Joining Pipes with Butt Welding
A butt weld is a type of weld where the ‘butt end’ of the workpiece (pipes or tubes in our business) is welded to another in the same plane circumferentially. Butt welding is the most common type of joint that is used in piping systems. This type of welding is commonly used for pipe joints that do not require assembly or replacement, such as long-distance or underground pipelines.
A butt weld is a simple and versatile design of a welded joint. The butt weld is formed by simply inserting two pieces of metal next to each other and then welding along the weld seam. It is critical that in a butt weld, the surfaces of the workpieces are joined in the same plane and the weld metal remains within the places of the surfaces. The workpieces are therefore almost aligned and do not overlap, in contrast to overlap joints, for example.
Due to its simplicity, butt welding is the most widely used joining technique for a large number of applications in various industrial sectors. This fundamental welding technique has a number of different welding formations that are suitable for different welding thicknesses.
The pipes need to have plain ends or beveled ends to be able to perform the butt joint welding. A bevel is performed on the edge to create space for a welding torch, so the full wall thickness of the pipe or tube can be butt welded. The thickness and diameter of the pipes should be the same. In addition, the quality of the bevel is the determinant of the weld quality since the welding operation needs to be done from the outside of the pipes. While the most common pipe bevel shapes for butt joint welding are V-bevel and J-bevel, a butt weld can be performed with any shape of pipe bevel. Rather than the bevel shape, the welding on the edge is what makes it a butt weld.
Even though almost all kinds of bevel shapes can be butt welded, they have advantages and disadvantages. As mentioned, V-Bevel and J-Bevel are the most common pipe bevel shapes for butt welding, so we’ll be discussing the main differences between these two.
The angle of a J-bevel is commonly lower than the angle of a V-bevel, which means less space for the welding torch can be created with a J-bevel. This makes the welding process difficult for the welder. While it is a challenge for a J-bevel, the total volume of the weld will be less due to the limited space that the J-bevel created. That means less material (welding wire) and less time is required for welding, which reduces production costs.
For the pipes with small wall thickness, the gap will always be small, so there is no significant difference between the amount of material or time for welding. Then, V-bevel is commonly the best option. If the wall thickness increases, the effects of the difference in volume would be significant. That’s why the usage of a J-bevel is more common on large wall-thickness tubes than on smaller wall thicknesses.
Another way to decrease the welding volume on large wall-thickness tubes is to use a compound bevel. This can be done for a V-bevel and for a J-bevel, but it is more commonly used for V-bevels. The first part of the bevel will be the 30°/37.5° standard bevel, but after 19mm of the inside of the land (or root), it changes to 10°.
There are various advantages that butt welds offer in general. Butt welds have for example a high strength with complete fusion, butt welds are easy to inspect, butt welds are easy to machine, and provide deformation control.
Our stationary pipe beveling machines, the Beaver Series, can create perfectly beveled ends in desired shapes, to make the pipes ready for butt joint welding. We offer a full range of pipe beveling machines with manual, automatic, and CNC control options for metal pipes between 3” and 56”.
As we all know, SAW is a very efficient process for fast filling of open bevel butt joints in heavy wall piping and spooling. The Rotoweld 3.0 with SAW option is a very versatile and powerful machine. In addition to its unique fully automated, defect-free MIG root-pass, it offers a broad selection of options for the fill passes, namely spray MIG, flux core, and SAW. Whether your scope of work is carbon steel or stainless steel, standard wall, or heavy wall, the Rotoweld will significantly increase (4-8 times) your productivity and will ensure 100% reproducibility of the quality of the welds.
Contact us for more information about the options of our beveling machines, and the Rotoweld.