PTFE seal wins 2011 innovation award

Turcon M12, a PTFE-based material launched in 2011 by Trelleborg Sealing Solutions, has received a 2011 Innovation Award from Flow Control Magazine. According to the company, the PTFE-based sealing material has unrivaled performance in key hydraulic sealing characteristics such as friction, wear, and high-pressure operation. Testing shows Turcon M12 resistant to most media, including a broad range of lubricants, and has outstanding wear resistance and friction characteristics. The cost-effective material also provides an extended seal life, as well as a wide operating window in temperature, pressure, and velocity.

 “Turcon M12 has exceeded even our expectations,” said Trelleborg Sealing Solutions Product Manager Nancy Getz. “On most every parameter it is better than, sometimes significantly, than previously recommended compounds or was at least equal to them.”

Trelleborg Sealing Solutions
www.trelleborg.com

Three ideas for more reliable turbines

 

Reliable equipment is needed to decrease turbine costs and downtime. Large amounts of time and resources are often spent on finding methods to reduce the risks of large components failing. Turbine gearboxes are one such example. However, more often than not, it is the small components such as seals and bolts that are central to reliability, performance, and ultimately, profitability. UK-based James Walker has identified at least three options that can help the industry overcome these problems.

Reducing the risks of bolt failure
Some 90 to 95% of all bolted-joint failures are caused by insufficient bolt tension on installation. So to improve reliability and reduce equipment failures, it is essential that correct tension is generated at installation and maintained throughout the life of the bolt. Traditional tightening procedures, such as torque and hydraulic tensioning, measure the effort applied but not the tension generated across the bolted joint. Hence, torques is not an adequate measure of correct bolt tension.

Advanced bolt tension technologies can reduce the risks of bolt failure by accurately measuring tension across bolted joints. The company says its RotaBolt offers accurate installation to within ±5% of the customer’s specified design tension. This reduces the risk of bolts loosening in operation due to factors such as vibration or thermal cycling. Additionally, the tension-control fasteners allow monitoring any loss of tension across the bolt by a simple tactile or visual check requiring no specialist expertise or tools. This technology can reduce the risks of equipment failure while also improving safety and significantly reducing maintenance costs.

Reducing the risks of seal failure
Poor seal performance lets lubricants leak, compromise performance and accelerate equipment failure. As more wind farms are installed in challenging environments, rapid on-site seal replacement with the minimum of disassembly is essential to minimise the loss of energy production. However, retrofitting such components is a vital consideration often absent in seal design.

Seal manufarturers have developed on-site joining technology to fit the wind industry. For example, Walkersele OSJ-2 is an on-site jointed seal concept from James Walker that can replace a typical turbine main shaft seal in less than 30 min without major disassembly. On-site joined seals offer the same integrity, life, and performance as the seal fitted during manufacture by an OEM. Timely seal replacement will help to reduce the risks of equipment failure.

Vibration elimination
Shaft and blade vibration can cause fatigue and ultimately, the premature failure of turbine components. To improve performance and reduce maintenance requirements, vibration must be minimised or eliminated.

Vibration control reduces the risks of equipment failure. Companies such as James Walker Tiflex have developed vibration attenuation and structural isolators. A range of machinery mounting options, foundation pads, and structural bearings can isolate structures from plant vibration and equipment from structural disturbance. Many years of sound and vibration attenuation engineering experience and state of the art research let’s Tiflex provide tailored solutions to specific turbine, tower resonance, and vibration problems.

“As demand for energy grows, technology in the wind industry must improve equipment reliability”, said Keith Tripp, marketing director of James Walker. “Recent activity has focused upon maintaining the reliability of large components. However, smaller components are also important and should not be overlooked. Investment in technology that reduces the risks of equipment failure will in turn reduce the costs of maintenance and improve the long term reliability of renewable-energy generation.”

James Walter Group
www.jameswalker.biz/windenergy

Special polyurethane improves abrasion resistance

The Timken UltraWind P1 Seal is a significant wind-turbine bearing seal with a polyurethane design that provides increased resistance to abrasion for longer wind-turbine service life and more reliable performance than most other commonly used sealing materials. “Seals have an integral role in maximizing wind-turbine uptime and productivity because they prevent lubrication leakage and bearing contamination,” said Hans Landin, director of Process Industries original equipment and wind energy at Timken. “However, over time the cumulative impact of abrasive forces caused by varying loads and speeds, as well as extreme temperature fluctuations, rain, snow, debris, and lubrication challenges, can significantly reduce seal performance in wind-turbines. The new UltraWind P1 Seal addresses the problem with the latest polyurethane technology.”

