Failure Analysis of a Firefighting Pipeline Fracture

A firefighting pipeline failure accident occurred in a large high-rise office building. To investigate the cause of the accident, a series of tests were conducted, including material, physical and chemical property tests, full-scale hydrostatic and burst testing, and microcharacterization tests. The results indicated that the chemical composition, metallographic structure, hardness, and tensile properties of the pipeline body all met the requirements for Q275 material specified in the GB/T 3091-2015 standard. The hydrostatic test and hydrostatic burst test for the same batch of pipeline also comply with the relevant requirements of GB/T 3091-2015. However, the wall thickness and outer diameter of the pipeline failed to conform to the requirements for the DN150 specification. Additionally, the firefighting pipeline fractured circumferentially along the bottom of the groove. The fracture surface is flat and without obvious plastic deformation, showing a quasi-cleavage morphology. The groove rolling process resulted in an asymmetric structural mutation at the groove and also caused work hardening and deformation of the structural flow lines. Ultimately, under the action of loads such as internal pressure, water flow impact, and uneven torque, a sudden brittle fracture occurred at the root of the groove.