Before talking about the welding of pipes and tubes, let's argue about the difference between them. Well to be honest there is no difference between a pipe and circular tube because both are of same geometrical shape made from same material and even by same manufacturing process. Except the use of dimensions to define their size, is the only major concern to differentiate them. In case of a circular tube the outer diameter (normally refers to as O.D) is used to define the tube size while in case of pipe, sizing is based on internal diameter (refers to as I.D). Moreover in pipe, the outer diameter maintains and the internal diameter varies depending on schedule.
The above picture shows the joining of tubes, by using a gas welding process. This process is common by the name of oxyacetylene gas welding in which highly flammable gases (mixture of oxygen and acetylene) are burnt to produce considerable amount of heat. The high energy flame makes a coalescence of joint material either by fusing of base metal or by blending of externally added filler rod with the base metal. Further improvements have been made by the use of other combustible gases with pure oxygen.
Oxyacetylene process has slight resemblance with Tungsten Inert Gas process with difference of flame production instead of an arc to serve the same purpose. The similarities between these processes are;
- Same feeding mechanism
- Use of filler rod
Although OA process or flame welding is used for tubing and joining of pipe in several applications but in case of pressure welds where high strength and metallurgical properties are required, arc welding is used.
