How are hydraulics used in wind turbines?

Hydraulics will probably provide the heavy-duty muscle in the nacelle. The systems there will be made of two-position valves, proportional valves for precise control, hoses, lubricants, fittings, and pumps.

Valve selection provides a good example of the complexity that comes in just selecting one component. Selecting a proportional hydraulic valve for pitch control is an important task. From a functional viewpoint, valves in turbine hydraulics are not required to do anything unusual. They simply control the flow of fluid to cylinders in response to sensor signals in a fairly straightforward closed-loop servo control circuit.

However, the valves are subject to temperature extremes, high and variable rotational and vibration loads, and long periods between maintenance. Servicing such valves requires the attention of specialized personnel.

In response to the wind industry’s need for more precise control, proportional valves are being equipped with an improved control interface featuring CANbus communication using the CANopen protocol. These electronic controls are packaged to industry IP67 environmental standards to meet the needs of the next generation of wind turbines.

Fittings and hoses should be considered critical components. They are key components in gearbox lubrication, typically an active system with constantly circulating fluids.

Hoses with class-zero leakage do not weep in extreme temperature variations or on cool down, so selecting them eliminates a potential source of fluid loss. Such hoses also promote a safer working environment inside the nacelle by keeping its floor drier and delivering extended service lives.

Premium hoses made with Teflon PTFE are resistant to bulging under pressure, making them a good choice for critical braking circuits. They are also chemically inert which is important in gearbox lubrication circuits.

Color coding these devices helps prevent assembly errors on shop floors, and potentially catastrophic failures on a system in service.

Low pressure course on hydraulics for wind turbines

A four-and-a-half-day training course is aimed at sales and maintenance personnel who must understand hydraulics systems used in wind turbine operation. Wind Turbine Fundamental Hydraulics will be offered by industrial manufacturer Eaton Corp.

“Nearly half of the utility-grade wind turbines in service depend on hydraulic pitch and yaw controls. Many of the others use electric drives controls but may use hydraulics for braking or a forced lubrication system,” says Eaton’s Manager-training Services Tom Blansett. “The new course will provide a solid foundation in hydraulic fundamentals and operating principles with special emphasis on wind-turbine operations, including pitch and yaw control, braking, and cooling and filtration systems.”

Classes are slated for July 27 to 31, aug 17 to 21, and Oct 5 to 9, all in Maumee, Ohio.

The course will focus on component construction and operation with a goal of understanding the interaction of individual components in an integrated wind turbine hydraulic system. Topics include:

• Hydraulic principles and fundamentals
• Graphic symbols
• Hydraulic fluids and reservoirs
• Gear, vane, and piston pumps
• Pressure controls
• Directional controls
• Flow controls
• Cylinders
• Hydraulic motors
• Contamination control
• Electro-hydraulic valves
• Screw-in cartridge valves
• Accumulators