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Company news

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06 Sep 2022

The dross box: when the glass is lifted out of the tin bath

HAMLAR / Germany. In float glass production, the dross box is the interface and sluice between the tin bath and annealing lehr. This point in the production process poses particular challenges, because the glass ribbon, which is still very fragile, requires the utmost precision in handling under extreme ambient conditions. The trick is to transfer the glass ribbon from a liquid and full-surface support to a roller conveyor. The Grenzebach dross box can master this tricky process step thanks to innovative technology. Valuable process improvements are achieved with customizable roller technology, special roller sealing and safe maintenance options. 

Roller technology: individual height adjustment provides production flexibility

The rollers are special features of the Grenzebach dross box. The glass ribbon, which is still flexible, is lifted out of the tin bath by three individually driven rollers (LOR = lift-out rollers) and conveyed to the annealing lehr. Thereby, the lift-out rollers form a curve geometry, which can be adapted to the respective production requirements by individually adjusting the height of each roller. This also allows for an equal distribution of the load on all rollers. The result is a flexibly adjustable lift-out curve with settings that can be optionally saved for the respective glass thicknesses.

The special roller sealing contributes to a particularly high level of insulation of the Grenzebach dross box. This results in less heat loss and a more homogeneous temperature distribution across the entire width of the glass. The ambient temperature at the edge no longer substantially deviates from the temperature in the center of the glass ribbon. This provides better glass quality and reduces the risk of a cross breakage.

The rollers are constantly cleaned over three-part graphite bars with pneumatically adjustable contact pressure to ensure a clean process.

Dross box housing – protected against deformations

The dross box is not welded to the tin bath but attached to it by means of a clamping device, which is firmly fixed after the tin bath has heated up to 620 °C.  This way, thermal expansion is accounted for and deformations due to heat effects will neither occur on the housing nor on the U-channel.

 Maintenance and operation: roller exchange during operation

The Grenzebach dross box can be locally and decentralized controlled with the innovative user interface. During maintenance, operators benefit from increased work safety and improved accessibility to the end plate and when changing rollers. Rollers can be changed during operation. The resulting glass loss during roller exchange is minimal. Similarly, the graphite bar change can be performed quickly and easily in a very short time.

Additional features of the Grenzebach dross box:

  • Default design up to 650 °C, optionally up to 850 °C
  • Dross box for normal and extra-wide float lines
  • Retrofitting of existing equipment possible
  • Injection of N2 and SO2 possible
  • Housing with stainless steel lining, insulated and gas-tight, including corrosion and SO2 protection
  • Retrofitting of camera systems and illumination optionally possible

Hot end: new annealing lehr offers improved process control

In addition to the innovative dross box, Grenzebach customers also benefit from an optimized annealing lehr with new design. Building on the expertise of CNUD EFCO, Grenzebach has completely redesigned the annealing lehr and now offers a flexible annealing point, improved process control, more precise simulations, and a significantly reduced energy consumption.

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06 Sep 2022

New annealing lehr with adjustable cooling capacity increases glass quality at reduced energy consumption

HAMLAR / Germany. Controlled cooling in the annealing lehr is one of the crucial process factors on the way to the ideal glass quality. Grenzebach's new annealing lehr enables to adapt the cooling capacity exactly as required. Individually controllable sections are a major step forward and increase flexibility at the annealing point. This provides users with new options to achieve the ideal glass tension for a wide range of production scenarios. The new design and improved cooling technology thereby offer powerful added values and also result in significantly reduced energy consumption. This also includes increased occupational safety and optimized maintenance possibilities.

Linear cooling curves crucial for glass quality

In float glass production, the glass is fed to the annealing lehr, which can be up to 200 meters long, via the dross box after the tin bath. The glass ribbon cools down from about 600 °C to about 60 °C. In this production phase, the decisive factor is the temperature curve around the so-called annealing point, which lies in the temperature range between 505 °C and 525 °C, depending on the specific composition of the glass. At the annealing point, the glass changes from elastic to solid state. Ideally, the cooling curves before and after this point should be as linear as possible. The reason for this is that the correct temperature profiles and cooling rates are crucial for the glass tension. If the tension is too high, cracks might appear in the glass ribbon. If the stresses are too low, though, the glass cannot be processed sufficiently well later on.

With the new generation of annealing lehrs, Grenzebach increases the flexibility at the annealing point and thus offers customers new possibilities to achieve the perfect glass tension for all kinds of production scenarios. Based on the 40 years of experience of CNUD EFCO, Grenzebach has completely redesigned the annealing lehr.

