Thickness Measurement at the Zhoushan Ship-Repair Yards

Inspection services for ships at Zhoushan

Each service has its own page with the method, the class requirements and what the report contains.

Gauging inside the Zhoushan repair yards

Hull gauging in Zhoushan happens almost entirely inside a yard, either in dock or at the yard's repair quays. In dock, the team gauges bottom and side shell, cargo and ballast tanks, and holds as they are made available; at the quay, work continues on deck structure, piping and tanks once the ship has floated out. The yard controls access, hot work and staging, so every day starts with the yard's own permit and safety routine, and the gauging sequence follows the yard's cleaning and staging plan rather than our own preference.

Coordination between three parties decides how well a docking goes: the owner's superintendent, who sets the scope; the class surveyor, who decides where readings are needed and verifies them; and the yard, which renews the steel. We issue readings on the class TM report formats with substantial and excessive wastage marked, so the yard can raise steel renewal quantities and the surveyor can confirm the extent before plates are cut. The gauging programme is shared with whoever runs the blasting and coating schedule as well, because blasting, coating and gauging compete for the same tank access and staging, and their order has to be agreed tank by tank.

• COSCO Shipping Heavy Industry (Zhoushan) — renewal survey gauging, steel renewal estimates and re-gauging of renewed areas on large tankers, bulk carriers and container ships in dock.
• Private repair yards across the archipelago — docking-survey gauging and piping inspection for owners booking mid-sized tankers, bulk carriers and container ships.
• Repair quays and lay-by berths — completion of deck, piping and tank gauging after undocking while the ship finishes its yard programme afloat.
• Scrubber and ballast water treatment installations — wash-water, overboard and sea-water piping gauging, with crack detection at shell penetrations and pipe supports.
• Zhoushan anchorages — pre-docking gauging of ballast tanks and holds while the ship waits for its dock to become free.

Survey, emission and market context for Zhoushan dockings

Ships docking in Zhoushan sit under the Tokyo MoU port state control regime while in Chinese waters, but the stronger regulatory driver here is class. The yard period is where the renewal survey requirements of IACS UR Z7, and for ESP ships the requirements of UR Z10.1 to Z10.5 and the 2011 ESP Code, have to be met. For oil tankers, chemical tankers and bulk carriers at the third renewal survey and beyond, the gauging covers transverse sections, cargo and ballast tank structure and suspect areas, and it must be complete and reviewed before the surveyor can close the survey.

Commercially, Zhoushan competes on dock capacity for the largest ships, and international owners send tankers and bulk carriers here alongside the Chinese fleets. Charterers' vetting and oil-major requirements push older tankers toward CAP, which needs a thorough gauging record, and an owner can plan a CAP survey and a renewal survey into the same dock period. Scrubber-fitted ships also bring China's domestic emission rules into the yard discussion: open-loop discharge is restricted in some Chinese waters, and repairs to wash-water systems are often scheduled into the docking.

Wherever a ship is outside a sulphur emission control area, the global 0.50% sulphur cap applies, and many of the ships calling at Zhoushan meet it with an exhaust gas cleaning system rather than compliant fuel. Scrubber wash-water piping, the overboard discharge and the hull penetration around it corrode quickly in service, especially on open-loop systems, and are worth adding to the gauging scope.

How a thickness measurement job runs at Zhoushan

A gauging job at Zhoushan runs the same way whatever the ship type. The sequence below is what the superintendent, the attending surveyor and the yard can expect from us.

Access to the archipelago is through Ningbo Lishe International Airport or Shanghai Pudong, then by road over the bridges that link the islands to the mainland; Zhoushan Putuoshan Airport handles domestic flights. Yard access is controlled by the yard itself, with gate passes, safety induction and work permits arranged through the owner's site team or the ship's agent. Technicians travel from India on Chinese business visas, and the invitation letter the visa application needs is easiest to obtain once the docking contract is signed — so tell us the dock date as soon as it is fixed.

• Send the vessel name or IMO number, ship type, class society, the survey due (annual, intermediate, renewal survey number, CAP or owner's condition survey), the port and dates, and the scope you expect.
• We confirm the scope against the class rules for that survey, prepare the thickness measurement plan with frame and section references, and say whether the measurement will be credited to a class survey.
• Mobilisation is planned around visa lead times and the vessel's schedule; the ship's agent arranges port access, and the yard or ship arranges staging, lighting, ventilation and gas-free certificates.
• Gauging with calibrated ultrasonic thickness gauges: through sound coatings only where the gauge's through-coating mode has been verified on a coated reference, otherwise on cleaned bare steel, with every reading tied to its frame, strake and location on the sketch.
• Readings are compared with original thicknesses as work proceeds; substantial and excessive corrosion and any cracks are reported to the attending surveyor and the superintendent the same day.
• The final report is issued on the class thickness-measurement formats with sketches, a summary of locations exceeding the allowable margins, piping tables where piping was in scope, and the gauge calibration and technician certificates.

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