TPT November 2022

T E CHNOLOG Y

than conventional gouging. The process is also well suited for repair work on the weld seams to mill out local defects. For circular and longitudinal seam milling INGERSOLL supplies V-shaped side milling cutters with radius R7/R8 in the radius section and opening angles from 14 degrees to 16 degrees. In addition, customised side milling cutters are also available. The diameters of these large tools are mainly between 850mm and 1,060mm. The side milling cutters are equipped with different milling tips for the radius and sides of the tool. Generally, these are milling tips with negative cutting geometry. The radius milling tips are mounted in a hardened and replaceable L-insert due to the extremely high load. This is not needed for the side milling tips, since the side angle results in a lower load. Depending on the component, vibrations occur on the pipe body during machining. This is a major problem, because these can cause chipping on the milling tips and subsequently lead to wear. Gräbener Maschinentechnik GmbH www.graebener.com

efficient, economical preparation of the external weld seams. The process is fast, material-saving and precise. For the external weld seam preparation, it is necessary to cut out the root area of the internal weld. This was traditionally done with a so-called air gouge by spark erosion and manual grinding. With the Graebener longitudinal and circular seam milling machine and the INGERSOLL side milling cutter, a tulip shaped groove is milled right into the root of the inner weld seam. The angle of this external weld seam preparation, which was conventionally approximately 60 degrees, is reduced to 16 degrees by the milling process using a side milling cutter as standard. This reduces the welding consumables and the relating welding time. The total cost saving for this weld seam preparation with Graebener machines is 38 per cent compared to conventional processing. In several cycles, the cutter penetrates up to 150 mm deep to the root layer of the inner seam. The clean, uniform groove, which requires no further finishing, is the prerequisite for an automated submerged-arc welding process. The milling process is also 10 times faster

seam milling machine is available as a demonstration unit. New wind farms are also being built off the coast of Japan. Here, a manufacturer of monopiles wants to carry out the complete assembly process outdoors rather than in a hall. To meet this requirement, Graebener is developing machines that are also suitable for outdoor use. The monopiles for wind towers are always assembled from several individual cylindrical and conical steel rings, the so-called pipe shells. Typical dimensions for such a pipe shell are a diameter of 13m and maximum lengths of 4m. With wall thicknesses of 120mm, this results in an individual weight of up to 150 tons per pipe shell. After bending, the pipe shells are first welded longitudinally from the inside and then from the outside. This is followed by the assembly of up to six sections into one section. Three to four of these assembled sections form the so-called monopile. A monopile has a total of approximately 192m longitudinal and 940m circumferential welds and a total weight of up to 2,500 tons. The milling machines from Graebener enable very

The stationary PBM pipe end preparation machines, for fast beveling of all types of materials, are the strongest bevel machines in the market.

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NOVEMBER 2022