TPT May 2010

W elding T echnology

Welding pipelines, tubular parts and fittings 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 purpose of a pipeline is to transport media from one place to another. In this type of a pipeline only a few pieces are required: threaded joints in smaller pipelines and flange joints in bigger pipelines, unless the pipes are welded. But most pipelines have further purposes in addition to merely transporting media. Pipelines distribute media from feeder point to several locations or reversely collect media from several feeder points to collection locations. A pipeline built for distributing/collecting media differs from a pipeline built for transporting media by one critical tubular part – a tee. There are several types of tees according to different usage purposes and standards. With the use of a tee the aim is to create a situation at the installation on-site where joining the pipeline’s distributing part would correspond to joining it to a straight pipe with different joining techniques. The requirements set by the usage purpose define the material and surface quality requirements of tees in addition to joining techniques. Particularly in the food, pharmaceutical and semi-conductor

This welding method is named Larikka CylinWeld. Larikka CylinWeld is excellent for manufacturing tubular parts. Joining the surfaces of two round parts forms a mathematical pattern and the simplest approach is from inside and on the central line of either tubular part. Larikka CylinWeld utilises the TIG-welding method and the welding takes place inside the tubular part. The welding process is fully automatic and the inner surface quality of the weld area is smooth. This result is achieved from the light arc travelling over the sharp corners of the joining point as the corners melt forming a round corner. Further, the root is on the part’s outer surface making the visual check of full penetration of the weld simple. Larikka CylinWeld is also very suitable for the welding of collared and straight seams. Larikka CylinWeld is applicable for the welding of single parts where the part rotates and the welding is down-hand welding, which is theoretically the best welding situation. However, with Larikka CylinWeld it is also possible to weld long manifolds. Equipment’s functions can be applied so that the pipe is stationary and the electrode rotates inside the pipe. The operating range of Larikka CylinWeld is wide with the smallest diameter being 4mm and the largest 200mm, and in special cases it can be even larger.

A 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 to 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 0-90 degrees. Controlling the full penetration of the weld and smoothness of the inner surface is difficult, causing lots of expensive after-work. 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 in 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 orbital welders, which produce qualitative results on-site. As the pipe diameters get smaller and the wall thickness in relation to pipe’s diameter grows (becomes thicker) there are no working collaring methods (for branching) available. For manufacturing this kind of “small” tee a new welding method has been developed by Lacol Ltd. RITMO SpA, a manufacturer of welders and accessories for plastic pipes, has launched ALFATEL-800, a workshop machine designed to weld pre-insulated district HDPE pipes and valves for both heating and cooling lines. ALFA TEL-800 produces pre-insulated HDPE elbows within the 400-800mm diameter range, and jackets for valves within the 400-710mm diameter range. District heating is an efficient and low- environmental impact system for distributing heat generated in a centralised location for residential, commercial and industrial heating requirements. Heat is distributed to the customer via a network of insulated steel pipes under pressure. An insulating foam

LACOL Ltd – Finland Fax: +358 2071 21449 Email: maarit.aalto@lacol.com

Welding pre-insulated district HDPE pipes and valves

wrapped around the pipe minimises heat dispersion, and the external HDPE jacket protects the lines. ALFA TEL-800 has a machine body with facer and interchangeable heating elements. The fitting segments are loaded onto the machine carriages and tightened by clamps. The hydraulic movements of carriages, heating element, facer and clamps are driven by a handy control panel. Ritmo SpA – Italy Fax: +39 049 9901993

Email: info@ritmo.it Website: www.ritmo.it

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M ay 2010

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