EN
The trend towards electric mobility holds further growth potential for the precast concrete sector. The necessary expansion of the grid infrastructure results in an increasing demand for transformers to convert the supplied medium voltage into low voltage that can be used by end consumers and industry. In Germany, a significant proportion of transformer stations, unless installed in buildings, is realized as a precast concrete station. For a variant of these transformer stations, the non-accessible compact substation, RATEC developed a formwork solution initiated by customer requirements several years ago.
In 2018, Ratec delivered the newly developed formwork for the first time to a plant of German utility and transformer station producer Scheidt GmbH & Co. KG. The following year, Ratec was awarded a follow-up contract to supply another site with its formwork. Finally, a third formwork has been installed in the summer of 2020.
"We are delighted that we have been able to build on the two previous successful projects," says Joerg Reymann, Managing Director of Ratec GmbH. After 2018 and 2019, this is the third collaboration between Scheidt and the Hockenheim-based formwork specialist: With this project, it has been possible to roll out Ratecâs highly variable formwork solution for the construction of transformer stations at all Scheidt locations throughout Germany.
Highly variable formwork for a wide range of station types
The customerâs initial objective was to modernize its existing production and replace the old formwork, and in that course increase flexibility and accelerate set-up times of the form-work. Therefore, the design of the new formwork had to be extremely variable and allow the customer to produce two transformer station sizes with a single formwork while at the same time also covering different design variations. Ratec developed the requested formwork in modular design, which can cover a large number of the different design variations for two types of stations.
Project #1
The fiÂrst installed formwork is designed for the production of transformer stations measuring 2.4 x 2.1 x 2.3 m (L x W x H) and 2.9 x 2.1 x 2.3 m (L x W x H). To change between the two element lengths, the formwork core can be converted from one to the other length. This variation also had to be provided for in the design of the base frame and the outer panels of the formwork. The outer panels are moved manually and are securely closed by corner bracing.
The various interior workings of the stations are achieved with the help of interchangeable attachments which are securely held in place on top of the core by a hydraulic tensioning device.
More than 23 different attachments make it possible for the customer to realize its broad program of up to 14 differing variations. For openings in one or more of the elementsâ side walls, Ratec also provided the according steel frames, that are attached on the outer panels and held by high-performance magnets.
Previously the conversion from one variation to another took up to a half working day, now the change from one attachment to the other within one station size is completed in significantly less time. At the same time, it is no longer necessary for an employee to enter the core in order to fix attachments from inside, as the upper parts are tensioned by hydraulic mechanism from outside.
Projects #2 and #3
In the two subsequent projects, the installed moulds are largely identical and differ from the first projectâs solution mainly in their size, and in the concept and design of the attachments.
The length of the formwork can again be varied, now be-tween 3.10 m and 3.60 m, the height between 2.59 m and 2.84 m. The width of the formwork is 2.41 m. The change of length is performed again by utilizing an intermediate piece which is inserted between or removed from the two halves of the core.
The height can be changed by using a special frame that serves as the bottom formwork for the lower elements. In contrast to the first project, fewer upper attachments are needed for the different station variants. Only the inner walls of the substations vary and are produced by different inserts for the core which are tailored to the respective geometry.
The customer has a total of 2 x 3 interchangeable inserts avail-able for his variants, which are placed by crane and then hydraulically tensioned. This reduces the time and effort required for changing inserts. With the two lengths, two heights and the inserts, this formwork type covers a total of twelve different station variants.
Interchangeable insert for the core to form the inner walls of a station
Example of two different shapes of the possible concrete elements
Easy handling, short set-up times, versatile application possibilities
For demoulding, the inner core is designed with a draft angle, which means that the walls are formed slightly conically. To support the demoulding process, the bottom formwork is raised hydraulically by about 10 cm before the element is lifted. Overall, the bottom formwork has more than 60 tons of lifting force that is transferred over four cylinders.
Each formwork is also equipped with a vibrating unit for the use of normal or exposed aggregate concrete, that provides 14 kN vibrating force.
As the formwork can cover different lengths, heights, and shape variations, it is suitable for all common station types that Scheidt manufactures on behalf of its customers. Another advantage is the easy handling and very short set-up times: Changing the attachments for another station type usually takes less than 20 minutes. The versatile applications also accelerate processes in the plant.
âFor about 2.5 years we have been working together with Ratec in the ïŹeld of formwork construction, and we are entirely happy", comments Georgine Scheidt, Managing Director of Scheidt GmbH & Co. KG. "We are excellently accompanied from the first idea, over first plans to the start of production. In this way further development is simply a pleasure. We are looking forward to many further projects".
The follow-up orders demonstrate that Ratecâs solutions prove their value in practical use and simplify production processes over the long term. Throughout the past projects, Ratec has thus further expanded its expertise in this specialist area and rounded out its portfolio. This is supported by a growing demand and new projects, that are currently in progress or planning.