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Rachel Doornekamp | July 21st, 2021
Consistent inspection is crucial for the overall safety, efficiency and structural integrity of ship hulls and offshore structures. Ships can be inspected regularly underwater - without being put into dry docks - with visual inspections. Visual inspections consist of visually documenting various waypoints on the hull to check for any structural defects, biofouling, marine growth or other issues. Visual inspection is widely considered to be the most economical and fastest way to obtain an early assessment of the condition of a vessel and its components.
This consistent underwater visual inspection is an important task to confirm and improve upon the operations safety and efficiency of ships and other floating vessels. With consistent visual inspection operators can determine maintenance schedules and workloads best suited to each vessel while minimizing cost and downtime.
While occasional dry-docking will always be necessary, underwater inspections can help reduce the number of dry-dockings required. Minimizing dry-docking time is important in order to reduce downtime and save money over time.
CVI or close visual inspections are crucial for hull maintenance. A detailed and close up visual examination, a CVI is used to identify areas requiring more in depth inspections. More specifically a CVI is an extensive examination of a specific area, section or component to detect and potentially identify damage, failure or irregularity.
CVI typically makes use of additional equipment to enhance the quality of the inspection. Normally available lighting is often supplemented with a direct source of bright light such as auxiliary lights or flashlight, or perhaps even sonar tools in particularly murky and turbid waters.
Furthermore, CVI often entails surface cleaning to gain clear access to all components of the area being inspected. Specific tools such as probes, gauges and measuring tools are also often used to acquire further insight into the hull or structure. Finally, more extreme access procedures may be required to ensure close inspection to all aspects of the component being inspected.
The qualifications applicable to CVI can be both PCN or CSWIP.
A CVI is suitable for a number of structures and components including:
Deploy a ROV to perform quick, safe and affordable hull inspections
General Visual Inspection (GVI) is quite simply a visual inspection of overall condition with a report following the inspection to report on the status of the structure.
GVI is conducted further back than a CVI and looks at more of an overview of the entire area. Typically completed at approximately an arm’s length away from the component, operators are searching broadly for any defects or issues. While a mirror may be required to enhance visual access to exposed areas, a GVI is conducted under normally available lighting conditions. Daylight, flashlight or ROV lights are usually the only light used for GVI and sometimes nearby structures or objects may have to be moved out of the way to gain access.
GVI looks to detect a number of things including:
It is important to note that GVI does not fall under any zonal inspection.
Both CVI and GVI are valuable processes to ensure safety, efficiency and structural integrity. As suggested by the names, GVI are more broad, while CVI are more in depth and specific. For instance, when there is a notable finding on a GVI, a further CVI can be carried out after to gain additional insight into the defect or irregularity.
Inherently, visual testing is part of all test methods. CVI however relies more on additional tools such as probes, lighting and caliper tools to add insight to the visual findings. Regardless of type of inspection, visual testing methods are one of the most important tools an inspector can use.
|Overall Goal||To gain a general view of the component or hull and make note of any defects or irregularities.||To conduct a detailed inspection of the component or hull and identify defects or irregularities.|
|Lighting||Basic lighting is often used - may use some additional lighting.||Typically uses additional lighting to create optimal viewing conditions.|
|Tools||Basic access tools are utilized to gain general insight into the hull.||Advanced tools such as calipers, probes and gauges are used to get a thorough view of the hull.|
|Distance||Inspections are conducted within an arm’s length.||Inspections are conducted in a very close and detailed view.|
|Access||Basic access to the hull or component is required. Mirror may be used to gain a visual of hidden sections.||Complete access is required to conduct a CVI.|
There are several useful tools that operators can use to conduct hull maintenance inspections. While underwater inspections can certainly be completed by human divers, submersible Submersible ROVS or remotely operated vehicles provide a safe and convenient alternative.
ROVs can safely enter a variety of hazardous and turbid environments without risk to human life. Furthermore, a submersible vehicle can be deployed at a moment’s notice with one to two employees - allowing teams to save time and money during operations.
Additional tools can be integrated into ROVs to enhance both GVI and CVI procedures for optimal inspections.
Aiming to provide solutions for every mission, Deep Trekker makes tough tasks easy. Constantly seeking to develop the most durable, innovative, portable and affordable underwater ROVs and submersible robots to solve a suite of underwater problems, Deep Trekker is on the cutting edge of submersible technology. When you buy an ROV from Deep Trekker, you buy the team, the ideas, the vision and the support.
As always, our team of industry professionals is here to answer any questions you may have about how submersible robots can aid in your next hull maintenance inspection. When you’re ready to get a vehicle of your own, reach out to get your own customized quote .
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