1. The pipe is abraded by the fly ash and the installation and maintenance quality are unqualified.   

2. The water supply quality is not qualified, making the pipe inwall corrode, scale and overheat. 

3. The water pressure and temperature change are too big, thus water hammer happens. 

4. When the boiler is started, stopped or the feeding water to the boiler is stopped, the economizer recycling valve is not opened timely, so the water feeding speed is too fast, thus causing the pipe to damage. 

5. The welding quality is unqualified or the materials are unqualified.