Physicochemical Analysis: Stop chemical composition analysis of cracked stainless steel flanges. The analysis results show that the chemical composition and welding data of the stainless steel flange meet the relevant specification requirements. The Brinell hardness of the flange neck surface and the sealing surface are stopped respectively, and the Brinell hardness value meets the requirements. On the premise that the chemical composition of the material is qualified, the pipeline equipment meets the technical requirements, the hardness test is qualified, the pressure test operation standard, and the cracking of the pipeline flange during the pressure test process, find out the defects and internals. The organization of the flange or other unknown elements are relevant.
Analysis of the nature of the cracks The appearance of cracks was cut from the flanges of the pipeline leaks and the flanges were macroscopically inspected. Cracks were found to be present on the inside and outside of the flange with a length of 3 mm and a width of 0.5 mm. Rust spots were created; more cracks were also found inside and outside the flange bolt holes.
Why do stainless steel flanges crack?
Numerous non-metallic inclusions are found on sealing surfaces of stainless steel flanges and other locations. Various non-metallic inclusions are scattered on the flange sealing surface to form small pits. The size of the dimples is 2.0mm and the edges of the dimples are 0.8mm. Tiny cracks are visible to the naked eye. On-site macro inspections were performed on other austenitic stainless steel flanges from the same batch.
Many flanges are defective to varying degrees, and some have obvious cracks visible to the naked eye. The results of the macro inspection further showed that the butt welded flanges and flange leakage were related to the elements of the flange itself. To further explore the true cause of flange leakage, profile crack morphologies were randomly selected from the same manufacturer and batch.
