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E Selected Subsea Bolt Failures Table E.1 is a summary of selected subsea bolt failures but does not include data from proprietary failure databases. TABLE E.1â Selected Subsea Bolt Failures Date Identification Fastener Summary/Comments Reference â2002 Specific application not First Major riser bolt/insert environmentally Adamek, identified assisted failure since drilling vessels began using 2017 impressed current systems (ICS) in 1998-2000. As a consequence, bolt hardness was reduced to HRC34; an ICS safety alert was issued related to removal of metallic coating from bolt holes. The number of incidents was not reported. Adamek noted that âriser bolt/insert cracking observed on several vessels with ICS; no failures observed on rigs with fixed anode systems.â The number of incidents was not reported. 156
Appendix E 157 TABLE E.1â Continued Date Identification Fastener Summary/Comments Reference May 21, Flanged riser bolt/bolt âThe boltsâ inserts (nuts) that secure the drilling BSEE, 2014 2003 insert failure riser failed between joints 39 and 40. The inserts and the boltsâ material was AISI 4340 Transocean (TO) Discover with a material hardness of 34-38 HRC and Enterprise (DE) yield strength of 145 ksi. The 2003 Combined RCA Report . . . identified that the bolt inserts and bolts fractured due to severe, accelerated, environmentally assisted corrosion. The high material hardness, yield strength, bolt design, impressed current and thermal spray aluminum coating were identified as contributing factors for the failure.â (Product Advisory issued by Vetco Gray on April 8, 2005) 2012-2013 Flanged riser bolt/bolt Per QC-FIT Report, Appendix G, âRiser BSEE, 2014 insert failure bolt inserts (nuts) & bolt fractures due to environmentally assisted cracking, hydrogen Transocean (TO)- embrittlement. Corrosion brittle fracture. High Pathfinder material hardness, coating/material compatibility TO-Horizon issues, strength loading.â The number of bolts TO-Millennium and bolt inserts or details for each were not TO-Deepseas identified. Per QC-FIT Report, Appendix H, âIn 2003, four other TO rigs: TO-Millennium, TO-Horizon, TO- Deepseas, and TO-Pathfinder bolt inserts failed in the same brittle corrosion fracture manner as the 2003 TO-DE and the 2012-2013 H4 connector bolt failures of TO-DI, TO-DAS, TO-Deepwater Champion and P-10K. The same third laboratory performed the RCA for both of the 2003 and recent 2012-2013 bolt failures.â Before Shaffer Division of Studs used in the construction of a blow out Jones and 2010; National Oilwell Varco preventer (BOP) stack; three fractured, 3-in.- Buehler, specific (NOV) for Diamond diameter Inconel 718 studs were evaluated out 2010 date Offshore Drilling, Inc. of 20 (11 had fractured, and 9 exhibited stripped not threads). identified November Blind shear ram bolt âBlind shear ram (BSR)/shear ram (SR) bolts BSEE, 2014 1, 2012 failures fracture during a 15,000 psi pressure test (stump test). . . . A similar failure also occurred on an Transocean (TO) ENSCO 8506 drilling riser. The bolts failed due Discoverer India (DID) to tensile overload and bolt hardness due to incorrect heat treatment. The initial identified contributing factor for the failure was QC issues with GEâs subcontracted vendor regarding communication and improper heat treatment procedures for the raw bolt material.â
158 H i g h - P e r f o r m a n c e B o lt i n g Te c h n o l o g y TABLE E.1â Continued Date Identification Fastener Summary/Comments Reference December Transocean (TO) Lower marine riser package (LMRP) separated BSEE, 2014 18, 2012 Discoverer India (DID) from blow-out preventer (BOP); Thirty-six H4 connector bolts, AISI 4340, fractured; bolts identified as 2-in. diameter, approximately 9 in. long; Stress Engineering Services indicated âfailures of the incident bolts initiated due to hydrogen stress crackingâ and âit is likely that atomic hydrogen present in the bolts due to the plating process (and not removed via a subsequent bake-out) played a major role in the failuresâ (GE issued GE Safety Notice SN 13-001, REV. NC H4 Connector Bolt Inspection). January 5, Transocean (TO) Four fractured bolts were received for analysis BSEE, 2014; 2013 Discoverer Americas by SES. The total number and bolt details for the SES, 2013 (DAS) application were not indicated. The SES report did note that the application appeared to âuse the same series of connectors and part-numbered boltsâ and âexhibit similar fracture features as those removed from the DIDâ (see December 18, 2012 above). January Petrobras 10,000 (PB10K) Per QC-FIT report, PB10K was in service about BSEE, 2014; 25, 2013 2.5 years when bolt failures discovered in SES, 2013 response to GE safety notice. Five fractured bolts were received for analysis by SES. The total number and bolt details for the application were not indicated. The SES report did note that the application appeared to âuse the same series of connectors and part-numbered boltsâ and âexhibit similar fracture features as those removed from the DIDâ (see December 18, 2012, above). January 5, Transocean (TO) Per QC-FIT Report, Appendix G, âH4 connector BSEE, 2014 2013 Discoverer Clear Leader bolts failed inspection were rejected.â The bolts were inspected by magnetic particle techniques and the number of bolts and bolt details were not indicated. January 5, Transocean (TO) Per QC-FIT Report, Appendix G, âH4 Connector BSEE, 2014 2013 Deepwater Champion bolts had significant corrosion products, fractures.â The number of bolts and bolt details were not indicated.
