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118 cases · 287 images

Crevice Corrosion in a Subsea System — Aspect Before Analysis

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Aspect of the external surface of the broken cylindrical roller bearing presenting a polished external diameter and a the rupture with brittle characteristics (flat and parts that were lost).
726
VIEW
ML00131 / Apr.2018
Brittle Failure of a Soft Roller Bearing
M - Wear Resistant SteelP - Roller BearingAp - Mechanical IndustryCd - Heat Treatment Defect
Cm - Aspect Before AnalysisDf - Fracture
The four bolts have fractured in the same position, close to the end, and the corrosion marks in the thread suggest that they have been tightened only a few fillets in a tapped hole. This condition could be responsible for overloading the fillets, relaxing the applied bolt preload, and intensifying cyclic stresses.
192
VIEW
ML00130 / Jun.2018
Fatigue Fracture of Overloaded Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - O&G Well DrillingCd - Mechanical Fatigue
Cm - Aspect Before AnalysisDf - General View
Aspect of the internal surface of the tube, presenting the aspect of the root, after welding and heat treatment.
63
VIEW
ML00129 / Apr.2018
Non qualified WPS for High Strength Steel
M - Low Alloy Medium Carbon QTP - Welded Testpiece for QualificationAp - Oil and GasCd - Non qualified
Cm - Aspect Before AnalysisDf - Internal Surface
Aspect of the hydraulic cylinder, new, stored in tropical conditions under a plastic cover, that allowed a condensation condition and damage.
92
VIEW
ML00128 / Apr.2018
MIC of a Stored Hydraulic Cylinder
M - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - General View
Allen stud, 1/2" nominal diameter, cadmium plated and chromate treated, cracked during assembling external parts in a gate valve.
63
VIEW
ML00127 / May.2018
Hydrogen Cracks of Cadmium Plated Studs
M - Low Alloy Medium Carbon QTP - Allen StudAp - Oil and GasCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Aspect of the broken bolt, 5/8" Allen, socket head cap screw, originally 1 3/4" long, broken in subsea service under cathodic protection. The bolt presents a zinc coating.
116
VIEW
ML00126 / Mar.2018
Hydrogen Fracture of Subsea Allen Bolts
M - Low Alloy Medium Carbon QTP - Coated ProductAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
Aspect of the CuZn platesheet where it is corroded (cooling medium side). The (hot) air cooler uses treated seawater as the cooling medium and the corroded regions are associated to the regions in the heat exchanger of higher temperatures, and the leakage occurred in regions of contact of the platesheet to cooper alloy tubes.
1167
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - Aspect Before AnalysisDf - Corrosion
Macroscopic aspect of the crack in the valve ring surface. A leakage was detected during testing after 6 months out of service and the inspection identified several transverse cracks in the forged ring. The valve was installed for one year, but it was not drained during the time it was out of service. The cracks were located in regions that were rusted and presenting a biological fouling.
50
VIEW
ML00124 / Feb.2018
MIC of a Martensitic Valve Ring
M - Martensitic Stainless SteelP - ForgingAp - EnergyCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - At the Surface

