TPT January 2012

126

anuary

2012

www.read-tpt.com

›

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.

Larikka CylinWeld –

the cylinder internal welding

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.

The welding seams of Larikka

CylinWeld have undergone

both X-ray and pressure tests

with good results. X-ray test

results were class 5.

Also, the pressure

tests proved great

material strengths.

For

example,

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.

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

Figure 3

Drilled main pipe and punched

branch pipe ready for welding

Figure 2

Larikka CylinWeld machine