Thick web switches:
The term thick web switches most commonly refer to a new [2002] design of sturdier BG switches on prestressed concrete sleepers, which can handle higher turnout speeds. These are made for 1:8:5 turnouts(less commonly, 1:12), with 160mm (less commonly 115mm) throw, and have clamp locks, spring setting devices(SSD), and the ZU-1-160 thick web rail. In 2003 or 2004, IR decided to use these switches on all the Class. A routes and other high-density routes with traffic above 20GMT/year.
The new switches have been designed to be easily installable on top of existing prestressed concrete sleepers supporting older switches.Principally two types of welding are used for rails. One is Flash Butt Welding, and the other is Alumino-Thermic Welding, also known as Thermit(e) welding. The third kind of welding, known as Gas Pressure welding, is used much less often, and a fourth kind, Metal Arc Welding, is very rarely used.