Local stress analysis of tailing lugs in a vertical pressure vessel

During the process of erecting a vertical pressure vessel from a horizontal to vertical orientation (0 degrees to 90 degrees) using tailing lugs, it is necessary to use a tailing lug with low local stress around the lug-shell attachment to prevent damage to the vessel shell during the lifting process. Two methods of local stress analysis, WRC-537 bulletin and FEA using ASME BPVC Section-VIII Division-2 are studied and evaluated in this paper. The WRC-537 method, which is known for being conservative, produced higher stress values compared to the FEA solution. This paper also examined the impact of various dimensional parameters related to tailing lug size and shape on local stress around the lug-shell attachment. In cases where single lug configurations fail to achieve the minimum required local stress values, paired lug configurations are purposed as a possible alternative solution towards reduced local stress. This paper also discusses the benefits of paired lug configurations over single lug configurations regarding the lower localized stress, especially for vessels with thin shells and large diameters. Paired lug configurations are found to have about four times lower localized stress compared to single lug configurations. When comparing rectangular and circular attachments, this study has found that rectangular attachments tend to have lower localized stress.