Selects type and size of pipe or other related materials and equipment according to specifications. Selects equipment and plans layouts, assembly, and welding, applying knowledge of geometry, physical properties of metal machining, weld shrinkage and welding techniques. May be required to use Gas-Metal Arc, Flux-Cored Arc, Gas-Tungsten Arc, Submerged Arc, or Shielded Metal Arc welding processes.  Lays out, positions, aligns and fits components together in various body positions. Bolts, clamps and welds together metal components of products such as piping systems, plate, pipe and tube or structural shapes, using arc and arc gas welding equipment. May weld in flat, horizontal, vertical, or overhead position. May tack weld assemblies together.  Connects cable from welding unit to obtain amperage, voltage, slope and pulse as specified by procedure or supervisor. Obtains specified electrode and inserts electrode into portable holder or threads consumable electrode wire through portable welding gun.