Lisbon's Vasco da Gama Bridge is the longest in Europe, spanning a total distance of 10.7 miles. Taking three years to complete, the bridge opened for traffic in 1998 to celebrate the 500th anniversary of Vasco da Dama's discovery of the maritime route from Europe to India.
The arc temperature may be upto 20,000 K. Although TIG welding produces the highest quality welds, it is a slow and expensive process. Metal inert gas welding process (MIG) is economical with consumable electrode fed at a predetermined rate. Plasma arc welding (PAW) has made substantial progress in utilising the high heat energy of an ionised gas stream.
Gas welding is accomplished by heating the ends or edges of metal parts to a molten state with a high temperature flame. The oxy-acetylene flame, with a temperature of approximately 6,300 Â°Fahrenheit (F), is produced with a torch burning acetylene and mixing it with pure oxygen. Hydrogen may be used in place of acetylene for aluminum welding, but the heat output is reduced to about 4,800 Â°F. Gas welding was the method most commonly used in production on aircraft materials under 3â16-inch in thickness until the mid 1950s, when it was replaced by electric welding for economic (not engineering) reasons.