Evaluation of design and fabrication methods for underwater welding in open-lake environment

The flexible pad concept and underwater fillet welds circumvent the problem of degraded mechanical properties associated with underwater welded connections. The connection pad allows joint flexure, diminishing maximum stresses prior to reaching the underwater welds and improving energy absorption of the tubular joint. Air welds, at maximum stress locations withstand more of the load energy, and reduce the loads that actually reach the wet welds, placed at locations of less stress. The design evaluation conclusions obtained by computer aided engineering design system (CAEDS) analysis were subjected to field testing. Finite element method calculations of stress distribution and the strain energy absorbed in the flexible connection pad are considered. The modelling of two design variables, pad geometry and weld position, provided optimum connection pad designs. This evaluation of this field test compares performance characteristics between field environment wet welds and laboratory wet welds. This project compares impact tests; static load tests; hardness analyses; macro- and micro-structure studies. The operational characteristics of underwater welding on tubular tee flexible pad connections in the field versus laboratory conditions are also compared. This field testing repeated methodology developed during previous laboratory testing. Results and conclusions are similar. (A)