SOURCE: Trelleborg Sealing Solutions

May 13, 2008 08:00 ET

Trelleborg Sealing Solutions Supplies a Specially Engineered Sealing Configuration to a Leading Wind Turbine Hydraulic Actuator Manufacturer

FORT WAYNE, IN--(Marketwire - May 13, 2008) - Trelleborg Sealing Solutions offers maximized seal life with its sealing system as supplied to AVN Energy, contributing to minimal turbine maintenance requirements and meeting the dynamic criteria due to constant movement of the actuator. Having worked with them on stall machines, Denmark-based AVN Energy A/S approached Trelleborg Sealing Solutions to jointly develop a sealing system to meet the challenging requirements of continuous pitch systems. The specified solution is a complex arrangement of seals ranging from O-Rings to specialized Turcon® PTFE-based geometries and Slydring® in Orkot®. The unique configuration is specially engineered to enhance lubrication and optimize friction characteristics, at the same time preventing any external leakage.

"The replacement of stall machine turbines by continuous pitch systems has put extreme demands on hydraulic actuators," said Tom Carew, who is responsible for the renewable energy segment in the Americas. "The position of stall machines would shift only once every ten minutes, but in continuous pitch wind turbine systems, the nacelle and angles of the blades constantly change in small amounts once every rotation, on average 15 times per minute. This means that instead of producing six long strokes per hour, the turbine's hydraulic actuator must now initiate nine-hundred short strokes in the same period, 24 hours a day, seven days a week, for a targeted 20-year period."

The seals within these hydraulic actuators are integral to its performance, and optimizing seal life is critical to the long-term effectiveness of the total system. Seals must operate at 3,625 psi/ 250 bars with constant pressure on the rod from behind and differential side loads that control positioning. Wear has to be minimized, and dynamic movement that is continuous in short strokes needs to be facilitated. Temperature resistance is required down to -22°F/ -30°C as standard and to -40°F/ -40°C in the Arctic, with maximum temperature capability of +140°F/+60°C.

Extensive testing concentrated on all aspects of assembly design in conjunction with the seal configuration. The aim of this was to maximize service life and achieve the operators' 20-year target for turbine life with as little as possible maintenance. Some of the seals within the system are expected to achieve that time span without replacement, but it is impossible to guarantee it for all. The hydraulics are therefore designed for easy exchange of the seal set, which is mounted in a module that can be quickly bolted on and off.

The minimum life expectancy of the sealing configuration, allowing for the seal that has the shortest predicted life, is seven years, but replacement is recommended after five. Other than this, and routine rod replacement, the actuators should run without maintenance except for the systematic checking that the operators do for any leakage or loss of pressure.

Trelleborg Sealing Solutions, formerly known as Busak+Shamban, is one of the world's leading developers, manufacturers and suppliers of precision seals. They support their aerospace, industrial and automotive customers through 30 production facilities and more than 40 marketing companies globally. Within their portfolio are some of the longest established sealing brands, including Chase Walton, Dowty, Forsheda, Palmer Chenard, Shamban, Skega and Stefa along with a large number of proprietary products and materials such as Turcon®, Zurcon®, Orkot®, Isolast®, Stepseal® and Wills Rings®.

Trelleborg is a global industrial group whose leading positions are based on advanced polymer technology and in-depth applications know-how. Trelleborg develops high-performance solutions that seal, damp and protect in demanding industrial environments. The Trelleborg Group had annual sales 2007 of approximately SEK 31 billion, with about 25,000 employees in 40 countries. The Group comprises four business areas: Trelleborg Engineered Systems, Trelleborg Automotive, Trelleborg Sealing Solutions and Trelleborg Wheel Systems. The Trelleborg share has been listed on the Stockholm Stock Exchange since 1964 and is listed on the OMX Nordic List. www.trelleborg.com.

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