PURPOSE: To enable steam generated from a waste heat boiler to be applied for performing soot blowing operation without passing through an over-heater by a method wherein water pipes having anti-corrosion metallic flame spraying layers at their surfaces are arranged at portions where they may be easily damaged by the soot blowing operation.

CONSTITUTION: Water pipe rows facing directly against a soot blowing device 3, i.e., the water pipe row of the first row counted from the soot blowing device 3 under their grid-like arrangement and the water pipe rows of the first and second rows under their zig-zag arrangement are constructed by the water pipes having anti-corrosion metallic flame spraying layers at their surfaces. In any case, the water pipe rows 2 subsequent to the third row are easily attacked directly by steam, so that a necessity of the metallic flame spraying layer is reduced. As the metallic flame spraying material, nickel-chrome system having as its main substance chrominum of high hardness may well be adapted and a thickness of the metallic flame spraying layer may be of several hundreds micron. With such an arrangement, even if the steam from the waste heat boiler is supplied to the soot blower device without passing through the over- heater, the water pipes may not be damaged.