TPT January 2012

T echnology U pdate

Floor-mounted seam milling machine

LOOKING back 20 years ago when the Gräbener company was running its own pipe mill the product range encompassed steel piles of a maximum possible production length. This was the reason why Gräbener Großrohr began developing milling machines for high-quality and economical circumferential and longitudinal weld seam preparation on the outer surface of shells prior to being submerged-arc welded. Nowadays, pressure vessel and pipe manufacturers find it hard to imagine life without the special milling machine types for circumferential and longitudinal weld seam preparation manufactured by Gräbener Maschinentechnik GmbH & Co. KG (GMT), a member of the Graebener Group. The 150 machines developed and produced over the years have become state-of-the-art when it comes to provide vessel shells or pipes, prior to welding, with precise seams at a reasonable cost level. Now Gräbener took the next step on the ladder by developing a special longitudinal

seam milling machine for the production of wind tower segments. The machine can be erected on the bare shop floor and is particuarly useful because it does not need a foundation pit. The new floor-mounted longitudinal seam milling machine is designed to be used by manufacturers of offshore wind tower segments (monopiles). The production sites of such companies are usually situated on the waterfront, thus profiting from an advantageous infrastructure, the only disadvantage being the sandy underground of such sites. Considering this, the demand for a floor-mounted milling machine, which does without an expensive foundation pit, was obvious. As a consequence, the milling unit of the machine had to be tilted by 45 degrees. This milling position allows an erection of the machine on the bare shop floor. Not to forget that there are still applications

requiring the traditional version of the machine being erected in a foundation pit and having a milling unit working in 6-o’clock position. In the case of the floor-mounted longitudinal seam milling machine, the workpieces such as pipes with external diameters of up to 8,000mm and lengths of up to 4,000mm are placed, aligned, and clamped on a pipe support with adjustable pipe rotators. For better monitoring, a camera travelling along with the milling process – which can reach a depth of 90mm – is installed which displays the process on a screen installed in the operator’s area. For achieving a constant milling depth during the milling operation, the machine is equipped with a milling height adjustment device for automatic height copying. Gräbener – Germany Email: m.butz@graebener-group.com Website: www.graebener-group.com

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