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FAILURE ANALYSIS
Failure Analysis of Type 316L SS Drain
Nozzle Elbow in H2
S Service
GEOGY J. ABRAHAM AND VIVEKANAND KAIN, Bhabha Atomic Research Centre, Mumbai, India
hydrogen sulfide (H2 of 130 °C and pressure of 25 kg/cm2
A plant reported repeated failures of a Type 316L stainless steel (SS) (UNS S31603) elbow of a pipeline system carrying water saturated with S) at a maximum temperature . Examination
revealed branched cracks and adherent black spots on the inside diameter. Analyses were carried out to ascertain the cause of failure.
62 MATERIALS PERFORMANCE March 2012
A
PaLZWOMV []TÅLM 02
ustenitic stainless steels (SS), such as AISI Type 304 (UNS S30400) and 316 (UNS S31600) are used in the annealed condition for S) service. ASTM
A403 Type 316L SS (UNS S31603) is normally suitable for H2
sensitized condition.1
S service in non- If, however, the
material undergoes prior sensitization or in situ sensitization, it becomes suscep- \QJTM \W []TÅLM [\ZM[[ KWZZW[QWV KZIKSQVO (SSC).2
The austenitic SS are used to a
UI`QU]U :WKS_MTT + PIZLVM[[ WN HRC.3
SSC susceptibility include the H2
pipeline system elbow was carrying water saturated with H2
S at a maximum
temperature of 130 °C and pressure of SO KU2
.
Experimental Procedure The failed elbow was subjected to a
series of metallurgical examinations. The following examinations were made on the as-received longitudinal section of the
elbow. z >Q[]IT IVL TW_ UIOVQÅKI\QWV UIK- roscopic
z Electron probe microanalysis -85) WN \PM JTIKS [XW\[ WV \PM inside diameter (ID) of the elbow z Microstructural and microhardness
Results Visual Examination
Visual examination of the elbow using
a magnifying glass revealed branched KZIKS[ I\ \PM W¼KTWKS XW[Q\QWV WN \PM MT- bow. Low magnification examination using a stereo microscope indicated the XZM[MVKM WN JTIKS [XW\[ [KI\\MZML ITT W^MZ
NACE International, Vol. 51, No. 3