Watertight Integrity Audits to Mitigate Risks of Progressive Flooding

Abstract

Experience in the offshore industry demonstrates that while mobile offshore drilling units (MODUs) are designed to provide watertight integrity (WTI), incidents continue to test the WTI of MODUs. Owner investigations sometimes show flooding has progressed to hull compartments beyond the original breach. With the worldwide MODU fleet increasing to nearly 1,000 units in the next few years, the industry is seeking a greater understanding about the threat of progressive flooding during an incident and the benefits of available control measures. One such control measure to be discussed in this paper is a program of comprehensive, owner-driven audits to verify the crew's maintenance performance. On a vessel built to support a drilling process (e.g., a MODU), maintenance attention naturally focuses on the drilling process. In day-to-day operations, drilling equipment is susceptible to wear and tear, which can occasionally lead to downtime and an immediate need for repair and maintenance. Safety-critical marine equipment might only show flaws on those rare occasions when it must function as intended, without failure, such as in a marine safety drill or emergency. A natural tendency for "complacency" and "errors in risk perception" can affect the timely maintenance of marine equipment differently than drilling equipment. WTI audits address the need to properly assess the maintenance requirements of specific marine equipment on board the vessel. These rig-specific, owner-driven audits would supplement periodic class surveys to verify how well the crew is performing marine maintenance. The benefits that can be realized include avoiding major flooding incidents across the industry MODU fleet; improving industry safety performance, especially for aging rigs, non-self-propelled rigs, and newbuilds; reducing unexpected downtime during out-of-service periods; and increasing the crew's awareness, which can lead to improved competence, quality and safety culture. Ideally, best practices and lessons learned from the WTI audits would be shared with the industry to improve watertight design and owner inspection practices.