TPT January 2012

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January 2012 127 ›
Article
of the branch part (figure 3). Parts are directly ready for the welding
process.
Fix and weld
For the welding process parts must be fixed together. Larikka
CylinWeld has three devices for handling parts: 1) a welding cassette;
2) a positioning device; and 3) a welding chamber. The same welding
cassettes can be used in welding both single Tees and manifolds.
The weldable parts to pipes can be flanges, pipes, threaded nipples
or any other parts where there is a hole and the material thickness is
suitable. Furthermore, a very effective production situation is created
by using two welding cassettes, where one cassette is in welding
while the other cassette is being loaded.
The handling of parts is also very cleverly and simply realised in
Larikka CylinWeld. First, the base part of the cassette is dropped
inside the positioning device. Next, the branch part is dropped to the
guiding pins which are on the central line of the positioning device.
After this the main pipe is put into the cassette so that the tip of the
guiding pins goes inside the main pipe’s hole. Now the weldable
parts are positioned into the welding cassette so that the branch
pipe’s arc is against the main pipe’s hole. Also, the central lines
of the weldable parts and inside electrode’s axis of revolution are
concentric and parallel. As the welding cassette is closed the parts
are pressed tightly against each other thus forming a shielding gas
atmosphere for controlling the inner and outer shielding gas during
the welding (figures 4 and 5). After fixing the parts, the welding
cassette is removed from the positioning device and is loaded into
the welding chamber (figure 6).
By the start command the pneumatic actuator of the welding
chamber locks the chamber to its position and connects the
outside shielding gas as well as the earth current contact. The
fully automatic welding begins after the programmed pre-purging
time and it processes according to the pre-programmed welding
parameters. After the cooling time the pneumatic actuator releases
the cassette which can be then unloaded from the machine and
unlocked. The welded part can now be removed from the cassette
and the welding result can be immediately visually checked for a full
weld penetration since the root is on the part’s outer surface.
During the welding the arc flame has travelled over the sharp inner
corners of the tubular parts’ joining point and melted these corners
into a good, round corner. The welding has a positive welding bead
both inside and outside (figure 7). Thus, the welding result of Larikka
CylinWeld fulfils all the characteristics of quality tubular parts: 1) the
large radius of the inner corner of a branch; 2) smooth inner surface;
3) good flow technical properties; and 4) good material strength.
Conclusions
Small tubular parts are manufactured better from inside. Larikka
CylinWeld makes the difference in manufacturing quality Tees and
manifolds from stainless steel and other high alloy with its cylinder
internal welding approach. It enables manufacturers of tubular
parts to respond to the increasing demands on material savings,
production process optimisations and reduction of the carbon
footprint without compromising the quality of pipelines.
Figure 4: A manifold and a 6x1mm Tee in a
welding cassette inside positioning device
Figure 5: Manifolds in welding cassettes
Figure 6:
A 6x1mm Tee in the
welding chamber
Figure 7: Larikka CylinWeld Tees: welding seam from inside
Larikka Ltd – Finland
Tel: +358 20 7121 444
Fax: +358 20 7121 449
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