It's easy to get lazy when you think about the welding process and to forget how amazing it can be: You hold in your hand a torch that has the potential to be as hot as the sun, that gives you the ability to melt and join metals, and that produces a weldment that is actually stronger than its components.

My thought processes were jolted awake on a recent visit to Switzerland and a visit to a Swiss company – Alstom – a manufacturer of giant turbines that are used in gas and steam electrical power generating units. Those turbines are designed to produce as much as 1,100 megawatts of electrical power a year at sites around the world.

What woke me up to the amazing nature of welding was watching how the company made the rotors that are at the heart of its turbines. These are automated processes that are unique to this Swiss company, and they are impressive.

Depending on the size of the turbine, Alstom uses six to 12 castings that range in size from 3.28 ft. (1 meter) in diameter to more than 8-ft. (2.5 meters) in diameter to build its rotor bodies. The castings are thick-walled drums ranging from 3 ft. to 8 ft. in length, and with walls that are about 4 in. (100 mm) at their thinnest cross sections. (Just a quick disclaimer: all of these dimensional measurements are approximate.) The drums are made of high strength steel, and the factory produces out more than 200 turbines a year, for which it processes more than 8,000 tons of steel.

The cast drums then are assembled vertically — one rotor section placed atop another — and TIG welded together to form the rotor bodies. The weld that holds each section together is about 1-in. wide; the longest rotors are more than 72 feet (22 meters) long.

After the TIG process – which is, in effect, merely a tack weld – the assembled rotor bodies are wrapped in inductive heat blankets. They are still vertical, and they're pre-heated to a target temperature.

Once the pre-heating cycle is complete, the entire rotor body is carefully lifted, turned on its side, and installed into a lathe that holds it horizontally while the segments are fully welded together by a submerged welding process.

The rotors turn slowly in the lathe as the submerged arc welding process lays down nearly 8 in. (200 mm) of metal to complete the connection of the rotor segments. The processing of one rotor takes hours to complete.

Here is what amazed me: Those initial 1-in. wide TIG welds, that hold together the six to 12 segments, keep the entire rotor assembly together, with vertical and horizontal stability. The assembled rotor body can weigh as much as 450 tons, and those welds hardly seem robust enough to carry that weight. Yet Alstom relies on them while it lifts and lays the rotor bodies down, and as it turns the rotors in a lathe.

Later on, the completed welds are checked ultrasonically for integrity, and then are machined so that turbine blades can be installed. The turbines will spend years in service, producing electrical power.

Alstom says its welding construction for rotors has its origins as far back as 1929, and provides low-stress and lower weight rotors for its turbines.

The process is a remarkable use of welding, a process that, often times, can seem to be an ordinary practice.