As any wind farm owner and operator can attest, maintenance plays an integral part in keeping your assets up and running. Having the proper tool on hand for the job can go a long way to lowering inefficiency while improving safety.
Movement and vibration can create heavy stress on a wind turbine, which means technicians must frequently venture up-tower to recalibrate and retighten bolts. However, given the physical dimensions of the nacelle, technicians must perform these tasks in tight spaces.
Because of the rigorous physical demands faced by technicians, not having the proper tool can slow down maintenance, or, more troubling, may increase the chances of a task being performed with a tool that is less than optimal.
“Technicians are often wedging tools into tight spaces in the nacelle,” according to Jason Junkers, director of marketing at Hytorc Industrial Bolting Systems, adding that wind turbine manufacturers – depending on the maker – each have some type of difficult-to-reach application, whether it be GE’s yaw drive bolts or the gearbox suspension bolts on a Siemens machine.
“But it doesn’t have to be that way,” explains Junkers. “There’s always a way to make maintenance simpler, safer and more efficient.”
Given that the average wind turbine encompasses approximately 1,500 bolts on a wind turbine, several manufacturers have come out with torque-related tools, such as wrenches, to control accuracy and ensure proper tightness – making the technician’s job easier in the process.
Adding a twist on a commonly used bolting tool, Hytorc introduced an air-powered, impact wrench, which alleviates the problem of working in tight spaces. Known as the Thrill Gun, it works similarly to the air guns used by NASCAR pit crews.
The tool combines the speed of an impact wrench and the power and accuracy of a hydraulic torque wrench.
After the nut is driven down completely, the tool can be flipped into torque mode, ensuring the final torque is properly tightened, according to Junkers.
Columbus, Ohio-based Proto Industrial Tools, a division of Stanley Black & Decker, has designed a torque multiplier to help tighten the bolts on large fasteners that hold the gearbox together and ensure correct usage, explains Stanley Black & Decker’s Jon Bigden, senior product manager of wrenches and torque.
SPX Technologies, an Owatonna, Minn.-based provider of torque and tensioning tools, has introduced a compact hydraulic pump, called the PE39, that eases the weight of the machine that powers the torque wrenches needed for up-tower maintenance.
As its name implies, the PE39 weighs 39 pounds – nearly half the weight of a traditional hydraulic pump, which can weigh as much as 75 pounds. In the past, technicians often needed to build a make-shift pulley system to hoist the cumbersome pump up-tower.
Steve C. Jones, product applications specialist at SPX Power Team, explains that the lighter weight makes up-tower operations and maintenance applications much easier. The pump can be operated in either the horizontal or vertical position, allowing for access to constrained areas of the nacelle. The universal motor of the PE39 will operate up to +/-20% of normal voltage.
Not to be outdone, Hytorc introduced the Flash Gun – a torque gun that operates without a hydraulic pump.
And just as wind turbines have advanced, so too have the tools and equipment used to service them.
“Today’s tools are precision instruments – and need to be cared for as such,” instructs Bigden, who adds that safety training must not be overlooked.
“Having your people trained correctly is absolutely a cost savings. Safety is not only the right thing to do for your business. It is the right thing to do for your employees,” he explains, especially when the wind industry’s heavy industrial loads and components are factored in.
Though it seems like a no-brainer, even the most seasoned technicians can benefit from continual training, particularly when it comes to using new tools or simply the latest version.
For example, if a technician overtorques a fastener, he can increase more stress on a bolt. Or if a technician incorrectly releases a torque multiplier, the force created could result in spring-back for the technician.
As wind turbines advanced, so too have the tools needed to service the units.
Torque or tensioning?
With the plethora of torque-related tools in the marketplace, there is a growing debate about the proper way to ensure bolt tightness during wind farm construction. Increasingly, some are saying that tensioning – and tension-related products – should also be considered.
The issue stems from the variability in torque and tension specifications supplied by original equipment manufacturers. Wind turbines’ bolted joints are typically designed by mechanical and electrical engineers, and these designs are dictated by a German-based standard known as VDI 2230, which determines joint stress thresholds.
To properly calibrate torque and tension, installers have to apply mathematical equations, such as the tightening factor, to ensure accuracy. The tightening factor is defined as the ratio of the maximum tension divided by the minimum tension, and it reflects the accuracy of the tightening method.
VDI 2230 accounts for the tension scatter, or variation from the target, caused by the tightening technique via the tightening factor. Simply put, the higher the tightening factor, the more scatter you get, according to Barnaby Myhrum, applications engineer at Bellows Falls, Vt.-based Applied Bolting Technology. “The more scatter, the larger the bolts needed to increase safety.”
The VDI 2230 standard recommends a tightening factor of 1.6 for torque wrenches.
“The decision whether to torque or tension is determined by the manufacturer of the turbine and is spelled out in [the manufacturer’s] specifications,” Jones says. “Some manufacturers require the use of tensioning for the entire structure, while others specify torque as the controlled bolting method for tower sections, blades and other areas of the turbine. Typically, foundation base bolts are tensioned.”
Other products, such as direct tension indicators (DTIs), feature lower tightening factors, which can play a crucial role in the dimensioning of bolted joint connections.
Applied Bolting Technology sells a DTI called the Squirter. As its name indicates, when a bolt is properly tightened, a small amount of orange silicone appears from under the product’s squirt locations. DTIs are used in structures to verify tension in each bolt. The Squirter is certified by Germanischer Lloyd to guarantee target tensions +/-10, equating to a tightening factor of 1.2. w
Wind Turbine Tools Step Up In Class
By Mark Del Franco
Modern tool technology makes wind farm maintenance and operations simpler, safer, and more efficient.
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