In addition to its durable polyurethane base, the Timken UltraWind P1 Seal contains a variety of other features, including:

• A flexible sealing lip that handles misalignment or run-out in the application of the bearing. The lip’s special profile also helps minimize heat generation and cone wear while helping to accommodate bearing deflections.
• A corrosion-resistant, stainless steel garter spring that helps prevent rust.
• A machined design for a broader, more diverse range of applications, plus ease of installation via stress minimization. This design also allows for multiple positions at the cone lip OD contact; and

The Timken Company
www.timken.com

Why are seals important in wind turbines?

Component design often overlooks the importance of well engineered seals. A properly engineered sealing system increases the mean time between component failures, reduces manufacturing costs associated with the use of exotic coatings, and reduces power consumption due to unnecessarily high friction.

Application data required to select a seal includes:

•Size – shaft, housing bore, available seal width

•Temperature – continuous and maximum

•Application parameters – equipment, sealing surface    misalignment to housing bore, dynamic shaft run-out

•Media – type and level of lubricant

•Pressure – continuous and maximum

•Shaft surface speed – continuous and maximum.

From these, select either lip seals or isolators.

Lip seals are typically retained in a housing bore by a rubber-to-metal or metal-to-metal press fit, requiring considerable installation force. Press fits can let metal shavings enter a bore housing, leading to contaminated lube and premature bearing failure. Also, nicks, burrs, or scratches on a shaft surface can damage a seal lip and produce a leak. A mounting tool prevents damage, such as lip roll-over.

By comparison, isolators are easy to install. Isolator seals facilitate the installation and maintenance of sealing systems. They usually have O-rings on their inner and outer diameters to seal on the shaft and against the bore respectively. To prevent damage to O-rings, the sealing surfaces of the shaft and bore must be cleaned prior to installation. O-rings are not dynamic sealing elements so they are not subject to wear. Once the equipment is cleaned and inspected, the isolator can usually be installed by hand pressure alone.

There are many other sealing tasks in a nacelle. Hydraulic equipment, of course, needs them. Leak detectors (sensors) on some seals measure leakage. Onboard electronics then provide some analysis and can send results to a computer or telephone. This allows remotely monitoring a seal and scheduling an exchange when necessary in a normal maintenance interval.

German DIN 3760 standards describe function and lifespan for such seals. The sensor-seal combination is available in many different dimensions. The seals protect motors and machines in original equipment and provide options for maintenance personnel. Designs in special materials are available especially for wind turbines.

Where blades meet hubs also call for a seal. These junctions must all be weather tight yet allow rotation. Several designs in a range of materials are well suited for these applications. For instance, a form-pressed continuous ring also works well on the large dimensions encountered in wind turbines. Its good performance is due in part to a rust-proof tension spring which presses permanently against the seal rim. The seal comes in 200 to 1,700-mm diameters.

Profile rings for large seal areas are batch vulcanized for advantages over glued rings. Profile rings come in standard materials and others. The rings are said to ensure long working lives, low torques, high resistance, and security against press out. They are well suited for sealing pivoting large diameter bearings found on pitch and yaw mechanisms.

One of the more unusual sealing tasks on turbines deals with offshore foundations. Wind-power stations there are built using structures such as monopiles and tripods. How the turbine is installed depends on soil properties, water depth, and contractor experience. A monopile (single leg) provides an application example. After the pile is driven into the sea bed, its top will extend up to about 16-ft below the water surface. A transition piece, about 80-ft high, is lowered over the top of the pile and will clear the water by some 40 ft. The space between the pile and transition piece is sealed by an inflatable grout seal, much like an inner tube. This seal inflates with a few psi to close the substantial gap between monopole and extension. Grout is then pumped into the gap above the grout seal to produce a strong joint. A floating crane then installs the tower to the extension and the turbine.

A super seal for temperature extremes

Isolast J9876, a recent perfluoroelastomer, provides the most comprehensive media resistance at elevated temperatures of any perfluoroelastomer on the market, according to its developer. Seals in this material, from Trelleborg Sealing Solutions, extend their life in aggressive, high-temperature environments at an optimized cost-to-performance ratio. Equipment suppliers and process managers benefit from the advantages of a single material: reduced stocking, simplified procurement and prevention of early failure due to fitment of a seal in the incorrect compound.

