L51649 A Study of Processes for Welding Pipelines

The construction of a pipeline involves the joining, end to end, of a series of standard lengths of pipe together with other connections to the necessary valves, pumps, etc. Technically, when considered in isolation, this is a relatively simple joining operation and a number of processes can be used to perform it. When all of the production constraints are taken into consideration, however, the selection task becomes considerably more complex. Pipe diameter and wall thickness ranges are wide and new pipe materials are continuously becoming available. On land the terrain can vary from prairie to mountains and from swamps to urban surroundings. A significant proportion of pipe laying is also being done at sea in water depths which can exceed 3,300 feet (1000m). Regardless of all of these changing circumstances, one factor remains constant, a need to produce a technically acceptable pipeline at the lowest possible overall cost. This report reviews the development of welding processes in two main categories, Fusion Welding and Forge Welding. Non Destructive Testing (NDT) is also reviewed. Within each category, each process is considered separately in terms of process principles, general applications, application to pipeline welding, equipment for pipe welding, consumables, process tolerance and skill requirements, weld quality and inspection, process economics, limitations and future developments. Similar areas areconsidered in the section on NDT.