Weld fittings (also called "welding fittings") are attached by welding. In most cases weld fittings are not fabricated by welding. Instead, they are usually formed by cutting short pieces from pipe, so it would be incorrect to call them "welded" fittings.
Since they first became available in the United States around 1930, weld fittings have continuously gained acceptance as the most effective and economical pipe joining method for many industrial applications. In many industries welded piping systems have replaced their predecessors -- the threaded and/or flanged designs.
This is an updated version of the product training course introduced by Supply House Times in 1979, authored by Don Arnold.