1. Over-high output increases the wear of rotary kiln mouth shell, and causes the overheat deformation of the kiln shell.

2. The heat flow is too large but the cooling zone is short or even no. The working environment of the kiln mouth is bad, the temperature of outlet material is 1300-1400°C, and the secondary air temperature is 1000-2000°C.

3. The cylinder temperature is too high, the thermal expansion is large, while the strength of the high temperature resistant materials is seriously attenuated.

4. The guard bolts at kiln mouth are loosen, so that the refractory materials fall off, and thus the shell is burnt.

5. Improper handling during burning contaminated soil causes severe corrosion of the cylinder shell.

6. The corrosion of sulfur, phosphorus and chlorine on the kiln shell reduces the thickness and strength of the kiln cylinder, also reduces the plasticity of the steel and increases the brittleness of the steel, which may lead to brittle failure of the kiln cylinder.