Appendix E 159 TABLE E.1â Continued Date Identification Fastener Summary/Comments Reference June 2014 Seadrill West Capricorn Twenty HC Connector studs were received by SES, 2013; SES for analysis. Of these, nine were completely BSEE, 2014 fractured and four exhibited significant cracking based on magnaflux testing. The material was AISI 4340 steel with average bolt hardness values between 31 and 41 HRC. The 3-in. diameter double-ended studs were 18 3/4 in. long. The SES report indicated that the âstuds exhibited multiple fracture origins at the root of the threads in what is likely the first engaged threadâ and âthat Environmentally Assisted Cracking (EAC) was the most probable cause of the observed fractures.â Cameron issued a product advisory on July 15, 2014 Not BrazilâPetrobras Vessel Per QC-FIT Report, Appendix G, âSevere BSEE, 2014 specified in Gulf of Mexico Region corrosion fractured failed H4 connector bolts.â The number of bolts and bolt details were not indicated. Not BrazilâNoble-Paul Wolf Per QC-FIT Report, Appendix G, âFractured bolts BSEE, 2014 specified in Gulf of Mexico Region identified during leak during pressure test.â The number of bolts and bolt details were not indicated. Not Norway Vessel (BP Per QC-FIT Report, Appendix G, âChloride Stress BSEE, 2014 specified Operator) in Gulf of Corrosion Cracking (Cl-SCC) fracture failure of Mexico Region bolts for valve. Likely same alloy material as H4 connector bolt.â The number of bolts and bolt details were not indicated. Not DNN-GL Failure Presentation summarizes results from the DNV- Heiberg, specified Investigation Database GL failure investigation database and notes 2017 Incidents varied and not that 9% of the failure investigations were on specified fasteners. Of these, 65% were brittle fractures. Of these brittle fractures 57% were attributed to hydrogen embrittlement, 29% to temper embrittlement, and 14% to other/undetermined causes. SOURCES: Adamek, F.C., Adamek Engineering and Technology Solutions LLC, âA Historical View of Subsea Bolting,â presentation to the Workshop on Bolting Reliability for Offshore Oil and Natural Gas Operations, April 10-11, 2017. BSEE (Bureau of Safety and Environmental Enforcement), QC-FIT Evaluation of Connector and Bolt Fail- ures: Summary of Findings, QC_FIT Rpt. #2014-01, Office of Offshore Regulatory Programs, August 2014. Heiberg, G., 2017, âBolted Connection: Is It a Need for Improved Requirements?,â Paper No. OMAE2017â62730, 36th International Conference on Ocean, Offshore, and Arctic Engineering, June 28, 2017. Jones, R.L., and W.M. Buehler, Examination of Three Failed Inconel 718 Studs, Report No. 0091-10- 19492R, Stork Testing and Metallurgical Consulting, Inc., March 1, 2010. SES (Stress Engineering Services, Inc.), Site Inspection, Metallurgical Examination, and Mechanical Damage Analysis of Discover India LMRP, Report No.: PN1252494, February 27, 2013, Houston, Tex. SES, Metallurgical Failure Analysis of HC Connector Studs from West Capricorn Facility, Report No. 1253345-FA-RP-01, October 6, 2014, Houston, Tex.