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Crevice Corrosion in a Subsea System — Aspect Before Analysis

Product: Piping Condition: Damage clear all

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Vertical piping in a corrosive oil producing system of a FPSO. The line is a nominal diameter 14" sch 10S (pipe thickness about 5 mm) and the flanged branch line is a 2" nominal diameter welded to the main pipe using a weldolet (forged fitting). The fatigue induced cracking occurred longitudinal to the main pipe, originated at the margem of the weld interface with the pipe.
1481
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - Aspect Before AnalysisDf - General View
Region of the leakage close to the welded joint between the pipe and the 90° elbow, in the 1 1/2" nominal diameter piping, SCH 40 (3.7 mm thick). See the schematic drawing in the next figure
966
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Aspect Before AnalysisDf - Leakage

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ML00150 — Vibration Induced Fatigue in a SS Oil PipingM - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Macrography of the section transverse to the ND 14" main pipe (that is only 5mm thick) and to the ND 2" branch that is a weldolet fitting welded to the main pipe and flange. This image is interesting because it shows clearly how thin is the pipe compared with the fitting thickness and the large amount of welding required to assure a full penetration weld in the weldolet.
220
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - NaOH Electrolytic Etched MacroDf - Transverse Section
Transverse section of the 14" pipe in the center of the 2" branch using a weldolet fitting welded to the main pipe. The internal side of the pipe is to the top of the figure and the through wall fatigue cracking is located at the margem of the weld. It is possible to see that it is a full penetration weld and the fitting thickness is several times larger than the pipe thickness.
174
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - Electrolytically Etched MacroDf - Crack
Detail of the fatigue cracking, staring from the margin of the weld. The crack propagated though wall of the pipe (5 mm). The larger thickness of the weldolet requires a large amount of deposited weld metal, about 20 mm that is 4 times the pipe thickness. It is an interesting aspect to be considered by designers.
176
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - Electrolytically Etched MacroDf - Fatigue Crack
After cutting the pipe and opening the crack, the fracture appearance shows a clean fracture, flat, starting from the margem of the weld of the pipe (right side of the figure), and propagating through wall into the pipe (aproximately 5 mm thickness). The external side of the pipe is to the right side of the figure (presenting the weld finishing) and the internal side of the pipe is to the left side of the figure.
176
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - Fracture Surface AspectDf - Fracture
The same fracture appearance of the previous figure, looking at a higher magnification by scanning electron microscopy. The fracture is clean, flat, starting in the right side of the figure, at the margem of the weld and propagating into the pipe thickness. The external side of the pipe is to the right side of the figure and the internal side of the pipe is to the left side of the figure.
154
VIEW
ML00150 / Dec.2018
Vibration Induced Fatigue in a SS Oil Piping
M - Duplex Stainless SteelP - PipingAp - FPSOCd - Vibration Induced Fatigue
Cm - Fractography by SEMDf - Fracture

+29 more from this case →

ML00065 — Erosion Corrosion of Monel PipingM - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Schematic drawing presenting the External piping surface
339
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Identification drawingDf - Leakage
Aspect of the piping cut in the longitudinal direction, presenting the leakage region close to the welded joint between the pipe and the 90° elbow. The original SCH 40 (3.7 mm thickness) presents an actual average thickness of 2 mm all through the piping extension, evidencing a general thinning. See the schematic drawing in the next figure.
364
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Aspect Before AnalysisDf - Leakage
Schematic drawing presenting the internal piping surface
234
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Identification drawingDf - Leakage
Detail of the internal piping surface, showing lack of deposits and a shinning surface, suggesting erosive conditions.
226
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Surface AspectDf - Leakage
Macrography of the pipe to fitting welded joint, in a region where the thickness loss is almost uniform. The pipe is in the left of the figure and the elbow is in the right, with a general thinning (average of 2 mm, considering that the original thickness was 3.7 mm), and a slightly more intense thickness loss at the weld metal near the elbow side.
183
VIEW
ML00065 / May.2017
Erosion Corrosion of Monel Piping
M - NiCu AlloyP - Seamless PipeAp - Chemical IndustryCd - Erosion Corrosion
Cm - Kalling Etched MacroDf - Welded Joint

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