Modern joining techniques set new standards in the field of plate processing and pipe production, for example the multiple-wire submerged-arc welding or the laser/laser-hybrid welding. In addition to this, the customers' quality requirements are ever increasing due to the application of computer-aided machine controls and various narrow-gap welding processes.


However, an optimum welding seam preparation requires one thing above all else: Experience. Profiting from the experience gained while operating a pipe mill (Gräbener Großrohr 1974 - 1997) and constructing special machinery for several decades as well as the consistent implementation of user know-how, Gräbener Maschinentechnik today is able to offer machines and equipment designed according to state-of-the-art principles. This experience and know-how give Gräbener's customers a decisive edge with regard to production and quality over the international competition.

Pre-bending Press

Pre-bending Press

During the production of LSAW pipes, Gräbener pre-bending presses, suitable for a plate thickness between 40 and 75 mm, are used for pre-bending the edges of plates with a length of up to 18 metres in a step-by-step process. This production step ensures that the open-seam pipes do not show any straight ends at the plate edges after the actual bending process.




4-Roll Bending Machine

4-roll bending machines have been developed for thick-walled offshore wind tower sections, piles, mooring posts, large vessels, and tanks.


The Gräbener 4-roll bending machine with supporting yoke is equipped with relatively slim rolls with hardly any crowning. The number of exchange rolls necessary is decreased considerably and an optimum straightness of the pipe shells to be formed is ensured - for small and large material thicknesses. Due to the small number of exchange rolls, standstill times because of roll changes can be avoided which, in turn, increases the turnout of the machine and its efficiency.


The supporting yoke clamps the top and bottom rolls and compensates the deflection by applying counter pressure to the rolls. Camber adjustments at the rolls are no longer necessary, bending capacity turns into pre-bending capacity, and the customer no longer needs to commit himself to a predefined production program.


Due to the supporting yoke function it is finally possible to raise the pre-bending capacity of a roll to the same level as the round bending capacity. Flame cutting of the straight edges, which has been customary so far, no longer is necessary thus saving working time and material costs while at the same time increasing the economic efficiency.


If the supporting yoke is not needed, it can be fully sunk in the foundation or even dismantled in a very short period of time.


3-roll bending machine

3-Roll Bending Machine

A 3-roll bending machine is still the most economic solution for the production of special shells for the construction of vessels and cones.


Each lateral roll and the upper roll can be adjusted. Therefore, an economic production of cones is possible without damage to the longitudinal plate edges. High asymmetric forces during extreme conical bending require a high stiffness in the tilting bearing column. Each machine is designed using FEA calculations.


The 3-roll bending machine uses a quick and modern machinery concept which mainly is applied in today's vessel, apparatus, and pipeline construction. In addition to these fields of application, such a bending machine can also be used for bending cones and straightening plates.


Today, a manufacturing length of 12.2 m is the most common requirement for the production of line pipes. For the production of pipeline pipes, the Gräbener 3-roll bending machine is equipped with individually adjustable support rollers. In addition to this, Gräbener Maschinentechnik also offers various exchange rolls. The 3-roll bending machine - due to its speed and easy handling - also is an economic production solution for conventional API pipes with small and medium wall thicknesses.



Bending Press/Post Bending Press

Bending Press / Pipe Forming Press

The Gräbener pipe forming presses are used for offshore pipes, jackets and special pipes with increased yield points and large wall thickness / pipe diameter ratio since these technical requirements exceed the physical limits of a traditional roll bending machine. The results are pipes with higher stability which also leads to cost reductions since less material is needed.


The Gräbener pipe forming presses form large-format plates to pipes with a diameter of 16 to 64 inches, a length of up to 60 feet (18.3 metres) and a wall thickness of up to 74 mm. What's more, all of the above pipe dimensions can be formed without having to change the tool.


Post Bending Press


This machine is used to post-bend the straight ends of the longitudinal edges of open-seam pipes (max. 40 mm wall thickness) step by step. Heavier thicknesses are pre-bent on the pre-bending press. It is no longer necessary to use roller-type machines, which damage the root face and crush the edges of an open-seam pipe.


Depending on the tooling, pipes with gap widths of approx. 50 to 120 mm can be post-bent. 




Continuous Root Tacking Machine

During the production of large pipes using a bending press, a gap remains between the longitudinal edges of the bent steel plate. With the Gräbener continuous root tacking machine, the gap can be ideally adjusted before tacking the open-seam pipe. For this purpose, the pipe ends (longitudinal edges) are pushed together in a controlled way.


The pipe is run through the machine and is guided by rollers in all four directions. The upper and lateral rollers can be adjusted by hydraulic cylinders. The rollers are adjusted against each other so as to push the longitudinal edges of the open-seam pipe together. Hence, an accurate and optimum tack-welding process is guaranteed.


The welding gap is detected using a 2D laser scanner which processes the data accordingly. This leads to a constant gap welding which is an ideal basis for the subsequent continuous tacking process.


Machines for diameters from 280 to 2,134 mm (11 to 84 inches) are available.



Calibration/Straightening Press

Calibration and Straightening Press


These press types serve for calibrating and straightening LSAW pipes. The pipe is calibrated step by step. The respective pipe section is placed into the semicircular lower tool. Press forces and tool geometry are designed in a way that material spring-back can be compensated. Stresses in the weld seam are reduced.




Impanding Press

Impanding Press


This type of press has been developed for impanding LSAW pipes. The pipe is moved through the machine and impanded by the tool in a step-by-step process. Press forces and tool geometry are designed so as to compensate material spring-back.




End Bevelling Machine

End Bevelling Machine


End bevelling machines prepare the ends of pipes of diameters between 406 and 1600 mm on the face side with straight or bevelled chamfer.

End bevelling machines for large pipe mills can either be designed as one-sided or two-sided systems.










A hydrotester is used for leak tests at LSAW pipes by generating high water pressure inside the pipe.









Engineering en

Engineering of Complete Pipe Mills for Large LSAW Pipes


Apart from machines for the production of large LSAW pipes, Gräbener Maschinentechnik also offers the engineering of complete pipe mills. Using state-of-the-art CAD-technology, all pipe mill modules are synchronized from the very beginning - from the milling of the plates to the final check of the pipe.




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