Turbine Installation
Towers, nacelles and blades pre-assembled at a marshalling port, loaded out in sets and lifted into place from a jack-up vessel. The campaign is a repeating cycle, and the weather decides how many times it turns.
Last updated 2026-08-24
Typical duration
One to two offshore seasons for a full array, running as a repeating vessel cycle - a well-drilled crew can complete a machine in a few days when conditions allow, but the season, not the turbine, is the unit of programme.
What is Turbine Installation?
Turbine installation is where offshore wind stops looking like civil engineering and starts looking like a production line at sea. The components are enormous - tower sections that arrive as complete rings, a nacelle the size of a house containing the entire drivetrain, and blades well over 100 metres long on the largest machines - and none of them can travel by road at that size. They come to a marshalling port by sea, are laid out in a yard designed around their footprint, and are pre-assembled there as far as the method allows. The port is not a staging area, it is a factory floor: the more work that is completed alongside a quay, the less has to be done offshore where a day costs a fortune and the weather has a vote.
The offshore end of the job is a cycle that repeats. A jack-up vessel loads a set of turbines - as many complete machines as its deck space, crane capacity and sea-fastening allow - sails to the array, jacks up on a foundation location, lifts the tower, sets the nacelle, fits the rotor, hands the machine over for mechanical completion, jacks down and moves to the next position. When the set is finished the vessel sails back to the marshalling port and reloads. The vessel is the constraint on the entire campaign, so everything is organised around keeping it working: components ready in the right order, tooling loaded, technicians rested and the next position surveyed and clear. A vessel that arrives at the port to find the components are not ready has just wasted the most expensive asset on the project.
The contrast with onshore wind is instructive. Onshore, the hard problems are roads, bridges, swept paths and getting a large crawler crane to a hilltop; the wind still matters for lifting but a crane can wait a day at modest cost. Offshore there is no craneage over land at all, and the entire supply chain is measured in vessels, quays and tides. The consolation is that the lifting platform is already there and already huge, and once a jack-up is standing on its legs it is a remarkably stable place to work. The penalty is that access, weather and logistics dominate everything, and the operation that cannot be finished inside the window does not get started. Every lifting limit, sea state limit and hold point comes from the vessel, the lifting equipment supplier and the turbine supplier - they own those numbers, and they are the only ones who should be quoting them.
Compare the methods at a glance
When and why is Turbine Installation used?
Turbines go up once the foundations are in, surveyed and released, and the sequence is rarely negotiable - a turbine needs a completed structure with a working access platform, a boat landing and, ideally, its cable pulled in and hung off ready. The method chosen for the rotor is the biggest single decision in the campaign, because it trades deck space against lift count against weather sensitivity. Lifting a fully assembled rotor is fewer lifts and less time aloft, but it is a huge sail area that becomes unworkable as soon as the wind picks up, and it eats deck space on the way out. Lifting blades individually gives a smaller, more weather-tolerant lift but multiplies the number of them and demands precise control of a very long, very flexible object as it is offered up to a hub that must be indexed round between each one. What makes this stage matter beyond its own cost is that it is the last chance to work on the machine with a heavy-lift vessel present. After the vessel leaves, any component change means bringing one back, and the economics of that are brutal enough that a great deal of effort goes into never needing to.
Types of Turbine Installation
Explore each method in depth - benefits, limitations, plant and quality control on its own page.
Single-blade installation
The nacelle and hub are set first, then blades are lifted and bolted one at a time using a dedicated blade yoke, with the hub indexed round between each fitting. Each lift is smaller and less weather-sensitive than a full rotor, and blades stack efficiently on deck, so the vessel carries more turbines per trip. The cost is lift count, tooling complexity and the fine control needed to offer up an extremely long, flexible component to a bolted root connection in a moving environment.
Pre-assembled rotor
The three blades and hub are built into a complete rotor at the marshalling port and lifted as one, then offered up to the nacelle in a single operation. It is the fastest method offshore and puts the least work at height, which is precisely why it is attractive. It is also the most weather-sensitive lift on the project, since the assembled rotor presents an enormous sail area, and it consumes a great deal of deck space and quayside assembly area for every machine carried.
Bunny ears with a single blade
A compromise method: two blades are fitted to the hub onshore, the assembly is lifted as a unit resembling a pair of ears, and the third blade is fitted offshore as a single lift. It reduces offshore lift count without carrying the full sail area of a complete rotor, and it spreads the weather sensitivity across two different operations. Deck stowage is awkward, and the method has become less common as turbines have grown and single-blade tooling has matured.
