TL;DR

Offshore wind winch demand is pulled by two vessel types carrying two different equipment lists: the service operation vessel (SOV), which holds station while a heave-compensated platform puts technicians onto a turbine, and the crew transfer vessel (CTV), which lands technicians and handles anchors and lines. The INI IYJ-C hydraulic mooring winch publishes 400 kN rated pull on the first rope layer at 12.2 m/min, a maximum pull of 500 kN, a 38 mm rope, 250 m of drum capacity and 324 L/min at 24 MPa rated system pressure. Because an SOV and a CTV do different deck jobs, they should not be specified from the same winch list, and the winch order is where build-out turns into equipment demand.

What does offshore wind growth actually do to winch demand?

It converts turbine counts into vessel counts, and vessel counts into deck equipment packages. A wind farm needs service vessels continuously, and each one carries its own mooring, towing and anchor handling equipment.

According to DNV's offshore service vessel guidance, the segment splits into roles defined by the job on board and the equipment fitted to do it, and the vessel holding station for turbine access is a different machine from the one ferrying people across. Because the two roles need different equipment, the winch demand that follows offshore wind growth is not one order stream but two, with two separate specifications.

For suppliers, that is the part I spend my time on. The question is not whether offshore wind grows, but which vessel your line can build to, because an SOV package and a CTV package share almost nothing below the winch level.

How do SOV and CTV deck jobs differ?

The difference is who holds the vessel still, and for how long. An SOV stays on station for hours while technicians work on the tower, nacelle or blades, so its mooring and positioning winch must hold a defined load for a defined period.

A CTV's job is shorter and sharper: land the team, run the tow line, set the anchor, get clear. Its winches see high peak loads over short cycles, and the governing constraint is turnaround time between turbine calls.

Because the duty profiles differ, the same winch model rarely serves both, and copying a specification between vessel classes is the most common mistake I see in the marine winch inquiries that reach me.

The vessel-to-winch mapping table

This is the mapping I use when a yard asks me what an SOV or a CTV needs. Every figure in the last column comes from the published INI product page, so each line can be checked before it becomes a specification.

Two things deserve a pause. First, the pull numbers are not comparable across rows, because a mooring winch and a tow winch are sized against different loads, so the number that matters is the one matching the deck job. Second, every row is a package, and buying the winch separately from the gearbox and the pump leaves a matched assembly problem on the quay.

What does the SOV mooring winch data sheet really tell you?

My rule is simple: read the first layer, not the maximum. The published IYJ-C model IYJ488-500-250-38-ZPGF is rated at 400 kN on the first rope layer at 12.2 m/min, 200 kN at 24.4 m/min in the two-rope-fall arrangement, with a maximum pull of 500 kN.

The rest of the data sheet is where the engineering sits: a 38 to 38.38 mm rope over five layers, 250 m of drum capacity, 324 L/min of flow, rated system pressure of 24 MPa against a maximum of 30 MPa, a 250 mL/r motor, a drum displacement of 62750 mL/r, and an IGC220W3 planetary gearbox at ratio 251. Because rated and maximum pressure are separate numbers, the winch carries headroom from 24 MPa to 30 MPa, and that margin is what a yard relies on during a peak pull.

The mechanical configuration is what I tell yard inspectors to look at: valve blocks with brake and overload protection, a hydraulic motor, a planetary gearbox, a belt brake, a tooth clutch, a drum, a capstan head and a frame, with customised modifications available. INI states that total transmission efficiency on the IYJ-C series is improved by 6 % to 10 % against traditional units.

What does a CTV need that an SOV does not?

A CTV needs speed of turnaround and rope handling, not endurance under a standing load. Its workhorse is the ship machinery winch, and the published INI figures are more modest than the SOV mooring winch: 50 kN rated pull at 1.5 m/s of wire speed on a 35 mm wire, 32 kN at 2.3 m/s, with drum speeds of 19 rpm and 29 rpm.