Aims of the new design were:

  • Higher flexibility at the annealing point during production regarding tonnage and glass thickness
  • A modular construction of the annealing lehr with improved process control
  •  Improved possibilities for simulations to optimize the annealing lehr during the project engineering phase
  •  Reduced energy consumption and emissions through highly efficient cooling and lower heat losses
Optimizations at the hot end: advantages of the new annealing lehr

The new annealing lehr allows for a cooling capacity that is precisely adapted as required. The individually controllable heating and cooling sections enable the process to be controlled more precisely and to react flexibly to changes. Shorter modules lead to shorter control zones, so that the process can be responded to even more precisely. Thus, the annealing point is kept flexible through adapted temperature curves. In addition, the controllable cooling can also be used to optimize the distribution of the tension across the glass ribbon. The contraction of the glass during cooling is compensated by segmented drive trains with controlled servo drives. The risk of scratches is significantly reduced. These changes result in substantially increased glass quality and, at the same time, drastically reduced energy consumption. These energy savings are due to a highly efficient cooling process and optimized insulation. The optional heat recovery also contributes to energy efficiency, which is further increased.
With the new design, production is now much more flexible with regard to tonnage and thickness range.

Easy maintenance – changing rollers during operation

The innovative drive design makes maintenance of the annealing lehr much easier and also offers increased protection of personnel during maintenance thanks to innovative protective covers – also during operation. Users also benefit from a greatly reduced noise level and intuitive system operation.

Eyes on the future – prepared for further automation and digitalization measures

The design of a float glass line is complex. Far-reaching challenges need to be addressed in order to meet growing customer and environmental demands in the future. A virtual, digital image opens up extended possibilities for greater planning and process efficiency. "We are working intensively on the topics of data science and process models", says Markus Gruber, Senior Vice President Business Unit Glass at Grenzebach. "Our aim is to simulate and understand processes better in order to shorten the project engineering phase, reduce investment costs and increase production efficiency."

The new annealing lehr is already perfectly prepared for future adjustments: Featuring considerably more sensor technology, the annealing lehr enhances the data situation and renders even more accurate simulation and process control possible. The interface to higher-level control systems and the associated digitalization potential are also included.

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28 Jul 2022

Grenzebach at glasstec 2022

"Let us be your guide through the world of glass – from hot to cold": This is Grenzebach's motto at this year's glasstec from 20th to 23rd September 2022 in Düsseldorf. After the integration of CNUD EFCO at the end of 2019, Grenzebach will now present current developments for the hot and cold end on their more than 500 square meters-big booth B23 in hall 15:

  • New annealing lehr: with cooling capacity that is precisely adapted as required, flexible annealing point and significantly reduced energy consumption.  
  • Innovative dross box with adjustable roller height, improved insulation and uniform temperature distribution, as well as optimized control and maintenance.
  • New conveyor technology for optimized glass production with direct drive, reduced number of components and simpler access to key components.
Solutions for the digitalization of flat glass production

Grenzebach also addresses the digitalization of highly efficient flat glass production lines. The perfect solutions are provided with the digitalization eco-system SERICY. Be it in cut-to-size optimization, in the digitalization of previously analog information through the recorder app, or through targeted handling recommendations from an operator guidance system based on an AI-trained process model.

Foundation of the Grenzebach Envelon adds solar-active façades to the business area

Grenzebach taps into the field of solar-active building façades, or building-integrated photovoltaic systems, with the foundation of the Grenzebach Envelon GmbH in October 2021. The Grenzebach Envelon GmbH is a system provider for solar-active facades and building envelopes and provides an attractive and aesthetically pleasing option for efficient decentralized power generation. As part of the Grenzebach Group, the ENVELON brand combines years of experience in solar and facades with the engineering art and the Grenzebach glass industry expertise.

Grenzebach Envelon presentations on the glasstec:

  • glasstec Conference: Presentation from Jochen Weick, Vice President Sales and Business Development of Grenzebach Envelon GmbH: "Glass in active building façades" on 20th September from 11:40 AM - 12:00 PM
  • Special show "glasstec technology live": Presentation of a colored, solar-active building façade of the Grenzebach Envelon GmbH
A new partnership for more efficiency in the glass industry

Since mid-2022, Grenzebach and the family-owned Nikolaus SORG GmbH & Co. KG, specialist for glass melting and conditioning technologies, are working together in close cooperation. The two leading suppliers of glass production technology are combining their expertise in this partnership to provide their customers with even more comprehensive support. The core task of this cooperation is the provision of engineering services related to glass production and the development of turnkey projects. On the glasstec, the two companies are presenting their services shoulder to shoulder at neighboring booths.

"After a break due to the pandemic, we are now very happy to be back in direct contact with customers and partners", says Markus Gruber, Senior Vice President Business Unit Glass at Grenzebach. "At glasstec, Grenzebach has the perfect platform to present ourselves as one of the leading manufacturers of production equipment for float glass manufacturing. We have a lot in store for you – stay tuned!".


 

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