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Optimization of Re-Torque and Relaxation Parameters of the GUCP

[+] Author Affiliations
Ali P. Gordon, Brian Drilling, Kent Williams, Scott Hebert

University of Central Florida, Orlando, FL

Catherine C. Kammerer, Frank Baldwin

United Space Alliance, LLC, Cape Canaveral, FL

Paper No. PVP2011-57682, pp. 57-65; 9 pages
  • ASME 2011 Pressure Vessels and Piping Conference
  • Volume 2: Computer Technology and Bolted Joints
  • Baltimore, Maryland, USA, July 17–21, 2011
  • Conference Sponsors: Pressure Vessels and Piping Division
  • ISBN: 978-0-7918-4452-6
  • Copyright © 2011 by ASME


Self-loosening of bolts in non-permanent connections has been the subject of a myriad of investigations; however, because the vast majority of these studies focused on applications with long-term service conditions involving creep and/or cyclic (working or vibratory) loading, there are no analytical techniques that have been developed to address the load decay behavior of bolted assemblies with gaskets under a primary followed up by a secondary torque. The Ground Umbilical Carrier Plate (GUCP) includes a gasketed ASME-type flange assembly that transfers pressurized, cryogenic hydrogen from the Space Transportation System (STS). Although the threaded stud material is nominally elastic under service conditions, the gasket material, a polytetrafluorethylene (PTFE) matrix filled with 25% chopped glass fibers, undergoes viscous, strain hardening deformation. The consequence of over-torquing the assembly is yielding the stud. Alternatively, the consequence of under-torquing is premature loosening and subsequent fuel leakage. As such, identifying the interactions between assembly configuration, initial torque, etc. to relaxation behavior of the assembly has been identified as a means to reduce the dwell period (the time between initial torque and re-torque). Research is carried out to identify the optimal torque parameters that confer a minimal dwell period. This article documents the Gasket Relaxation and Re-Torque Optimization (GRRO) program used to modify procedures employed when connecting the flanges to the fuel tank of the Space Transportation System prior to a launch.

Copyright © 2011 by ASME



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