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Failure Analysis Of 4-Inch Welded Fittings In Treated LPG Service

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Caustic stress corrosion cracking (SCC) is known to occur in carbon steels under tensile stress and exposure to caustic solutions from 115°F to boiling temperatures. Alternating wet and dry conditions tend to increase SCC susceptibility. Localized overheating of the metal, such as solar radiation, heat tracing, steam outs and excursions should also be considered. Caustic SCC was first reported in 1980 when the top of a continuous kraft digester vessel blew off in Pine Hill, Alabama. It was found that the tensile residual stresses present in non-stress relieved carbon steel weld seams and the corrosive environment (caustic) were responsible for the cracking

Product Number: 51322-17850-SG
Author: Sudhakar Mahajanam
Publication Date: 2022
Industries: Corrosion Monitoring and Control , Coatings and Linings , Coatings
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Caustic stress corrosion cracking occurs in carbon steels under tensile stress and exposure to caustic solutions. In this paper, we present metallurgical analyses performed on a pipe-to-tee weld and a tee-to-flange weld that leaked during operation. The pipe was in treated LPG service in a saturated gas plant. Wet fluorescent magnetic particle inspection indicated the presence of crack-like indications parallel to the welds on the outside and inside surfaces of the pipe, with more crack branching being observed on the inside surface. SEM fractography revealed that the fracture surface of these cracks was predominantly intergranular, which was confirmed during metallographic examination as well. Several temperature spikes above the acceptable range for caustic SCC were also reported by the client. Based on these observations, it was concluded that the cracks occurred as a result of caustic SCC and initiated on the inside surface of the welds.

Caustic stress corrosion cracking occurs in carbon steels under tensile stress and exposure to caustic solutions. In this paper, we present metallurgical analyses performed on a pipe-to-tee weld and a tee-to-flange weld that leaked during operation. The pipe was in treated LPG service in a saturated gas plant. Wet fluorescent magnetic particle inspection indicated the presence of crack-like indications parallel to the welds on the outside and inside surfaces of the pipe, with more crack branching being observed on the inside surface. SEM fractography revealed that the fracture surface of these cracks was predominantly intergranular, which was confirmed during metallographic examination as well. Several temperature spikes above the acceptable range for caustic SCC were also reported by the client. Based on these observations, it was concluded that the cracks occurred as a result of caustic SCC and initiated on the inside surface of the welds.

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Failure Analysis Of Hydrotested 12-Inch Type 304 SS Pipe Sections

Product Number: 51322-17852-SG
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Pre-commissioning hydrostatic testing of pipelines and the resulting corrosion (MIC) issues are often linked to test water quality, as well as post-test cleaning operations. In a 1998 study, it was reported that localized corrosion (pitting/crevice corrosion) accounted for 20% of failures in the chemical process industry with an estimated one half of those being MIC failures. Identification of MIC failures is not straightforward. Common characteristic features such as pit clustering, “tunneling” of pits, tuberculation, high microbiological counts, presence of sulfides (in the case of sulfate reducing bacteria (SRB)) and preferential weld attack have been used to anecdotally pinpoint field failures towards MIC.
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Failure Analyses On A Super Duplex Stainless Steel Tube Material Before And After Slow Strain Rate Testing In Sour Conditions – Part 2: A Case Study On Local Corrosion

Product Number: 51322-18320-SG
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Publication Date: 2022
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The investigation on the specimens in the SCC susceptible conditions is included in Part 1, AMPP conference paper C2022-179982. In this Part 2, a case study is presented on the local corrosion on specimen surface or shoulder area although high ductility ratios in two testing conditions.    
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Expected Service Life And Cost Considerations For Maintenance And New Construction Protective Coating Work

Product Number: 51322-17616-SG
Author: Jayson L. Helsel, Robert Lanterman
Publication Date: 2022
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Major manufacturers of protective coatings, steel fabricators, painting contractors, galvanizers, and end users, were surveyed to identify surface preparation and coating application costs, coating material costs, typical industrial environments and available generic coatings for use within those environments, and expected coating service lives (practical maintenance time).
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