Chris McKerihen / EIT Design Engineer /Rad Torque Systems / www.radtorque.com
It’s necessary to re-torque a wind turbine’s bolts at OEM prescribed intervals because bolts occasionally work themselves loose. Several hundred of them may need checking on a typical utility-scale turbine. Recent electric wrenches provide a more efficient tool for that task. One version from our company comes with several advantages over other torquing techniques.
The E-RAD series of wrenches provides a fast, reliable, and safe way for installing and removing heavy duty fasteners. The company adds that the tools are lighter, faster, stronger, and more accurate than conventional bolting tools. For instance, compared to hydraulic wrenches, the electric tool significantly decreases tightening times through the delivery of smooth and continuous torque. The relatively low weight of the tool comes in part from its patented planetary gearbox combined with an ergonomic design. The two features provide the highest power-to-weight ratio, controlled bolting system on the market.
Tests show that the servo control shuts off at required torque with an accuracy of ±3% and a repeatability of ±2%. Conventional methods often determine bolt torque by monitoring a pressure gauge, which makes accuracy unreliable.
Tool operation has been simplified in the E-RAD. A user would digitally enter a required torque and angle (rotation the socket head must turn after reaching a particular torque value) and press the trigger. The tool runs and shuts off at the required setting. An LED light on the wrench provides an indicator telling users the tool has met the required torque.
A few electric wrench specs
How does it work? The electric wrench uses an ac servo, brushless motor while an internal CPU stores a torque-verses-current calibration curve. When the motor reaches a required torque – identified by electrical current – controls shut the motor off. To control the application of the additional angle, the wrench’s ac servo motor drives an encoder which tracks and records 4,096 points on a 360 degree rotation of the motor drive.
Each electric wrench from the company is equipped with a controller case to provide the user-machine interface. A touch screen allows for adjustments to torque and angle. Digital-data collection allows for full traceability of each torque sequence which also creates computer reports.