The present work analyses the failure of a Ni-Cu MONEL 400 alloy tube, which operated as part of a pipeline in a petrochemical distillery installation. The pipeline is used to carry a stream of gaseous hydrocarbons containing hydrochloric acid (HCl) into a reaction tower filled with caustic solution (NaOH), in order to remove HCl from the stream, before the later is directed to a burner. Failure occurred in the form of through-thickness cracking at a bended tube of the pipeline. Metallographic examination revealed intergranular cracking, as well as substantial branching of the observed cracks. Although nominal chemical composition of the component was found to lie within the specified range, EDX microanalysis indicated significant segregation of S and Cl on grain-boundaries. Failure was attributed to stress corrosion cracking (SCC), due to the effect of hypochlorous acid (HClO), formed by the reaction of HCl with atmospheric O2, which entered the tube during shutdowns/startups of the installation. The phenomenon was assisted by residual stresses, originating from the lack of stress-relief annealing after the in-situ bend forming of the tube during assembly of the line, by local reduction of ductility due to bending, as well as by the segregation of S on grain-boundaries.