Bolting Reliability for Offshore Oil and Natural Gas Operations Proceedings of a Workshop (2018) / Chapter Skim
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4 Panel 3: Subsea Fastener In-Service Performance
4 Panel 3: Subsea Fastener In-Service Performance
Pages 60-88
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From page 60... ...
operations team lead for BP's subsea BOP reliability team working within the global wells organization. The subsea BOP reliability team is engaging in new ways of working with drilling contractors and BOP suppliers to improve the reliability of subsea BOP equipment.
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From page 61... ...
In the Gulf of Mexico, ambient conditions at 6,000 feet below sea level are roughly 2,700 psi of external pressure, and from 3,000 to 10,000 feet, the temperature range is between 34 to 37 degrees Fahrenheit. While laboratory testing is meant to duplicate these conditions, Fleece noted that laboratory test results rarely match in-service performance, a discrepancy he suggested could be reduced by using hyperbaric chamber testing at seafloor temperatures.
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From page 62... ...
SOURCE: Trent Fleece, BP.
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From page 63... ...
There is not a history of or established mechanism for sharing root cause analysis data within the industry, and there are commercial and legal hurdles to overcome. FIGURE 4.2 A comparison of multiple failures reveals some common factors, including hardness, coating, and failure mechanism.
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From page 64... ...
Fleece described the four root cause analyses that he participated in as follows: • Riser bolt insert failure (2003)
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From page 65... ...
It is also updating critical bolts with a hardness over 35 HRC, improving quality control for third-party manufacturers, adding sampling requirements, updating torquing procedures, increasing overall engineer rigor and oversight, increasing failure reporting, and complying with 20E, which eliminates zinc electroplating and coating. These are voluntary actions, and the group submits a quarterly progress report to BSEE as part of its self-monitoring.
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From page 66... ...
A comprehensive bolt action plan also addresses design, material, and manu facturing processes, including quality assurance and control for 20E bolts, Fleece said. Eliminating zinc plating and torquing properly are also important, and in service monitoring can also have a big impact.
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From page 67... ...
As other workshop presenters noted, the industry is committed to mitigating EAC by reducing material hardness, improving quality throughout the supply chain, and enforcing 20E's specifications for critical bolt manufacturing. Environmental factors that can generate hydrogen are also being addressed to some extent; for example, zinc has been identified as a creator of hydrogen and a catalyst for hydrogen penetration in bolts, and therefore eliminated from use.
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From page 68... ...
Adamek posited that increased bolting failures might be linked to changes in the operation of oil and gas drilling equipment. Roughly 20 years ago, new drilling ships were deployed that used CP systems of impressed currents to apply active voltage to the hull, replacing older equipment that used anodes to protect the hull from corrosion.
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From page 69... ...
However, there is a difference between conditions in what we would typically call "deep water" and conditions at 10,000 feet below sea level, and it is not yet known how that increased depth would affect performance, as ROVs have measured voltages as low as −1,500 mV. Pointing to the fact that cracking occurs even in low-strength bolts, Adamek stressed that addressing material hardness alone will not solve this problem.
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From page 70... ...
, applied the practice to critical bolts, and suggested more ways the industry could improve reliability. There are many possible root causes of a bolt failure, including the heat-treating process, threading method, casting process, component design, installation, hard ness, and many other factors.
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From page 71... ...
operating in a water depth of 6,000 feet with flanged risers and using 6-ram BOPs, this amounts to an estimated 800,000 bolt-years of exposure to failure. Given this context, the fact that there have been relatively few bolt failures means that these are, by and large, very reliable bolts, Armagost said.
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From page 72... ...
. The various industry players, including API's multi-segment task group and bolting work group, the International Associa tion of Drilling Contractors/International Association of Oil and Gas Producers BOP reliability group, and the manufacturers, are working to improve bolt reli ability.
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From page 73... ...
The BOP reliability database Fleece described is another avenue to improving critical safety equipment. It has broad support from the oil and gas companies, drilling contractors, and equipment manufacturers.
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From page 74... ...
Instead, this subgroup of critical bolts has historically been held to a different standard, one that was similar to 20E BSL specifications. As bolt failures started to occur, a consensus grew for API to create specifications that would incorporate best practices for this subgroup to minimize failures on critical safety equipment.
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From page 75... ...
As other workshop presenters mentioned, the material for critical bolts should not be piled together or tightly packed into a basket during heat treatment and quenching. Instead, it should be stacked individually with space around each piece to ensure homogenization (Figure 4.6)
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SOURCE: Tom Goin, U.S. Bolt Manufacturing, Inc.
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From page 77... ...
