Using Explosion-proof Static Control Bars in Hazardous Situations
January 24th 2008

Alupa is one of Europe’s leading providers of vacuum metallised paper. The company produces over 18,000 tons of paper every year for use in a range of applications, mainly by manufacturers of labels, cigarette packaging and gift paper.

Since 1996, Alupa has manufactured paper with widths of 2.2m and at a speed of 700m/min on a Polytype AG coating machine. This particular machine is set up to work with water-based coatings.

However, in order to achieve an even better gloss finish on some specific products, Alupa decided to change the process and use solvent-based lacquers.

The Process Plan

On the first run, the paper is coated with a solvent-based lacquer that closes the pores in the paper and gives it a smooth surface. The paper is then metallised with aluminium under vacuum conditions. Finally, the metallised paper goes through the coating machine again and is coated with a second solvent-based lacquer, which serves as a primer for the subsequent printing process.

A Problem Arose

In practice, the first run on the high-speed coating machine resulted in major unforeseen safety problems. The treated paper was very dry and consequently became loaded with static charge. Static discharge resulted in sparking in several areas, with the associated immediate risk of fires or even explosions.

The Solution

The first attempt to resolve the problem relied on the installation of a large number of conventional AC static control bars. However, in order to provide effective control of the static, the bars had to be mounted very close to the web. This resulted in contamination of the bars due to splashing from the coating process and a rapid loss of ionisation efficiency.

Alupa then looked to Meech International and its range of Ex products for an effective solution. Meech’s Ex products are certified by Baseefa to comply with Article 9 of the Council Directive 94/9/EC (ATEX). They are particularly suited to coating, laminating, finishing and gravure printing applications, where the highest safety standards are mandatory.

Alupa installed Meech’s explosion proof 976Ex Pulsed DC bars directly before and after the coating rollers. The main advantage of these ATEX certified bars is that they provide highly effective long-range ionisation without the need for air assistance. Contamination from the coating head was therefore avoided. The removable emitter pin assemblies also allowed quick and easy maintenance with minimum downtime.

Alupa was immediately able to achieve its goal of higher quality products without the associated fire and explosion risks.

More articles from Meech International Ltd: