Hull and Tank Thickness Measurement for Ships Calling at Lerwick

Inspection services for ships at Lerwick

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

Where vessels are gauged in and around Lerwick harbour

Lerwick has no drydock for seagoing ships, so most gauging here happens afloat. Fishing boats are the exception: the slipway in the harbour and the engineering firms that maintain the fleet can haul smaller craft out of the water, and a hull on the slip is the best chance to gauge bottom shell and sea chests from outside. Larger pelagic trawlers, ferries and offshore vessels go to yards on the Scottish mainland, in Norway or in Denmark for their dockings, and a Lerwick call shortly before that docking is the natural moment to take the readings that become the yard's steel list.

Ferries are gauged during the hours they lie alongside at Holmsgarth between sailings, which suits deck, car-deck, void-space and piping work planned in short blocks. Supply vessels and project ships at Greenhead and Dales Voe lie on open quays with room to stage equipment, and the time they spend waiting on weather or loading suits a full scope on cargo tanks and working decks. The deep outer anchorages give a further option for ships that do not need a berth, with the agent arranging boat transfers. Whichever berth is used, gas-freeing and permits for tank entry are arranged by the ship before the team boards.

• Holmsgarth ferry terminal — deck, void-space and piping gauging on ro-pax ferries during their time alongside between sailings.
• Fish market and fishing quays — fish hold, refrigerated sea-water tank and shell gauging on trawlers tied up between trips.
• The harbour slipway — bottom shell, keel and sea-chest readings on smaller fishing boats and workboats hauled out for repair.
• Greenhead base — cargo tank, working-deck and crane-foundation checks on supply and standby vessels between charters.
• Dales Voe quay — deck and structure gauging plus crack detection on transport barges and heavy-lift ships after offloading.
• Bressay Sound and the outer harbour anchorages — targeted gauging by boat transfer on ships waiting for a berth or for weather.

Port state control, fisheries and the North Atlantic setting

Inspections of foreign-flagged ships at Lerwick are made by the Maritime and Coastguard Agency, which applies Paris MoU targeting under UK law. Many of the vessels that matter most here sit largely outside that regime, though: fishing vessels are covered by the UK's own fishing vessel safety rules, ferries by passenger-ship surveys, and offshore vessels by charterer audits as well as class. For a superintendent, that means the reason for gauging varies by fleet. A trawler owner may want hull and fish-hold readings before an insurance survey or a sale, a ferry operator before the annual passenger-ship inspection, and a supply-vessel owner before a charterer's audit.

Weather is the other regulator. Lerwick lies at around sixty degrees north, open to North Atlantic and North Sea storms, and winter gales can keep ships in port for days or stop boat transfers at the anchorage altogether. Daylight shrinks to under six hours in midwinter, which matters for deck and shell work but not for tank interiors under lighting. Summer is the busiest season for cruise calls and many offshore campaigns, while the pelagic fleet's quiet months follow the mackerel and herring seasons. Planning a Lerwick job around those patterns, with a fallback day built in, avoids a team arriving to find the vessel gone or the anchorage closed.

Ships trading to Lerwick 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 Lerwick

A gauging job at Lerwick 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.

The usual route for the team is a flight to Aberdeen, Edinburgh or Glasgow and an onward Loganair connection to Sumburgh, Shetland's main airport at the southern tip of Mainland, followed by the drive north to Lerwick. NorthLink's overnight ferry from Aberdeen is the alternative when flights are disrupted by weather or when heavier equipment travels with the team. Technicians mobilise from India on UK visas, so a booking made well ahead of the vessel's expected days in port helps. Quay access and harbour boat transfers are organised through the ship's agent and Lerwick Port Authority.

• 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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