Specialist Article
Pipe Cold Bending Machines from Schwarze-Robitec
Bending the Costs Downward
Bert Zorn, Managing Director of Schwarze-Robitec, on the possibilities of pipe bending in plant and pipeline construction.
There are many kilometres of pipe on oil platforms, complex chemical plants, refineries and large power stations. All feature similarly large stretches of pipeline. In view of these quantities, pipe fitting plays a special role in plant and pipeline construction; the conduit system must be installed quickly and efficiently. Moreover, these constructions are essential for the function and efficiency of the plants.
Challenges of pipe bending
A cursory glance at an oil pumping facility clearly shows the central challenge: The pipes form a highly complex network and the conduit system inevitably includes many bends. As such, a large number of different formed pipe bends in a variety of dimensions, forms and angles are used in the piping installation. These components need to be welded to the straight, long pipes on the construction site to form the desired pipeline. As a result, these processes represent considerable costs in the construction of these plants. First, the curved elements must be produced in advance, is some cases at an off-site facility. Second, these components must be transported to the work-area and welded to the corresponding pipes, including the associated cost of logistics that can generate additional costs. Additionally, it is often vital to check every finished weld joint for compliance to industry standards or special customer requirements. The processes of using ultrasound or x-ray technology to inspect the welds can also cost a great deal of time and money. It becomes clear that the many pipe bends and the processes involved to produce a complete assembly can offer a tremendous potential for savings in plant construction – if ultimately, many of the in-situ welded bends could be replaced by pre-bent pipelines that are able to be fabricated to the exact specifications of the construction site.
In order to meet these production requirements, there are essentially two options: Cold and warm bending. With warm bending, the pipe is initially partially heated at the desired bend location. Through the factors of temperature and pressure, the material begins to flow. The disadvantages of the warm bending process are that it takes a long time to form the material and the energy consumption used in the production process is very high.
Time and Cost Advantages of Cold Bending
In comparison to the option of warm bending, cold bending offers several advantages, because this procedure eliminates the energy-intensive and protracted heating process. Only the properties of the material are what set certain limits to the plasticity. Otherwise, the pipe can be shaped into almost any form. For example, with the CNC 320 HD bending machine from Schwarze-Robitec, the cold bending of a pipe with a nominal diameter of 12” NPS takes only around one minute – in contrast to the 30 minutes at least that would be needed for the warm bending process. In addition, there are other advantages. For example: With cold bending, materials can be processed that cannot be bent warm or for which heating is simply not permitted because it changes the microstructure of the material. As a result, cold bending has therefore only two real constraints: The space available in the workshop and the length of the machine. If during the bending process the long pipes do not axially collide, they can be processed into complex shapes directly in one pass. Additional positive points of the cold bending process are: The pipe is clamped in an index head and held in place by means of a collet in the transport unit and index head. After the first bend, it is directly transported forward and rotated as required. As a result, three dimensional pipe systems can be created very quickly without a single weld joint.
When the bending radius is critical
What is particularly important in plant construction is the achievable bending radius of the pipe – and it is precisely in this area that the mechanical engineers from Schwarze-Robitec have exceptional experience. The machines allow bending of pipe with very small radii, even when the pipes are very large and thick-walled. What does this mean in regards to plant construction and why is this characteristic so important? The critical advantage of the ability to produce a small radius becomes apparent when installing the pipe: the tighter the bend of the pipe, the less installation space is required – ultimately, the entire pipe system or platform requires less floor area. Moreover, a great deal of pipe can be saved with a small bending radius. The saving with a 180-degree bend and a bending radius of 1.5x D is around 3.5 metres compared with a conventional 5x D bend – on larger production facilities, this small value naturally offers a huge effect on cost reduction. Only recently, the German mechanical builders constructed and delivered a machine to a customer in the refinery and offshore oil industry. The machine is able to process pipes up to 16” NPS with a radius of 1.5x D. As a result, a 16” Schedule 40 (323.5 by 10 millimetres) pipe, for example, can be bent with a radius diameter of only 485 millimetres – all of course in observance of the required standards (for example in respect to reduction of the wall thickness and ovality).
Focus on quality
The technology developed by Schwarze-Robitec is always based on a very rugged machine frame. It reliably resists the huge forces that arise during bending and has abundant power reserves for the clamping functions. In addition, the issue of quality control is particularly important for the specialists at Schwarze-Robitec. For example, the SpringMatic system can measure the pipe bend while still in the bending machine and correct its curvature as necessary. The measuring and correction process takes only a few seconds. As a result, even pipes with unknown properties or widely fluctuating quality can be processed directly with a high level of accuracy.
The machines in the CNC-MW series from Schwarze-Robitec also ensure additional productivity in the bending process. The reason for this is that setup times are minimal. To achieve this, the production facilities use stacked tooling with various nominal diameters constructed one above the other. If a new batch of pipes with a different nominal diameters are used in the production sequence then only the bending mandrel and collet insert need to be changed. This process takes only a few minutes. Consequently, the current bending process is able to continue with unchanged speed and accuracy. Likewise, the processing of flanged pipes is unproblematic. Even before bending, the flanges or sleeves can be welded on. The sophisticated control of the machine and its stable structure ensure accuracy. The stable structure of the machine prevents twisting and the pipe therefore going out of specification, or the flanges ending up at the wrong angle.