“This new material represents the next generation of Isolast, our proprietary perfluoroelastomer,” says Muzaffer Sheikh, Isolast Product Manager. “Isolast provides a balance between outstanding thermal performance and compatibility to most all media. Its flexibility means equipment manufacturers and processors can select it for all their demanding sealing needs.”

Isolast J9876 has a continuous operating temperature range from +19 to +527F (-7 to 275C) with occasional peaks to 599F (315C). The material’s media resistance at high temperatures means excellent long-term physical property retention. The compound comes in any size O-ring, gasket, molded part, or rubber-to-metal bonded components, including door and gate seals.

Many seals for turbine tasks

There is a lot of sealing work in a nacelle. Hydraulic equipment, of course, needs them along with areas such as where blades meet hubs. These must all be weather tight yet allow rotation. Simrit Americas, Plymouth, Mich., manufacturers several designs in a range of materials for these applications. For instance:

Simmerring seals meet and exceed DIN 3760 standards for seal function and lifespan. Available in over 3,500 different dimensions, the seals protect motors and machines in original equipment and provide options for maintenance personnel. Designs in NBR and FKM materials are available especially for wind turbines. The seals can also be equipped with a leakage sensor.

Simmerring Radiamatic, a form-pressed continuous ring, works well on the large dimensions encountered in wind turbines in part due to rust-proof tension spring which presses permanently against the seal rim. The seal comes in 200 to 1,700-mm diameters.

Profile rings, large seal areas, are batch vulcanized for advantages over glued rings. Profile rings are available in standard materials, such as NBR, CR, and others. Profile rings ensure long working lives, low torques, high resistance, and security against press out. Profiles are well suited for sealing pivoting bearings.

Accumulators store hydraulic fluid at pressure for a constant, uninterrupted supply for hydraulic blade positioning and braking. To ensure such functions, Simmerring accumulators are adapted to individual applications. Users also benefit from lower costs of smaller pumps.

Vibrations in wind power plants cause increased wear on equipment and noise. The company offers a large selection of conical mounts, ultra bushes, layered springs, circular mounts, Mo-mounts and V-mounts for wind applications. Conical mounts work on generators in wind turbines with high damping effect on vertical vibrations, while absorbing vertical forces and insulating structure-borne noise.

Adhesives, sealants, and more for wind-turbine manufacturing

To support growth in the wind energy market, Henkel Corp., Rocky Hill, Conn., has developed a range of products for manufacturing and maintaining wind turbines. These include structural adhesives, mold-release agents, machinery adhesives, sealants, grouts, cleaners, surface treatments, tapes, and metalworking materials. Company wind-turbine products, such as Loctite, Teroson, Bonderite, Frekote, Multan, and P3, are used for blade and nacelle manufacturing, tower assembly, hub, bearing and gearbox assembly, field installation, and maintenance.

The company formulated the first Germanischer Lloyd-certified two-component structural polyurethane adhesive, as well as MMA adhesives for blade bonding and repair. These adhesives cure at room temperature and provide crack-resistant, long-lasting bonds on composites and metals. Loctite machinery adhesives such as threadlockers, thread sealants, retaining compounds, and gasketing materials, prevent fasteners from loosening, seal pipes and flanges, and bond cylindrical components. Applications include blades, gearboxes, hubs, brakes, and pitch and yaw bearings.

In addition, says the company, butyl tapes and sealants are used to vacuum form composite laminates, while Frekote, semi-permanent mold release agents, are used when molding large-scale composite components such as blades and nacelles. For waterproofing blades, nacelles and towers, and general turbine maintenance, Henkel sealants offer flexibility, primerless adhesion, short cure periods, and temperature resistance. For tower installation, Loctite high-strength grouts withstand high-torque loading and are available in grades for deep pours.

Furthermore, says Henkel, its Multan and P3 metalworking products are used during machining, forging and general forming processes and for short-term corrosion protection. Bonderite and Alodine metal surface pretreatment materials protect towers, hubs, and gearbox components from corrosion. Henkel cleaners are environmentally responsible formulations for cleaning during manufacturing and on-site maintenance of blades, nacelles, and towers.