The past 12 months have been a peak period for the European wind industry with more new capacity installed than ever before. In just the first half of 2015 Germany, the UK and the Netherlands between them installed 584 new turbines with a capacity of 2342MW. Across Europe this brought the total installed capacity to 10,394MW from 82 wind farms in 11 countries.

Globally North America and China are also key growth markets with India also considerably increasing capacity. The Global Wind Energy Council uses three potential growth models to predict future activity and under all of these scenarios these regions, as well as Europe, are set to maintain major growth (see charts).

Wind turbine maintenance is a critical aspect of successful operation of the growing army of wind farms. To get tools and equipment up to the nacelle which houses the generator, gearbox, drive train and brake, a service hoist has traditionally been fitted inside the hub. "We make hoists to suit each individual application," says a technical specialist at a leading international manufacturer. "Every turbine and every manufacturer have different specifications," he explains.


For onshore wind turbines electric chain hoists are most common. Cheaper than their wire rope counterparts, these stalwarts of vertical lifting also tend to be more compact as they don’t have the drum element that wire rope hoists need, however they do require more vertical space thanks to the chain bag or box. The chain bag or box can itself be customised to suit the space. "The size of a wire rope hoists means that it is just too big to mount it in the nacelle," says Ian Robinson, a sales manager at German manufacturer SWF Krantechnik.

The company’s SK series of electric chain hoists have a standard lifting height of 140m with speeds of up to 32m/minute and lifting capacity of up to 1000kg. "The ones that we use most commonly [in wind turbine nacelles] are around 250kg or 500kg with 60/70m lifting height," says Robinson.

Japan’s Kito Corporation too is a major player in the market. "For Kito, fixed suspension, electric chain hoists in single and three phase are our most common supply item," explains Scott Miller, managing director at Kito Europe. "These are mainly used inside the tower shaft itself, or occasionally outside the nacelle from a pivoting jib crane or similar fixture. In the last few years, the 60m – 90m lift lengths have been replaced by 110m – 150m lifts."

This is a side effect of the ever growing turbines which have longer blades, taller towers and larger nacelles. In just 12 months the average size has increased from 3.5MW in 2014 to 4.2MW in 2015. But despite the greater heights speed remains crucial. "Required lifting speeds are 24 mpm and faster, in order to minimize maintenance worker "down time". This too has increased the demand for dual speed lifting vs. traditional single speed hoists," says Miller.

Miller says that working loads are also increasing and notes the challenge between getting the speed and efficiency requirements for low cost. "It seems that hoist manufacturers have "pushed the envelope" on the balance between speed, durability and low price; and we are seeing an increase in WTG [wind turbine generator] hoist failures. Kito trains and certifies more than 75 WTG Service Technicians per year, and they frequently show us photos of broken chain guides, snapped or severely worn chains, burned out motors and related hoists failures.

Supporting this trend, we can see more WTG manufacturers spending the time and money to properly qualify a hoist mechanism for their application. They seem to recognize they can pay a little more now, or pay a lot more later," he says.


The technical specialist agrees and says that burned out motors in particular is an issue. Turbine manufacturers must pay particular attention to the duty motor rating and avoid overuse which will induce additional heat into the motor. Other major manufacturers of electric chain hoists used in this segment include Konecranes with its tXN electric chain hoist and Terex owned Demag with the Demag DC-Wind chain hoist.

"The Demag DC-Wind chain hoist is specially designed to meet the needs of wind turbine manufacturers and operators, which makes it one of the most frequently used hoists in the industry," says Dr Thomas Bönker, head of business line components at Terex Material Handling. "Based on the reliable DC chain hoist the DC-Wind is designed for efficient and safe transport of loads weighing up to 1,500 kg and with hook paths up to 180 metres."

The firm also offers a wire rope version with faster lifting speeds. "With our DS 10-Wind rope winch we offer a very compact solution for efficient maintenance and services. DS 10 Wind is available in graded sizes up to 1,000 kg lifting capacity, hook paths up to 180 metres and lifting speeds up to 48 m/ min."