Complete know-how
Naturally, the structure of these specialised machines is heavily dependent on the specific requirements of the customer. Schwarze-Robitec therefore supplies customised solutions. An important criterion in the construction of the machine is also the energy efficiency of the production facility. At the same time, the experts at Schwarze-Robitec have a wealth of practical experience with the different pipe materials and as a result, with the corresponding tool and machine requirements. With this complete know-how, Schwarze-Robitec develops answers for the most difficult production jobs. As such, the experts have previously constructed production facilities with a pipe length of over 40 metres and integrated high-rack pipe storage into the automatic pipe feed to the bending machine. Of course, the machines and their control have the latest EDP networking, quality control functions and simulation technology. Not be underestimated is the advantage that is closely bound to the promise “Made in Germany”: the reliability of the production facilities. In recent decades, Schwarze-Robitec has delivered over 2500 cold bending machines to customers on all continents. Many machines supplied thirty or more years ago are still in use today. Here, Schwarze-Robitec guarantees spare parts availability over many years; for the entire operating life of the machines. In addition, international customer service is available – for maintenance on-site or for the optimisation of production processes.
Bending complex pipelines quickly and accurately which results in saving considerable time and expense with installation – these are the central advantages of the Schwarze-Robitec technology. In view of increasing international energy demand and the associated investments in an efficient, state-of-the-art manufacturer infrastructure, the German mechanical engineers are expecting great market opportunities for their bending solutions.
Status: June 2013
Volume: 8.927 characters (without spaces and information boxes)
(Information box 1)
The bending tool
The experts from Schwarze-Robitec construct tooling and stacked bending tooling that are designed perfectly for the respective application. For special applications, the tools have automation components, which allow “bend in bend” processes, which can be preheated or can process special materials. The outstanding quality and precision in bending is ensured by a sophisticated structure comprising bend former, clamp jaw (for clamping the pipe), pressure die (as a counterbearing for the bending moment to be applied) and possibly a bending mandrel and wiper die.
(Information box 2)
Technical specifications of the CNC 320 HD pipe cold bending machine
Max. capacity of the machine:
External pipe Ø x wall thickness
Standard steel: 323.9 x 17.5 mm
Stainless steel: 323.9 x 8.8 mm
Max. moment of resistance: Approx. 1225 cm³
Max. bending radius to pipe centre: As desired by the customer
Max. pipe length: 6000 mm
Max. bending angle: 180° + deflection
Max. bending angle accuracy: ± 0.1°
All values correspond to the standard configuration and can be adjusted according to the wishes of the customer.
Photos (Captions):
Picture 1
The experts from Schwarze-Robitec construct tooling and stacked bending tooling that are designed perfectly for the respective application.
Picture 2
For an oil platform or refinery, hundreds of kilometres of pipes are installed – including countless pipe bends. Great cost savings can be achieved with pre-bent pipelines. Expensive welding and checking processes are no longer required.
Picture 3
The CNC 220 MW HD pipe cold bending machine from Schwarze-Robitec: The stacked tooling is clearly visible in the foreground. With it, pipes of different nominal diameters can be processed quickly.
Picture 4
Modern controls make operation of the production facilties easier. They can be programmed as desired. There is always an integrated quality control.
Picture 5
The robust machine design of the CNC-HD range is designed for constant use under great load.
Picture 6
The machines allow bending radii that are only slightly larger than the pipe diameter.
Picture 7
The CNC 320 HD pipe cold bending machine can process steel pipes with a maximum external diameter of 323.9 mm and a maximum wall thickness of 17.5 mm.
Schwarze-Robitec GmbH – The Company
Having been founded in 1903, Schwarze-Robitec is among the international leading experts in the area of tube bending machines. Since 2011, the company has been run by Managing Directors Bert Zorn and Hartmut Stöhr. At the head office in Cologne, the cold-bending machine specialist currently employs 130 staff. The company is represented worldwide through long-standing partners. As early as in 1977, Schwarze-Robitec produced the world’s first CNC tube bending machine. Over 2,400 machines have been sold to date, many of which have been in unrestricted use in production for over 35 years. In addition to tube bending machines and bending tools, the range supplied by Schwarze-Robitec also includes tube perforating machines, measuring systems and solutions in special engineering. Without exception, the Schwarze-Robitec list of references includes all of the prestigious manufacturers from the automotive industry, energy sector and shipbuilding. Furthermore, the company’s solutions are used in aerospace and many other industries. More information about Schwarze-Robitec can be found online at www.schwarze-robitec.com.
Company Contact Schwarze-Robitec GmbH
Bert Zorn • Schwarze-Robitec GmbH
Olpener Straße 460 - 474 • 51109 Köln • Germany
Phone: +49 (0)221-89008-0 • Fax: +49 (0)221-89008-9920
E-mail: • Internet: www.schwarze-robitec.com
Advertising Contact
Corinna Hellwig • Schwarze-Robitec GmbH
E-Mail:
Press Contact
Susanne Unmack • additiv pr GmbH & Co. KG
Public relations for logistics, steel, investment goods and IT
Herzog-Adolf-Straße 3 • 56410 Montabaur • Germany
Phone: +49 (0)2602-950 99-12 • Fax: +49 (0)2602-950 99-17
E-mail: • Internet: www.additiv-pr.de
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