Assessment of sigma phase embrittlement in austenitic stainless steels such as Type 304H, commonly used in fluid catalytic cracking (FCC) units. Other austenitic stainless steels used in other refining process units are also discussed. The detection and measuring of the amount of sigma phase were made using metallography.
This paper reviews the concerns of applying excessive levels of cathodic protection current to pipelines and the need for establishing an upper potential limit. Coating disbondment, hydrogen induced stress cracks, stress corrosion cracking, hard spots and the problems associated with measurement of a true polarized pipe-to-electrolyte potential are addressed.
During plant shutdown maintenance, some components cannot be removed out of service immediately for metallurgical examination due to high cost involved and loss of production hours. The best alternative is to replicate the lab based metallography work under the field conditions. Field Metallography and Replication (FMR) also known as in-situ metallography is a powerful non-destructive test (NDT) tool used to examine the microstructure of the component when it is still in service. Moreover, FMR is also used to study the microstructural alterations for the fitness for service assessment.
This paper provides case studies of materials in Natural Gas Processing facility where FMR was used as an NDT tool without sectioning the component. This paper discusses the damage mechanisms such as sigma phase embrittlement, stress relaxation cracking and creep.
An unexpected failure of 316L Stainless Steel instrument tubing occurred in a high pressure Hydroprocessing unit resulting in a shutdown of the unit. The tubing system consisted of a compression type fitting commonly used in instrument systems and had only been in service for 3 years when the failure occurred. The failed tubing samples were removed for metallurgical analysis and determination of damage mechanism.
Metallurgical analysis and finite element analysis of the tubing identified excessive cold working leading to hydrogen embrittlement as the primary mode of failure. This paper details the investigation into the failure to arrive at the root cause and the preventive measures adopted to assess the installed population of tubing in similar service.