Steel Pipes:

Steel pipes are commonly used for pipes having diameter greater than 1200 mm. Large size steel pipes are created from steel plate made to circular form. The edges of the plate are either lap welded or butt welded. Lap welded pipe is re-heated and re-rolled so that the wall thickness becomes uniform.

Smaller sized pipes are made from billet bars or ingots of hot steel. The ingots are pierced and rolled into a cylinder of the required dimensions. Such pipes are known as seamless pipes. These pipes are usually 9 to 10 m long.

These pipes get rusted quickly which reduces their life as well as carrying capacity. To protect pipe from rusting these are provided with inside and outside coating with bitumen. Such pipes cannot sustain high negative pressure that might develop under certain conditions. To protect steel pipes from negative pressure their shells are coated from inside and outside with 1 : 2 cement mortar (popularly known as Hume pipe). Hume pipes combine the advantage of steel (being strong in tension) and those of concrete (being strong in compression). Life of steel pipes is generally taken as 100 years under ordinary conditions.