Nowadays tubesheet welding is becoming an essential process as much industrial equipment like heat exchangers, steam turbines, condensers, air coolers or boilers are composed by thousands of metal tubes. These tubular constructions are usually assembled on thick metal plates and TIG welded (GTAW) for best performance and long lasting. Automated tube to tubesheet welding has replaced manual welding for advanced productivity and reproducibility of the tube-to-tube sheet joints and of course to shorten production times of industrial tube heat exchangers.
Orbital tube-to-tubesheet welding: Applications and Equipment
Tubesheet welding applications
Tube-to-tubesheet orbital welding applications are used to manufacture boilers and tube heat exchangers for all kinds of industries, however the heaviest equipment is found in the plants of chemical or petrochemical industries and electric power stations.
Nearly all weldable metals and alloys are used in the ﬁeld of tube to tubesheet welding applications, but the range of the tube dimensions is relatively restricted. Their diameter range covers 12.7 mm to 101.6 mm, the wall thicknesses are between 0.5 mm and 5 mm. Most of the tube diameters measure between 19.05 mm (3/4") and 38.1 mm, with wall thicknesses between 1.65 mm and 3.4 mm.
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Orbital Welding Equipment
In most cases, equipment used for automated tube-to-tubesheet welding is strictly adapted to the application and desired level of automation:
- Tubesheet welding machine is featuring three controlled axes (gas, current, rotation) is composed of a stationary installed power source so called a Smart Welding Station and a tube to tubesheet welding head, which executes fusion welding without the addition of ﬁller wire.
- Welding equipment, with four controlled axes (gas, current, rotation, wire), comprises a stationary installed welding power source and a tube to tubesheet open welding head. This equipment is suitable for single pass welding; two passes must be welded in two separate steps.
- Welding equipment ﬁtted with ﬁve controlled axes (gas, current, rotation, wire, AVC) is composed of a TIG / GTAW power source designed to control 6 axes and a welding head of the type TS 8/75 tube to tube sheet welding head with AVC conﬁguration, allowing the chaining of multiple passes with ﬁller wire. The raising of the torch between the passes can also be programmed and is carried out without interruption of the weld cycle.
- Welding equipment furnished with six controlled axes, (gas, current, rotation, wire, AVC, oscillation), comprises a PC Smart Welding Station power source and a tube to tubesheet welding head of the type SPX compact so called TIG 20/160. The equipment allows multi-pass welding; the torch can be displaced in radial direction.
Orbital tube to tubesheet welding weld preparations
Speciﬁc requirements of tubes and weld preparations
In orbital tube-to-tubesheet TIG welding, planning brings success:
- The tubes must be seamless or with ﬂattened weld seam
- Joints must have J-preparations, ensuring reliable melting of the base of the tube edge, especially in the vertically down position.
- If a good thermal conduction is requested, the play between the tube and the bore can be eliminated by a slight expansion of the tube.
- The contact zone between the tube and the tubesheet must be clean, to avoid the formation of unacceptable blowholes.
- A full expansion of the tubes inside the tubesheet must never be carried out before automatic welding, as this causes explosive degassing effects.
Depending on the application, orbital TIG welding of ﬂush tubes with or without ﬁller metal is possible, using different joint designs:
- Standard preparation
- Relief groove
Welding of ﬂush tubes without ﬁller wire
Most often standard preparation is carried out for welding ﬂush tubes. For applications without ﬁller wire on tube diameters between 10 mm and 32 mm, specially developed welding heads are used and the complete sequence is carried out automatically.
Welding of ﬂush tubes with ﬁller wire
Welding equipment ﬁtted with four or ﬁve controlled axes can be used. The open tube to tubesheet welding head should be configured accordingly:
- Integrated or external wire feeder
- With or without AVC
- With or without shielding gas chamber
- Torch angle of 0° or 15°.
Welding of protruding tubes
Protruding tubes are always welded using ﬁller wire, but with welds beginning with a fusion pass, different joints can be used: Standard preparation without groove, J-preparation or V-preparation.
Welding of recessed tubes
Joint designs are: Standard preparation without groove, J-preparation, V-preparation, Welding behind the tube plate (frequently used in the petrochemical industry).
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 welding heads.
Nowadays, as a smart factory-oriented company, Polysoude products are all designed to be ready for Industry 4.0.
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