Ultimate capacity of pad eyes in lifting operations

Abstract

Lifting is an essential part of almost every offshore operation, which includes a variation of structures with different sizes, shapes and weights. To ensure safe lifting operations, lifting equipment must be utilized. Among these lifting equipment, pad eyes and shackles play a significant role. These pad eyes must have high safety, reliability and appropriate costs. To test and analyze the capacity of pad eyes, traditional checking methods, such as laboratory testing are usually used, which can be exhausting, time-consuming and somewhat expensive. Therefore, a simpler, equally precise, less time consuming and more cost effective would be a proper alternative solution. This alternative approach to the traditional checking methods would be the FE simulation software, Abaqus/CAE. The purpose of this thesis is to compare the FE simulation results of the capacity of the pad eyes, with the experimental and theoretical results of the pad eye capacity obtained from the previous study “Offshore Hook-up Project Management”[1].

To conduct the simulation analyses of the design load capacity of pad eyes, several tests had to be made. Theses tests included different pinhole sizes in the pad eyes, different strain directions of pad eye pinholes, and different loads that acted on the pad eyes. The purpose of this is to check the importance of following the requirements given in related standards. Each of the simulation tests that were carried out in two different cases. The first case was when the pad eye was without a plate, while the second was when the pad eye was firmly welded to a base plate. The purpose of this was to see how the addition of the plate to the pad eye affected the load capacity of the pad eyes.

The results that were obtained showed that the addition of the plate to the pad eyes increased the capacity of the pad eyes. They further showed that the larger the pinhole size, the less capacity the pad eye had, which indicates the importance of following standard’s requirements. It was also observed that a reduction of the load capacity was recognized for angled loading relative to the vertical loading case, even though theoretical capacities provide the same for both cases. Finally, when the results were compared, it revealed that some of the simulation results were close to the experimental and the theoretical results, while others were somewhat far from them. Some factors, including the uncertainty of material behavior, may have caused these deviations.