The Problem with Welding

In the Norwegian sector of the North Sea, 300 km southwest of Stavanger, lies the Ekofisk oil field, one of Europe's most productive offshore developments. On March 27th, 1980, workers had just finished their shift on the Edda production platform, one of the field's many installations, and returned to the Alexander L. Kielland, a semi-submersible rig serving as their

floating accommodation. At 6:30 p.m. that evening, in rough seas, one of the accommodation platform's horizontal bracing members suddenly fractured. The load it carried was redistributed to adjacent members, causing them to fail and one of the five primary columns supporting the structure to break away. 20 minutes later, the unstable platform capsized and sank below the water.

123 of the 212 workers on board lost their lives. It remains the deadliest industrial disaster in Norway's history. The investigation that followed traced the loss of the rig to a surprising culprit, a fillet weld used to attach a sensor to the structural member that failed. To understand how a single weld could bring down a 10,000 ton offshore

platform, we need to dive into how welding works, the different welding processes, and the major problem with welds, the weaknesses that can hide within them. The idea behind welding is simple. It's the joining of two pieces of metal by melting them together at the joint, usually with some filler metal added to strengthen the bond. When everything

cools, you're left with a single fused piece. It's that melting of the base metals that sets welding apart from processes like brazing or soldering, where the filler melts, but the base metals stay solid. Because the base metals melt together when welding, the joint materials need to be compatible, capable of forming a sound joint when fused together.