The failure occurred upstream of a venturi which was no longer used. The pipe wall was found to be abnormally thin. It seemed that wet steam had caused erosion of the pipe, a well-known phenomenon, particularly before venturis where droplets of condensate can be ‘kicked back’. Some marks on the upper surface of the pipe were assumed to have been caused by high velocity liquid flow. The lower 20–30% of the surface was free from these marks but there was an explanation for this: condensate would dam up against the venturi to form a liquid pool and prevent erosion.