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Butt welding: how to prepare thin wall tubing before welding?

As an expert in the global tube working process (tube cutting, facing or beveling and orbital welding), we highly recommend you to pay attention to the following 3 steps. It will help you to best prepare your tubes before welding !

# The quality of the tube

When it comes to orbital welding, the tube is the central element. Unfortunately, its choice and the quality check are often neglected and not listed as a priority. The quality of the tubes and accessories that need to be welded, varies according to the applications and the industrial sectors. The orbital process was initially used for aerospace applications where the tubes have always been of a very high quality. But in the food processing industry, for example, the tubes are often of inferior quality.

Particular attention must be paid to the tubes’ geometric tolerances regarding the diameters (ovality) as well as at the thickness consistency. Moreover, the quality and the regularity of the arrangement of the material’s elements, particularly of sulfur, have a major importance and influence on the weldability and therefore the butt-welding parameters.

 

# A perpendicular and burr-free cut of the tube

The tube preparation is a critical factor in order to get the best fit up possible. It is important to ensure that the cut will be square and clean.

Thanks to an orbital saw which consists in cutting a tube by rotating the saw blade around a stationary tube. The concentric clamping prevents from deforming the tube (concentric clamping). Also, thanks to the cut efficiency there is less effort on the material allowing the cut to be smoother than any other method.

If you want to weld tubes, elbows etc. with an orbital welding equipment, it is really important to be able to position the elements in the most adequate way possible without any gap between the tubes. This is only possible if you take good care of the preparation of the tube. It is highly recommended to use a tube cutting machine that provides a perpendicular and burr-free cut.

Such a cut can be achieved with orbital cutting machines. These machines rotate a cutting motor with a saw blade around the tube. Thanks to the concentric clamping system, thin wall tubing keep their geometry : no deformation due to overtightening (thanks concentric stainless steels jaws) and no deformation due to the cutting effort since the blade works more efficiently.

 

This cutting method guarantees a very precise cut (Perpendicularity tolerance <0.25 mm/<0.010”). This precision is required to allow the orbital welding machine to close the joint between the tubes reliably and thus make a perfect weld seal.

Orbital cutting is therefore well suited to the requirements of an automatic welding. This preparation (orbital tube cutting) is used for tubes with wall thicknesses of more or less than 3 mm.

 

# A chip-free cut adapted to electropolished tubes

Electropolished tubing are used to reduce friction of the fluids on walls inside the tube. The semiconductor or pharmaceutical industries often use this type of tube. In this case, a cut with a tool that generates chips is not accepted because the chips could scratch the inside of the tubes. Therefore, companies use cutting tools that do not generate small chips: this can be described as “cutting without chips.”

As this cut leaves a significant burr due to the wheel, the tube needs to be faced to make it perpendicular to the axis. The tube-facing process results in a perfect burr-free tube by unrolling the chips outwards, so as not to damage the electropolished inner face.

 

The PREPARATION OF THE TUBE IS ESSENTIAL FOR BUTT-WELDING TO ENSURE QUALITY WELDING AND REPEATABLE PROCESSES.
THE QUALITY OF THE TUBES AND THE PRECISION OF THE CUTTING PROCESS ARE TWO PRIMARY ELEMENTS (AMONG OTHERS).

 

To learn more about orbital cutting, feel free to download our guide! It will explain you in details the technology and the advantages.  You can also find all our orbital cutting, facing, beveling and welding machines in our catalog!

 

handbook-orbital-cutting

 

 

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Écrit par
Frédéric Legrand

CEO and founder of AXXAIR