TPT September 2013

Technology News

Pipe production efficiency MODERN, highly technological pipe and tank construction has potential to accelerate and optimise certain production processes, including seam milling technology that allows an exact edge preparation of weld seams for the SAW process. depend on the seam type and the seam volume, Graebener Maschinentechnik has specialised in processes for optimum seam geometry. When welding top quality materials of high yield strengths, the CO 2 weld pass must be removed completely up to the root pass in order to avoid welding defects.

heat brought into the material. In order to optimise this process, Graebener developed circ and long seam milling machines. The weld pass is milled using a side and face milling head while the pipe or the tank is rotated. Welding volume and welding time are reduced, surface quality is increased and the geometry of the seam volume is more even. At the same time, the subsequent welding process can be automated, working conditions are improved, and chips generated during the milling process are recycled. According to Graebener the costs per metre weld seam can be reduced, sometimes by more than 50 per cent, by shorter processing time of the seam preparation, reduction of welding metal, shorter welding time and lower energy consumption. Graebener Maschinentechnik GmbH & Co KG – Germany Website: www.graebener-maschinentechnik.de

Increasing yield strengths and the application of materials of increasing quality such as X80 require that the weld pass of the open-seam pipe is removed beyond the root pass. This, for example, is a clear stipulation in the specification for the manufacturing of offshore wind towers, because the optimum seam preparation is vital for an economical and high-end welding process. The removal of the CO 2 weld pass and the generation of a flawless outer SAW seam are the crucial processes for the quality and economic efficiency of the welding operations. The SAW process has also been improved by new electronic systems, welding heads or wire/flux combinations. Since quality and costs of a weld seam

However, some companies in the sector of tank and apparatus construction still remove the CO 2 weld pass on tanks or pipe shells that have already been tacked or welded on the inside, by means of carbon rod gouging with subsequent grinding, and carry out a manual weld seam preparation. The process of carbon rod gouging in combination with manual grinding and welding was considered the only feasible process for removing the root pass of inside welded root passes. With this process, employees face a high noise level, extreme heat and dust. In addition, the accuracy of the weld seams regarding depth guidance and seam width suffers due to the extreme

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S eptember 2013