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51317--9518-Chloride Stress Cracking of an Austenitic Stainless Steel Pipe Fitting in a Hydroprocessing Unit

Case study: Cracking occurred in a (UNS S32100) type austenitic stainless steel nozzle fitting at a low point in the reactor effluent piping in a Gasoil Hydrotreater unit following start up. Normal preventive measures had been taken.  The failed sample was removed for metallurgical analysis and determination of mechanism(s).

Product Number: 51317--9518-SG
ISBN: 9518 2017 CP
Author: Hayrik Allahverdian
Publication Date: 2017
Industry: Petroleum Refining
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$20.00
$20.00

A cracking occurred in a stainless steel branch nozzle fitting at a low point in the reactor effluent piping in a Gasoil Hydrotreater unit following start up.Normal preventive measures were implemented to protect the piping system against Polythionic stress corrosion cracking (PTASCC) during shut down (neutralization & nitrogen purging) however cracking occurred in the 321 type austenitic stainless steel weldolet right after the start up. Materials selection of low point drain including the fitting is in accordance with good engineering practice. Failures of such fittings in similar applications are unusual and are not found in literature.The failed sample was removed for metallurgical analysis and determination of the damage mechanism(s). This paper provides the case history and the investigation in to the root cause.

Key words: Chloride, Polythionic Acid, Caustic, Stress Corrosion Cracking, Hydroprocessing Unit, Hydrotreater, Austenitic Stainless Steel, Failure Analysis.

 

A cracking occurred in a stainless steel branch nozzle fitting at a low point in the reactor effluent piping in a Gasoil Hydrotreater unit following start up.Normal preventive measures were implemented to protect the piping system against Polythionic stress corrosion cracking (PTASCC) during shut down (neutralization & nitrogen purging) however cracking occurred in the 321 type austenitic stainless steel weldolet right after the start up. Materials selection of low point drain including the fitting is in accordance with good engineering practice. Failures of such fittings in similar applications are unusual and are not found in literature.The failed sample was removed for metallurgical analysis and determination of the damage mechanism(s). This paper provides the case history and the investigation in to the root cause.

Key words: Chloride, Polythionic Acid, Caustic, Stress Corrosion Cracking, Hydroprocessing Unit, Hydrotreater, Austenitic Stainless Steel, Failure Analysis.

 

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