Analysis of the corrosion and leakage causes of the propane dehydrator inlet pipeline in an alkylation unit

• Failure mechanism of a propane dehydrator inlet pipeline in an alkylation unit was systematically investigated. • Unlike conventional corrosion induced by H 2 SO 4 or HF, a failure issue under lower temperature conditions at operational temperatures below 60 °C was investigated, which are often overlooked. • Finite element analysis was conduct to reveal the causes of failure, indicating the possible two-phase flow that induces scouring corrosion on the pipe wall. The corrosion and leaking mechanism of the propane dehydrator inlet pipeline in an alkylation unit was studied via analysis of macro-observation, chemical composition, mechanical properties, metallographic, fracture morphologies, EDS and XRD, combining with numerical simulation. The corrosion and thinning of the pipeline from the propane extraction system in the alkylation unit, extending from the propane-water wash mixer to the propane extraction dehydrator, is primarily caused by erosion-corrosion. Under the designed operating pressure and temperature conditions of the pipeline, propane is near or within the two-phase boundary between liquid and gas. At locations where structural discontinuities occur, propane is prone to vaporization, forming a two-phase flow, which leads to erosion-corrosion of the pipe wall. This is the main cause of the corrosion in this pipeline.