Energetic developments

UK gear manufacturer David Brown is at the heart of plans to develop a record-breaking 7MW wind turbine. Sam Shead reports

UK gear specialist David Brown has received £1.2m in government funding to make new energy-saving gearboxes for 7MW offshore wind turbines.

Offshore wind turbines have been getting bigger and better since the first wind farm was installed in Denmark in 1991. Nowadays, the general rule is the bigger the wind turbine the more energy it can produce.

Burbo Bank Wind Farm Now Fully Operational
Wind turbines are increasing in power and scope

With this in mind, South Korean company Samsung Heavy Industries (SHI) is developing a 7MW offshore wind turbine that promises to be the most powerful of its kind when it’s demonstrated towards the end of 2012. The firm plans to test the new generation of wind turbines at Fife Energy Park off the east coast of Scotland before taking orders to build them at its European facility in Methil, Scotland.

“We found there was a high rate of interventions related to gearbox issues between 10 and 6 years”

In order to help SHI achieve its goal, David Brown, a company that is perhaps best known for having its initials on the back of several Aston Martin models, will be delivering an innovative new gear system that will be able to generate three to five per cent more energy than existing gearboxes.

This increase in energy output could be key to energy companies that are deciding which gearbox to go with in an age when government is desperately trying to bring down offshore wind’s cost of energy from £150 per megawatt hour to £100 per megawatt hour by 2020.

Ian Farquhar, managing director of wind energy at David Brown, said: ‘We’ve probably got in David Brown the most comprehensive gear-making capability in the world.’

Farquhar explained that David Brown works in an environment where in the design and production of a gearbox, the cost or consequence of failure, in relation to a wind turbine, is extremely high.

But how exactly did David Brown end up in the wind-energy market? Scottish entrepreneur, Jim McCull, bought the 152-year-old Huddersfield-based gears company back from the US after it had a 10-year-spell at Textron. The £368m sale went through in November 2008 and the company is now targeting new and developing markets.

There is a gap in the wind-energy market for gear boxes

David Brown began assessing the performance of the existing gearboxes in wind turbines and found some alarming statistics.

‘Offshore wind turbines are designed to survive for more than 25 years. But we found that there was a very high rate of interventions related to gearbox issues between six and 10 years,’ said Farquhar.

“Our estimates tell us that the market for gearbox repair was $150m last year. By 2020 that will grow to $2bn”

Farquhar went on to establish a business unit of David Brown that specifically looked at post-warranty inspection work, which helped the firm to identify a lot of common gearbox failure issues.

‘We saw that because of the very variable and poorly understood loads that the winds drive into these gearboxes, there are a lot of misalignment effects in the forces going through the gearboxes and therefore a lot of bearing failures and gear tooth failures,’ he explained.

The costs of repetitive gearbox failures are enough to plunge wind-energy companies into spiralling financial difficulties. ‘One manufacturer quoted to me the cost of an insurance claim for one written-off gearbox can be up to $500,000,’ said Farquhar. ‘Our estimates tell us that the global market for gearbox repair was maybe $150m last year. We believe that by 2020 that market will have grown beyond $2bn.’

David Brown spotted the gap in the market for more reliable gearboxes and launched a service and repair business to mend broken gearboxes. This enabled it to gain additional valuable experience on the trends and failure modes of existing equipment, which it used to provide a series of upgrades to existing turbines, for companies such as Vesta, one of the world’s oldest and largest wind-turbine companies.

But as you may have guessed by now, in addition to repairing gearboxes it is also manufacturing customised gearboxes for new customers, such as Samsung Heavy Industries. ‘Having seen all of these different design models, common failure modes, and having an understanding for some of the challenges that exist offshore, we can design a specific application for a customer,’ said Farquhar. ‘We’re very much like the Saville Row of gearboxes in that we will design something specific to the customer.’

Building a gearbox for the world’s most powerful wind turbines Farquhar explained that one of the key criteria for wind turbine gearboxes is that they are as light as possible.

Heavy gearboxes require stronger tower structures and present greater transportation and erection issues. Approximately 20 per cent of the mass of a wind turbine is associated with the gearbox, the largest single contributor after the blades.

The compact, low-weight gearbox that has been designed for SHI will still weigh between 50-90 tonnes but Farquhar claimed it is 10 to 15 per cent lighter than any competitor product on the market.

The gearbox is a multi-stage epicyclic (planetary) unit, which means it has several outer gears revolving about a central or ‘sun’ gear. The planet gears will be mounted onto a movable arm or carrier and provide a link to the outer annulus gear, which will have a diameter of approximately 3m. David Brown claims the system will offer a combination of high power density, efficiency and structural integrity.

