Summary
Commercially significant amounts of crude oil and natural gas lie under the continental shelf of the United States. Advances in locating deposits, and improvements in drilling and recovery technology, have made it technically and economically feasible to extract these resources under harsh conditions.1 Offshore drilling in the U.S. Outer Continental Shelf (OCS) has progressed to greater depths of water over the years; currently deep-water wells are located in areas where the water depth is 1,000 ft. (305 m) to 10,000 ft. (3,050 m) and beyond.2 The preponderance of oil exploration in the OCS occurs in the Gulf of Mexico where significant resources have been identified. These resources are recovered by drilling, producing, and transporting the product to the market using platforms, barges, ships, and pipelines. There remains considerable potential for further exploration and recovery of oil in the OCS; the Gulf of Mexico will continue to be an important location for oil exploration and recovery into the future.
Extracting these offshore petroleum resources involves the possibility, however remote, of oil spills, with resulting damage to the ocean and the coastline ecosystems and risks to life and limb of those performing the extraction. The environmental consequences of an oil spill can be more severe underwater than on land because sea currents can quickly disperse the oil over a large area and, thus,
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1 American Oil and Gas Historical Society, “Offshore Petroleum History,” http://aoghs.org/offshore-history/offshore-oil-history/, accessed March 13, 2017.
2 Bureau of Ocean Energy Management, “Assessment of Undiscovered Oil and Gas Resources of the Nation’s Outer Continental Shelf,” 2016, https://www.boem.gov/2016-National-Assessment-Fact-Sheet.
cleanup can be problematic. As the water depth increases, the response time to well control events become more challenging. Due to concern about the possibility of oil spills, state and federal governments have passed numerous laws restricting oil exploration and production and providing for oversight of drilling operations.3,4
The U.S. Department of the Interior began regulating the offshore energy and mineral extraction industry in the late 1940s; its jurisdiction was formalized by the Outer Continental Shelf Lands Act (OCSLA) of 1953. After the April 2010 Deepwater Horizon tragedy in the Gulf of Mexico, the regulatory structure was changed. The Bureau of Safety and Environment Enforcement (BSEE) was established to provide emphasis on safety, enforcement, prevention of oil releases into the environment, and rapid response in case an oil release does occur. Other agencies are charged with OCS oil and gas lease sales, marine safety, and revenue generation.5
At the request of BSEE, the National Academies of Sciences, Engineering, and Medicine studied subsea threaded fastener failures. The result is this report of the Committee on Connector Reliability for Offshore Oil and Natural Gas Operations, which is based on the somewhat limited data provided to the committee. This report summarizes strategies for improving the reliability of fasteners used in offshore oil and natural gas exploration equipment, as well as best practices from other industrial sectors. Bolted connections are an integral feature of deep-water well operations. In any offshore subsea wellhead and marine riser system, there are numerous large fasteners (primarily bolts), typically between 5 cm (2 in.) and 9 cm (3.5 in.) in diameter, in a wide range of applications. Most fasteners in subsea drilling riser systems hold together and transfer load through components of the systems used daily to drill the well and to transport drilling fluids. A fewer number of fasteners are directly related to holding together critical well control components or maintaining the well pressure boundary mechanical integrity. Therefore, the structural reliability of these bolted connections is directly linked to maintenance or loss of the pressure boundary while the system is in-service.
The overarching objective of this study is to identify actions that can improve the reliability and thus reduce the probability of a fastener failure that could cause an unintended release of oil, natural gas, or drilling fluids into the ocean environment. The focus is on critical bolting—bolts, studs, nuts, and fasteners used on critical connections. A critical connection is defined as one which, if it failed, would result in the release of hydrocarbons and drilling fluids into the sea. An example
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3 R. Jervis, W.M. Welch, R. Wolf, and USA Today, “Worth the Risk? Debate on Offshore Drilling Heats Up,” ABCNews, July 14, 2008, http://abcnews.go.com/Business/story?id=5367966.
4 E. Kuhr, “To Drill Or Not to Drill—Debate Over Offshore Testing and Drilling in the Atlantic,” Time, January 14, 2014, http://time.com/3249/to-drill-or-not-to-drill-debate-over-offshore-testing-and-drilling-in-the-atlantic/.
