Ultrasonic Thickness Measurement for Offshore Vessels in Stavanger

Inspection services for ships at Stavanger

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

Where offshore vessel gauging happens around Stavanger

Most measurement on Stavanger offshore vessels takes place alongside at the supply bases, where quays, cranes and storage space allow tanks and decks to be opened and worked while the ship is off-hire or between voyages. Liquid mud, brine, base-oil and fuel tanks on supply vessels need cleaning and gas-freeing before entry, which the owner arranges at the base before the team starts. Vessels waiting in the Boknafjord for a base slot can occasionally be reached by launch for a small scope, weather permitting. Work on open deck at the bases is planned around crane operations and the North Sea weather that sweeps the quays in winter.

For docking surveys, offshore vessels go to repair yards on the Norwegian west coast, around Haugesund, Bergen and further north, or to yards in Poland, the Netherlands or Denmark. A vessel docking abroad may still call at Stavanger before or after, and that call is a good moment for pre-docking gauging of the tanks and decks most likely to need steel, so the yard specification is realistic before the ship sails. After the docking, a further call can be used to close out any measurements the yard programme did not reach.

• Dusavik supply base — tank, deck plating and cargo-rail gauging on platform supply vessels between voyages, once tanks are cleaned and certified for entry.
• Other supply bases in the Stavanger region — anchor-handling deck, stern roller and winch-foundation measurements on AHTS vessels between rig moves.
• Offshore construction quays — moonpool structure gauging and crane-pedestal crack detection on well-intervention and subsea vessels during mobilisation.
• West-coast repair yards — docking-survey and renewal-survey gauging including bottom and shell plating, following alongside work in Stavanger.
• Boknafjord anchorages — limited scopes on vessels waiting for a quay slot, with launch access arranged by the agent.
• Ferry and cruise berths in the city — machinery piping and deck measurements on ferries during scheduled stays.

Norwegian shelf requirements and the Stavanger offshore market

Norway is a Paris MoU member, and Stavanger lies inside the North Sea SOx ECA at 0.10% sulphur. Most offshore vessels here burn marine gas oil or LNG or run battery-hybrid systems, so exhaust gas cleaning is uncommon on this fleet. Vessels working on the Norwegian continental shelf meet operator vetting and Norwegian regulatory requirements in addition to class and flag surveys, and structural condition records are among the items vetting inspectors and operator auditors examine when assessing a vessel's maintenance.

Offshore vessels are not ESP ships, so the extensive cargo-tank gauging tied to the later renewal surveys of tankers and bulk carriers does not apply in the same form. What matters instead is where offshore work wears the steel: anchor-handling decks gouged by chain and wire, stern rollers and towing pins, shark jaws and winch foundations under heavy cyclic load, cargo rails and deck plating struck by containers and pipe, moonpools in the splash zone, and liquid cargo tanks holding corrosive brines. Many Norwegian offshore vessels also spent long periods laid up during the downturn in North Sea activity in the second half of the 2010s, and those reactivated hulls warrant a fresh baseline.

Ships trading to Stavanger are inside a sulphur emission control area, where fuel must not exceed 0.10% sulphur unless an exhaust gas cleaning system (scrubber) is fitted. Scrubber wash-water piping, the overboard discharge and the hull penetration around it are among the fastest-corroding parts of a modern ship, so they belong in the gauging scope at every docking and, on open-loop systems, between dockings.

How a thickness measurement job runs at Stavanger

A gauging job at Stavanger 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.

Stavanger Airport, Sola, south-west of the city, has direct connections to Oslo, Copenhagen, Amsterdam and other European hubs. Supply bases are ISPS-controlled and require site inductions and work permits, which the vessel operator or the ship's agent arranges; anchorage work needs a launch booked through the agent. Norway is part of the Schengen area, and the team travels from India on Schengen visas. Because offshore off-hire windows can be confirmed late, we agree a provisional mobilisation window early so that visas are in hand when the date 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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