Ultrasonic Thickness Gauging for Offshore Wind, Survey and Cargo Vessels in Lowestoft

Inspection services for ships at Lowestoft

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

Dry dock, slipways and berths for gauging at Lowestoft

The dry dock and slipways in the inner harbour set Lowestoft apart from the other ports on this stretch of coast. They are sized for workboats, standby vessels, tugs, pilot craft and smaller coasters rather than large merchant ships, and owners bring vessels to them from well beyond Suffolk. While a vessel is dry, the team can gauge bottom and side shell, sea chests, the rudder and stern frame, and any internal tanks the repairer has opened, and mark areas of substantial corrosion on the steel so the renewal can be scoped before the dock is flooded again.

Afloat, the outer harbour is the more practical place for longer jobs on bigger vessels, because it avoids the bridge and gives direct access from quays used by the energy industry. ABP has been adding berth space in the outer harbour for offshore energy vessels, which brings more service ships into a sheltered quayside position. Berths along Lake Lothing are sheltered and quiet, well suited to a vessel laid by between contracts or a coaster discharging over a couple of days. There is little call for anchorage work, since the approaches are open to the North Sea and most vessels simply come alongside.

• Inner-harbour dry dock: docking survey gauging of bottom plating, sea chests, rudder and stern structure on workboats, standby vessels and small cargo ships.
• Slipways on Lake Lothing: shell and tank readings on smaller craft hauled out for repair.
• Outer harbour energy quays: hull, deck and tank gauging on service operation, survey and supply vessels between campaigns.
• Wind farm operations berths: hull and fender checks on crew transfer vessels in the evening or on weather days.
• Lake Lothing cargo and lay-by berths: hold, tank and condition gauging on coasters and on vessels laid by between contracts.

Port state control, charterer vetting and the southern North Sea

Foreign-flagged cargo ships and some offshore vessels at Lowestoft are subject to port state control by the Maritime and Coastguard Agency, applied through UK regulations that keep the country within the Paris MoU. Much of the local fleet, though, answers more often to its charterers than to port state control. Wind farm operators inspect crew transfer vessels against their own standards and industry guidance, and gas operators vet the standby and supply vessels they hire, so a technical manager who can show recent thickness readings on hull, deck and tanks is in a stronger position when the next inspection comes round.

Survey and research vessels add requirements of their own. They carry hull-mounted transducers and gondolas, sometimes moon pools, and long runs of sea-water cooling pipe, and the plating around those openings needs careful attention when gauging. Older standby vessels, some converted decades ago from trawlers, are at an age where corrosion in the double bottom, void spaces and fuel tanks is the main question at each renewal survey. As the gas fields wind down and the wind farms grow, owners are deciding which of these vessels to keep, and thickness readings feed directly into that decision.

Ships trading to Lowestoft 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 Lowestoft

Most of the work on a Lowestoft job happens before the team boards: scope, plan and access are settled first, so the time on board goes on measurement.

For Lowestoft the team usually flies into London Stansted or Heathrow and travels on by rail or road; Norwich Airport is the nearest airport but has only a small international network. Lowestoft station is served by lines from both Norwich and Ipswich. The technicians travel from India on UK visas, which take longer to arrange than many dry-dock slots, so we ask for the docking date as soon as it is fixed. The repairer issues yard passes for dry-dock work, while the agent or vessel operator arranges access to the port's quays.

• 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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