5 Bureau of Safety and Environmental Enforcement (BSEE), “History,” https://www.bsee.gov/who-we-are/history, accessed August 2, 2017.
is the bolting that connects the blowout preventer (BOP), an essential piece of safety equipment, to the wellhead on the seafloor and also attaches the shear rams to the BOP.
To date, a few dozen mechanical failures among thousands of bolts in critical pressure boundary applications have been reported in the field, with the overall bolting failure rate estimated to be in the range of 10−4 to 10−5 based on the total reported failures divided by the number of fasteners employed in-service.6 However, this small number provides little comfort, or basis for analysis, given the “censored data” problem produced by lack of an industry wide program to inspect for bolts that are progressing to failure, or have failed completely and are merely being held in position by gravity. Sobering accounts, such as the failed studs on the Seadrill’s West Capricorn (WC) that were only discovered (and thus reported) because an engineer put his hand on one, illustrated the compelling need for an industry wide continuous connector monitoring problem so that such failures can be discovered in progress, and not by accident.
Managing risk for low-probability, high-impact events is quite challenging. The root cause of these events is usually difficult to precisely determine and thus eliminate because they occur so infrequently, and measuring success requires large data samples over an extended period. The management of the risk requires improvements in standards, procedures, human factors, materials, controls, inspection, improved regulations and maintenance as well as sharing of best practices among/within the oil and gas industry and the government; taken together, these actions can be grouped as continued improvement in the safety culture. These actions require expenditure of time and effort that can be challenging to justify without taking the view that reducing low-probability but high-impact events is cost effective in the long term.
No major oil spills have resulted from a fastener failure. But there have been minor releases and near misses caused by unexpected bolt failures, and to the committee’s knowledge, no injuries or fatalities have resulted from the reported fastener failure. The question is this: Is this lack of catastrophic failures due to excellence in engineering and field implementation, or is it due to fortuitous circumstances in which bolts failures were detected early before a major system failure occurred, or is it a combination of both? The answer is still unknown, but the committee found multiple opportunities for improvement in the engineering design, specification, manufacturing, and application of these critical fasteners, and life cycle oversight of the fasteners. The overall proactive strategy discussed in this report is one of risk reduction by prioritized continuous incremental improvement. This strategy
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6 K. Armagost, Anadarko Petroleum Corp, “Root Cause Failure Analysis In Support of Improved System Reliability,” presented at Connector Reliability for Offshore Oil and Natural Gas Operations Workshop, Washington, D.C., April 11, 2017.
is based on accurately accessing equipment field performance before failure and acting on the results, devising roadmaps to conduct and implement research and development in areas that have the potential to improve the reliability of fasteners. Reactive strategy of improved communication of failures and promulgating best practices related to fasteners throughout the entire oil and gas industry, including all the supply chain and equipment operator stakeholders, is also discussed in the report.
The design of a drilling riser system and, its components, is a challenging engineering task requiring numerous technical disciplines at multiple companies. The bolted flange connectors within the drilling riser system are deceptively simple pieces of equipment. But because of the varied and dynamic forces acting on a bolted flange connector in subsea drilling applications, the design of a flange connector is complex. There are uncertainties in the quantitative assumptions commonly made in the design of a riser and its components. Of particular importance are the assumptions related to the operating environment, installation, operation, and maintenance practices that occur in shops and on rigs that affect the loads on the riser/BOP system. The challenge for the design engineer is to integrate the various levels of uncertainty to arrive at the appropriately conservative design for each mechanically-fastened connection, and then for each individual fastener/bolt. Because bolts are subject to multiple time-dependent failure modes in addition to mechanical overloads, all potential failure modes must be identified and the risks must be mitigated during the design process.
Further, there are important environmental factors that directly influence the rate of degradation of fastener materials, such as ocean water salinity and chemistry, the presence of hydrogen from cathodic protection systems or the presence of hydrogen, hydrogen sulfide (H2S) and carbon dioxide (CO2) from natural sources. Because drilling rigs and riser systems are designed to move to different ocean drilling locations and be employed by different operators over their lifetime, the design of a riser system must accommodate operating requirements beyond any specific location. Thus, unless the connectors are conservatively designed for every environment, a design analysis and risk assessment should be conducted each time a rig’s location is changed.
