Dynamic Hull Monitoring

Hull Stress Monitoring is a real-time understanding of the forces impacting the vessel. By understanding this information, vessel operators can get a clearer picture of how operations and environmental conditions affect structural loads, helping them avoid excessive stress, improve safety, and optimise vessel performance. For vessels, this information can support fatigue assessment, help identify areas requiring greater inspection attention, and enable more informed maintenance and asset-integrity planning.

Traditional methods rely on static models, manual calculations or periodic inspections which only take a snapshot at that time, and this may not always accurately capture actual operation conditions. Traditional inspections require frequent checks of known hotspots without real-time indication of when they may become problematic. An advanced Hull Monitoring System allows the degradation of these maintenance hotspots to be projected into the future, giving teams a predictive view of when these areas need immediate attention or when they are not high priority. This dynamic monitoring enables a more proactive understanding of the vessel, including earlier detection of potential issues, increased safety, more informed operational decision, cost savings through targeted inspections and reduced reliance on conservative estimated which helps extend the vessel lifespan.

They provide continuous, up-to-date insight into the vessel's structural condition. This allows operators to make informed decisions based on actual data. Key benefits include but are not limited to a holistic understanding of how the impact of vessel operations affect the overall vessel’s lifetime, early detection of abnormal or high strain values/loads, key instrument and DCS data stored indefinitely for lifetime extension and maintenance optimisation, informed targeted maintenance that highlights the operational impact on maintenance, reduced downtime through targeted inspection and maintenance, improved safety for the crew, vessel, and the cargo and extended vessel lifespan via targeted maintenance and stress reduction, leading to improved return on investment.

There is no requirement for Hull Monitoring systems to meet DNV requirements, though if a vessel is wishing to attain the associated class notation or where classification requirements form part of the project specification, the system must meet the applicable class requirements. SMS Hull Monitoring System supports the requirements for hull monitoring and Smart Vessel class notations.

The best hull monitoring systems incorporate a combined approach with the operational data, loading information and real-time sensor. By integrating operational and load data, the system can understand how different activities affect the vessel and generate a Structural Health Report. The impact on local details, as part of this Structural Health Report, uses Finite Element (FE) modelling to accurately assess the impact. In a joint approach with the vessel owner the system is put through known operations to effectively calibrate the sensors, allowing it to inform a Risk Based Inspection (RBI) methodology for those critical details identified and informed by the Hull Monitoring System.

The FPSO system mirrors the design for sea-going vessels , with instrumentation placed at key structural points along the hull. This data feeds into the Hull Monitoring System, which actively tracks force impacts at select hotspots across the hull. This information can then be used to assess fatigue accumulation and structural condition over time, supporting more targeted inspection, maintenance and asset-integrity planning.

The cost of a hull monitoring system varies depending on the size and type of the vessel, the number of sensors required, and the level of analysis and integration needed. For offshore vessels and assets such as FPSOs, costs can range from £500k to £2m+ including initial assessment, design, installation and continuous running and support costs. This depends on factors such as system complexity, installation scope, and whether advanced features like real-time analytics, fatigue assessment, or integration with other systems are included. Each system is typically tailored to the specific vessel and operational requirements, so a detailed assessment is usually needed to provide an accurate estimate.

For Hull Stress Monitoring the sensors primarily used are strain sensors, a full Structural Health Monitoring system can incorporate many more depending on the vessel operators’ requirements, Wave Radar, Inertial Motion Units (IMUs), Corrosion / Wall Thickness Monitors are among some of those items which can be incorporated into the Structural Health Monitoring system.

Hull Monitoring systems integrate with digital twins by directly providing real-world sensor and operational data that can be used to update and validate structural models. This data can also be provided to third parties for the means of verifying or updating their existing digital twin models. SMS’s Structural Health Monitoring system operates as a Fatigue Life digital twin, returning the expected Fatigue life of critical details over the lifetime of the vessel. This allows operators to move from reactive monitoring to predictive decision-making, improving safety and optimising maintenance and operations.

Fibre Optic strains sensors are installed at selected locations across the structure and transmit strain measurements to a central interrogation unit. Because the sensor locations are known, the measured strain data can be used to assess how the structure is responding to operational and environmental loads. SMS Dynamic Hull Monitoring can then use this information, together with engineering models, to assess stresses and fatigue at critical structural locations.

The recommendations for Hull Stress Monitoring can be found in the following documents for their respective classification society. 1. ABS – Guide for Hull Condition Monitoring System 2. ABS – Guide for Smart Functions for Marine Vessels and Offshore Units 3. ABS – Guidance Notes on SafeHull Finite Element Analysis of Hull Structures 4. ClassNK – Guidelines for Hull Monitoring 5. DNV – DNV-CG-0508, Smart vessel 6. DNV – applicable Rules for Ships relating to digital features, monitoring and survey arrangements 7. DNV – applicable guidance for Finite Element Analysis

Hull Potential Monitoring measures the electrical potential of the hull relative to the surrounding environment to assess the effectiveness of the cathodic protection systems and help manage corrosion risk. On the other hand, Hull Structural Monitoring, examines the forces impacting the hull such as loads and stresses during operation. It uses sensors to track strain, stress, and fatigue, helping operators understand how the vessel behaves under real operating conditions and identify potential structural issues. The SMS Structural Health Monitoring system has the potential to incorporate both types of monitoring, should it meet the vessel operators’ requirements.

Naval Vessel Health Monitoring Systems take the typical Hull Health Monitoring System and apply their fundamental principles but are adapted to meet the more demanding operational and integration requirements of naval vessels. These requirements can include increased robustness, shock and vibration resistance, cybersecurity, integration with naval shipboard systems, and vessel-specific operational requirements. These can vary greatly between vessel but are not great departures from the commercial type systems.

The return ROI of hull monitoring comes from improved safety, reduced operating costs, and extended asset life. It depends on the size of the vessel and the scope of the Hull Monitoring System: 1. Combining the Hull Monitoring system with a targeted maintenance program can reduce the cost of maintenance in the long term. 2. Optimising the operational manoeuvres can allow for extending the Fatigue Life of operational assets, allowing assets to continue operating beyond their Design Life.

Hull monitoring provides continuous information on the actual structural loads and stresses experienced by the vessel. This data can be combined with engineering models to assess how fatigue is accumulating at critical structural locations over time. By understanding the vessel’s actual operating history and resulting fatigue accumulation, operators can identify areas requiring greater attention and make more informed decisions about future inspection and maintenance activities. The system supports: 1. Early identification of high-risk structural areas 2. Prioritisation of inspections based on measured and modelled structural condition 3. Targeted, proactive maintenance planning 4. Reduced inspection effort in areas shown to present lower structural risk 5. Prediction of future fatigue accumulation and remaining fatigue life. This information can also support Dynamic Risk-Based Inspection (DRBI), allowing inspection priorities and intervals to be informed by the vessel’s evolving structural condition rather than relying solely on fixed inspection schedules.