More from these cases

ML00131 — Brittle Failure of a Soft Roller BearingM - Wear Resistant SteelP - Roller BearingAp - Mechanical IndustryCd - Heat Treatment Defect
Aspect of the broken cylindrical roller bearing, presenting the internal diameter full of cracks; and the fracture revealing two different morphologies, flat and smooth close to the external diameter (that appeared white in the macrography); and rough close to the internal diameter (that appeared dark in the macrography).
107
VIEW
ML00131 / Apr.2018
Brittle Failure of a Soft Roller Bearing
M - Wear Resistant SteelP - Roller BearingAp - Mechanical IndustryCd - Heat Treatment Defect
Cm - Aspect Before AnalysisDf - Fracture
Aspect of the internal diameter surface presenting several cracks in the axial direction, caused by the contact with the shaft. The roller bearing presented a too low hardness level (21 HRc average) in this ID position.
90
VIEW
ML00131 / Apr.2018
Brittle Failure of a Soft Roller Bearing
M - Wear Resistant SteelP - Roller BearingAp - Mechanical IndustryCd - Heat Treatment Defect
Cm - Aspect Before AnalysisDf - Internal Surface
ML00130 — Fatigue Fracture of Overloaded BoltsM - Low Alloy Medium Carbon QTP - FastenerAp - O&G Well DrillingCd - Mechanical Fatigue
The corrosion marks in the thread surface indicate that the bolt was not properly tightened in the tapped hole. The length of thread engagement should be at least 1x of the bolt diameter, in this case 3/8".
170
VIEW
ML00130 / Jun.2018
Fatigue Fracture of Overloaded Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - O&G Well DrillingCd - Mechanical Fatigue
Cm - Aspect Before AnalysisDf - General View
Macroscopic aspect of the bolt fracture. Part of it is flat from the bottom of the thread.
166
VIEW
ML00130 / Jun.2018
Fatigue Fracture of Overloaded Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - O&G Well DrillingCd - Mechanical Fatigue
Cm - Aspect Before AnalysisDf - Fracture
The head of the bolts presented the marks that indicated they were manufactured to meet ASTM A449 type 1 bolt, that is a medium strength low alloy steel, quenched and tempered.
148
VIEW
ML00130 / Jun.2018
Fatigue Fracture of Overloaded Bolts
M - Low Alloy Medium Carbon QTP - FastenerAp - O&G Well DrillingCd - Mechanical Fatigue
Cm - Aspect Before AnalysisDf - At the Surface
ML00129 — Non qualified WPS for High Strength SteelM - Low Alloy Medium Carbon QTP - Welded Testpiece for QualificationAp - Oil and GasCd - Non qualified
Aspect of the external surface of the tube, presenting the aspect of the cap and temper bead passes, after welding and heat treatment.
54
VIEW
ML00129 / Apr.2018
Non qualified WPS for High Strength Steel
M - Low Alloy Medium Carbon QTP - Welded Testpiece for QualificationAp - Oil and GasCd - Non qualified
Cm - Aspect Before AnalysisDf - External Surface
ML00128 — MIC of a Stored Hydraulic CylinderM - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Aspect of the hydraulic cylinder surface presenting white stains in a region where the damage was still in the begining.
73
VIEW
ML00128 / Apr.2018
MIC of a Stored Hydraulic Cylinder
M - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - External Surface
Aspect of the hydraulic cylinder surface presenting white stains and black oxides in a region that started a localized dissolution under deposit.
72
VIEW
ML00128 / Apr.2018
MIC of a Stored Hydraulic Cylinder
M - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - Corrosion
Detail of the cylinder external surface, with deep dissolution as the worst damage morphology.
65
VIEW
ML00128 / Apr.2018
MIC of a Stored Hydraulic Cylinder
M - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - Corrosion
Detail of a localized dissolution at the surface of the chromium plated cylinder. Note the dimension of the corrosion pitting, shallow.
33
VIEW
ML00128 / Apr.2018
MIC of a Stored Hydraulic Cylinder
M - Low Carbon SteelP - Chromium PlatedAp - OffshoreCd - Localized Dissolution
Cm - Aspect Before AnalysisDf - At the Surface
ML00127 — Hydrogen Cracks of Cadmium Plated StudsM - Low Alloy Medium Carbon QTP - Allen StudAp - Oil and GasCd - Hydrogen Embrittlement
Allen stud, 1/2" nominal diameter, cadmium plated and chromate treated, cracked during assembling external parts in a gate valve.
40
VIEW
ML00127 / May.2018
Hydrogen Cracks of Cadmium Plated Studs
M - Low Alloy Medium Carbon QTP - Allen StudAp - Oil and GasCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - Fracture
Allen stud, cadmium plated and chromate treated. The fracture appearance is brittle.
38
VIEW
ML00127 / May.2018
Hydrogen Cracks of Cadmium Plated Studs
M - Low Alloy Medium Carbon QTP - Allen StudAp - Oil and GasCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - Fracture
ML00126 — Hydrogen Fracture of Subsea Allen BoltsM - Low Alloy Medium Carbon QTP - Coated ProductAp - SubseaCd - Hydrogen Embrittlement
Aspect of the fracture of a small Allen bolt, nominal diameter 5/8" 1 3/4" long, class 12.9, that was operating in subsea environment during 5 years. The fracture is rusted but the thread still presents the zinc coating.
81
VIEW
ML00126 / Mar.2018
Hydrogen Fracture of Subsea Allen Bolts
M - Low Alloy Medium Carbon QTP - Coated ProductAp - SubseaCd - Hydrogen Embrittlement
Cm - Aspect Before AnalysisDf - General View
ML00124 — MIC of a Martensitic Valve RingM - Martensitic Stainless SteelP - ForgingAp - EnergyCd - Brittle Behavior
Macroscopic aspect of the crack after cleaning the ring surface. Transverse cracks were identified associated to pitting corrosion.
44
VIEW
ML00124 / Feb.2018
MIC of a Martensitic Valve Ring
M - Martensitic Stainless SteelP - ForgingAp - EnergyCd - Brittle Behavior
Cm - Aspect Before AnalysisDf - Localized Corrosion