting device 20 has a plurality of tie rags 22 for partially connecting both ends of the horizontal pipes 12, and has supporting fittings 24 and 26 for supporting the U-shaped pipes 14 from a furnace wall pipe in the combustion gas passage. The intermediate supporting device 30 has a plurality of clamping members 32 for clamping the central portions of the horizontal pipes 12 in a vertical direction, and has a supporting pipe 34 passing through a plurality of clamping portions in a vertical direction, extending there and fixed to the clamping portions.