6/4/2012 9:11:00 AM
NEWS BRIEFS
Battling Bolt Fatigue on Wind Turbines
Calling wind turbines “fatigue machines” on par with helicopters, Windpower Engineering & Development magazine is tracking better ways for engineers to measure tension and prevent corrosion.
One solution is a direct-tension indicator that squirts.
“It’s a washer that tells when a target tension had been reached in a bolt, regardless of the applied torque,” writes Seven Bushong of Windpower. “When the bumps on the washer sufficiently compress, a brightly colored silicone squirts from cavities under the bumps.”
Other trends reportedly deal with keeping bolts tight, including the use of a locking washer to eliminate fastener failure.
“The device consists of two preassembled washer-shaped pieces that have inclined cams on one side and a series of radial ridges on the other,” Windpower quotes a spokesman for a locking disc manufacturer. “The cam sides are placed between the nut and joint material.”
In addition, Bushong writes about replacing conventional high-strength friction-grip bolts with tension-control versions that reduce installation time when installed with an electric shear wrench.
“Guaranteed tension and a visual inspection eliminates the likelihood of operator error and ensures engineers that connections are tightened according to specifications,” Bushong writes.
Lighter and smarter wrenches are another bolting trend. In an industry full of hydraulic wrenches and bolt pullers, electric wrenches are attracting attention in wind energy because the margin for error is a lot less with an electric wrench; the tools can be “locked” to a particular torque value, enabling them to perform with ±3% accuracy.
As accountability increases, more wind-turbine manufacturers require proof that each bolt has been installed and maintained at the appropriate torque specs, Windpower explains.
“Recent electric torque wrenches allow collecting such data,” writes Bushong. “On-board data loggers report how many bolts have been torqued along with failed torques and over torques.”
A few electric torque wrenches let users tighten bolts to a torque or an angle. ©2012 GlobalFastenerNews.com
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