This paper discusses the prescribed requirements contained within the various ASME B31 Piping Codes and ASME B&PV Code, Section III that specifically address the need to recognize the restraint introduced by piping support friction. In addition, the requirement for the design of sliding supports (pipe shoes) and brackets to resist the forces due to friction in addition to the loads induced by bearing is also reviewed and discussed. As part of the required piping analysis, the questions surrounding the inclusion of the maximum coefficients of static friction and the impact of these often excessively large values on equipment nozzle loadings is reviewed in considerable detail, especially in light of the qualitative guidelines contained within WRC Bulletin 449. Included in the discussions of the considerations associated with the assumed restraint provided by support friction is the mathematical treatment of extrema (i.e., maxima and minima) with respect to calculated nozzle loads based upon the analyst’s choice of the largest published coefficients of static friction. Example problems taken from the authors’ decades of experience in the field are reviewed in light of the time dependent heat up and cooldown rates for the piping systems discussed herein. In most cases, the analyses show that not only is it highly improbable that the choice of only maximum values of coefficients of friction at each support will exist, but rather it is impossible that this often abusive practice by the unsuspecting analyst for the “worst case” frictional coefficients to exist simultaneously in a piping installation. Finally, recommendations for the considerations of the potential restraint induced by piping support friction in the rigorous piping analyses are tendered.
Nozzle Load Considerations and Misconceptions Introduced by Piping Support Friction
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Antaal, BS, & Williams, DK. "Nozzle Load Considerations and Misconceptions Introduced by Piping Support Friction." Proceedings of the ASME 2017 Pressure Vessels and Piping Conference. Volume 3B: Design and Analysis. Waikoloa, Hawaii, USA. July 16–20, 2017. V03BT03A041. ASME. https://doi.org/10.1115/PVP2017-65970
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