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Crevice Corrosion in a Subsea System — Aspect Before Analysis

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The location of the threaded fitting started leaking after less than five years in service. Although the corrosion rate was not high, the localized material loss in the threaded surface of the carbon steel flange allowed the connection leakage.
769
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - General View
The drilling connector, 21" diameter, presented a crack at the margin of the weld in the forging side (left side of the weld in the figure).
745
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - Aspect Before AnalysisDf - General View
Macrography of the longitudinally seam weld of the 24" diameter tube, showing that it was welded from both sides and there is a segregation line in the center of the tube thickness.
737
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - NItal Etched MacroDf - Seam
Aspect of the wire rope, 1 1/2" diameter, presenting regions of flattened areas at the surface of the outer wires. It is a 6 x 19 Seale construction, right regular lay.
552
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Aspect Before AnalysisDf - General View
Aged microstructure of the HP stainless steel, modified with 1%Nb, cast fitting, tubular, operating for 6 years in a furnace which design temperature is 1100°C. The material presented a network of primary carbides, white and grey, and an austenitic matrix with coalescing secondary precipitation. Some voids. The Vickers identation indicates a hardness value about 260HV 100g in the aged austenitic matrix.
492
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Microhardness identations
Optical micrography of a longitudinal section of the fractured bolt, at the thread. The material is austenitic, free from carbides, and the threads were almost removed by the stress corrosion cracks.
756
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Oxalic Acid Electrolytic EtchDf - Stress Corrosion Cracks
Polished cross-section showing rounded graphite nodules within a ferritic matrix, bordered by an irregular oxidized region at the surface edge.
910
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Oxide Layer
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.
1480
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

More from these cases

ML00184 — Dissimilar Steels in a Threaded ConnectionM - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
The painting of the valve body was detaching at the vent location where the fitting was installed, not fully tighted. Three threaded fillets were outside of the body.
190
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Aspect After CleaningDf - Painting Detachment
The austenitic stainless steel fitting was removed from the valve body and presented the sdhesion of oily deposits.
150
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - Surface Deposits
The cleaned fitting is sound. No corrosion, only surface stains.
121
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Aspect After CleaningDf - General View
The threads of the carbon steel valve body is corroded. The offshore ambient is wet and chloride rich, creating an aggressive environment for the carbon steel threads.
99
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Surface AspectDf - Corrosion
Not only the threads were corroded but all regions under the painting that was detached from the surface.
86
VIEW
ML00184 / Apr.2023
Dissimilar Steels in a Threaded Connection
M - Low Carbon SteelP - ForgingAp - OffshoreCd - Localized Dissolution
Cm - Surface AspectDf - Corrosion

+8 more from this case →

ML00178 — Cold cracks in Cr-Mo Welded ForgingM - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Circumferential weld aspect. Two passes in the cap. This forging to pipe welded joint, 22 mm thick, was welded by an automatic process in a narrow gap. The pipe is to the top of the image and the forging is to the bottom of the image.
165
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - Aspect Before AnalysisDf - External Surface
The dye check image shows the detected crack, 50 mm long, at the margin of the weld in the forging side.
137
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - Aspect by NDTDf - Cracking
Macrography of the welded joint between the forging and the pipe, showing it was welded in a narrow gap, indicating by the arrow the location of the crack at the margin of the weld, in the forging side.
129
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - NItal Etched MacroDf - Welded Joint
Quenched and tempered structure of the F22 steel forging, presenting about 230HV10 average hardness.
133
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Base Metal
Tempered martensitic structure for the F22 forging base metal.
129
VIEW
ML00178 / Jan.2022
Cold cracks in Cr-Mo Welded Forging
M - CrMo SteelP - ForgingAp - O&G Well DrillingCd - Welding Defect
Cm - Nital Etched Micrography by OMDf - Tempered Martensite

+14 more from this case →

ML00177 — Cr-Mo Seam Welded TubeM - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Identification of the regions of metallographies of the base metal, heat affected zone (HAZ) and weld metal. Locations in the root, in the center of the thickness and close to the tube OD (external surface).
118
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - NItal Etched MacroDf - Welded Joint
BASE METAL SURFACE - Ferritic structure, grain refined.
90
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Base Metal
BASE METAL SURFACE - The micrography (transverse to the tube) presents the ferritic/pearlitic/bainitic structure.
75
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Granular structure
BASE METAL SURFACE - The microstructure of the base metal is ferritic/pearlitic/bainitic.
74
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Grain refined structure
HAZ SURFACE
72
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Last Bead HAZ

