Failure Analysis on Cracking of Sulfuric Acid Pipeline in a Petrochemical Plant

The leakage failure of sulfuric acid pipelines will cause serious damage to the production and surrounding environment due to the strong corrosive nature of sulfuric acid. Taking the main pipeline of sulfuric acid transportation in a petrochemical plant as the analysis object, the cracking causes of the pipeline were analyzed and discussed by using chemical composition analysis, metallographic examination, tensile test and hardness test. The results show that there were a lot of casting defects such as holes and microcracks near the inner wall of the pipeline casting mold line. The length of flake graphite in the material reached grade 2, and there was a small amount of phosphorus eutectic. The presence of these casting defects, slender flake graphite and non-metal eutectic led to an abvious decrease in the tensile properties of the material, which made the tensile properties could not meet the requirements of relevant standards and eventually led to the cracking leakage during the operation of the pipeline.