Underwater wet welding is presently accepted only for structural repairs to offshore facilities. The application of underwater wet welding to sub-sea pipelines and risers has been limited due to its perceived quality deficiencies compared to surface welds. These include the potential for excessive porosity, the risk of hydrogen cracking that results from the liberation of hydrogen in the welding arc and the accelerated weld cooling rates produced by the presence of the water. The present method for offshore tie-ins and repairs involves the use of either mechanical clamps, hyperbaric welding, or...
Underwater wet welding is presently accepted only for structural repairs to offshore facilities. The application of underwater wet welding to sub-sea pipelines and risers has been limited due to its perceived quality deficiencies compared to surface welds. These include the potential for excessive porosity, the risk of hydrogen cracking that results from the liberation of hydrogen in the welding arc and the accelerated weld cooling rates produced by the presence of the water. The present method for offshore tie-ins and repairs involves the use of either mechanical clamps, hyperbaric welding, or raising the pipeline to the surface. The underwater wet welding techniques currently used are not capable of producing welds that meet the workmanship based quality requirements of API 1104 for land pipelines, but may be suitable for sub-sea pipelines and risers based on a fitness-for-service basis. If it could be shown that underwater wet welding is capable of producing adequate quality welds, or if the deficiencies could be ercome by the use of for example, scalloped sleeves, a substantial cost savings could be realized.