As a simple and practical maintenance method

water discharge in hot state and drying using waste heat were widely applied in short term shut down of the thermal power plants.Against the large vibration occurred during water discharge of the boiler in a 700MW unit

several countermeasures were taken

such as determining the discharge time according to the helix tubes wall temperature

keeping the helix tubes wall temperature higher than the saturation temperature corresponding to the pressure during water discharge

and adding the hydraulic damper.After the improvement

the vibration reduced significantly

with the largest vibration amplitude below 1mm.