How to make pipes manufacturing

Most pipes used for the transmission and distribution of liquids and gases under pressure are made of ferrous, cementitious, or plastic materials. Other materials of more limited and specialized application include stoneware, used for sewerage and drainage by gravity; aluminum, used because of its light weight for surface irrigation and emergency water supplies; and copper and lead, used for small-diameter service pipes to feed individual properties.

Ferrous pipes

The latest advance in iron pipe technology has been the replacement of the relatively brittle gray iron by ductile iron, a material with properties of ductility and strength similar to those of steel. This is achieved by converting the small carbon content of iron (about 3 per cent) from flake to spheroidal form, by adding small quantities of magnesium ferrosilicon alloy to the molten iron prior to casting.

Steel, because of its weldability and its high tensile strength – about 35,000 psi (2500 kg/cm2) for mild steel, and up to 60,000 psi (4200 kg/cm2) and more for high-tensile steel – is the most versatile of all pipe materials. Pipes are made by a number of processes. In diameters up to 12 in. (300 mm), seamless pipes are produced either by extrusion under pressure or by hot rotary piercing. In the latter process a heated cylindrical steel billet is passed between two rolls whose axes are set at an angle, and pierced by a pointed mandrel.

In large diameters, up to about 60 in. (1500 mm), the pipe is usually manufactured from steel plate of the required thickness, whose length – usually about 40 ft (12 m) – is that of the finished pipe and whose width is the pipe’s circumference. The plate edges are trimmed for welding and the circular shape is cold-formed in presses. The edges are welded longitudinally either by electric-resistance welding or by submerged-arc welding.

Very large diameter pipes – up to 100 in. (2500 mm) and more – require two or more longitudinal welds. Alternatively, they can be made by spiral or helical welding. In this case the pipes are fabricated Above: Underground furnaces in which clay waste pipes are manufactured and glazed from steel plate in rolled form, and the weld spirals around the pipe at an angle that is dependent upon the relationship between pipe diameter and plate width. Spirally welded pipes can be made in very long lengths, but the practical limit imposed by transportation constraints is about 80 ft (24 m).

Galvanized mild steel (GMS) pipes are small diameter steel pipes usually made by a seamless process. They are protected against corrosion by dipping in a bath of molten zinc, a process known as galvanizing. They are rarely used in diameters over 4 in. (100 mm).