Cracking in C3 cut/propylene Horton spheres

摘要

A Horton sphere(80-S-05)for storing C3 cut/propylene was fabricated of SA 537 Class 1 material at site as per ASME Section VIII Div.2 in 1989.It has been in propylene storage service for the past 16 years.Internal inspection and nondestructive testing(NDT)of the sphere revealed numerous cracks at the toe of the weld.Presence of sulfur in energy dispersive spectrum(EDS)analysis of the deposits collected from cracks suggested sulfide stress cracking(SSC).The cracks were repaired and the sphere was stress relieved.