Three details are what a CTV owner feels on every turbine call, and they are the ones I check first. The rope options of 18, 28, 35 and 45 mm across eight layers, with a stated drum of 1260 mm by 1960 mm by 1872 mm, decide what the vessel can do with a tow line and an anchor. The self-feedback adaptive wire arrangement device decides how neatly the flaked rope comes back on deck. Because the anchor and tow jobs run back to back all season, the arrangement device and the clutch are wear items that decide downtime, so they belong in the maintenance plan from day one.

Why do class certificates decide the supplier shortlist?

Because the yard, not the winch maker, carries the class obligation. According to DNV rules and standards, class rules cover the arrangement and performance of this kind of deck machinery, and the same logic runs through Lloyd's Register rules and ABS rules and resources, so a winch without type approval becomes the yard's problem.

INI's own certificate list is where I start when a buyer asks about class approval. It includes an EC type-examination certificate for winches issued by the Norwegian Classification Society (DNV) in 2015, described on the site as the first domestic certificate of EC type recognition issued by that society, EC type-examination certificates for the IYJ 2.53 hydraulic winch covering 2018 and the 2018 to 2023 period and for the IYJ34 winch in 2020, UDEM certificates from 2021 for the hydraulic winch, motor and pump and transmission device, CE certificates from 2016, a Manned Winch Certificate, and CCS quality, occupational health and environmental management certificates from 2021 issued by China Classification Society.

Because those certificates are model-specific and time-limited, ask which certificate covers the exact model you are pricing, and whether it is still inside its validity period. A certificate list on a website is a starting point, not an approval.

What changes when the winch, gearbox and motor come from one maker?

The measurable benefit is interface count, not a discount number. INI builds hydraulic winches, motors, planetary gearboxes, slewing drives and complete hydraulic systems from one base in Ningbo, and has done so for more than twenty years. A package drawing the winch, gearbox, motor and pump from one maker removes several supplier interfaces, several incoming inspections and several warranty chains from the build programme.

For offshore wind that matters twice over, because the vessel is built to a class yard's schedule and a late gearbox or motor delivery lands on the docking date. Payment terms on the offshore machinery winch are listed as L/C, D/A, D/P and T/T. Because the sourcing advantage is structural rather than promotional, I would argue for it on schedule risk and interface count, and leave the price conversation to the quotation, because that is the part a buyer can verify anyway.

Ningbo also matters as a logistics point rather than a marketing point: a deepwater container and breakbulk port with short road links into the Yangtze River Delta supplier base, which is why so much of the export machinery built here travels by sea.

What the winch data sheet must prove before the order is cut

Seven checks, in the order a yard would run them.

1. Confirm that rated pull and line speed are quoted for the first rope layer and not only for the bare drum, because the first layer is both the fastest and the least effective.
2. Ask how many continuous hours the winch may run at rated pull before the oil and brake temperatures need recovery.
3. Require motor displacement, pump flow, system pressure and gearbox ratio to be stated together, so that the delivered speed matches the quoted speed.
4. Confirm rope diameter, rope breaking strength, number of layers and drum capacity in metres as one consistent set.
5. Confirm the brake arrangement and the overload protection function, including whether a belt brake and tooth clutch are fitted for holding under load.
6. Check which class society issued the type certificate for the exact model, and whether it is still inside its validity period.
7. Confirm the electrical environment, since the winch controls must meet shipboard electromagnetic compatibility requirements. According to IEC 60533:1999, which sets minimum emission, immunity and performance criteria for electrical and electronic equipment on ships, this is a technical constraint rather than a paperwork item.

My starting point when you are quoting offshore wind work

Start from the deck job list, not from the winch catalogue. Write down what the vessel does on a turbine call, how long it holds station, what rope it handles and which class society will be built to, and only then look at the winch family. If the job list says hold station, you are in mooring and positioning territory; if it says turn the vessel around every two hours with a tow and an anchor, you are in ship machinery and anchor territory.

The full winch range, from the offshore machinery winch to the IYJ-C mooring and positioning winch, the IYM series anchor winch and the IYPJ series hydraulic capstan, is collected on the winch category page, and the certification portfolio is published on the certificates page. Send the deck job list and the class requirement through the contact page and you will get a configuration proposal with the parameters behind it.

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