Abstract: To ensure the safe operation of chemical pipelines, the types of damage to pipe under the impact of the flood were summarized. Based on the stress analysis of pipe and junction under flood impact, a model was built for judging the bolt failure of pipe flange connection under flood impact. Through this model, the bolt safety conditions of pipe flange connection under flood impact was judged, and the flood speed and the critical length of pipe failure were calculated when the pipe junction failed. An example of the chemical pipe connected by flange-plate type steel pipe flange was presented in this paper. In this example, the critical water velocity and critical length were calculated for different outer diameter pipes under flood impact. The results show that for a pipe under the impact of the flood, the higher the flood velocity is, the shorter the failure length of the pipe will be, and that at same water velocity, the larger the pipe diameter is, the longer the critical length of pipe failure will be.

Key words: flood, pipe, flange, failure, critical length