Английский для сварщиков. Гричин С.В. - 126 стр.

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126
process and relevant rules like selection of gases, cleanness, weldability of
specific materials and consequential mechanical strength specifications such
as tensile and bend loading, are very important.
Orbital-welding is presently used whenever the quality of the weld
joint has the highest priority. These demands are not only limited to
mechanical strength and X-ray qualification, but also to the important aspects
of the aesthetics of the weld seam. For any users a uniform, flat and smooth
root-pass is the main reason for using this process. Consequently, it is
favoured in the following areas: chemical industry, pharmaceutical industry,
bio-technology, high-purity water systems, semiconductor industry, aircraft-
and aerospace industry. Moreover, because of the weld joint's uniform
outside shape and almost complete absence of need for any post-polishing,
Orbital-welding is even used for bends on door-handles, hand-guards, or in
dead foot-elements for champagne-glasses! Interested applicants for this
technology should certainly note that they have to confirm a couple of
indispensable premises.
The following presents the basic rules for this process, valid for all
manufacturers and systems.
Even knowing that some competitors are announcing features, which would
potentially violate the basic physical laws of nature and knowledge,
moreover, making promises and statements which are at least detected as
impossible to meet when the welding system must work under high duty-
cycle production conditions. Indiscriminate and exactly defined dimensions
with tolerances must be thorough and complete. The much liked standpoint,
that the welded tubes and pipes are in accordance to DIN or ASME standards
are not acceptable criteria. These qualifications only define tolerances in
percentage to the wall thickness relating to pressure loading and not to
weldability using the Orbital-Welding-Process.
For the Orbital-Welding-Process absolute tolerance values are
necessary, and furthermore, the more complicated the application, the tighter
the tolerances must be. This means, that for an easy application like welding
a stainless steel tube of 53 x 1,5 mm, a tolerance in alignment of about 0,5
mm (about 30% of the wall thickness) can be compensated, but for much
more critical applications like welding a carbon-steel pipe of 114,3 x 3,6 mm,
the same percentage can result in unacceptable weld quality. Therefore, the
question of acceptable tolerances should be researched and defined for each
application individually.
That Orbital-Welding can be used successfully and economically is
proven by the constantly increasing number of users. Field experience has
shown that Orbital-welding can be justified based upon economic reasons
alone, where the welds can be done in squared-butt no-gap preparation

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