Lifting-eyes, known as pad eyes, were welded into the top corners of a module for lifting the module on to an offshore platform. Each pad eye consisted basically of a 50mm thick vertical plate measuring approximately 2m x 1m which contained a hole reinforced by rings welded to each side of the plate. This plate was welded to a 35mm thick base plate 0.5m wide and also to horizontal and vertical stiffeners.
Four pad eyes were inserted into the top corners of the module and welded to the main girders. Welding of the pad eyes, during sub-assembly and on the module, was carried out with basic electrodes baked at 400°C and stored at150°C and the joint regions were preheated to 100°C in accordance with the recommendations of BS 5235.
The steel was to DIN St-52-3M (analysis 0.18%C, 1.49%Mn, 0.43%Si, 0.017%S, 0.027%P). The steel had been aluminium treated during production. Magnetic particle inspection and ultrasonic examination of the pad eyes before they were inserted in the module showed that the welds met the requirements of ASME VIII and the pad eyes were then stress-relieved in the furnace.
Final inspection was carried out after all welding on the module had been completed and some toe cracks were found in the cruciform joints in two of the pad eyes. In addition to this there were indications of lamellar tearing in the base plates of each pad eye under the full penetration T butt welds.
Fortunately the toe cracks were shallow and could be ground out and repaired even though the access for the welder was somewhat restricted. However the only access for the repair of the lamellar tears was from the inside of the module. The base plate in each case had to be air carbon arc gouged and ground in the overhead position to reveal the defective areas which were then checked by dye penetrant examination. Welding repairs were then carried out with the preheat of the joint regions increased to 150°C to compensate for the lower energy input when welding in the overhead position.
Inspection of the repairs was carried out four days after completion of welding and the success of the operation was largely due to the skill of the welders working in the overhead position with restricted access and preheat.