A crucial aspect: sensor data quality

DNV GL is currently piloting the hull condition monitoring methodology, working together with several stakeholders in the maritime and oil and gas industries. The ambition is to enable owners to monitor their assets in real time, either through the innovative DNV GL Nerves of Steel user interface, which will be available on the DNV GL Veracity platform, or by using technology directly integrated in their own systems. Sensors are offered by hundreds of suppliers, but one wide-spread problem is data quality. If the data output of a sensing element cannot be trusted, it is useless in any decision-making process. "Verifiable data quality is a key requirement of authorities and across the industry," explains Lars Holterud Aarsnes, Nerves of Steel Project Manager. The DNV GL rules for alternative survey arrangements state that "any sensor data used shall be quality assured". To facilitate the implementation of this rule, DNV GL provides a quality assurance app for hull monitoring suppliers through its Veracity portal. The app's data quality dashboard applies sensor-specific rules to verify the plausibility of the statistical data collected so it can be useful to the owner.

Ranking of data quality from sensors on several ships of the same owner (left), and data quality ranking for each sensor on board ship 1. The red portion of each bar represents the share of poor-quality data. Ranking of data quality from sensors on several ships of the same owner (left), and data quality ranking for each sensor on board ship 1. The red portion of each bar represents the share of poor-quality data.

The term sensor, for the purposes of this discussion, includes not only sensors in the narrow sense but also the output of transducers and indicators as well as numerical and hybrid sensing elements. The DNV GL hull monitoring rules associated with the HMON class notation basically cover any sensor type. They require automatic on-board processing and storing of statistical data, which can be uploaded by the supplier to the Veracity cloud automatically or manually after conversion to the compact Veracity format. The quality dashboard then reads the data and presents it on a web interface. Any data quality issue is evident promptly, and data quality improvements following maintenance by the supplier can be confirmed by the system.

Building trust in data

Once the ship-owning company can see that the data is trustworthy, they can use it for decision support using the results dashboard. The leading provider of hull monitoring solutions has been feeding data to this data quality dashboard for many ships and owners. In addition to this standard app for assessing the quality of statistical data, DNV GL has established a Data Management Competence Centre to support tailor-made solutions involving alternative sensor types, data formats or dashboards. The data quality and decision support dashboards can be merged into a single one, which is frequently done to enhance awareness of the hull condition and take appropriate proactive steps to ensure safety and reduce operational risks and costs. This system can be used by all industries using statistical data for equipment monitoring, including oil and gas, and wind energy, and for purposes far beyond structural monitoring, such as fuel and emission studies, navigation, or tail shaft monitoring. Structural monitoring is quite common on FPSOs and gas carriers today. On cruise ships, yachts and passenger ships, where excessive vibration can lead to passenger complaints and reputational damage, it can play an important role in comfort monitoring. "Amazingly," says Dr Storhaug, "as little as 1% of the data available on board has been used for shore-side decision support on average! We encourage owners to make better use of this valuable resource. In many cases, the benefits become more numerous and apparent once the data is available." "Being able to supply monitoring data while demonstrating high data quality builds trust among all key stakeholders, from charterers and operators to insurance companies, and can ultimately be a significant competitive advantage," Aarsnes stresses.