Lay out, position, and secure parts and assemblies according to specifications, using straightedge, combination square, calipers, and ruler.  Welds components and assemblies, using shielded metal arc welding (SMAW), or gas metal arc welding (GMAW,) in flat, vertical, or overhead positions.  Installs and repairs equipment, such as pipes, valves, floors, and tank linings.  Observes tests on welded surfaces such as hydrostatic, x-ray, and dimension tolerance to evaluate weld quality and conformance to specifications. Removes rough spots from work piece and prepares weld joint, using portable grinder, hand file, or scraper.