Fabrication
Fabrication, when used as an industrial term, applies to the fabricating pipes by cutting, grooving and welding components. Small businesses that specialize in metal are called fab shops.
Cutting
The raw material has to be cut to size. This is done with a variety of tools;Special band saws designed for cutting metal have hardened blades and a feed mechanism for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but with a steel cutting abrasive disk. Cutting torches can cut very large sections of steel with little effort.Burn tables are CNC cutting torches, usually natural gas powered. Plasma and Laser burn tables are also common.Welding
Welding is the main focus of pipe fabrication. The formed and machined parts will be assembled and tack welded into place then re-checked for accuracy. A fixture may be used to locate parts for welding if multiple weldments have been ordered.The welder then completes welding per the engineering drawings, if welding is detailed, or per his own judgment if no welding details are provided.
Special precautions may be needed to prevent warping of the weldment due to heat. These may include; welding in a staggered fashion, using a stout fixture, covering the weldment in sand during cooling, and straightening operations.
Straightening of warped steel weldments is done with an Oxy-acetylene torch and is somewhat of an art. Heat is selectively applied to the steel in a slow, linear sweep. The steel will have a net contraction, upon cooling, in the direction of the sweep. A highly skilled welder can remove significant warpage using this technique.
Steel weldments are occasionally annealed in a low temperature oven to relieve residual stresses.
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