20E's threading standards list several variables, such as single-point cutting, rolled threading, and cutting and forming taps and nuts, for the small-batch production of BSL2 and BSL3 bolts. These variables are not required for less critical bolts because certain drilling conditions, such as shallow gas wells, require far looser specifications than bolts in BOPs 12,000 feet below sea level.
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From page 78... ...
Because it is impossible to inspect or test quality into a bolt after it is made, it is, in his view, vital to focus on controlling the process of making it. A DEEPWATER DRILLING CONTRACTOR'S PERSPECTIVE Peter Bennett, Pacific Drilling Peter Bennett is director of subsea support for Pacific Drilling Services, Inc.
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From page 79... ...
Although the company has not itself experienced any critical bolting failures, after learning about failures on other companies' equipment, Pacific replaced all of its in-service riser and wellhead connector bolts. Pacific was also part of the recall of a combined 10,000 bolts, which required, in some cases, the suspension of wells and bringing BOPs to the surface, causing significant production delays.
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From page 80... ...
As part of its overall strategy to improve bolt reliability, Pacific strengthened its torquing instructions and made efforts to ensure that all employees have the training specified for each piece of equipment they service and operate as required by BSEE's Well Control Rule. BSEE also mandates fully transparent failure reporting and documentation of root cause analysis efforts, a requirement for which Bennett expressed his support.
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From page 81... ...
12 Upper Annular Star/Clock 503 Moly 125 375 500 156171 105 NA NA 26‐35 NA Zn Phos A320 Grade L7 NA No STUD, TE, 1‐1/4"‐8UN X 16" LG A320 GR L7, +NN 13 Lower Annular Star/Clock 503 Moly 125 375 500 156171 105 NA NA 26‐35 NA Zn Phos A320 Grade L7 NA No STUD, TE, 1‐1/4"‐8UN X 16" LG A320 GR L7, +NN 11 6 H125004‐6 for GE material GE material Never‐seez bolt kit specification for specification for COC ‐ US FJ40 P/N 14 LMRP Connector Star/Clock 1200 3600 4800 130 31‐34 Phosphate SCREW, CAP, HEX COLLAR, 2.000‐8UNR‐2A X 9.000 LG Regular Grade H10004‐32 bolt 4340 bolting for 4340 bolting for H10004‐32 p/n H4 connectors H4 connectors GE material GE material 11 Never‐seez 10004‐18 bolt specification for specification for 15 GE Stack Connector Star/Clock 1725 5175 6900 130 31‐34 Phosphate Waiting on COC SCREW, CAP, HEX COLLAR, 2.250‐8UNR‐2A X 12.25 LG Regular Grade p/n 4340 bolting for 4340 bolting for H4 connectors H4 connectors 15 7 FIGURE 4.8 After seeing other companies experience bolt failures, Pacific Drilling undertook steps to identify all critical fasteners on its equipment and verify their safety. SOURCE: Peter Bennett, Pacific Drilling.
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From page 82... ...
The session's speakers presented on BOPs, EAC factors, root cause analyses, bolt manufacturing processes, and various strategies to improve reliability. Fleece discussed BOPs in detail, including their equipment, failure experiences, a collabo ration to share BOP failure knowledge, and BP's current bolt action plan.
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From page 83... ...
Haeberle recalled that all of the bolts on the affected GE BOP connector were improperly baked, but referred to BSEE's QCFIT report for details on how many bolts actually failed. Bolt Design and Manufacturing Processes One workshop participant offered additional context on the design of bolts.
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From page 84... ...
Adamek said in his view, although zinc plating probably introduced minimal hydrogen, the fact that the bolts failed after several years suggests that there were other contributing factors at play. Building on the notion that zinc may not fully deserve its negative reputation, Haeberle pointed out that zinc phosphate and zinc plating are distinct coatings, charge very different levels of hydrogen, and react differently to the environment.
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From page 85... ...
Fleece weighed in to note that critical bolts operate under a variety of different yield pressures, and changing bolt hardness and reducing yield often doesn't have a large operational impact. Matlock asked Turbeville if it was true that his company does not use high strength bolts.
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From page 86... ...
While these systems act as safeguards, Fleece said, there are broader issues that add complications to every task. Noting that the level of collaboration that resulted in the failure database, the work groups, and the task groups did not exist before 2015, he said persistence is now paying off, and collaboration and information sharing among companies is likely to help the human factors issue in the future.
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From page 87... ...
He indicated he would make inquiries in order to respond more fully. Kane then asked Bennett if he knew why his company hadn't experienced critical bolt failures.
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From page 88... ...
Holly Hopkins, API, responded that most of what API sends to BSEE is publicly available on the BSEE website. Mandel noted that she had trouble identifying it on that website, and Hopkins offered to help Mandel locate the infor mation.
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