TPT January 2012

A rticle

Larikka CylinWeld: Tubular parts manufactured better By Maarit Aalto, Marketing Director, Larikka Ltd, Finland

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.

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.

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

Figure 1: Pressure tested manifold 12x1.5mm and Tee 18x0.8mm

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