These tradespersons find employment in the construction, shipbuilding, mining and oil and gas industry. Boilermakers trained in structural fabrication may be involved in fitting, assembling and joining aluminium and steel in the construction or repair of towers, bridges, structural supports, girders and ships. Welder - First Class who constructs or repairs metal products by joining parts either manually (using a variety of welding methods including electric arc, MIG and TIG welding or oxy-acetylene welding) or by machine. These parts are used to complete structures and equipment (e.g. ships, bridges, pipelines, vehicles and domestic appliances). First class welders may specialise as special class welders, welding a range of metals (e.g. mild steel, stainless steel, cast iron, aluminium, copper, brass, diecast metal and magnesium). After further assessment, first class welders may specialise as pressure welders, assembling, welding and repairing pressure vessels such as storage tanks, pipelines and gas cylinders to special test standards.