An integral part of the design process is the identification and review of all applicable, up-to-date specifications and standards that must be followed, as well as incorporation of all recommended best practices. It is important to realize that industry standards typically represent minimum requirements and thus, at the discretion of the design engineer, may be supplemented. Since some rigs are moved internationally, additional country-specific specifications and standards may need to be considered.
Once the loads and environmental factors are established, fastener materials and protective coating systems can be selected to provide the required service life.
Typically, medium carbon, high hardenability alloy steels are used, such as AISI 4130 or higher strength AISI 4340.7 For applications in which hydrogen sulfide or other corrosive gases are present, a corrosion-resistant alloy is used; the iron-nickel superalloy, Alloy 718, is commonly selected. These alloys can be processed by a variety of methods, and the resultant quality levels depend on the initial chemistry and the processing route. Oftentimes, there is no requirement to track each processing step for a particular fastener. Thus, the pedigree of the material depends on the integrity of the adherence throughout the entire supply chain to qualified manufacturing processes as verified by specified quality assurance methods. Thus, re-creating the exact processing steps for fasteners that fail in the field is challenging because there normally is scant traceability of specific processing steps for a specific fastener.
The critical requirement for pressure boundary fastener installation is to ensure that sufficient tension is accurately created within the bolt (without exceeding design limits) to safely maintain compressive contact between the mating surfaces as specified by the design engineer who can adopt or exceed industry specifications. During service, the fasteners must be preloaded in sufficient tension to sustain the required compressive forces on the flanges during service conditions. These fastener tensile loads applied during installation must be maintained over the lifetime of the connection. Procedures must be put in place to minimize the possibility that the specified applied tensile loads that meet the connector compression requirement are accurate, will not exceed bolt yield strength, and not degraded during service. Damage-induced modifications to fasteners include corrosion, fatigue crack nucleation and growth, and crack nucleation and growth by environmentally assisted cracking mechanisms, including hydrogen embrittlement8,9 and stress corrosion cracking.10
Fastener failures have an service environment, mechanical, human, and material component. The predominant failure mode depends on the application environment and processing history. Detailed analysis of failures can determine the root cause, which is necessary to devise appropriate corrective actions to minimize future failures through improved mechanical design, material selection, or
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7 B. Lillebø, Det Norske Veritas, Bergen, Norway, “Bolting Materials Subsea,” presentation at Materials in Offshore Constructions, Esbjerg, June 2, 2006, http://www.offshorecenter.dk/log/filer/1_7%20DNV.pdf.
8 D.A. Jones, “Environmentally Induced Cracking,” Chapter 8 in Principles and Prevention of Corrosion, 2nd ed., Prentice Hall, Upper Saddle River, N.J., 1996.
9 B. Craig, “Hydrogen Damage,” pp. 367-380 in ASM Handbook Volume 13A: Corrosion: Fundamentals, Testing, and Protection (S.D. Cramer and B.S. Covino, Jr., eds.), ASM International, Materials Park, Ohio, 2003.
10 R.W. Hertzberg, R.P. Vinci, and J.L. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, Wiley & Sons, Hoboken, N.J.
manufacturing processing. These failure analyses should determine the root cause of each failure and assess contributing factors such as the system design, actual applied loads, and actual material properties. The failed connectors that have been studied, and where such studies were made available to the Academy committee, have fractured by both ductile and brittle mechanisms.
Brittle fracture can occur at low-stress loading. The general model for this kind of fracture, often referred to as the Griffith model, is that a microcrack is nucleated at a particle or defect and then, once it attains a critical size, it serves to concentrate the stress, and propagates rapidly across the sample in a manner consuming little energy.11 Many types of environments can cause low-energy fracture in steel, but environmentally assisted cracking is the most common for subsea applications.12 Essentially all metals used in structural applications are susceptible to hydrogen assisted cracking and embrittlement if the combination of tensile stress and diffusible hydrogen concentration in the material are high enough.
The availability of hydrogen in marine applications arises from a combination of sources. The sequence of cracking leading to failure involves hydrogen production, adsorption, subsequent diffusion of adsorbed hydrogen, and hydrogen accumulation in a fracture process zone often associated with the microstructure.