Terex also notes that the growing size of the turbine and its components means that a transportation solution inside the nacelle is also needed. For this purpose the company has developed a complete logistics system for use inside the nacelle that can be deployed under harsh offshore conditions – and it says significantly cuts lifting times.

The modular system is based on the proven concept of the Demag KBK light crane system and the DS10-Wind rope winch. The rope winch is supplied in four sizes and installed in the nacelle of the wind turbine together with the KBK installation. Thanks to the customerspecific configuration of the KBK modular crane system, any point of the nacelle can be served with Demag lifting equipment.

For offshore applications wire rope hoists seem to be more common with their increased lift speed being a key factor. "With a chain hoist because of gearing and motor size etc there seems to be more limited hoisting speeds available. With a wire rope hoist because it is bigger you can put a larger motor and gearbox on which increases the speed quite a lot. So as a generalisation you can get a faster wire rope hoist," says the technical specialist. This is particularly crucial for offshore wind farms where the greater time that crews are out on site the higher the cost will be.


However the environment offshore is also challenging and the moving turbines combined with high wind speed again presents a difficult problem for designers to solve. At the same time every site and wind farm requires uniquely specified lifting equipment meaning that standardisation is not usually possible. This has deterred some companies from supplying lifting equipment to the offshore sector.

A handful of others though have created bespoke products specifically for the offshore turbines which as well as nacelle hoists also require a crane on the platform to move materials from moving vessels to the turbine. These davit cranes are then paired with a hoist or nacelle crane of the same capacity to coordinate lifting. "When you are picking off a floating vessel there are some inherent risks that you don’t get with standard lifting," explains Mark Sidwell, director at the UK’s Granada Material Handling.

"The cranes that we design and build feature additional safety systems to allow for those unfortunate eventualities. One of the worst scenarios is that the load gets entangled on the boat and that starts to drift away from the platform. You need the hoist system on the davit to actually pay out that rope unlike any other piece of lifting equipment where you don’t want the hoist going down you do in this unique scenario of wind turbine lifting."

The basic range of the GMH davit crane, known as the Granada Python Foundation Crane, lifts from 700kg to 1500kg. Sidwell says that the increasing size of turbine is not having a major impact on the crane capacity needs with servicing equipment remaining pretty consistent."The crane capacity on a 3MW turbine is 1t. For 6MW turbines it is not 2t. They are only rising slightly. Maximum capacities we see at the moment are 1.5t."

To ensure the cranes can withstand the harsh environment the firm uses a higher grade of steel for its offshore cranes and applies a duplex corrosion protection system. Stainless steel and nylon fittings are used for their high durability and high quality components such as bearings from Thyssen Krup are standard. "There is high UV, high salinity, there is bird guano, all sorts of horrible things and we counteract that by supplying them with a very high level of corrosion protection backed up with regular routine maintenance which enhances the life of the crane," says Sidwell pointing out that a lack of use for offshore cranes and hoists is as problematic as overuse.

Another company specialising in offshore cranes is Germany’s Palfinger which supplies platform cranes as well as two different types of cranes for the nacelle itself. The use of cranes within offshore turbines seems to be a feature of the larger models.

These enable coverage of a larger area within the nacelle and in the case of Palfinger’s knuckleboom model much heavier loads. With a capacity of up to 117t the knuckleboom models are used to lift generator parts of motors, whereas the telescopic boom cranes with a 6t maximum capacity are more suited for maintenance equipment such as tool boxes.

Whatever lifting solution is employed the demand for equipment is not going away, but with challenging conditions offshore it is not a market that all firms will compete in. For those that do the outlook is strong. "We see a lot of activity in the UK over the next 12-18 months, extensions to existing wind farms and some new. We then think there will be possibly a lull in the market while the further afield wind farms on round 3 get investment decisions or achieve funding," says Sidwell who is positive about future developments. "The market is extremely buoyant, there is a big pipeline of work. It is competitive but there is plenty of work out there."