Session: OAC-06-01 Continued Safe Operation of Existing Assets-1

Paper Number: 122685

122685 - Bolt Load Relaxation as a Result of Elevated Temperature, Specialty Washers and Pre-Loading Methods 

Specialty washers like wedge-lock and ASTM F3394 washers are commonly used in bolted joints to prevent loosening and minimize the risk of load loss. They can also serve as a stable base for applied torque and help prevent the back nut from turning during preloading. These washers achieve this through high friction patches on their bearing faces. The effectiveness of these friction patches in preventing loosening has been demonstrated in the DIN-25201-4 transverse shear vibration test.

At the 2022 PVP conference, a study titled "Effects of Washer Knurling on High Temperature Bolt Load Relaxation" examined how these features impact bolt relaxation after exposure to high temperatures. This new study builds on the original research, incorporating additional controls to account for potential side load influences during the preloading process. The relaxation study involved subjecting ASTM A193 Grade B16 bolts to a stress of 60ksi and exposing them to 750°F for 336 hours. The results showed that washers with friction patches experienced slightly less relaxation compared to the control hardware under these test conditions. In this study, preloading for the control hardware was done using a reaction arm, while the test hardware was preloaded with a reaction washer. This new study repeats the same loading conditions, but with added controls to eliminate potential variations in preloading methods.

Presenting Author: Michael Dolan HYTORC Corporation

Presenting Author Biography: Michael Dolan is an industrial bolting professional with over 2 decades of design and field experience. Mike has contributed innovations to the process of nuclear reactor pressure vessel fastening that are being utilized throughout the world today. Mike is the Chief Engineer of Fasteners at HYTORC Corporation in the USA. Mike has invented several specialized fastening products and is named on many of HYTORC's patents. These fastening products are reshaping the way industrial connections are being made today. In this role, he is engaged in helping industrial OEM's, EPC's and asset owners to optimize the process of producing high quality and convenient industrial size threaded connections. Mike holds a mechanical engineering degree from West Virginia University.

Authors:

Michael Dolan HYTORC Corporation
Emmanuel Derillac HYTORC Corporation