Little non-proprietary work has been reported regarding fully characterized subsea bolting material failure modes using state-of-the-art sophisticated failure analysis methods. Further, there is little evidence that most failure analyses have evaluated failure modes beyond metallurgical assessment of failed components
Even though hydrogen embrittlement has been found to be the primary cause of recent bolt failures, there is insufficient quantitative understanding of other controlling variables such as the actual loads and the extent of materials degradation by mechanisms such as hydrogen embrittlement in field deployment. Consequently, progress has been hindered towards developing mitigation strategies, including best practices, standards, industry alerts, probabilistic assessments of risk, etc.
The failure of a single bolt on an undersea flanged connector is cause for concern, but would not pose an immediate risk of hydrocarbon leakage because the numerous bolts in a typical subsea connector flange provide redundancy. However, redundancy is lost when a “cluster failure” occurs. A cluster failure is defined as the failure of multiple bolts in a single undersea flanged connector. A cluster failure can potentially cause a catastrophic cascade failure in which all remaining fasteners
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11 R.P. Gangloff, “A Review and Analysis of the. Threshold for Hydrogen Environment Embrittlement of Steel,” in Corrosion Prevention and Control, Proceedings of the 33rd Sagamore Army Materials Research Conference (M. Levy and S. Isserow, ed.), U.S. Army Materials Tech Laboratory, Watertown, Mass., 1986.
12 Personal communication, Tom Goin, president U.S. Bolt Manufacturing, Inc., August 15, 2017.
become overloaded and fracture precipitating a complete loss of the well pressure boundary.
Since 2012, four cluster failures have been publicly reported. While these failures, which are discussed in Chapter 2, appear to occur much less frequently than single bolt failures, the lack of knowledge regarding the root cause of these failures is cause for concern. The first three cluster failures had a common thread—they were from the same series of connectors and part-numbered bolts. The failure was attributed to inadequate post electroplating heat treatment—that is, failing to bake out hydrogen that may have diffused into the material during the electroplating process. However, in the fourth cluster failure, the failed studs exhibited virtually the same failure mode and features observed in the three previous cluster failures while some of the studs possessed none of the attributes that were supposedly the cause of the earlier failures. The committee believes that the root cause of these cluster failures, possessing very different hardness, heat treating, and ingot creation is better explained by consideration of the various factors (e.g., coatings, impressed current systems, sacrificial anodes, etc.) which potentially contribute to the electrochemical nature of environmentally assisted cracking. Experiments with a full-scale simulation in the laboratory would provide definitive information relative to the root cause.
There is a keen interest in improving the reliability of offshore equipment and structures, and in reducing safety and environmental risks of damage to the environment to as close to zero as possible. With many disparate views on the preferred approach, there must be a forum by which everyone has an opportunity to contribute their ideas and have them adequately investigated to enhance the development of offshore resources. Traditionally in engineering design, materials selection, manufacturing, installation and operation, this forum has been accomplished through the development and use of standards and specifications, The national significance of standards is depicted in Figure S.1, which is a quotation from the May 14, 1900, law establishing the National Bureau of Standards (now known as the National Institute for Standards and Technology [NIST]). This quotation is engraved in stone in the lobby of the NIST main administrative building (Building 101) in Gaithersburg, Maryland.
Bolt manufacturers must keep track of more than 1,000 specifications that address various aspects of high-quality bolt design and manufacturing, which includes more than 500 specifications and standards (American Section of the International Association for Testing Materials, American Petroleum Institute, American Society of Mechanical Engineers, American Society for Nondestructive Testing, etc.), plus well over 500 customer-specific standards and discrete part drawings.13 Multiple changes to specifications and standards are often made
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13 Personal communication, Tom Goin, president U.S. Bolt Manufacturing, Inc., August 15, 2017.
in response to bolt failures or technology changes. Complicating the challenge is that applicable specifications commonly reference other specifications—thus, understanding the rationale and details of these changes, and then making the appropriate alterations to bolt manufacturing process sheets is a daunting process of change management throughout the supply chain.
The bolting industry has a multitude of proprietary standards that do not foster cooperation and shared expertise across the industry. Therefore, there is a need for leadership in harmonizing standards, using a balanced group of subject matter experts from industry, government, and trade organizations to provide uniformity and improved clarity for the supply chain.
