Renewal Survey Thickness Gauging for Tankers Calling at Antwerp

Where is renewal survey gauging done at Antwerp?

The location decides how much of a renewal programme can be completed in one visit. At a chemical jetty the ship is working cargo under the terminal's permit system, so only deck-level and pump-room measurements are realistic, and tank entry depends on cleaning and a gas-free certificate that the master will not rush. Lay-by quays inside the dock system are better for structure: the ship has finished discharging, tanks can be ventilated, and there is time to rig staging for the upper parts of ballast tanks.

The floating docks at EDR Antwerp Shipyard are where the bottom and side shell are gauged dry, together with the sea chests and the areas that are only reachable when the ship is out of the water. A sensible renewal programme at Antwerp splits the work: tank structure and cargo piping while the ship is afloat at a lay-by quay or between parcels, then shell plating in dock. The thickness measurement plan states which frames and strakes belong to which stage, so nothing is gauged twice.

• Chemical jetties: deck plating, pump-room and manifold areas under the terminal's permit rules.
• Lay-by quays inside the locks: cargo and ballast tank structure once cleaned and gas-free.
• Floating docks at EDR Antwerp Shipyard: bottom and side shell, sea chests, rudder and stern area.
• Anchorage waits: little beyond deck level, unless the ship has a tank cleaned and certified.

How is the gauging scoped for coated and stainless chemical tankers?

A parcel tanker mixes tank materials, and the programme follows them. Stainless cargo tanks are gauged with the gauge calibrated to the material's sound velocity and are reported separately, since they are rarely the limiting item. The carbon-steel ballast tanks and the cofferdams around heated cargo tanks usually are, so they carry most of the readings. Where a tank is coated, we measure through sound coating only after verifying the gauge's through-coating mode on a coated reference sample; where the coating is blistered or flaking, readings are taken on cleaned bare steel and the coating condition is noted beside each section.

The extent that the class rules set is the minimum. Superintendents often add suspect areas from the previous survey, bulkheads next to heated tanks, and the deckhead and upper stiffeners where condensation and heat cycling concentrate wastage. We agree the final list with the attending surveyor, and the sketches show which readings are rule-required and which were added at the owner's request.

• Transverse sections across the cargo area, as many as the rules require for the ship's age.
• Selected longitudinal plating and stiffeners in cargo and ballast tanks.
• Cofferdam and heated-tank bulkheads, where wastage is typically worst.
• Deck plating and hatch or tank-access coamings.
• Suspect areas carried over from earlier surveys.

How should a renewal survey thickness job be planned around Antwerp's locks and berths?

Plan the survey backwards from the dock slot. Once the date for EDR Antwerp Shipyard or another yard is fixed, the afloat gauging should be finished far enough ahead for the readings to feed the steel estimate. That usually means starting at the first cargo stop after tank cleaning, not at the last. Tell us the expected sequence of berths, the date and lock window if the ship enters the dock system, and when each tank will be certified gas-free.

Lock transits and tidal passage on the Scheldt fix the arrival time, so our travel is timed to the agent's berth estimate. A technician from India needs a Schengen visa for Belgium, which is why the vessel's schedule is needed early. The ship's agent registers the team for gate access in the ISPS-controlled port areas, and the ship arranges staging, lighting and ventilation. If the cargo plan changes, the programme is reshuffled around the new berth sequence, and sections not reached are carried to the next stop or to the dock.

Where special survey thickness measurement sits in the survey cycle

Every renewal survey asks for more thickness measurement than the last, and for oil tankers, chemical tankers and bulk carriers the ESP Code adds close-up survey on top. The table is the usual shape of the work; the class rules and the surveyor set the exact extent, which is why the measurement plan for a job at Antwerp is agreed in writing before mobilisation.

Who does the work, and when class approval applies

Atlantis mobilises its inspection team from India to the vessel, for each job. There is no office or agent at the port; the team travels to the ship, which is why the planning step comes first. Work is planned and supervised by our Responsible NDT Level III, the founder, who holds ASNT NDT Level III in UT, RT, MT, PT and VT and has more than eleven years of international field experience. Technicians are qualified and certified under the company's written practice to ASNT SNT-TC-1A, and Atlantis is certified to ISO 9001 and ISO 14001.

Thickness measurement that a classification society credits to a class survey has to be carried out by a firm approved by that society under IACS UR Z17. Atlantis is in the process of obtaining UR Z17 approval from DNV, Lloyd's Register and ABS. Until a certificate is issued, the readings we take are for the owner's own decisions, not for credit to a class survey, so tell us the vessel's class and the survey due when you enquire and we set the scope for the right purpose. Owner's and charterer's condition gauging, pre-docking steel estimates, pre-purchase and on-hire or off-hire gauging, and scrubber and piping condition checks between surveys do not need class approval.

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