The leakage of slag-catching tubes on the water-wall of boilers has continuously occurred in one power plant.For this

the macroscopic inspection

chemical elements analysis

tensile testing

metallographic examination

scanning electron microscope and energy spectrum analysis have been carried out.The results of analysis show that the drop-off of refratory material from outer wall of the slag-catching tubes makes the high-temperature flue gas to produce differentical expansion at there

the annular fatigue cracks were occurred on the outer side of the tubes

at the same time

impurities in the water have concentrated in the bottom of etch pits and grooves

resulting in corrosion under deposit

and forming cracks

the cracks on inner and outer walls further expanded and linked up

making the slag-capturing tubes on the water-wall to be cracking and leaking.For this

it is recommended that the refractory material laid on the outer surface of water-wall should be inspected during the time of major and temporary repairs

timely repairing the dropped off refractory materials

and ensuring the tightness of condenser

as well as controlling the oxygen-dosing amount.