Monolithic manhole bases with CAPITAN by BFS

Fast-track upgrade at the Czech business B&BC a.s.

 Today, B&BC a.s. is one of the largest producers of concrete and precast items in the Czech Republic. The company headquartered in Zbůch, about 10 km south of Pilsen, was established back in 1949. In 1992, the formerly state-owned company was privatized. Then, a few years ago – in 2008 –, the business made a major step forward. The new owner, Peter Brezina, took over the company and merged it with APB Pilsen, initiating a comprehensive upgrade and modernization process. Some of the manufacturing equipment was replaced completely, such as the paver production line.

Among other items, the range offered by the company includes products for road construction and other landscaping-related purposes, special blocks and fences, filigree floor slabs and precast stairs. The second production facility operated by the company, the concrete plant located at Zruč (also near Pilsen), produces a wide range of ready-mixed concrete grades.

However, about half of the production volume is comprised of the pipe and manhole range supplied by the main plant also called „Prefa Zbůch“. Investing in cutting-edge manufacturing equipment for the production of monolithic manhole bases was a major step towards shaping a state-of-the-art, dynamic enterprise.

Capitan by BFS

In spring this year, the Capitan system supplied by BFS GmbH was installed for this purpose, which is a system for producing manhole bases „from a single cast“, using negative channel molds configured to meet the specific job needs. A multiaxial EPS (polystyrene) block milling center cuts these molds from a single piece, which creates smooth and clean mold surfaces with a seamless appearance.

An important aspect in selecting this technology was to enable the production of a complete range of premium monolithic manhole bases for all inlet types, sizes, gradients and angles. „Also, the BFS Capitan system achieves very smooth surfaces, especially for the channel,“ explains Production Manager Pavel Záhořík. „Since the takeover of B&BC by APB Pilsen, we have increasingly been concerned with ensuring premium product quality. This is where the monolithic manhole production process plays a crucial role, and Czech customers of B&BC are also very much focused on an outstanding appearance of the products“.

The Czech market requires an incredibly diverse range of pipes to be connected to the manhole, including many types of plastic pipes supplied by a large number of producers, cast pipes and concrete pipes with integrated seal. This diversity posed a special challenge to the BFS engineers. Due to the highly flexible Capitan system, all of these requirements were fulfilled perfectly. Both commonly used plastic pipe sleeves and the integrated seals for connecting concrete pipes can be integrated in the pipe recess during concrete pouring. In many cases, plastic pipes can even be connected without plastic sleeves, says Volker Nusser, BFS Area Sales Manager.

Configuration – milling – concrete pouring

The Capitan custom configuration tool is the key to economically producing the manhole bases. This proprietary BFS tool is based on a 3D design software and calculates all product parameters. Specific manhole data, such as standard or terminal manhole, manhole diameter, number of inlets, types of pipes to be connected, gradient of the pipe connection within the manhole wall, gradient of the channel routing and channel height, are all entered in this system. The program even handles tapered channels with great ease. Wall thicknesses and manhole heights can be calculated automatically. The software also provides options for oversizes for clinker linings, reductions in wall thicknesses (by shifting the blockout cores), various base gradients or stepped base surfaces. At the end of the process, a 3D model is calculated, which can be submitted in datasheet format to the client for approval prior to production start. In addition, the user interface has been designed with ease of use in mind and automatically monitors all data inputs to detect any errors committed.

This information is transferred from the work scheduling office to the production facility, where the final milling program is passed on to the block milling center. This center uses EPS blocks available in various standard sizes to produce both negative channels and blockout cores (for pipe connections). The EPS cuttings are extracted and collected for recycling purposes. Within an extremely short period, this process thus creates perfectly smooth, seamless, accurately fitting negative molds that are exactly mirrored by the manhole base after concrete pouring.

It takes only a few work steps to connect the milled negative channels and blockouts to each other, using a specially designed bolt system. At the same time, anchor bolts are driven into the underside of the negative channel. These anchors subsequently enable the effortless lifting of the EPS molds from the hardened concrete.

What is crucial in this regard, however, is a special release agent that is then applied to the negative molds using a brush (a spray process can also be used). Thereafter, the negative channels are moved into a UV chamber in order to ensure better hardening of the liquid agent. At a later stage, the patented release agent system developed by BFS enables quick demolding without residues, which makes it possible to lift or pull out the EPS molds very quickly.

Once completed, the finished negative channel is moved upside-down and positioned on the steel core in the BFS casting mold. This means that the manhole base is also in upside-down position when curing.

The Czech factory currently uses 32 custom casting molds in sizes adjusted to regional demand.

B&BC manufactures manhole bases in diameters of 1,000, 1,200 and 1,500 mm in accordance with the European standard. Heights vary between 500 mm for DN 1000 and 1,650 mm for DN 1500, wall thicknesses range from 155 to 290 mm. The Capitan system makes it possible to produce inlets in diameters of up to 1,000 mm, both with integrated and add-on seals. At B&BC, up to 30 items can be produced per day.

A conveyor transfers the concrete mix from the adjacent factory building into a bucket which is moved to the individual casting molds by a crane. The molds with the inserted EPS blockouts are gently filled with self-compacting concrete (SCC). It should be noted that less than 30 minutes have passed per manhole base up to the concreting stage, including data input in the product configuration tool and the customized milling process.

The manhole base hardens overnight. On the next production day, the BFS turning bar lifts it from the mold and turns it by 180 degrees. The only items left in the concrete product are the negative molds, which can be removed quickly and effortlessly: the blockout cores are withdrawn in a single piece using a simple, manually operated pulling device, and the channel mold is easily released manually from the early-strength concrete or is lifted in immaculate condition using the bolted anchors referred to above.

This demolding process results in a manhole base with very smooth surfaces and EPS negative molds that can be re-used. „Commonly used channel molds can be re-used, from highly customized molds, smaller channels can be milled”, Volker Nusser comments. It should be noted that the blockout cores in particular can be re-used several times.

A modular system prepared for the future

But there is always continuous improvement: „As demonstrated at the 2010 bauma already, we are also working on a process where both polystyrene and other mold materials can be used,“ Volker Nusser adds.

At its in-house laboratory, B&BC is currently evaluating the option of re-using the polystyrene in production, with promising prospects regarding possible solutions.

The modernization efforts made at the Zbůch site are far from being completed. The entire company premises are currently being redesigned. State-of-the-art factory buildings that will accommodate the new production lines for the existing range and the planned expansion are already under construction. As a result, the Capitan system is to be moved into a new building as well, followed by an upgrade to fully automated operation.

„The decision in favor of this system was absolutely right,“ Pavel Záhořík says full of confidence. „We are very satisfied with this method of producing monolithic manhole bases. Also, we can easily respond to growing demand by purchasing additional casting molds.“ Getting prepared for the future – this is what is currently driving B&BC a.s. with the aim to achieve superior production quality and to meet the increasing demand for premium construction materials. The business intends to strengthen its position in the Czech building materials market whilst implementing its vision of a state-of-the-art, dynamic enterprise.

A major step in this direction is certainly the purchase of the Capitan system supplied by BFS. Other precast producers are apparently of the same opinion since the German engineering company already sold 10 of these systems in Central Europe after the initial presentation at the 2010 bauma show – a true success story indeed!

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