Galvanizing Systems / Air Knives

Industry-leading results for the selective application of zinc or aluminium on continuously processed steel strip

DUMA-BANDZINK galvanizing and aluminising systems are characterized by outstanding coating results using a minimum of Zn/Al layers. Moreover, the equipment is robust in service and easy in maintenance and handling. Our equipment offers zinc coating from 30 to 350 g/sqm with highest surface uniformity on products such as GI, GA, Galfan, Galvalume and high-quality ALSi surfaces. It is designed for high speeds of up to 200 meters per minute or even more via continuous development.

Features of our galvanizing systems:

  • Massive finish to avoid vibrations
  • High accuracy of pressure distribution
  • 2- or 3-roll systems
  • Permanent strip adjustment in pass line via individually adjustable stabilising rolls and correction rolls
  • Rapid assembly and quick equipment replacement
  • Quick pressure regulation via DUMA-BANDZINK’s patented radial controller (less than 6 seconds for pressure changes)
  • Considerable noise reduction
  • Significant nitrogen cost reduction
  • Highly reliable lip-cleaning device
  • Anti-adhesion lip coatings

Characteristic of our air knives

Radial Controller

The radial controller is used to ensure a fastest possible pressure control of the stripping medium directly at the product. Therefore,it is installed directly in the air knife. The radial controller consists of steel bodies especially developed for this purpose. By adjusting the steel bodies to each other pressure control is maintained. After the requested system pressure is established, stripping pressure as well as air flow rate are adjusted precisely and evenly directly at the air knife exit across the entire knife width. This is effected via adjusting the steel bodies, which affects both flow rate of the stripping medium as well as knife pressure. Stripping pressure is controlled via specially developed algorithms of the radial controller according to the preset pressure value for strip upper and strip lower side.

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Integrated Solution

Our recente development is the integration of DUMA-BANDZINK JetPro Air Knives and eMASS® strip stabilization of EMG Automation which successfully combines two market leading technologies for increasing the product and process quality in coating lines.

This combination provides the following advantages for you:

  • Optimum synergy between air-knife design and strip stabilisation system
  • Better surface quality (coating uniformity +/- 2% across strip incl. strip edges)
  • Higher exposed throughput (increased automotive exposed line speed +10-20 m/min.)
  • Reduced zinc and nitrogen consumption (min. 1,5 Mio. US$ savings)
  • Reduced investment costs (compared to conventional settings)
  • Operational savings (compared to conventional settings)

Here you can find more information regarding eMASS® strip stabilization of EMG Automation.

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Strip width adjustment

The knife gap length adjustment integrated in the air knives can be moved to coating width during operation. This prevents discharge of the stripping medium outside the stripping area and leads to a significant noise reduction as well as a substantial nitrogen saving when operation in nitrogen mode is executed.

Knife lip cleaner

Knife lip cleaning device is designed in such a way that the flow direction of the stripping medium is not affected during operation. The automatic cleaning procedure is executed via cleaning sheets installed on a carriage above the knife lip. These sheets are designed in such a way that during one cleaning operation upper and lower knife lip front as well as the knife gap are cleaned in one step. When the cleaning process is started the cleaning sheets pass through the complete knife gap. While passing small zinc particles and zinc built-ups are removed. The complete knife lip cleaning device is protected by a specific cover.

INNOWEAR knife lip coating

Our new developed knife lip coating serves to avoid any zinc or aluminium built-ups within the zinc bath or aluminium bath cartridge. The coating is absolutely scratch-resistant and features a Vickers hardness of 2100 HV. For explanation: a Vickers hardness of 700 HV corresponds to a Rockwell hardness of 60 HRC.

Contact-free edge mask

Until 2008 the galvanizing machine of DUMA-BANDZINK were equipped with edge masks operated via touch rolls. Those devices equipped with special, smooth-running air cylinders are operating very gently. Nevertheless, damages caused by the touch roll on the sensitive material especially with thin strips at high line speeds cannot be entirely avoided. For this reason, DUMA-BANDZINK GmbH has developed a contact-free edge mask. This mask is available in two different versions:
1. Full set of edge masks for replacement of existing edge masks or as equipment for new installations.
2. Retrofit kit for mounting on an existing edge mask.The kit can be placed easily on the existing edge maks.
Here, a specially developed sensor is moved by an adjustment drive. This sensor sets the position of the edge mask. In case of a malfunction of the electronic equipment it is possible to maintain operation using the additionally supplied touch roll in conventional manner. For mounting of devices some minor adjustments of the mechanical, pneumatic and electrical equipment are required.

Regarding the full set, the electromechanical adjusting mechanism is directly integrated into the housing of the edge mask. Here, the complete edge mask is replaced. The existing edge mask can be used as spare part. Here too, an adjustable sensor sets the position of the edge mask and a usual operation via touch roll in conventional manner is possible. The advantage of the complete set is the compact version. Mounting of the retrofit kit can be effected within a few days.

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Preheating furnace

After switching on the preheating furnace the heating gas fans forward the air of the preheating furnace from the furnace top and guide it via louvers to the manifold of the furnace bottom. Now, the interior space is permanently heated. Consequently, an air circulation between furnace top and bottom is maintained so that the zinc bath rolls are enclosed by hot air and thus heated.
The air is circulated via the heating elements. Though, only the required energy is fed according to a preset heating curve.
Control of the requested heating energy is effected automatically via program control by gauging the interior furnace temperature and adjusting the respective heating elements. The heating elements as such can be heated to a temperature of up to 650° C. This temperature is sufficient to achieve an interior preheating temperature of more than 400° C.