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Prevailing torque locking is a technique used to provide secondary locking in threaded fasteners to ensure that these fasteners remain securely tightened over time, even in the presence of vibrations, thermal expansion, and other dynamic loads.

The aerospace industry in particular has widely adopted this method in their assembly process for several reasons:

  • Safety: In aerospace applications, there is no room for error when it comes to the reliability of fasteners. Failure of a fastener due to loosening can result in catastrophic consequences, so it is critical that fasteners remain securely tightened over the life of the aircraft or spacecraft.
  • Maintenance: In aerospace, regular maintenance and inspections are critical to ensuring the safe operation of the aircraft or spacecraft. Prevailing torque locking reduces the need for frequent re-tightening or inspection of fasteners, which can save time and reduce maintenance costs.
  • Environmental factors: Aerospace applications often involve extreme environmental factors, such as high temperatures, humidity, and exposure to chemicals. Prevailing torque locking can help ensure that fasteners remain secure in these harsh environments, reducing the risk of failure due to environmental factors.

The prevailing torque locking mechanism can be achieved through various methods, including nylon inserts, deformed threads, anaerobic adhesives, or friction coatings. When the fastener is initially installed, the locking mechanism engages and creates a strong, secure connection between the two components. The locking mechanism prevents the fastener from loosening due to vibrations or other external forces, ensuring that the joint remains secure over time.

Implementation of prevailing torque locking in aerospace follows well-defined standards and the use of an Industry 4.0 compliant electric screwdriver is a must.

Because there will often be variations in amount of prevailing torque generated by these methods from joint to joint, the use of a tool that can provide a smart compensation strategy becomes crucial to avoid tightening to an insufficient clamp load.

One such tool is Kolver’s K-DUCER line of electric screwdrivers with torque and angle control. The K-DUCER has functions that dynamically detect the amount of torque needed to overcome the resistance of the locking mechanism and automatically add it to the target torque and achieve the desired clamp load. 
This ensures that the preload applied to the joint is consistent for each fastener, even when faced with variable levels of prevailing torque and friction between each joint.
The torque graph of the fastening process is shown in real-time and every aspect of it is securely traced and stored.
While especially common in the aerospace industry, prevailing torque locking can be used in any applications where safety and reliability are critical, for instance in parts of the automotive world such as in engine and structural components.
Using this method, combined with a smart screwdriver like Kolver’s K-DUCER, ensures that critical components remain securely fastened, even in harsh operating conditions and under continuous stress, and that any errors during the assembly process are immediately detected and resolved.

If you need help implementing full transparency and traceability in your assembly operations, contact any of our specialists and we will be happy to help!