Pictured: The SR 320 tube bending machine from Schwarze-Robitec produces complete tube systems for manifolds, pressure and steam lines from one work piece within a few minutes

According to estimates by the International Energy Agency (IEA), the energy demand of the world population will increase drastically in the coming years: in 2030, around 5.5 billion people will have access to the electricity supply – this is equivalent to growth of 1.5 billion consumers within only slightly more than two decades. To meet the increased energy demand, in addition to investment in renewable energies, the construction of new power plants and modernisation of existing facilities in particular are vital. One critical criterion here is to significantly improve efficiency in the power plant process. The requirements for the installed tube systems and tube materials are therefore also increasing, as they make a noticeable contribution to increasing efficiency. Schwarze-Robitec have developed special bending machines for precisely this application area, which bend high-strength, thick-walled high-pressure tubes as well as boiler tubes, tube coils and entire membrane tube walls accurately and both time and cost-effectively.

The requirements for liquid and steam line systems in modern power plants are increasing: significantly higher pressure, flow and temperature values result in increasing strain on the systems. At the same time, the legal constraints and requirements are intensifying. Leakages can result for example in costly repairs or – which is worse – investigations, fines and even a deactivation order from the relevant regulatory authorities. This makes the use of durable, safe and effective tube systems and solutions all the more important. Whereas thick-walled high-pressure tubes and pipes have been welded together for decades from various straight and pre-bent tube components, modern tube bending processes offer significant advantages with respect to safety, subsequent maintenance and the requirements of the present tube parameters as well as last but not least appreciable benefits in terms of manufacturing costs and times.

Efficient production of manifolds, steam and pressure lines

The semi-automatic SR 320 tube bending machine and the automatic CNC 320 HD from Schwarze-Robitec GmbH produce complex tube systems in one operation from a single tube for example for pressure and steam lines, manifolds and similar tubes. Being equipped with special tools, the machines bend thin and thick-walled tubes with a maximum diameter of 323.9 x 17.5 mm. With a tube size of 323.9 x 10 mm, for example, they have no problem producing a bending radius of 1.5 x D, which is equivalent to a bending radius of 485 mm in the example mentioned. The semi-automatic machines in the SR series are particularly suitable for the production of single bends and small series. The automatic, CNC-controlled machines are also suited to complex tube systems with several bends or large batch sizes.

“Compared with the induction bending processes, our cold bending process offers huge time savings in the production process,” Schwarze-Robitec Plant Manager Jürgen Korte explains.

“Whereas hot shaping of these work pieces takes around eight hours, our customers require an average of only six minutes for one bend.” Depending on the specific application, Schwarze-Robitec offer the machines from their heavy duty machine series for various diameters and wall thicknesses up to 610 x 21.4 mm. The machines are available in semi-automatic design with SR control and in automatic design with CNC control. All machines can be equipped e.g. with a tube magazine and tube feed and enlarged up to fully automatic bending cells.

Economical production of boiler tubes and tube serpentines

Very different but similarly exacting requirements now also exist for boiler tubes and tube serpentines in power plant construction. The production of smaller boilers with greater capacity, for example, requires the use of extremely tightly bent tubes. Depending on the tube diameter, it is not uncommon for the required minimum bending radius to be 1xD (sometimes under 1xD). The semi-automatic booster bending machines and automatic CNC pressure bending machines from Schwarze-Robitec are designed precisely for these requirements. The unique cold-bending process from Schwarze-Robitec offers utmost precision and surpasses the tolerance requirements for wall thinning and out-of-roundness e.g. of European standard EN 12952, American Society of Mechanical Engineers ASME B31.1 and all other international standards. The CNC-controlled booster bending machines are also equipped with a tube positioning device, which facilitates fully automatic bending of tube systems. For efficient processing of very large and complex tube serpentines, Schwarze-Robitec offer the CNC TWIN series machines: this machine series, which is available in three different sizes up to diameter 88.9 x 11 mm, uses two vertically and horizontally movable bending heads (1x left-bending, 1x right-bending), which alternately bend the tube clockwise and anticlockwise. Consequently, the tube serpentine does not need turning after each bend, which ensures quick and economical production processes and the manufacture of large leg lengths.

“Of course, our machines also guarantee the processing of high-strength materials, for example such as high temperature steel alloy T91,” managing director Bert Zorn adds. Moreover, they are able to produce different bending radii within one tube system. Furthermore, adding a Terminal End Bender to the machine is easily possible.

Precise processing of complex tube walls

Schwarze-Robitec also offer a specialised bending technology for the bending of entire membrane tube walls, which is common in the construction of modern boilers and power plants: the FL machine series processes tube walls with a maximum width of 3,600 mm and a length of 25,000 mm or more quickly and accurately by means of the compression bending process. The machines are equipped with a most modern CNC control, which also takes into account e.g. the springback when bending the membrane tube wall. Only recently, the bending specialists delivered one of the world’s largest membrane tube wall bending machines to an Indian customer. With this machine, costumers are able to bent tube walls precisely in particularly large dimensions; the users secure considerably reduced costs and production times as well as lower installation costs. Equally, this machine offers the option of diagonal bending. “Overall, we have been developing and producing tube cold bending machines designed especially for the specific requirements of power plant construction for over 45 years,” Schwarze-Robitec Managing Director Bert Zorn summarises. “Every machine is a customised solution, which we adapt precisely to the individual production needs of the customer.”