Failure analysis of a sheared 2” steam injection pipe of a vacuum heater

The steam injection pipe has failed by corrosion. The pipe was found to have got completely choked due to deposition and coke formation. Analysis suggests that there was failure elsewhere in the system which led to stoppage of steam flow through the pipe. The deposition in the localized region was promoted due to creation of a stagnant zone because of no steam flow. Subsequently, the rise in temperature due to poor heat transfer resulting from this deposition aggravated the situation further. Based on the severity of oxidation and scale formation on the outer surface of the pipe and microstructural changes observed in the steel, it is estimated that the pipe material was exposed to temperatures higher than 8000C for a prolonged time