During a recent major inspection campaign, significant areas of buckling were discovered across several primary bulkheads of an FPSO hull. The traditional 'string line' method of measuring the deflections was extremely time consuming and it was very difficult to provide a consistent baseline for the measurements. In addition hull structures are rarely completely flat and Class limits for buckling of this type are not clearly defined.
Surface mapping using laser scanning was proposed, however the laser scanning provider was not familiar with how to baseline and process the data, or what tolerances to use in order to provide meaningful results to compare against Class buckling limits. Initial attempts resulted in overly conservative assessment and excessive repair areas.