Specialist hydraulic hoses help keep wind turbines turning

Paul Boughton

When a new technology grows as fast as wind energy has done over the last few decadesconventional parts and solutions often no longer fit. Siemens Wind Power is one of the major wind turbine manufacturers that have helped develop wind-power technology.

With its headquarters in BrandeDenmarkthe company was founded as Bonus Energy A/S by Peter Sørensen in 1981. Sørensen was the sole owner until December 2004when he sold Bonus to Siemens.

As one of the top-five wind turbine makers in the worldSiemens has installed more than 5000 machines with a total capacity of more than 3300 megawatt (MW) around the globe.

Its earliest turbines were 22–55 kilowatt (kW)while today’s multi-megawatt giants are up to 3.6 MW in size. When Siemens developed its 1.3- MW model in 1999the company devised a new oil cooling and filter system for the turbine gearboxes.
Normal hydraulic hoses – typically 6-20 mm in diameter – were too small or too stiff from steel reinforcements.

“We were looking for something bigger – 38 mm (1.5 inches) at first” says Tommy FriisSenior BuyerSiemens Wind Power. “They had to be flexible – some of the hoses must be up to eight meters long. And we knew we’d need something that could go up to at least 63 mm (2.5 inches) or bigger. Today we’re at 102 mm (4 inches).”

Cleaning standards

The hoses would also have to be cleaned to very high standards (ISO 18/16/13). Otherwiseparticles in the gear oil could cause a failure. Siemens had trouble finding a supplier that could meet its demands.

“At firsteverybody said our plan would not be possible” says Friis. Trelleborg could not only meet  Siemens’s strict demands for the partbut it made investments in a cleaning system to further seal the cooperation. “They’ve been willing to take action when it was needed” says Friis.

Green power generates popularity

With current global demand for energy exceeding the world’s crude production capacitycausing oil prices to soarwind power is becoming an increasingly viable industry.

Over the past 15 yearsthe global wind-power industry has been growing at an annual rate of more than 30 per cent.

Consequentlygreen power (wind powersolar powersmall-scale hydroelectric powergeothermal powerbiomass fueland so forth) is rapidly becoming a smart investment.

According to the European Wind Energy Associationin 2003wind turbines worldwide attained a record capacity of 39 294 MWmeeting the needs of 47 million people. Its US counterpartthe American Wind Industry Associationestimates that wind installations worldwide will deliver more than 75 000 MW over the next decade and become a close to USD 75 billion industry.

The powerful global growth is expected to continue if policy incentives (fixed price and quantity systemsrenewable portfolio standard laws) remain and technological advances in wind-turbine manufacturing continue to extend product life and reduce operation and investment costs for electricity production. Demand for green power is also on the increasesince coala principal energy sourcecontributes the largest amount of pollutants to the greenhouse effect. While most agree growth will continueit is also believed this will mainly take place in the top five wind-power producing countries – Germanywith a 36 per cent shareSpainat 16 per centthe US at 16 per centDenmark at seven per cent and India with five per cent.

Trelleborg’s cleaning system for its gear-oil hoses has resulted in continuing cooperation with Siemens Wind Power.


The key to Trelleborg’s continued success of its hose supply to Siemens Wind Power lies in a key investment for a cleaning system.

The hoseswhich range from 38–63 mm in diameter and up to eight meters in lengthtransport oil from the gearbox to the filter/oil cooler and back.

“When Siemens was unsatisfied with the level of particles in the oil at firstTrelleborg invested in a completely new cleaning systemwhich flushes new hoses with oil at high pressure” says Frits JohansenDistrict ManagerTrelleborg Industrial Supply Products Denmark. “Since thenno problems have occurred.”

Johansen continued: “After each compression test and cleaningthe test results are transferred electronically to Siemens” says Johansen. “This gives them documentation in the further process. The order number is also embossed on the casingso we have traceability. We can always tell when the hose was produced.” 

Jack Jackson is with Trelleborg Industrial Supply Products Denmark. www.trelleborg.com/industrialhose


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