Thickness Measurement for Offshore Support Ships, Ferries and Workboats in Den Helder

Inspection services for ships at Den Helder

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

Docks, slipways and quays for gauging in Den Helder

Damen Shipyards Den Helder is the docking yard in the port. It operates several floating docks, the largest of which takes ships of over a hundred metres, together with open and covered slipways and a repair berth, and it can arrange the historic graving dock at Willemsoord, part of the former naval dockyard, for longer refits. Ferries, offshore support ships, workboats, tugs and government vessels pass through it, and the yard also keeps a site at Oudeschild on Texel. With a vessel in dock, the team gauges to the thickness measurement plan while the hull is dry, covering bottom and side shell, sea chests, the rudder and stern area and whichever tanks the yard has opened and ventilated.

Afloat work centres on the offshore supply quays and the berths used by the ferries and harbour craft. A support vessel alongside between contracts can usually empty and ventilate ballast, fuel and drill-water tanks over a few days, which allows proper internal gauging rather than a hurried external check. Deck plating under the cargo rails, crane and A-frame pedestals, towing and mooring fittings and the tank tops beneath deck cargo are the areas charterers question most often. Ferries are gauged at their lay berth or between sailings, depending on what the operator can release. Access to the naval base itself is restricted, and any work inside it is arranged only through the navy and its contractors.

• Damen Shipyards Den Helder floating docks — bottom shell, sea chests, stern frame and tank gauging on ferries, offshore support ships and workboats while they are dry.
• The yard's open and covered slipways — hull and internal readings on tugs, pilot boats, fishing vessels and other small craft hauled out for maintenance.
• Willemsoord graving dock, arranged through the yard — refit dockings long enough for a full renewal survey programme worked alongside steel renewal.
• Offshore supply quays — internal tank, deck and pedestal gauging on supply, standby and walk-to-work vessels lying alongside between charters.
• Texel ferry berths — car-deck, ramp, void and shell readings on the Marsdiep ferries when one ship can be released from the timetable.

Inspectors, charterers and a changing North Sea at Den Helder

Port state control in Den Helder is the work of the Human Environment and Transport Inspectorate (ILT), applying the Paris MoU regime, and the same inspectorate acts as flag state for the Dutch-flagged ferries and harbour craft based here. Offshore support ships face a second audience in their charterers: gas operators and wind farm owners audit vessels before and during a contract, and a ship with gaps in its structural records or overdue tank inspections can lose work before any regulator becomes involved. Recent thickness readings, located on the TM plan and tied to the class survey history, are the evidence those audits look for.

The fleet working from Den Helder is changing with the North Sea itself. Dutch gas production is declining, so a growing share of offshore work is the decommissioning of platforms and pipelines, while offshore wind construction and maintenance keep expanding. Vessels move between those markets, often after conversions that add motion-compensated gangways, cranes or extra accommodation, and each conversion raises questions about the deck and hull structure carrying the new equipment. Ships of 500 GT and above calling at EU ports must also carry an Inventory of Hazardous Materials under the EU Ship Recycling Regulation, which becomes a practical matter for older support vessels nearing the end of their working lives.

Ships trading to Den Helder 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 Den Helder

A gauging job at Den Helder 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.

Amsterdam Schiphol is the usual arrival airport, and from there the team travels north to Den Helder by train or by road. Access to the offshore supply bases and the shipyard is controlled, and anything inside the naval area needs its own clearance, so the ship's agent or the yard registers the technicians in advance. The team comes from India on Schengen visas, which take time to issue; because contract gaps and docking slots here are usually fixed some weeks ahead, we use that notice to apply early and book travel to the confirmed date.

• 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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