TPT January 2012

A rticle Manufacturers have tried to collar these pipe diameters despite difficulties. This has led to great compromises because of the collar quality. In short, as the pipe diameters get smaller and the wall thickness in relation to pipe’s diameter grows, ie becomes thicker, there are no working collaring methods (for branching) available. Resulting from long development work of both collaring and welding techniques, Larikka has developed a very clever solution for manufacturing tubular parts like Tees where all the collaring problems have been elegantly solved – no collaring at all. This new solution is named Larikka CylinWeld and it approaches the manufacturing these kind of “small” Tees and other pipe components qualitatively and economically by welding cylindrical parts from inside as its name reveals – cylinder internal welding. Due to this innovative approach to the welding process all above mentioned challenges in manufacturing tubular parts can be avoided. The simplest approach to the mathematical pattern which the joining surfaces of two hollow parts form is from inside and on the central line of either tubular part. This kind of a mathematical pattern is easy to control with current servo technics. Since the weldable parts must be fixed together for the welding process and most commonly this is made from outside the parts, the inside of the pipe parts remains free for the welding process. Larikka CylinWeld is an application of TIG-welding which cleverly utilises this vacant space inside of pipe parts. In Larikka CylinWeld the electrode is directed inside the parts to be welded either through the branch or the main pipe. Thus, the welding takes place inside the tubular parts. There are two significant things that happen when tubular parts are welded from inside. Firstly, a round inner corner is formed as the arc flame travels over the sharp inner corners of the tubular parts’ joining point and melts these corners. This kind of smooth and round corner inside is flow-technically and in terms of material strength a very good end result. Secondly, the root is on the part’s outer surface making the visual check of weld’s full penetration easy. Larikka CylinWeld – the cylinder internal welding

Figure 3 : Drilled main pipe and punched branch pipe ready for welding

Noteworthy is that the branches’ welding seams did not rupture. Instead, the material ruptured outside the welding seams of branches as shown in figure 1. Larikka CylinWeld (figure 2) consists of a power source, a user interface for controlling the welding process, a welding chamber and a fixing cassette for fixing the parts. The fixing cassette is equipment to which parts can be easily fixed for the welding process. The positioning devices force parts into a correct position in the cassette locking them for the welding. The cassette also directs the parts into proper position in relation to the welding electrode as the parts are loaded within the cassette into the welding chamber. Together the cassette and the welding chamber form a shielding gas atmosphere for controlling the inner and outer shielding gas during the fully automatic welding process where the movements of the welding and the power control are executed according to the pre-programmed parameters. Thus, no special skills or know-how are required from the person operating Larikka CylinWeld. Larikka CylinWeld is very suitable for welding diverse and challenging tubular parts either with saddle weld or straight seams to collared parts. It is applicable for the welding of single parts where the part rotates and the welding is down-hand welding, which theoretically is the most ideal welding situation. Furthermore, with Larikka CylinWeld it is also possible to weld long manifolds. The equipment’s functions can be applied so that the pipe is stationary and the electrode rotates inside the pipe. Since the welding takes place inside the pipe it is possible to weld branches very close to each other. Also, the operating range of Larikka CylinWeld is wide: the smallest diameter is 4mm and the largest 200mm, in special cases even larger. Larikka CylinWeld concept and the welding chambers are widely patented. Manufacturing tubular parts with Larikka CylinWeld Tubular parts have been manufactured under limitations of available manufacturing techniques and weldable parts have been produced to meet the requirements and possibilities of the welding. Also, for Larikka CylinWeld process the parts are prepared by the conditions set by the welding. The following describes how manufacturing tubular parts with Larikka CylinWeld works. Drill and punch Preparation of parts for the welding is very simple. Firstly, a hole is drilled to the main pipe. Secondly, an arc is punched to the pipe end

The welding seams of Larikka CylinWeld have undergone both X-ray and pressure tests with good results. X-ray test

Figure 2 : Larikka CylinWeld machine

results were class 5. Also, the pressure tests proved great material strengths. For example, a 3-branch manifold of a 12x1.5mm stainless steel pipe lasted 1,700 bar and a Tee welded from a thin-walled 18x0.8mm stainless steel pipe lasted 480 bar before rupture.

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J anuary 2012

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