Quayside assembly and wet tow
Used with floating substructures: the complete turbine is assembled on the floater alongside a quay using land-based cranes, commissioned as far as possible in sheltered water, and then towed to location and connected to a pre-installed mooring spread. It removes the heavy-lift vessel from the offshore scope almost entirely, which is transformative for cost, but it demands a port with the depth, quay strength and area to build and hold complete floating turbines.
Best suited for
- Fixed-foundation arrays where a heavy-lift jack-up can stand safely at every position
- Projects with a marshalling port close enough that the sail time between load-outs does not dominate the cycle
- Single-blade methods where weather exposure is high and the season is short
- Pre-assembled rotor methods where the port has the assembly area and the weather record supports the larger lift
- Floating projects where complete turbines can be assembled and commissioned alongside a quay and towed out
Turbine Installation: step by step
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Step 1: Receive and pre-assemble at the marshalling port
Components arrive by sea and are inspected on receipt, because transport damage found at the quay is a supplier problem while the same damage found offshore is a campaign problem. Tower sections are stored upright or on saddles, nacelles are kept sealed and dehumidified, and blades go into racks that support them the way the supplier requires. Then the port does its real job: pre-assembly. Depending on method, that means bolting tower sections together, building rotors or bunny ears, fitting internals and ancillaries and completing as much commissioning preparation as can be done ashore. Every hour of work moved from the sea to the quay is an hour bought back from the most expensive part of the programme, and the port layout is designed around exactly that arithmetic.
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Step 2: Load out a turbine set and sea-fasten
The vessel comes alongside and a set of complete turbines is loaded - the number set by deck area, crane reach, stability and the sea-fastening arrangement, not by ambition. Components are moved by self-propelled modular transporters and quay cranes, positioned to a load plan that has already been checked for weight distribution and lifting sequence, and then sea-fastened to an approved design so nothing shifts in transit. The marine warranty surveyor reviews the load-out and the sea-fastening because a component that moves on passage can damage itself, the vessel and everything around it. Tooling, spares, consumables and the technicians travel with the set, since the vessel becomes self-sufficient the moment it leaves the quay.
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Step 3: Sail, position and establish a stable platform
The vessel sails to the array and approaches the first position under a plan that accounts for the foundation, the cables already on the seabed and the exclusion zones around both. A jack-up lowers its legs, preloads them against the seabed and raises the hull clear of the water to create a stable working platform - a process that depends entirely on the ground conditions assessed for that specific location. Floating installation vessels hold station on dynamic positioning instead, trading absolute stability for speed of repositioning. Either way the vessel establishes exactly where it can reach, what it can lift and in which direction, and the crane operator, the deck crew and the turbine technicians brief the sequence together before anything is unhooked.
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Step 4: Lift and bolt the tower
The tower goes up section by section, or as a complete pre-assembled tower where the vessel can handle it. Each section is lifted, guided onto the flange below, and bolted through a connection that carries the entire machine for its whole life. Flange faces are checked and cleaned before mating, because contamination or damage in a bolted joint is a defect that gets designed out at the yard and reintroduced by carelessness offshore. Bolts are tensioned or torqued using calibrated equipment to the pattern and values the turbine supplier specifies, and the results are recorded per joint. Internals - ladders, platforms, lifts, cabling and the switchgear at the base - are already fitted or go in as the tower rises, so that the machine is habitable and workable as soon as it is complete.
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Step 5: Set the nacelle
The nacelle is the heaviest single lift and the one that most obviously benefits from a stable platform. It is rigged to the supplier's lifting arrangement, lifted clear of the deck, brought over the tower and lowered onto the top flange while tag lines and, on larger machines, motion-control systems keep it under control. Yaw orientation matters, so the nacelle is set the way the design requires rather than the way it happens to swing. Once landed, it is bolted down and the joint is tensioned and recorded like every other. Then the connections are made: power, control, safety systems and the service lift, so the machine can be worked on from the inside rather than from a crane.
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Step 6: Fit the hub and blades
With the nacelle set, the rotor goes on. Under the single-blade method the hub is fitted first and each blade is lifted in a yoke, brought to the hub, aligned and bolted at the root, with the rotor indexed round between blades so the next root connection presents itself in the right place. Under the pre-assembled method the whole rotor comes up as one and is offered to the main shaft in a single operation. Both are demanding lifts with long lever arms and very little tolerance for uncontrolled movement, which is why the wind and sea state limits belong to the vessel, the lifting equipment supplier and the turbine supplier, and why they are the limits that stop work most often. Root bolts are tensioned to the supplier's procedure and every result is recorded against that blade.