“Our motivation is not purely about maximising the selling price. We’re taking a whole-life cost view”

The gearbox will initially cost somewhere between £500,000 and £900,000 but the company hopes to reduce this over time.

Farquhar said: ‘Our motivation is not necessarily purely about maximising the initial selling price. We’re taking a whole-life cost view. The way in which we’re working with our customers means we are all motivated to try and make continuous improvements.’

Samsung has elected and signed a memorandum with Methil and Fife Council to potentially set up a £100m assembly facility in Scotland for 500 people. David Brown has an agreement with Samsung that it will set up an assembly facility in the same location if Samsung goes ahead with this plan.

On a more immediate note, David Brown is planning to expand its Yorkshire facilities in order to meet the demands of the new partnership with SHI.

Two new buildings that are being built in Mirfield will include a gearbox research and innovation centre, as well as a gear-manufacturing centre of excellence.

Farquhar said this one project could increase the current size of the company by three to four times.

David Brown is seeking to draw on its gear history to solve a relatively contemporary issue. The company is looking to make a significant difference to the wind energy market and its new gearboxes could help to reduce the price of wind energy, making this renewable source a far more attractive option.

drives, gears and motors

For hundreds more stories like these visit source.theengineer.co.uk

air of innovation
Drives and motors from ABB have helped Manchester Airport to save energy and cut CO2 production. A project to upgrade air-handling units (AHUs) with low-voltage drives and high-efficiency motors from ABB is enabling Manchester Airport to save 4,000MWh a year while cutting CO2 production by more than 2,000 metric tons a year. The project involved replacing drives and motors in 95 AHUs throughout terminals one, two and three. Each AHU has a supply drive and motor, and an extract drive and motor, with motors ranging between 3kW and 90kW.

analytical motors
The Baker DX series of static motor analysis equipment from SKF – which will replace older-generation Baker D-series and ST series surge test analysers – are suitable for performing motor and generator analysis in areas such as industrial motor test/maintenance, motor servicing and OEM manufacturing. The lightweight, portable instruments can carry out low-voltage inductance, impedance, phase angle and capacitance, coil, DC step voltage, winding resistance, megohm, DC Hipot, surge and DC bar-to-bar armature tests. The Baker DX series includes all of the motor test capabilities of the Baker D-series and ST-series testers, including compatibility with SKF power pack units. They feature an easy-to-use touch screen graphical user interface, are offered with a range of configuration options and accessories, and can include the test functions required by the user. Options include coil test, resistance-inductance-capacitance test, DC armature test, simple meg-ohm test and either singleor three-lead configurations.

hollow heart
Stber’s hollow-shaft geared motor will be on show at the Hannover Fair in Germany this spring. The company first revealed its PipeDrive at the SPS/IPC/Drives show in Nuremberg at the end of 2009, but the design – with motor windings and a new gear design – has taken longer than expected to put into production. It is now due to start shipping at the end of May. One of the PipeDrive’s most noticeable characteristics is its unusually large hollow shaft, with an internal diameter of 28mm or 38mm. This makes it large enough to accommodate supply lines, including not only power cables, hydraulic pipes and pneumatic hoses, but also shafts and laser beams.

hybrid rotation
NSK’s ultra-high-speed ball bearings are suitable for use in the drive motors and power generators of next-generation hybrid systems. The ball bearings can achieve rotations of more than 30,000 revolutions per minute and, according to the company, enable manufacturers to scale down the size and weight of drive motors and power generators. NSK’s devices feature a plate, installed at the lubricant port of the bearing module, which controls the flow rate of lubricants. It is designed to ensure that oil is supplied to the inner ring, where lubrication can easily become depleted, in order to reduce heat caused by friction.

rare earth mother
A tiny 1.9mm diameter motor has been manufactured by Faulhaber. The brushless 0206 motor, which can deliver 100,000rpm, was made using rare earth magnetic materials and a minute skew wound ironless rotor. Larger versions measuring 3mm and 5mm in diameter have also been developed, with planetary gearheads of the same size to complement. These versions also come with the option of integrated lead screws for precise linear move.

design essentials

The key facts to take away from this article

  • Gearbox specialist David Brown has been working with wind turbines
  • It has identified a lot of common gearbox failures on wind turbines
  • The company has its own low-weight gearbox aimed at turbines
  • David Brown hopes its customised gearboxes corner the market