TPT January 2012

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Article
Larikka CylinWeld:
Tubular parts manufactured better
By Maarit Aalto, Marketing Director, Larikka Ltd, Finland
Introduction
Larikka Ltd
Larikka is a specialist in processing technologies for tubular
parts and pipe components. The Larikka processing technologies
acknowledge the importance of inner surface quality and especially
the surface of the weld area in Tees and manifolds which is critical
on most areas of industry utilising tubular parts, eg food and
pharmaceutical industries.
After more than 20 years of experience in collaring methods for
tubular parts it was realised that this method had reached its
process limit and the 25-year search for a solution to solve the
issue of manufacturing such tubular parts that could not be collared
began. Now, Larikka demonstrates its innovativeness, know-how
and experience from over 45 years of the processing technologies
for tubular parts in the internal approach to welding stainless steel
and other high alloy cylindrical parts.
Challenges in manufacturing tubular parts
The requirements set by the usage purpose of the pipeline define
the material and surface quality requirements of Tees in addition
to joining techniques. Particularly, in the food, pharmaceutical and
semi-conductor industries the surface quality requirements are
such that Tee-joints made on-site do not fulfil these requirements.
For these reasons Tees have become
industrial products and commercial
goods.
The characteristics of a quality pipe
component and tubular part can be
summarised as: 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. However, there are several challenges in manufacturing
such tubular parts. One common problem for all manufacturers is
the geometry of the joining point of two tubular parts.
This joining point turns into a continuously changing arc which
follows the surface of the main pipe. The arc of cutting branch
pipe is identical with the arc of the main pipe. These arcs joined
together form the joining surface which is to be welded. In addition
to continuously changing arc the joining point of pieces to be welded
form an angle which changes between 0 and 90 degrees.
Controlling the full penetration of the weld and smoothness of
the inner surface is difficult causing lots of expensive after-work.
Furthermore, different kinds of fixings are needed to fix weldable
parts together for the welding process. The easiest and often the
only way to do this is to install the fixing equipment outside the
weldable pieces. Yet, these fixings cause several problems for the
movements of the welding head and weldable part to follow the pipe
surfaces’ mathematical arc.
In order to eliminate the welding and after-work problem several
pipe branching methods have been developed where a collar is
formed to the branch’s joining point and this way the branch location
resembles the end of a straight pipe. This type of joint is easily
welded manually and for this kind of welding there are several good
pieces of orbital welding equipment which produce qualitative result
on-site. However, collaring causes thinning of the material in the
collar area. The higher the collar the greater the thinning and the
risk of rupture of the collar.
As a compromise resulting from these characteristics markets have
settled for particular wall thicknesses in pipes which have been
determined more by the available manufacturing technique rather
than other facts affecting material strengths. Generally, pipes’ wall
thicknesses have remained at 1.5mm even when the outer diameter
is 15mm or smaller.
Figure 1: Pressure tested manifold 12x1.5mm and Tee 18x0.8mm
This article describes Larikka CylinWeld, the cylinder internal
welding method, and its capabilities in manufacturing tubular
parts such as Tees and manifolds from stainless steel and other
high alloy. The specific aims of this article are: To introduce
Larikka CylinWeld and to share insights of why to manufacture
tubular parts such as Tees by Larikka CylinWeld.