Abstract
The failure analysis of an elbow tube of a pyrolysis furnace after three
years of service which is only one third of the designed life span has
been studied. An investigation to identify the root causes of the failed
tube was carried out by macro inspections, chemical composition
analysis, metallographic microscopy, scanning electron microscope (SEM)
images and energy disperse spectroscope (EDS) analysis. Through analysis
of the failed tube samples, we found no evidence of bulging and
thinning, that the cracks originated from the pores and inclusions
inside the fusion line of the inner wall, under high temperature and
stress effects, that the cracks expanded towards the base material along
the circumferential direction of the tube until it breaks.