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Bolt and Connector Failures

Bolt and Connector Failures


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Leadership and staff of the Bureau of Safety and Environmental Enforcement have been working to address a recurring problem that raises serious safety and environmental hazard concerns - faulty connector bolts in safety critical equipment currently deployed offshore. There have been a number of failures - beginning over a decade ago around 2003 - of bolts that are used to connect blowout preventers, risers, and other subsea equipment. We have created this page so that government, industry, and other stakeholders can share the latest information related to these failures, including: root cause analyses of bolt/connector failures, safety alerts, industry standards and guidance, and other connector and bolt related information and guidance.

Under the Emerging Technology Branch, the Systems Reliability Section (SRS) observes and oversees quality-assurance and quality-control testing of offshore equipment. BSEE assembles a team of experts for the study, the Quality Control-Failure Incident Team (QC-FIT).

The BSEE formed a Quality Control Failure Incident Team to investigate the known failures and research possible causes and provide mitigation recommendations to the industry. The BSEE held a forum on August 29, 2016 with industry to discuss the failures and the results of the failure investigation, as well as ongoing research that BSEE was conducting on fastener safety. Bolt failures are a major problem in many industries, so BSEE decided to form the Interagency Bolt Action Team (IBAT) to collaborate with other industries having similar fastener failures to share the expertise, data, and experience to develop best practices on fastener safety to reduce these failures.

During drilling operations in the Gulf of Mexico (GOM), leaks were detected which identified failure, severe stress corrosion cracking fracture of bolts on the lower marine riser package (LMRP). The QC-FIT evaluated QA/QC concerns of bolts failure on the connector on a lower marine riser package (LMRP). There were QA/QC issues with second and third tier sub-contracted vendors that performed heat-treatment processes and QA/QC manufacture, design, and material properties (hardness) issues with the bolts for effective subsea operation.

After learning of the December 18, 2012 incident, BSEE worked with the operator to ensure that the company replaced any faulty bolts that were in use in equipment deployed on the Outer Continental Shelf, in a timely manner. Replacement bolts for all known H4 connectors were sent to customers worldwide. This process resulted in the replacement of more than 10,000 bolts over a relatively short time frame and short-term disruption of related deep-water activities. This report was completed and publicly released August 2014.

Key Findings and Recommendations

The failure of the GE H4 connector bolts was primarily caused by hydrogen induced stress corrosion cracking (SCC) due to hydrogen embrittlement. Bolt coatings were not processed in accordance with the latest edition of ASTM B633 coating standard. Existing industry standards do not adequately address bolting/connector performance in subsea marine applications. BSEE is working to improve industry standards by encouraging industry standard committees to develop a consistent set of standard material properties requirements for the manufacture of fasteners; Request API and ASTM further revise its relevant standards and request that industry issue guidance or a standard for the optimal voltage limits for cathodic protection systems.

  • The quality management system (QMS), which met the industry standards and certification programs, qualified and audited only first-tier level suppliers and not others in the supply chain. BSEE is encouraging industry to develop an improved quality management standard that addresses multiple tier subcontractors and promoting failure reporting involving critical safety equipment.
  • BSEE has initiated joint industry research initiatives that studies fastener design and fitness for service.
  • BSEE may develop regulations that ensure specific design standards are met.

QC-FIT Bolt Technical Evaluations

The QC-FIT conducted several technical evaluations on subsea critical equipment fastener failures which identified global concerns related to the design, manufacture, material selection, and its performance.

QC-FIT Bolt Reports

Bolt Forum

On August 29, 2016 BSEE held a forum to present BSEE’s research and ongoing projects to the industry and to facilitate a discussion on how to move forward mitigating these bolt failures.


BSEE formed the IBAT to bring together experts from many diverse industries to collaborate and develop the best practices for the design, manufacture, material selection, and performance of fasteners.


BSEE has reached out to the offshore oil and gas industry and standards organizations to try to work together to mitigate the fastener failures.

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