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Step 7: Complete the machine and reach mechanical completion
With the rotor on, the turbine is finished as a machine: rotor lock arrangements confirmed, remaining bolt tensioning completed and audited, covers and hatches closed, fluids checked, lightning protection continuity proven, cabling terminated and the tower dried and sealed against the marine atmosphere. A walk-down against the supplier's checklist produces a punch list, and the honest ones are closed out before the vessel moves. The turbine is then declared mechanically complete - it exists, it is bolted together correctly and it can be safely accessed - which is the trigger for the commissioning teams to take it on. It is not yet a generator, and treating mechanical completion as if it were is how projects end up with open items nobody can reach.
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Step 8: Jack down, move on and repeat the cycle
The vessel recovers its rigging, secures the deck, jacks down and moves to the next position, and the cycle begins again. When the set is complete the vessel returns to the marshalling port and reloads. The campaign is measured in these cycles, and the whole organisation exists to keep them turning: components ready in sequence at the quay, technicians rotating on schedule, tooling maintained, and a live picture of the forecast that lets the team decide which positions to attempt and which to leave for a calmer week. Progress is tracked machine by machine, but the number that actually matters is how many cycles the season will allow before the weather closes the window for the year.
Plant & equipment
- Jack-up installation vessels with heavy-lift cranes, and floating installation vessels on dynamic positioning
- Feeder barges and support vessels where the main vessel stays offshore between loads
- Blade yokes, rotor lifting frames and motion-controlled lifting tools supplied for the specific turbine
- Calibrated bolt tensioning and torquing equipment with recorded output
- Self-propelled modular transporters, quay cranes and blade racks at the marshalling port
- Sea-fastening frames, grillage and stoppers designed and approved for the passage
- Crew transfer vessels and service operation vessels with motion-compensated gangways
- Dehumidification and preservation equipment for nacelles and towers in storage and transit
Quality control & testing
- Receipt inspection of every component at the marshalling port, photographed and recorded before storage
- Flange face cleanliness and condition verified before every bolted joint is mated
- Bolt tensioning and torque results recorded joint by joint against calibrated tooling certificates
- Yaw orientation and tower verticality confirmed against the design before the joint is finalised
- Lightning protection continuity and earthing verified through the completed machine
- Blade root connection records held against the serial number of each individual blade
- Moisture, dehumidification and preservation records maintained through storage, transit and installation
- A turbine-by-turbine documentation pack closed out at mechanical completion, with punch items listed rather than forgotten
Safety watchpoints
- Working at height throughout the tower and nacelle, with rescue and recovery arrangements planned before access
- Heavy lifts over water and over people, with exclusion zones and dropped-object control enforced on deck
- Transfer between vessel and turbine, which stops when the sea state exceeds the vessel's access limits
- Confined and restricted spaces in the tower base, hub and nacelle, with access control and atmosphere checks
- Stored energy in the drivetrain and pitch systems, controlled by rotor lock and isolation before anyone enters the hub
- Lifting limits set by the vessel, the lifting equipment supplier and the turbine supplier, which are the only limits that count
- Long, flexible components under lift are unforgiving of uncontrolled movement, so tag lines and control systems are not optional
- Emergency response, medical evacuation and shelter planning all shaped by distance from shore and available vessels
Common defects to hunt
- Blade leading edge and surface damage from handling, racking and transport
- Contaminated or damaged flange faces mated in a hurry, compromising a bolted joint that carries the whole machine
- Bolt tensioning not achieved or not recorded, leaving joints that cannot be signed off without re-entry
- Nacelle and tower moisture ingress during storage or transit, corroding equipment before the machine has ever run
- Component damage during load-out, sea-fastening or a rough passage, discovered only when it is lifted
- Coating damage at lifting points and around fixings, becoming the first corrosion sites in a marine atmosphere
- Cable loops and internal cabling in the tower damaged or wrongly routed during assembly
- Punch items deferred at mechanical completion and then inherited by teams who arrive by boat rather than by crane
How long does Turbine Installation take?
Typical duration: One to two offshore seasons for a full array, running as a repeating vessel cycle - a well-drilled crew can complete a machine in a few days when conditions allow, but the season, not the turbine, is the unit of programme..