recommended because it has a usable filling volume of up to 25 liters. The compact power pack allows oil to be supplied at a pressure of up to 700 bar. It is available with all customary voltages (including 690V) and network frequencies. Depending on the arrangement of the hydraulic components and the space available in the nacelle, the unit is installed either horizontally or vertically. In environments with large temperature variations and/or high air humidity, it is advisable to equip the power pack with a silica gel filter to protect the oil against condensation. This is particularly important in the case of “cold-climate� variants. Directional-seated valves from HAWE Hydraulics are of particular interest for the brakes and the pitch drive. They offer a high level of security since they are leak-free and thus reliably maintain the operating pressure. In accordance with the safety specifications of German Lloyd, the hydraulic unit in a wind energy plant must be able to maintain the operating pressure at a constant level for at least six hours and up to seven days if this pressure is used to operate an active brake. With its compact power packs and leak-free directional-seated valves, the hydraulics specialist can verifiably meet this requirement. For wind power plant controls, HAWE Hydraulics uses zero-leak, seated valves similarly used for critical and safety-relevant clamping functions on machine tools. Without the use of seated valves, a larger pressure accumulator and pump unit would be necessary to properly maintain the operating pressure, due to leakage by spool valves and inadequate tightness of low-cost seat valves. The brake module with 3-way pressure control valve type CLK and integrated pressure-reducing functions is particularly well suited for the rotor brake, as well as small wind power plants up to 30 kW. This valve type is also included in the line of zeroleak seated valves and was developed for pressures up to 380 bar max. with pump pressures reaching 500 bar max. Volume flows of up to 22 l/min. are also possible. HAWE Hydraulics manufactures all pressurized parts from steel, which gives these components both strength and resilience. Since they are also designed for higher pressures, uncommonly found in wind power plants, the hydraulic controls are extremely reliable and durable in service.
Left: Brake module with leakage-free 3-way pressure-reducing valve type CLK or CDK. Right: Compact power pack type KA: The drive motor and the radial piston pump can be seen inside.
About HAWE Hydraulics North America: Since 1997, HAWE Hydraulics is a supplier of sophisticated controls to the mobile and industrial markets in North America. Based in Charlotte, N.C., the company offers application engineering, sales and service, after-sales support, and over two million dollars of product in inventory. Headquartered in Munich Germany, HAWE Hydraulik is an ISO 9001:2000 certified international supplier with a strong focus on rapidly developing niche markets. Circle 172
september/october 2013
19