Hull Thickness Measurement for Ferries and Åland-Owned Ships in Mariehamn

Inspection services for ships at Mariehamn

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

Where gauging fits at Mariehamn

At the Western Harbour ferry berths, work aboard a ro-pax depends on the ship being out of service for long enough: a planned lay day, a gap in the timetable or a technical stop. In those windows we measure vehicle-deck plating and stiffeners, scuppers and drain lines, voids and ballast tanks the crew has ventilated and certified, and piping in the engine room. Passenger safety rules and the ship's own procedures decide where the team may work while passengers are aboard, so most deck work is done with the car decks empty and closed to traffic.

There is no merchant dry dock on Åland, and the islands' ferries and cargo ships dock at mainland yards: Turku Repair Yard at Naantali, the shipyard at Rauma, which has docked Baltic ferries in recent years, or yards in Sweden, Poland and the Baltic states. For an Åland owner, the sensible approach is to collect deck, tank and piping readings during service calls and finish the bottom and remaining spaces in the dock, so the docking specification rests on measurement. Cargo ships at the port's freight berths can be gauged alongside while they discharge.

• Western Harbour ferry berths — vehicle decks, voids, ballast tanks and engine-room piping on ro-pax during lay periods
• Passenger terminal berths in summer — cruise ships and island cruises, with short scopes agreed with the ship in advance
• Freight berths — alongside gauging on cargo ships supplying the islands, during discharge
• Anchorage in the approaches — launch transfers to ships waiting off Mariehamn, weather and ice permitting
• Mainland and Baltic docking yards — where Åland-managed ships complete the bottom and full tank programme
• Ports and yards across Europe — gauging commissioned from Mariehamn for Åland-managed ships trading elsewhere

Åland's special status, port state control and ferry regulation

Port state control in Mariehamn is carried out by Traficom, the Finnish Transport and Communications Agency, under the Paris MoU, exactly as in other Finnish ports; Åland's autonomy covers many domestic matters but does not create a separate inspection regime for foreign ships. Passenger ships on the island routes are surveyed every year for their safety certificates, so structural findings on a ferry rarely wait long before someone asks about them. Because Åland remains part of the EU, voyages to and from Mariehamn count under the EU ETS and FuelEU Maritime like other intra-EU legs, and ships of 500 gross tonnage and above carry an Inventory of Hazardous Materials under the EU Ship Recycling Regulation.

Ice and ageing tonnage shape the technical side. Ferries serving Mariehamn hold Finnish-Swedish ice classes, and seasons of archipelago ice abrade the bow, the shoulders and the waterline band, while constant berthing wears fender lines and stern areas. Several ships on the Åland routes have served for decades, and their owners weigh steel renewal against replacement under the pressure of the EU climate rules. That decision rests on condition data: vehicle-deck plating, ballast tanks, voids and the ice belt measured consistently from one docking to the next. Åland-owned tankers and cargo ships trading elsewhere bring the usual ESP and renewal-survey requirements, which their superintendents plan from Mariehamn.

Ships trading to Mariehamn 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 Mariehamn

A gauging job at Mariehamn 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.

Mariehamn has its own airport with flights to the Finnish and Swedish mainland, and the islands are also reached by the same ferries the team may be gauging, from Turku, Helsinki or Stockholm. Long-haul arrivals from India usually come through Helsinki-Vantaa or Stockholm Arlanda. Ferry berths and passenger areas are controlled, so the ship's agent or operator arranges passes and the timing of access. Finland and Sweden are both Schengen states, and our technicians need a Schengen visa before travelling; we plan dates around the lay period once the operator confirms it.

• 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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