Static elimination / discharging or neutralisation

What is static?

Static is a stationary electric charge, which forms on the surface of non-conductors (insulators) and un-grounded or isolated conductors. Friction, pressure and separation are the main reasons for the creation of static. If two materials come in contact with each other and are then separated, electrons may be transferred from one to the other. A change in temperature also creates charge. Static electricity is thus an imbalance of positive and negative charges. When a moving web comes in contact with a rubber, steel, or an aluminium roller and then separates from it, static electricity gets created on both the web and the roller. As bare films, paper and rubber rollers are non-conductive, there is no free flow of electrons. Thus the static charge on films and paper dissipates very slowly. Metal rollers and foils being conductive allow free flow of electrons to ground, since they are invariably earthed. However, conductors will develop a static charge if they are insulated from the ground. The magnitude of the static charge will depend on the material, applied forces, separation rate, temperature and relative humidity.

 

Triboelectric series

 When different materials rub against each other, which material becomes positively or negatively charged depends on the materials’ abilities to hold or give up electrons. This ranking is called the tribo-electric series. A list of some common materials is shown below. Under ideal conditions, if two materials are rubbed together, the one higher on the list should give up electrons and become positively charged.

 

Problems created by static electricity

Static electricity can create unwanted problems. In many industrial situations, static charges reduce productivity and also create quality problems. Commonly encountered problems due to static are:

• Uncomfortable shocks to operator
• High reject rate
• Static attracts dust/residue on the shop floor
• Fire and spark hazard
• Breaks and jams
• Low speeds
• Web wander
• Improper sealing
• Improper stacking

 

Static discharge solutions

Valence helps you identify the source and magnitude of your static problem. We have a complete range of quality products and can provide economical solutions, backed by sound application engineering and post-sales service support. We help you place these equipment to an appropriate location, thereby minimising problems created by static.
AC static eliminators: Valence active static eliminating bars are of shockless type. Touching the electrodes will not give any shock. Powered by a high voltage source, the active bar provides very effective static elimination on moving webs and sheets. A single row bar is suited for most general purpose applications and the more powerful dual row bar is an ideal solution for more difficult and high speed applications.
DC static eliminators: For more effective static elimination at speeds as high as 900 m/min, the Valence DC static eliminating bar is a better option. These too are shockless and sparkless and can be positioned 150 mm away from the target where static needs to be eliminated.
Ionising blowers: A high volume curtain or stream of ionised air is produced. This is done by blowing air through ionising electrodes positioned at the exit of the air flow. The resulting ion cloud can travel a distance of one meter under ideal conditions. The Valence ionising blower can be used in a variety of industrial applications.
Passive static discharge brushes: The Valence passive static discharge brush is kept close to the moving web. The charged web is thereafter virtually free of static. These brushes can be used in potentially explosive environments. They do not require a power supply.
Digital static charge meter: The Valence digital static charge meter is a useful tool for checking static levels in various processes.