Standards, as prepared today, will not totally solve the fastener reliability issues as they are reactive to known issues, usually do not address potential issues, and the enforcement process is not always clear-cut. Outside of standards committees themselves, there is no well-defined, proactive process for proposing areas/topics to develop new standards or improve current standards for other stakeholders, such as regulators and academia. Specification for allowable parameter limits (e.g.,
allowable hydrogen level, bolt pre-tensioning levels, cathodic protection, material characteristics, and system loads) are made independently, when in reality the definition of various parameter limits is in fact a complex multivariable problem. There has been no focused attempt to establish the relative importance of each variable and the interaction between them. An industrial research and development (R&D) program is required to provide much needed data and analysis.
It is clear that safety critical components, such as those maintaining the pressure boundary, require a more in-depth approach to quality assurance and quality control and the enforcement of materials specifications than is typically required by commonly used quality standards. Engineering firms often opt to have an in-depth internal process for qualifying a vendor and ensuring that those vendors maintain qualification.14 These checks take the form of an initial audit of their quality management system and a full vetting of the product by the buyer’s engineering team. This process should include analysis of the variability in outcomes of the manufacturing process and a determination that variability is within overall acceptable tolerances. Firms at all levels of the supply chain should be periodically audited by the end user (i.e., the operating company) to ensure that quality is maintained. A somewhat simpler approach might be a requirement that all companies involved in the design, manufacture, and assembly of equipment containing critical bolts have appropriate API or ISO certifications.
Best practices from other industrial sectors which have dealt with low-probability, high-impact events suggest opportunity areas for BSEE and the oil and gas industry to consider going forward. Two industrial segments were reviewed to offer insight into successful strategies—commercial aviation and Naval submarines. The commercial aviation industry is regulated by the Federal Aviation Administration (FAA), U.S. Department of Transportation, which has the mission to provide the safest, most efficient aerospace system in the world.15 American commercial aviation has become the safest travel mode. In 2015, U.S. airlines flew 7.6 billion miles on airplanes with 10 or more seats with no fatalities, although there were close calls and accidents.
The FAA’s Aviation Safety organization is responsible for the certification, production approval, and continued airworthiness of aircraft; and certification of pilots, mechanics, and others in safety-related positions.16 This organization promotes safe flight through standards for design, material construction, quality work and performance of aircraft and aircraft engines. FAA Aviation Safety establishes
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14 One example was presented during the committee visit to Schlumberger on March 23, 2017.
15 Federal Aviation Administration (FAA), “About FAA,” https://www.faa.gov/about/, accessed June 2, 2017.
16 FAA, “Aviation Safety (AVS),” https://www.faa.gov/about/office_org/headquarters_offices/avs/, accessed June 2, 2017.
requirements for comprehensive aviation safety and oversees compliance through a variety of means. The FAA also employs Designated Engineering Representatives (DER) who typically work for an aerospace firm, including an OEM, but who have a responsibility to the FAA.17 The DER system enables the FAA to supplement its skill base by employing qualified technical people to perform certain examinations, testing, and inspections necessary to comply with applicable airworthiness standards.
Under FAA leadership, this regulatory approach effectively engages all stakeholders in the aviation industry to continuously improve aviation safety. An example of the FAA’s proactive response to a low-probability but high-impact accident is the establishment of the Jet Engine Titanium Quality Committee (JETQC). In response to an accident caused by a failed titanium fan disk which led to loss of life, the FAA formed JETQC to provide the industry an early warning system of potential problems in the manufacturing of critical titanium components.18 The JETQC includes membership from all premium quality titanium alloy suppliers and engine manufacturers. Under the direction of the FAA, the consortium has established a metric (i.e., identified metallurgical inclusions arising from processing), harnessed the efforts of the global industrial base to address the root cause of these inclusions, and measured and reported progress against the metric. The JETQC has established detailed specifications for reporting inclusions at all stages of the processes used for manufacturing premium quality titanium alloys. As a result of this initiative the number of identified melt inclusions in premium quality titanium material, which was already low, has been reduced by a factor of one to two orders of magnitude.
