The American Petroleum Institute (API) sets specifications for welding procedures and qualifications for personnel employed on pipeline welding in its “Standard for Welding Pipelines and Related Facilities”
API Code 1104
Before production welding is started, a procedure specification must be established and qualified to demonstrate that welds having acceptable mechanical
properties and soundness will result from the procedure. The quality and properties of the weld are determined by destructive testing. When tensile tests are performed, the tensile strength of the weld, including the fusion zone, should be equal to or greater than the minimum specified tensile strength of the pipe material.
The API Standard 1104 does not include welding procedures for joining steel pipelines; however, the API 1104 Committee has collected and cataloged successfully used procedures, and the Committee Secretary provides them on request as guides for
those wishing to use them as a starting point for qualification.
These API Procedure Specifications are identified by the position of the pipe (horizontal or vertical), whether rolled during welding or maintained in a fixed position, and the range of diameter and wall thickness for which the procedure is considered suitable. These are basically suggestions which the skilled welder can use, with proper material and equipment, to gain qualification.
When API 1104is applied to any pipeline project, it is mandatory that the method used in making, testing and inspecting welded joints is in complete conformance with the requirements of the Standard. The fabricator is expected to provide details of the procedure which are to be used on each particular pipe size.
Historical Background
First Pipelines. Pipelines were used to transport natural gas long before Edwin Drake drilled his first oil well. Hollow logs were used for this purposed in Fredonia, New York, in 1821. By 1862, cast iron pipe was used on a 6.4-km (4-mile), 50 mm (2411.) line at
Titusville, Pennsylvania. Soon after, wrought iron pipe came into the picture, with its various lengths joined by screwed couplings.
A search followed to find a way to make a tighter and stronger joint than the screw-type coupling provided. Attempts were made to weld pipelines with the
oxyacetylene process; the first of these was an 18-km (1 1 -mile) line laid in 19 1 1 near Philadelphia. In 1914, a 55-km (34-mile) pipeline was constructed near Enid, Oklahoma, followed by a longer line in the bay area of San Francisco, which supplied gas for the 1915 Pan American Exposition.
However, the real breakthrough in welding came in 1922, when the Prairie Pipeline Company welded a 20-cm (8-in.) diameter, 225-km (140-mile) line carrying crude oil from Mexico to Jacksboro, Texas, using oxyacetylene welding. The advantages of welding over screwed couplings were clearly demonstrated when the final cost of the project was 35% less than it would have been if couplings had been used. The cost
of the weld, labor and material was only $2.00 for each joint.
Pipeline Builders. After the surveyor’s crew had identified the right-of-way, the “brush crew” came on the scene to clear away brush and trees. Then the trenching crew dug the trench for the pipeline. Sections of pipe were then dropped alongside the trench.
The line-up and tacking crew came ahead of the construction gang. Aided by a tractor and hoist, they placed the pipe lengths on ball-bearing dollies to permit rolling. At four points in the circumference of the pipe, the tack welder made a tack weld, joining as
many lengths of pipe as the contour of the land required. This long tack-welded section, lined up on the dollies, was left by the line-up and tacking crew for the “firing line” crew, the welders.
Several welders comprised the crew which completed the welding of the long tack-welded sections. Helpers turned the pipe with chain pipe wrenches, enabling the welders to weld at the top of the pipe, in the flat downward position.