Keeping Up with the Wind Industry’s Need for Speed in Controlled Bolting Applications

Falling Prices and Rising Demand

The abrupt crash of crude oil prices, which began in the summer of 2014, has had an enduring effect on oil and gas prices. Since the crash, industry stakeholders have been forced to become more efficient in an effort to survive in an era where crude oil prices have struggled to surpass the $50-per-barrel mark.

While stories of the rise, fall and slow recovery of oil prices have dominated the headlines, the cost of wind energy has, albeit more quietly, also undergone a transformation. Over the past six years, the cost of wind energy in markets like the United States has dropped by over 65 percent. And while wind energy still represents only a modest share of overall energy production, it has grown, and by all accounts will continue to grow at a phenomenal rate.

Annual installations topped 63 GW in 2015, up 17 percent over the prior year. Conservative estimates expect this trend to continue, achieving a growth factor of 3 to 5 times by 2030.

                  Global Wind Energy Outlook 2016, Global Wind Energy Council, October 2016, p.19

A number of factors have played a key role in the drop of wind energy costs, and the popularity of wind energy. Foremost among these are efficiency gains. Increasingly taller towers with larger turbines, and rotors with larger diameters are achieving a greater rated capacity than ever before. This trend is expected to continue, as 7 and 8 MW machines give way to even larger ones with even more output.

MHI Vestas V164 8 MW feature 80-meter blades

Adwen AD-180 8 MW with 88.4-meter blades

The Bigger they are...

From their foundations to their nacelles, wind towers are bolted together. These bolts are constantly subjected to stress originating from several causes including vibration, fatigue cycles (caused by the constant rocking back and forth of the tower), and inclement weather. Consequently, applying a suitable controlled bolting method to achieve the required preload of the fasteners is paramount to the construction and maintenance of any wind tower. As wind towers get larger, the need for proper installation and maintenance becomes increasingly vital. Applied variations of only 10 percent outside of the specifications may result in vibrationinduced failure, if in a critical part of the structure.

To address this issue, OEMs have long specified highly accurate controlled bolting solutions for the installation and maintenance of wind towers. Hydraulic bolt tensioners are often used on foundations, while torque wrenches are typically used when bolting tower sections, blades, and various bolting applications within the nacelle. Standard solutions for these types of applications have long included hydraulic torque wrenches, due to their high degree of accuracy (up to 3 percent), and the high torque output they are able to achieve with a very small footprint.

Larger towers with greater output mean more bolts, and an even greater risk of improper fastening. Installation and maintenance contractors have looked to controlled bolting solutions providers for fastening systems that provide not only accuracy, but also increased productivity and fastening accountability.

The Smart Solution

In response to these developments, Enerpac, which produces manual and pneumatic torque wrenches, as well as hydraulic torque and bolt tensioning systems, recently introduced the ETW-Series Electric Torque Wrench to its arsenal of controlled bolting solutions. The ETW-Series Electric Torque Wrench was designed to offer productivity, accuracy and traceability, but also to be very simple to use.

The ETW (pictured at right) helps simplify and automate complex jobs, through the creation of automatic presets. The user inputs the desired torque, or torque and angle specifications, into the control box. These are then applied to the number of fasteners required for the job. For simpler jobs, torque values may be input directly into the gear control panel of the wrench, which also enables the operator to monitor and manage the fastening process, to ensure that each fastening is made to specification.

Once the input torque or specified torque and angle is achieved, the tool stalls, and a pass/fail indicator verifies that it is ready to move onto the next fastener. Records of each fastening, which are often required as part of a standard maintenance protocol, are automatically created during the fastening process. Once the job is complete, the operator can view a record of the job directly on the control box touch screen, or export the record to a computer via a USB port.

Overcoming Obstacles

One of the challenges encountered in the development of the ETW was how to balance the need for productivity with the high degree of accuracy required by the wind industry. High productivity means higher RPMs (rotations per minute), which in turn may cause excess torque if not properly controlled. Added to this is the fact that this plays out very differently in pre-tightened joints vs. soft joints.

The answer to this dilemma was the development of a patented algorithm, which actively monitors and controls the velocity of the rotation throughout the fastening process. This smart technology provides consistently accurate fastening both during installation, and when conducting torque accuracy checks.

The next challenge was how to take this sophisticated system and make it accessible to the average user. A number of factors have contributed to the creation of a workforce with minimal training and a high degree of turnover. To address this issue, the Enerpac engineering team focused on creating a PC-HMI (PC-Human-Machine Interface) that functions like popular mobile devices such as tablets or smartphones.

The result was a servo motor control box with a 7-inch interactive touch screen, and programming which allows the average user to easily navigate through the various features. The goal was to create a system which was so intuitive that the average user could be taught to use all the key features within minutes, and with only minimal training.

The Outlook

The average technician now has access to a sophisticated yet simple wind fastening solution, which provides accuracy, productivity and traceability. With the wind industry forecasted to more than triple in size within the next 15 years, and a workforce shortage anticipated over the same time period, this system’s value is sure to resonate with wind technicians and OEMs alike.



"Wind Turbine Technicians." U.S. Bureau of Labor Statistics. U.S. Department of Labor, n.d. Web.
Lamb, Shawn. "The Coming Shortage of Qualified Wind Techs." Wind Systems Magazine. n.d.
"Global Wind Energy Outlook 2016." Global Wind Energy Council. Web.