Session: Recent Experiences With Austenitic and Duplex Stainless Steels
Case Study of a 316L Stainless Steel Flange Crack from a Hydraulic Oil Pump Skid (C2026-00394)
Thursday, March 19, 2026
12:00 PM - 12:30 PM Central
Location: 370 EF
Earn .5 PDH
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A metallurgical failure analysis was performed on a flange used in a high point bleed line on a hydraulic oil pump skid after a leak had been discovered in service. The sample consisted of a weld neck flange and a reducer, both constructed from Type 316L stainless steel. A transverse crack was found in the flange base metal adjacent to the weld between the flange and the smaller-diameter end of the reducer. The crack features were examined with the aid of a scanning electron microscope (SEM), and a metallographic specimen was prepared through the origin area to determine the associated damage mechanisms. The chemical composition, using optical emission spectroscopy (OES), and hardness of the cracked flange were tested for comparison with applicable specification. Based on the examinations, the flange experienced environmentally assisted fatigue cracking that initiated at the outer surface and progressed inward. Geometric and metallurgical stress risers associated with connection design and fabrication likely contributed to the initiation of the cracking.
