Pipes & Tubes: There is no definite rule for distinguishing among the general terms pipe, tube and tubing. The proper designation has been determined by the usage of it. The word PIPE is generally used to apply to tubular products commonly used for pipelines and connections for conveying fluid from point to point. Pipes are generally used to connect large machines to other large machines and are generally not subjected to external pressures.
On the other hand the word TUBE is generally used to apply to tubular products used in the heat exchangers and boilers and in the machine and air-craft industries where the wall of the tube acts as a heat transfer media and as a result are subjected to both internal and external pressures. Tubes can also be easily coiled but the thickness and rigidity of the pipes makes them harder to bend.
The manufacturing method determines the characteristics of the pipe, Therefore the classification of pipes are based on the manufacturing process, the various classifications are: Seamless Pipes & Seamless Tubes: A heated billet is brought into contact with tapered revolving rolls in such a way that the billet is pulled into the space allowed between the rolls. The mandrel is placed in the space. The soft centre of the billet makes it possible for the rolls to draw the billet over the mandrel, producing a hollow shell. When the billet has entirely passed over the mandrel, it is in the form of a thick walled seamless tube. The heavy walled tube is then passed to a rolling mill which reduces the tube to piping of proper outside diameter and wall thickness. Depending upon the process condition (temperature), seamless tube/pipes is termed as Hot Finish Seamless or cold drawn seamless as the term implies.
SEAMLESS CDS – HFS pipes are further drawn by cold drawing method, this process is expensive & pipes/tubes produces through this method have better dimensional tolerances & mechanical properties.
ERW – Electric Resistance Welded – To make ERW pipes, a high frequency electrical current is transmitted to the material by means of copper sliding contacts so that the abutting edges initiate fusion as they come into contact creating a pipe.
EFW Pipes Electric Fusion Welding Flat Plate known as Skelp, is prepared in proper width and thickness for the desired pipe inside and outside diameters. It is then charged into an electric furnace and when the proper welding temperature has been reached is drawn through a funnel-shaped die so shaped that the plate is gradually formed into the shape of a tube, with the edges of the plate being forced squarely together and fused. The formed pipe then passes through a series of rolls in which it is sized or drawn to final dimensions. The pipes obtained through this process is called ELECTRIC FUSION WELDED TUBE (EFW) HSAW Pipes- Helical Submerged Arc Spiral welded Pipes: The raw material used in manufacture of Spiral SAW is H.R. Coil. It is continuously formed to require the specific diameter of the pipe, spirally welded at high speed and cut to required length.