Based on funds from the Naval Sea Systems Command (NAVSEA) under the Paint Center of Excellence Program, researchers in the Chemistry Division at the Naval Research Laboratory have developed a novel process to inspect the condition of exterior shipboard coatings that is faster, cheaper, and much less manpower intensive than current methods. The new streamlined process greatly reduces the time it takes to perform periodic inspections of exterior shipboard coatings that is expected to result in impressive savings to the U.S. Navy. In addition, the new process provides for a more accurate inspection by limiting the subjective results that occur with the current visual inspection process. This process can also be used for the inspection of civilian vessels with no procedural adjustments to the process.
According to Mr. John Wegand, program team member, at NRL's Center for Corrosion Science and Engineering Branch, Current methods of performing inspections of ship surfaces are slow, labor intensive and highly subjective. These inspections require significant time-consuming manual processes to measure dry coating thicknesses, check color metering, as well as the visual inspection for corrosion damage and blistering below the surface of coating materials. In 2009, our research team performed both a physical and camera-based inspection of the USS Nimitz. The manual method required a 65 man-day effort to perform the inspection of the entire topside coating with results taking an additional four weeks to complete. By contrast, we were able to perform the same inspection using digital hand-held cameras with the new process in less than four days including immediate access to over 3000 images depicting of the ship's surface condition for in-depth inspection.
The traditional inspection process involves both, human visual inspection and physical measurements performed over a five-day period by five NACE Certified and S-CAT trained engineers and technicians. In addition, six personnel lifts (two pier-side and four on barges) are required as well as eight to ten ship personnel to support barge/JLG logistics during the inspection process providing for conservatively a 65 man-day total combined effort. The inspection team must then wait four-weeks for the inspection report to be available.
NRL's new streamlined process, led by team members Mr. Paul Slebodnick and Mr. James Tagert, utilizes two specified digital cameras and an image collection protocol that provides detailed images depicting a vessel's structural zones as collected by a two-person team in only three days. The images are collected either pier-side or from a patrol boat at distances between 100 and 200 feet from the ship's surface; further advancements will eliminate the need for a patrol boat given that these images can now be collected from an adjacent pier.
The images or image sets are collected by team members who simply walk perpendicular to the surfaces being inspected with the light-weight digital camera system. The resultant image sets are next uploaded to an NRL developed software application that performs an automated quantification of the condition of the surface coatings. This software is referred to as the Automated Freeboard and Topside Coatings Analysis Toolset (AFTCAT). It consists of a grouping of advanced image processing and data interpretation algorithms that are used to quantify the conditions of the coatings. The Topside Corrosion Detection Algorithm (TCDA), one of the AFTCAT algorithms, was used to automatically assess the extent of corrosion damage and coatings degradation. Other prototypical algorithms were used to assess coating color-uniformity and the extent of coating failures due to flaking and delamination, and blistering at the individual image level.
In its final analysis, it is estimated that the new process will require a team comprised of two trained technicians to collect image sets over a three-day period. Logistical support will include access to an adjacent pier to photograph surface zones opposite of the ship's Quarter Deck. An additional technician will be required to run the AFTCAT on the image sets and automatically generate and complete the inspection reports over a two-day period. The research team expects the resultant new process to allow for the inspection of all vessel surfaces including catwalk zones on an aircraft carrier to be conducted during a total 10 man-day effort including the generation of the inspection report as opposed to the 65 man-day period of the present process they propose to replace.
Our new method represents a quicker, more accurate and greatly less expensive alternative to the present inspection process now used. An added bonus is the system can be adopted for the inspection of civilian vessels with no change in procedures or protocols, concluded Wegard.
This work is sponsored by the Naval Sea Systems Command (NAVSEA).