A Critical Review of ASME BTH-1-2005 in the Design and Analysis of Vessel Lifting Lugs

Abstract

This paper presents a critical review of the newly published ASME BTH-1-2005, which is intended to be a companion to ASME B30.20, Below the Hook Lifting Devices, a safety standard. The very limited structural design criteria contained in the latter standard was previously addressed in the literature by the current author and was compared against the various national and international regulations, codes, and standards in regard to the presumed factors of safety inherent in the designs of vessel lifting lugs. Based upon the criteria previously outlined and addressed, the current American National Standard ASME BTH-1-2005 is critically reviewed and the commentary that is now incorporated in such is analyzed in an effort to determine the adequacy of the updates in meeting and exceeding the current regulations in both the United States and Canada. The statutory and provincial regulations in both the United States and the province of Alberta, Canada are also reviewed and discussed with respect to the too often utilized phrase “factor of safety” (FOS). The implied implications derived from the chosen FOS are also outlined. Exemplar lugs on vessels are defined and the finite element analyses and closed form Hertzian contact problem solutions are presented and interpreted in accordance with the new ASME BTH-1-2005 structural design criteria. These results are again highlighted against the very limited design information contained within ASME B30.20. A review of the author’s prior recommendations made to revise the ASME B30.20 Below the Hook Lifting Devices safety standard are presented and discussed in light of the examples and technical justification presented in the following paragraphs. Contact stresses that are well known to exist between a lifting pin and clevis type geometry are also discussed in light of the new structural design criteria contained within ASME BTH-1-2005. Additional recommendations are provided for the design and analysis of vessel lifting lugs in consideration of current regulations.