Steel corrosion occurs when metals are exposed to a reactive substance, including oxygen, hydrogen, or water. Add a powerful electrolyte like salt to the mix, and this destructive process only accelerates.
Naval ships, aircraft carriers, and other sea vessels experience constant exposure to these elements as they are immersed in seawater, surrounded by ocean air, and operate using many saltwater-based systems—making corrosion a major ongoing challenge. In fact, it was reported that the U.S. Navy spends $3 billion a year combating rust alone on ships and vessels.
Due to the corrosive environment at sea, maritime vessels require continuous monitoring to maintain structural integrity and operational availability. If corrosion goes undetected or unaddressed, it can become dangerous for personnel and disastrous to the affected areas of the ship.
Maximize Efficiency During Dry Dock
Routinely, maritime ships and vessels are taken out of service and go into dry dock for a period of time, where the ship is lifted out of the water for cleaning, inspections, maintenance, and repairs. If any unexpected damage is found during the inspection, it can lead to unplanned costs, extended lead times, additional man-hours, and delays in the on-time completion of maintenance.
It is crucial to have processes in place to quickly and accurately identify, analyze, monitor, and fix any corrosion and damage on the ship because unscheduled maintenance can negatively impact mission readiness. Below, we discuss a few ship structures and the type of damage they are prone to—in particular, the freeboard deck, ballast tank, and hull.
Common Corrosion Points on Naval Ships and Maritime Vessels
Freeboard Deck
The freeboard deck is the uppermost deck that is exposed to both weather and sea. It is typically fitted with permanent means of watertight closings at all openings. These closings can include hatches, manholes, and watertight doors. It is imperative for these structures and the deck surface itself to remain weathertight.
As with most surfaces exposed to weather elements—wind, rain, sun, or seawater—the freeboard deck experiences wear. Carrying out periodic weather tightness inspections of the freeboard deck and components is recommended. In some cases, especially when water-sensitive cargo is on board, it is advised to use ultrasonic testing methods to ensure complete weather tightness.
Ballast Tanks
A ballast tank is a steel structure that enables the vessel to maintain its trim, or floating position, according to water level or weather conditions. Ballast refers to a heavy material—in this case, that heavy material is water—used to improve a ship’s stability.
Operators pump water in or out of this watertight compartment located in the bottom of the vessel to induce proper buoyancy or lower its center of gravity. For example, if entering shallow water at a port or canal, ballast tanks will be pumped out, as much more buoyancy is required to avoid contact with land. If in deeper water or inclement weather where more stability or weight is needed, water will be pumped into the ballast tanks.
By function, ballast tanks are constantly exposed to corrosion due to contact with highly corrosive seawater, both externally and internally. In higher temperatures, it occurs more quickly. While special epoxy coatings are applied for protection, they only provide a certain amount of corrosion resistance, and they thin over time.
Ensuring the integrity of the ballast tanks is crucial and requires periodic inspections to monitor the thickness of the protective coating and walls. Inspections are performed to detect damage and enable proactive maintenance and repairs. Typical types of damage include micro blistering, cracks, fractures, and rust.
Hull
The hull of a vessel is a critical structure that houses everything that’s inside and is often referred to as the body of a ship. It is watertight and protects its cargo and inner machinery from the elements, which includes anything from weather, water, and impact damage.
Some of the hull’s major components include the bow, or front; port and starboard—left and right sides; and the stern, or rear portion of the hull. Constructed from steel, the hull is constantly exposed to water. Portions of the hull are submerged below the waterline, increasing risks of corrosion, gradual weakening, and deterioration of steel which often cause thinning, cracks, or fractures. Additionally, certain types of organisms may attach themselves to hulls, such as barnacles, mussels, and sea slugs. When attached for long periods of time, they can lead to quicker deterioration.
More Data Coverage—Improved Mission Readiness
Maritime vessels are required by law to undergo routine inspections in an effort to help extend the life of the ship and keep crew members safe. However, the thoroughness, effectiveness, efficiency, and adaptability of inspections can widely vary based on the method being performed.
For example, a simple visual inspection can identify some of the easy-to-spot issues, but there is no knowing the depth and scope of the damage. Going a step further, a manual inspection provides thickness measurement data, but it is often insufficient due to missed defects located in areas not inspected. Failure to identify areas of concern raises the risk of unscheduled maintenance and structural issues while at sea.
Robotic assessments provide the most coverage, accuracy, and repeatability for naval ships, aircraft carriers, and other sea vessels. Constantly collecting data with every move, industrial robots can gather unprecedented amounts of data to provide a comprehensive understanding of the structure’s health. More coverage with denser data leads to rapid, accurate insights for condition-based and predictive maintenance. Digital data analysis and visualizations empower the ability to quickly drive actions and confidently prioritize maintenance plans based on the findings.
Not only do robotic inspections provide better visibility into asset health, but the inspections are completed significantly faster and safer than traditional manual inspections. Instead of installing a manlift or scaffolding to manually measure various points at heights, robots can easily take on these hazardous jobs with inspectors safely operating from the ground level. This drastically reduces lead times and man-hours with inspections being completed in a fraction of the time and with better data reporting.
Robotic Inspections Improve Structural Health Today and Tomorrow
Maritime ship damage needs to be rapidly identified and remediated to reduce last-minute repairs that extend the amount of time in dry dock and issues at sea that result in unplanned dry docking. With the right inspection methods in place, you can significantly reduce lead time, man-hours, safety risks, and unscheduled maintenance to ensure mission readiness. Robotic inspections help build a holistic, comprehensive understanding of a vessel’s structural health to increase data quality, efficiency, and reliability for years to come.
Download a case study to find out how Gecko Robotics helped several leading organizations understand the health of their critical assets to make data-driven decisions.
