customized manhole bases from a single cast
Betonfertigteilesysteme GmbH (BFS), from Blaubeuren in the German region of Swabia, thus introduces Capitan as a sophisticated method for producing monolithic manhole bases. The development team at BFS created in recent years, a method for the production of customizable monolithic manhole bases with an extremely smooth surface, flexible channel diameters and gradients, and variable heights of inlets, outlets and supply lines.
The Capitan system used enables low-wear production whilst reducing the time needed for the manufacturing process to minimum. A trend-setting instrument is created for the construction of underwater infrastructure with efficient flow rate. The specific conditions of each civil engineering project require tailor-made solutions. When constructing modern sewer lines, each manhole must exactly conform to the requirements on the installation site. Manhole heights and diameters, the design of the channel with its inlets and outlets, gradients and angles mostly differ from one case to another. For this reason, almost every manhole base must be manufactured to order. To date, the manufacture of these customized products required a high degree of manual work and skill and craftsmanship.
Betonfertigteilesysteme GmbH demonstrates with its new Capitan system how easy it is today to produce customized, accurately fitting manhole bases to an exceedingly high quality standard. The BFS patent engineers have actually succeeded in creating a system that results in a significant advancement in the production of manhole bases.
No rough edges!
The Capitan manhole production line makes it possible to manufacture monolithic manhole bases from a single cast. Channels are very easy to customize in terms of their gradients, diameters, inclinations and angles. Even different inclination angles of the inlets in relation to the outlet can be designed individually, as well as varying slope angles.
Three production steps towards the finished manhole base
The Capitan process comprises three production steps: configuration, milling and molding.
The system can be modified and includes a software suite for product configuration, a three-axis block milling center for the manufacture of the negative channels and blockouts, and a manhole base casting mold unit.
As in the case of conventional systems, production starts with the manufacture of a blockout element that mirrors the exact channel after casting of the manhole base. In the BFS system, this negative channel is milled from a single piece (i.e. without gluing or any unsightly transitions). For this purpose, EPS rigid foam is used as the blockout material that is milled exactly to the required shape on the milling center. The need to assemble individual parts has been eliminated. In just a single pass, clean, round-shaped transitions and accurately fitting, perfect channels are produced.
To visualize the specifications, the first step is to develop a CAD-based solid model on the computer using the specially designed BFS product configurator. This program has been tailored to the needs of precast plants and can be used to capture product information from the incoming order to production scheduling of the manhole base in easy, user-friendly steps, and to visualize this information in a two- or three-dimensional image. Each product is customized and assigned using the company name, construction project, type and number of manhole before the actual basic project data is entered. The input screen is then used to define the manhole to be produced in greater detail. Nominal diameter, number of supply lines, pipe connection design, diameters of inlets and outlets, angles and gradients of channels and linear displacements are all defined in this step. The BFS product configurator automatically calculates the wall thickness and manhole height. Upon a single click, the computer generates a visual model and summarizes all configured data in a manhole data sheet. After completion of this step, a CAD-CAM system is used to create an NC code that transfers the information to the downstream milling center in order to mill a negative channel from a block made of EPS rigid foam or sand in the second work step. The three-axis CNC milling center specially designed by BFS enables the milling of negative channels for nominal manhole widths from DN 1000 to DN 1500 and beyond. The milling chips are collected using an extraction system and can be fed into a recycling process. Another system extension also makes it possible to manufacture blockout cores from commercially available EPS blanks.
Just in time
All negative channels can be produced in advance or simultaneously. One employee can produce and assemble about 30 accurately fitting complete channels consisting of rigid EPS foam. It should also be noted that hazardous fumes such as those generated during the previously applied production steps, e.g. when cutting the EPS blanks with a hot wire, have been eliminated. Also to mention, the milling tool is subject to only a minimal degree of wear.
The final stage
When the negative channels formed by the blockout elements have been customized to the manhole, the complete channel with blockout cores or manhole lining is assembled in only a few quick steps and fixed by a special BFS-fastening system to the steel core of the specially designed BFS casting mold used for the manufacture of monolithic manhole bases. In the special casting mold, the mold shells can be exchanged using a quick-change system. A retractable core mold enables a quick demolding process. Prior to demolding, the mold is filled with conventional chuted concrete or self-compacting concrete via the BFS concrete feed system. The manhole base hardens and takes its specific contours overnight. The finished manhole base can then be taken out of the mold and turned by 180 degrees using the BFS turning unit.
The new Capitan process represents the art of engineering in many areas. Beyond the proprietary CAD program and the specially designed EPS block milling center, the BFS team also developed a process using a special release agent, for which a patent is pending. The agent may be either sprayed or painted, and, after curing of the product, the negative channels can be easily released from the hardened concrete in less than a minute. Another advantage is the smooth surface of the channels that ensures an optimal flow rate in the finished, demolded manhole base. Hence, finishing is no longer required after demolding. The range of accessories includes a toolkit for easy manual clamping and removal of the channels and blockouts. Appreciated at Capitan system are the low production costs, high process reliability, and the unique product quality.
The first system developed for series production is currently being successfully used by the Czech company Prefa Brno as. The company already operates the BFS system for the fully automated production of manhole bases using the gonio process, a Jumbo line for the production of large pipes, and an Atlantik automatic manhole ring system.
Prefa Brno
Prefa Brno is one of the leading manufacturers of concrete elements and precast products, specializing in the manufacture of reinforced concrete pipes and prestressed concrete products, and also applying the spinning technology in various areas. The company has been in business for 60 years. At the beginning, Prefa had been specializing in the production of precast elements for residential and industrial construction. In the 1990s, the business shifted its focus to the current product range. Today, items for sewage account for a major share of the company’s products.
In 1992, Prefa Brno, which had previously been state-owned, became a stock corporation. Prefa Brno a.s. currently operates five production facilities with a total of 400 employees. Among them, 105 people work at the Strážnice plant where concrete pipes, manholes, manhole bases and reservoirs are produced. This factory is the largest manufacturer of sewage products in the Czech Republic.
After the accession of the Czech Republic to the EU, Prefa Brno set ambitious goals and is working proactively on expanding its business to other Central European countries. This is where Prefa Brno is very successful due to the very high quality of its products. Production has been continuously expanded using state-of-the-art plant and equipment; this will also be continued in the future.
Prefa Brno has a clear environmental focus and makes every effort to continuously improve the related standards for its products. Safety at work and the creation of a favorable work environment are also key items on the agenda of the business. With the investment in the Capitan system, Prefa is determined to continue to meet the high quality standards in manhole production.
The company BFS is Capitan with your system back in the lead and is satistfied with the new orders, as well as the systems which will be delivered in the spring of 2011.