The U.S. Navy operates a fleet of more than 270 ships and 3,700 aircraft and is the largest Navy in the world. These assets have highly demanding operational requirements ranging from submarines operating at depth, to high-speed surface vessels, to aircraft designed for both aerial combat and carrier landings. The material requirements needed in these severe operational environments are high and require a stringent approach to design, qualification, inspection, and maintenance to meet safety and reliability standards. The Navy has established effective controls and processes to manage both standard and specialized processes and controls to meet high-performance requirements while mitigating risk.
On April 10, 1963, a Navy submarine, the USS Thresher, was lost at sea, along with all 129 crew and shipyard personnel aboard. Although the exact cause of this low-probability, high-impact event is not known because the USS Thresher has not
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17 FAA, 8110.37E—Designated Engineering Representative (DER) Guidance Handbook, https://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/1018533.
18 FAA, “FAA Engine Titanium Consortium,” FAA William J. Hughes Technical Center, http://www.tc.faa.gov/its/cmd/visitors/data/AAR-430/engtitan.pdf, accessed June 2, 2017.
been recovered, the inquiry found deficient specifications, deficient shipbuilding practices, deficient maintenance, and deficient operational procedures. As a result, the nuclear submarine fleet established the SUBSAFE program to ensure safety across the submarine fleet even as new designs are implemented. Since the loss of the USS Thresher, there have been no losses of SUBSAFE certified submarines.
In 1985 an independent organization was established within the Naval Sea Systems Command to strengthen and review compliance with the requirements of the SUBSAFE. These audits identified critical lessons learned: (1) mandatory disciplined compliance with standards and requirements; (2) a formalized engineering review system that resolves technical problems and issues; (3) safety and quality programs that support operations; and (4) safety and quality organizations that have sufficient authority and freedom to operate independently.
The human system is integral to the bolt landscape and the processes involved in the life cycle of a bolt in subsea service. A significant portion of the processes involved in the bolt life cycle is not fully automated. However, human systems have historically been neglected in developing strategies to improve bolt safety and reliability. It is critical that the complex human system at all levels be considered within all tasks that impinge on the bolt system, and that interventions to reduce bolt failures consider reducing human system failures. The human should be considered as a complex system component. For instance, explaining a failure as caused by “human error” will not improve safety and reliability unless the reasons why the human followed the wrong procedure or performed an incorrect action are identified and mitigated.
Individuals rarely work alone. Multiple disciplines must coordinate design, manufacturing, operation, and maintenance. Further, these processes are coordinated across multiple organizations encompassing all stakeholders. Communication across multidisciplinary teams and between scientists and field workers can be challenging throughout the bolt life cycle. Sharing information about bolt performance, failures, and near misses across different disciplines and organizations is critical to promote the safety culture required by oil and gas operations. Silos of information tend to be a barrier to a strong safety culture.
There are also issues that arise at the organizational level that impact human performance and ultimately system performance. Work and management processes vary by company and often conflict across companies. Companies may be hesitant to share information related to fastener failure because of liability concerns. However, the necessary direction regarding the sharing of critical pertinent information needs to be provided. The overarching rationale for information sharing is to promote an enhanced safety culture required to maintain a sustainable oil and gas industry.
The committee also identified multiple innovation opportunities that have the potential to significantly advance subsea fastener performance and reliability. These
opportunities are in the areas of: testing protocols, in-situ measurements, improving the hydrogen assisted cracking resistance of bolt alloys, coating technologies, new fastener designs, and human systems integration. Some of these ideas have the potential to pay off in the relatively near term, whereas others will need a much longer time horizon to fully develop and implement. The path ahead will require a dedicated R&D effort that follows a structured development process so that implementation can quickly follow successfully completed efforts.
An overarching finding of this study is that both BSEE and the oil and gas industry has made important advances in improving bolting reliability for deep sea drilling operations. The recent highlights are summarized in Appendix F. However, there are multiple opportunities for the industry and BSEE to work together to enhance the safety culture and further increase fastener reliability. Prudent risk management necessitates the continuous reduction of the potential for fastener failures. A meaningful comprehensive government-industry initiative could be constructed, aimed primarily at improving fastener reliability for the most critical subsea applications. The challenge is to reduce the probability of a subsea fastener failure, which is already low, by another 1 to 2 orders of magnitude over a defined period of time, such as the next 10 years. A resulting multi-faceted roadmap could contain key objectives and priorities that could be executed and implemented by the industry, much as was done in the FAA’s JETQC and the Navy’s SUBSAFE efforts. Industry should have a large role in determining the priority for addressing potential improvements. As an example, the roadmap for improving durability could address four phases of the life cycle of a bolt: New Equipment, In-service Subsea, On Deck on the Rig, and 5-year Full Inspection. The improvement opportunities could be divided into short-term actions (could be implemented within a year or two), intermediate-term actions (may require up to 5 years to develop and qualify), and long-term actions (development and qualification extending beyond 5 years).
