Whenever high-quality results are required, orbital welding is the first choice for the joining of tubes. The welding torch - in most cases, the TIG welding (Tungsten Inert Gas) process is used - travels around the tubes to be joined, guided by a mechanical system.
As the arc welding electrode rotates, or orbits, around the workpiece it joins the metal together by forming the orbital weld. This technique delivers highly repeatable welds with very high standards even with unusual materials such as stainless steel, titanium, aluminium… or thick tube and pipe walls, from semiconductor or pharmaceutical to oil and gas and nuclear industries.
What is Orbital Welding?
Orbital Welding has become a well-established method, for joining tubes. The welding torch travels around the tubes to be joined, guided by a mechanical system. The name orbital welding comes from the circular movement of the welding tool around the workpiece. Generally, orbital welding technique covers two main ﬁelds of application:
- Tube-to-tube / pipe-to-pipe joining.
This application can cover all tubing and piping requirements including butt welding and welding of ﬂanges, bends, T-ﬁttings and valves.
- Tube-to-tubesheet welding.
This group concerns the manufacturing of boilers and heat-exchangers and comprises the different welding tasks related to tube-to-tubesheet welding operations.
Orbital Welding, usually uses the TIG welding (Tungsten Inert Gas) process. An electric arc is maintained between the non-consumable tungsten electrode and the workpiece. The electrode supports the heat of the arc; the metal of the workpiece melts and forms the weld pool. The molten metal of the workpiece and the electrode must be protected against oxygen in the atmosphere, therefore an inert gas such as argon is used as a shielding gas. If ﬁller metal is necessary, it is fed to the weld pool, where it melts due to the energy delivered by the electric arc.
Orbital TIG welding is advantageous as nearly all metals can be joined, TIG welding can be carried out with or without ﬁller wire, furthermore, if ﬁller wire is applied, workpieces consisting of dissimilar alloys or batches can also be joined successfully. No slag or fumes are developed during welding. The orbital TIG welding process is very stable and reliable; the occurrence of weld defects can be reduced to less than 1% and all welding positions are possible. The affecting weld parameters can be adjusted in a wide range and mostly independently of each other. Finally, the arc voltage, which is directly related to the arc length, and the weld current intensity offer a wide range of variations and can be controlled automatically.
Orbital Welding Advantages
Compared to manual welding, Orbital welding equipment guarantees that approved weld sequences are reliably repeated, hence time-consuming repair work will be reduced to a minimum.
Consistent excellent weld quality
Generally, the weld quality obtained by mechanised equipment is superior to that of manual welding. Once an adequate weld program has been developed, the weld cycle can be repeated without deviations and without weld defects.
Required skill levels of the operators
The technology eliminates the need for certified welders. After training, orbital welding equipment can be operated by skilled mechanics, to achieve excellent results and becoming a professional orbital welder.
Orbital welding can be executed even under harsh or restrictive environmental conditions; once the orbital welding head is positioned, the weld can be accomplished without problems from a safe distance.
Traceability / Quality Control
Modern orbital welding machine is designed for real-time monitoring of the affecting weld parameters; a complete weld protocol can be generated and stored or output as a printed document. Sophisticated data acquisition systems operate in the background, if they are connected directly to a superior quality management system; automatic data transfer takes place without any interruptions to the weld procedure.
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Specificities of Orbital Welding
In TIG welding, current is generated through a non-consumable, tungsten electrode, establishing an electric arc between the electrode and the workpiece. The heat of the arc melts the metals which fuse together.
Two types of current may be applied:
- Direct Current (DC) - most frequently used to weld most types of materials
- Alternating Current (AC) - preferred for welding aluminium and aluminium alloys. The electrode is periodically switched between positive and negative polarity. During positive polarity, the oxide layer on the surface of the workpiece is cleared. During negative polarity, heat to melt the aluminium is applied.
Tungsten withstands the heat of the electric arc, keeping its hardness, even if it becomes red hot.
An electrode grinder is used to guarantee better ignition and improved arc stability
These may be introduced into the weld pool, to reinforce the welding weld seam.
Argon is commonly used as shielding gas in the TIG process. It provides excellent arc striking, arc stability and is compatible with all types of base materials.
Most applications of Orbital TIG welding require an outstanding quality to the inside of the root, the part of the weld which will be in direct contact with the transported medium. To avoid any risk of oxidation, the hot metal inside the tube is protected from the atmosphere, by using backing gas.
In Orbital welding, tasks are completed with tubes in a variety of positions. The continual changing situations: alterations of weld position, varying influences of gravity and thermal state of the workpiece must be accounted for by controlling the pool of molten metal throughout the complete weld cycle.
The most effective way to maintain control of the weld pool, is to use pulsed current. This alternates between high intensity, when the weld pool is at its maximum and low intensity, when the pool cools down, decreases volume and mitigates the effects of gravity.
The orbital weld cycle is divided into sectors. In each sector the parameters for the welding applications can be controlled and adapted.
Orbital TIG Welding – when quality is the primary concern
When high quality welds are required, orbital TIG welding is the ideal technology for tube-to-tube or tube-to-tubesheet welding applications. With or without filler wire, this is a stable, reliable process that can be used on a wide range of materials.
The Technology use for Orbital TIG Welding
The efficiency of this technology is due to a precise programming facility. With Polysoude’s latest generation of power sources, called Smart Welding Stations, the development of a welding program, easily created via the graphical operator interface, guarantees a high-quality weld through automation. The welding cycle can be repeated as often as necessary by the orbital welder, with the same result.
Polysoude provides a wide standard range of quality orbital welding machine, for orbital TIG/GTAW welding, as well as automated solutions integrating the latest technologies. Orbital welding equipment is generally composed of the following components: a programmable power source with a remote-control pendant, either distinct from, or integrated into the welding head, the welding head and a wire feeding device, if required by the application.
Who we are
Polysoude specialises in the design, development and manufacture of innovative arc welding solutions. The brand is synonymous with world-leading expertise in 3 core sectors: automatic orbital TIG welding systems, automated TIG and plasma welding solutions and TIGer™ weld overlay.
Situated in Nantes since 1961, the company manufactures a variety of power sources and orbital welding equipment, like a wide range of open and closed orbital weld heads.
Nowadays, as a smart factory oriented company, Polysoude products are all designed to be ready for Industry 4.0.
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