Failure investigation of natural gas pipeline

A study was carried out to investigate the probable cause or events that might have led to the failure of two parallel natural gas pipes, API 5L X42 carbon steel (NPS 8) and the SDR 17, 125 mm medium density polyethylene pipes. These two pipes were laid side by side in the same trench with a water pipe. The investigation was performed by analyzing the existing design and construction data, visual inspection of failed pipes, and pipe material analysis. Investigation from the relevant pipes data suggests that the leaked water pipe was the first to fail. The leaked water pipe created high pressure water jetting that mixed with the back?lling soil to form water–sand–soil slurry with high erosive properties. The impact of this erosive slurry upon the NPS 8 pipe had caused serious losses of pipe coating materials. This phenomenon explains the rapid thinning of the steel pipe body which later led to its failure. Evidence from the metallurgical study using photomicrograph showed that the morphology of the steel material was consistent and did not show any evidence of micro fractures

Impact of copper nanoparticles on tribofilm formation determined by pin-on-disc tests with powder supply: Addition of artificial third body consisting of Fe3O4, Cu and graphite

Copper, magnetite and graphite particles were mixed in order to observe their impact on the coefficient of friction (CoF) during pin-on-disc tests and on the tribofilm formation after testing. Pure magnetite powder provided a value of CoF of 0.4. Magnetite-copper mixtures tested at 400 °C revealed lower CoF values (~0.4) than those at room temperature (~0.6). Magnetite-graphite and magnetite-graphite-copper mixtures presented lower CoF values (~0.3). All systems formed a magnetite-based tribofilm and patches of metallic copper were found on the tribosurfaces of the mixtures containing copper. Carbon layers and graphite nanoinclusions were observed in the graphite mixtures. The incorporation of zirconia particles, a by-product of ball milling mixing, prevented the selective transfer of graphite and copper to the tribosurfaces of some of the samples