Gas cylinder rupture induced by local corrosion damage

Abstract

Commercial gas cylinders are common type of pressure vessels in many health care and technical facilities. Unexpected failures of gas cylinders occur despite of fact that the design, manufacture route, quality control, transportation, and handling are specified by various standards and regulations, particularly in domain of periodic inspection. A case study of the sudden failure of the 25 years old gas cylinder made of low-alloy steel is presented in this paper. Exploded cylinder was filled with commercial mixture of nitrogen and CO/CO2. Results of chemical analysis, mechanical testing and microstructure and fracture surface examination of gas cylinder material are given in this paper. Key results from failure analysis revealed micro corrosion pitting as a consequence of undesired traces of moisture. This slow crack initiation combined with gas mixture filling and exhausting cycles, promoted the local damage which could explain the mechanism of failure. In addition, the analysis of gas cylinder material in moment of failure is evaluated by using the critical distance parameter