Thickness Measurement and Crack Detection for Offshore Vessels at the Port of Blyth

Inspection services for ships at Blyth

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

Where vessels are gauged and crack-tested at Blyth

At Battleship Wharf, the work is shaped by cable. Once inter-array cable is coiled on a vessel's carousel, the deck and the structure beneath it cannot be reached, so carousel, tensioner and chute foundations are checked before loading begins or after the vessel comes back empty. During loading, the team can still work in areas away from the cable path, such as ballast tanks, accommodation and crane foundations on the other side of the deck, and engine-room piping. The sequence is agreed with the vessel's chief officer and the terminal so that nobody is working where cable is moving.

At the other terminals, construction and support vessels mobilise and demobilise, and cargo ships and barges load and discharge. A vessel lying between contracts is the best opportunity for a complete programme, because seafastening grillages can be removed and the deck plating beneath them gauged, and tanks can be opened in sequence over several days. There is no ship-repair drydock at Blyth that we would plan around, so a vessel that needs docking goes to the yards on the Tyne, at Hebburn, or on the Tees, where UK Docks runs four drydocks on the former Smith's Dock site. Our readings at Blyth let that yard plan its steel work in advance.

• Battleship Wharf: cable-lay vessels loading inter-array cable from quayside storage tanks, with foundation checks before or after loading.
• Bates Clean Energy terminal: installation and construction vessels mobilising or demobilising, with crane pedestals and seafastening areas examined.
• South Harbour: bulk and general cargo ships and barges, gauged during discharge where hatches and holds can be reached.
• Quays used between offshore campaigns: full ballast tank, deck and piping programmes on vessels idle for days or weeks.
• Drydocks on the Tyne and the Tees: where Blyth-based vessels go for docking, with our afloat readings feeding the yard's steel list.

What drives inspection work at Blyth

Port state control at Blyth is the Maritime and Coastguard Agency's responsibility, applied under the Paris MoU, which the UK still belongs to and enforces through its own legislation. Many offshore construction and cable vessels fly Dutch, Norwegian, Cypriot, Maltese or other flags and move between UK and Continental projects, so their owners are often managing several regulatory regimes at once. Wind developers and their main contractors vet the vessels they hire, usually through IMCA's Common Marine Inspection Document or OCIMF's offshore vessel inspection database, and a current record of structural condition helps a vessel through that vetting without awkward questions.

The engineering reason for inspection is fatigue. A cable carousel, a heavy-lift crane or an A-frame transmits large, repeated loads into the hull every time the vessel rolls or lifts, and the welds where foundations meet deck plating and underdeck stiffening are where cracks start. Ballast tanks on these vessels are cycled constantly to keep the vessel trimmed during lifts and cable lay, which strips coatings and accelerates corrosion. Neither problem is visible from the deck. Magnetic particle inspection of foundation welds and thickness measurement of the surrounding plating and tank structure give the owner a record to repair against before the next season's charter.

Ships trading to Blyth 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 Blyth

The sequence for a thickness measurement job at Blyth is short and written down, so the yard, the surveyor and the superintendent know who arranges what.

Newcastle International Airport is the nearest arrival point, and Blyth is reached from it by road through south-east Northumberland. The team travels from India on UK visit visas, which have to be applied for weeks ahead, so the date a campaign ends or a cable load begins is the date we plan back from. Terminal access at Blyth is ISPS-controlled: the ship's agent or the vessel operator arranges passes, and the terminal tells us when loading or mobilisation leaves the relevant deck areas free for inspection.

• 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.

Related