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An underwater class inspection is a three-way job. The class surveyor decides what must be seen, the ship supports the work, and the Diver brings the picture to the surface. When the three understand each other, the inspection is short and clean.
The surveyor attends on deck, watches the CCTV feed and tells the dive supervisor which areas to approach more closely. He can ask for Thickness Measurement, for a cleaned patch of plating or for another look at a weld. After the dive he decides whether the survey item can be credited. He is not a member of our team, and he is not asked to trust us blindly. The video and the numbers are there for him to review.
Societies such as ClassNK and ABS publish their own conditions for in-water surveys, and these follow the general IACS framework. They want a clear view of the shell plating, rudder, propeller, sea chests and all underwater openings. They want proof that the coating is sound, evidence of any damage, and a reliable record of the ship's identity and Draft at the time. Our team holds ClassNK and ABS certification, so we work to those expectations from the first day.
It helps if the master has the class certificate, the last dry-dock report, the hull plan and the anode layout ready on the day. If any condition of class is open for the underwater part of the Ship, please tell us before the dive so the surveyor can check it in the same session. We also keep a copy of our own dive log, the equipment calibration sheet for the thickness gauge and the Diver's qualifications for the surveyor to see if he asks.
Most inspections finish with only small items: worn anodes, minor coating damage, light marine growth, a rope strand on the propeller. Larger findings, such as a dent from berth contact or a crack near a weld, are reported at once and discussed with the surveyor before the Diver leaves the water.
Tell us which society classes the ship and whether a surveyor has already been appointed. We can coordinate his attendance with the agent and the dive window, which avoids the common problem of a ready dive team and a surveyor who arrives two hours late.
Not every ship at Nagoya is classed by ClassNK or ABS. Many are classed by other IACS members, and their surveyors may have their own forms and instructions. We ask for these in advance and adapt our report layout where we can. The diving work itself is the same: a clear view of the underwater Hull, readable measurements and a trustworthy record. Surveyors of any society are welcome on our dive control position.
Q1. Who decides whether an underwater inspection is accepted for class?
The class surveyor, based on the society’s rules. The dive contractor supplies video, photographs, measurements and the report, but acceptance rests with the surveyor.
Q2. What is the typical resolution of a hull thickness gauge used by divers?
Ultrasonic thickness gauges used in underwater work commonly read to 0.1 mm resolution.
Q3. How many class societies belong to IACS?
IACS has 12 member societies. ClassNK and ABS are both members.
Q4. Which documents should be ready on the day of the inspection?
The class certificate, the last dry-dock report, the hull plan, the anode layout and the current Draft readings. Having 4 to 5 documents ready usually saves an hour on the day.