Initially organizing an industry-wide effort to construct a comprehensive roadmap is likely beyond the purview of industry, if for no other reason to avoid the appearance of unlawful collusion. Thus, there is an opportunity for BSEE to undertake the proactive role of establishing a consortium to construct a comprehensive roadmap that could advance the safety of threaded fasteners. The multi-faceted roadmap could contain key objectives and priorities that could be executed and implemented by the industry, much as was done in the FAA’s JETQC and the Navy’s SUBSAFE efforts. Industry should have a large role in determining the priority for addressing potential improvements.
Summary Option 6.1 is a synthesis of suggestions in the report that deal with actions that BSEE could take to guide the oil and gas industry in constructing a multi-faceted roadmap for actions that could lead to improvements in subsea bolt-
ing reliability. New regulatory action would be guided by the statutory requirement to determine which best available and safest technology options meet an economic feasibility hurdle.19
Summary Options 6.1: BSEE could undertake the proactive role of working with the oil and gas industry to construct a comprehensive roadmap that could advance the safety of threaded subsea fasteners. The multi-faceted roadmap would contain key objectives and priorities that could be executed and implemented by the industry, much as was done in the FAA’s JETQC and the U.S. Navy’s SUBSAFE efforts. Industry should have a large role in determining the priority for addressing potential improvements. The roadmap could be divided into several sections:
- Investigate bolting cluster failures using a large-scale fully instrumented flange test rig that simulates subsea conditions on fasteners in bolted joints including structural loads, environmental conditions and cathodic protection. [Option 2.9]
- Research and development of specific innovation opportunities that have the potential to significantly advance the reliability of offshore fasteners in critical service. [Options 2.2, 2.4, 5.1]
- Identification of gaps in current standards and obtaining the necessary data to guide updating the standards. [Options 2.5, 3.1, 3.2, 3.3]
- Promotion of a strategic vision for the safety culture throughout the oil and gas industry. This would include collecting and disseminating information about fastener performance, failures, and near misses across different disciplines and organizations, and using this information to guide roadmap priorities. [Options 2.1, 2.3, 2.6, 3.4, 3.5]
Summary Recommendation 6.2 is a synthesis of the recommendations in the report that address actions which the oil and gas industry should take in concert to improve subsea bolting reliability. The activities to implement these recommendations could be incorporated into the comprehensive roadmap activity mentioned in Summary Option 6.1.
Summary Recommendation 6.2: Actions that the oil and gas industry should take to improve subsea bolting reliability include the following:
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19 BSEE, Statutory Requirements of OCSLA Regarding the Use of BAST, https://www.bsee.gov/what-we-do/regulatory-safety-programs/statutory-requirements, accessed November 13, 2017.
- Establish a comprehensive methodology/program to optimize the cathodic protection (CP) practice for critical assets containing fastener metallic materials. [Recommendation 2.7]
- Review the usage of materials in contact with fasteners that are known to poison the chemical reaction of atomic hydrogen converting to hydrogen gas. [Recommendation 2.8]
- Establish a standard accepted laboratory standard test method to assess the susceptibility to environmentally assisted cracking/hydrogen embrittlement of bolting materials and their coatings used in offshore applications [Recommendation 2.10]
- Conduct systematic studies to assess effect of bolt designs on hydrogen embrittlement susceptibility. [Recommendation 2.11]
- Review the standards relating to bolt tensioning, both in terms of loading as a percent of yield strength and in terms of preloading technique, to minimize the probability for excessive stress on bolts operating in subsea environments. [Recommendation 2.12]
- The oil and gas industry should promote an enhanced safety culture across organizations and disciplines that is reflected in work rules and that involves encouragement at all levels of the organization to improve the reliability of subsea bolts. [Recommendation 4.1]
- Support activities related to Summary Options 6.1