+20 more from this case →

ML00175 — Localized External Wear of a Wire RopeM - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Macrosection of the wire rope, transverse, showing 6 strands and an independent wire rope core (IWRC). Each strand presents three layers in a SEALE construction.
92
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Transverse Section AspectDf - Plastic Deformation
Low magnification micrography of a strain hardened pearlitic structure, in a longitudinal section, of one 3.2mm round wire of one strand.
62
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
Highly strain hardened pearlitic structure of one external wire, 3.2mm diameter, of one strand.
55
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Nital Etched Micrography by OMDf - Pearlite
Micrographic detail of the strain hardened pearlitic structure, in a longitudinal section, of a 3.2mm external round wire of one strand. This structure presented a hardness level about 500 HV (1kg), measured in the center of the thickness in the metallographic section.
47
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Nital Etched Micrography by OMDf - Strain Hardened
Metallographic aspect of the wire surface in one strand external wire, showing the presence of oxides.
42
VIEW
ML00175 / Aug.2021
Localized External Wear of a Wire Rope
M - High Carbon SteelP - Wire RopeAp - Oil and GasCd - Wear
Cm - Nital Etched Micrography by OMDf - At the Surface

+11 more from this case →

ML00173 — Welding Cracks in an Aged HP Cast FittingM - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Condition of the joint between the centrifugally cast tube (bottom) and the buttered fitting (top). During this welding the cast fitting (buttered) showed several cracks but after removal of the fitting it was clear that the cracks were formed during the buttering and not during the joining.
46
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Aspect Before AnalysisDf - General View
After removal of the cracked part of the fitting, the dye check test indicated the presence of several cracks in the internal diameter (ID), out of the buttered layer, that means, in the fitting base metal.
42
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Aspect by NDTDf - Cracks
Cast fitting microstructure. Network of primary carbides and austenitic matrix with coalescing secondary precipitation.
37
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Base Metal
Cast fitting microstructure. The material presented a network of primary carbided and an austenitic matrix with coalescing secondary precipitation.
37
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Aged Microstructure
Micrographic detail of the network of primary carbided, white and grey, and an austenitic matrix with coalescing secondary precipitation.
30
VIEW
ML00173 / May.2021
Welding Cracks in an Aged HP Cast Fitting
M - Heat Resistant SteelP - Cast FtittingAp - PetrochemicalCd - Welding
Cm - Kalling Etched Micrography by OMDf - Aged Microstructure

+13 more from this case →

ML00157 — Bolts Under Chloride SCC ConditionsM - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Aspect of a 5/16" bolt manufactured in an AISI 316 austenitic stainless steel, that was also operating inside the pressure vessel, but was not yet damaged. It is a hexagonal head bolt, 1 1/2" long, fastened with a hexagonal nut and a lock washer.
118
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Aspect Before AnalysisDf - General View
Low magnification micrography, by optical microscope, of the longitudinal section of a damaged bolt, in the center of the thickness. The microstructure is austenitic, free from carbides.
100
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Oxalic Acid Electrolytic EtchDf - Austenite
Micrography, by optical microscope, of the longitudinal section of a damaged bolt, in the center of the thickness. The microstructure is austenitic, free from carbides, strain hardened. The hardness values of the material are from 200HV1 to 300HV1, that meets the class 2 of strenght (ASTM A193 B8M class 2).
79
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Nital Etched Micrography by OMDf - Strain Hardened
Detail of the strain hardened austenitic microstructure. Micrography by optical microscope, of the longitudinal section of a bolt, in the center of the thickness.
76
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Oxalic Acid Electrolytic EtchDf - Strain Hardened
Aspect of a broken 5/16" bolt that was operating inside the pressure vessel in a condition that exceeds the limits of use of the AISI 316 steel. The fracture is located close to the position where there was the bolt head and the threads were "removed" close to the fracture surface.
75
VIEW
ML00157 / Feb.2020
Bolts Under Chloride SCC Conditions
M - Austenitic Stainless SteelP - BoltAp - Oil and GasCd - Stress Corrosion
Cm - Aspect Before AnalysisDf - Fracture

+8 more from this case →

ML00001 — Thermal Fatigue of Cast IronM - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Flat casting product presenting several thermal fatigue cracks all thorugh the surfaces. 1" thicknes.
171
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - Transverse Section AspectDf - Cracks Transverse to the Surface
Detail of figure 2, showing multiple fatigue cracks due to thermal cycles.
136
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - NItal Etched MacroDf - Cracks Transverse to the Surface
The 1" flat casting product presents a ferritic perlitic matrix and graphite nodules.
112
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Graphite in Nodules
Center of the flat casting product, presenting nodular graphite and ferritic perlitic matrix.
113
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Predominantly Ferritic Matrix
Nodular cast iron presenting a ferritic perlitic matrix.
109
VIEW
ML00001 / Dec.2017
Thermal Fatigue of Cast Iron
M - Nodular Cast IronP - CastAp - SiderurgyCd - Thermal Fatigue
Cm - Nital Etched Micrography by OMDf - Matrix of ferrite and pearlite

+4 more from this case →

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 →