Belling, Socketing of pipes

Socket means an opening or a cavity into which another part is deisgned to fit. A socketed pipe is a pipe with an expansion at one end to receive the end of a connecting pipe. 
A machine designed to make a socket in a pipe is called a socketing / belling machine. 
One end of the pipe is inserted into a small oven to soften it. Once softened the pipe end is given the  desired shape with the help of a mandrel. 
Heating by ceramic IR provides uniform pipe heating thereby resulting in even expansion and hence a good socket. Also, the heating is much quicker than other forms of heating resulting in increased output.