Basic countermeasures against static include grounding of metallic objects, grounding of workers and making the insulator conductive. Countermeasures against static to be applied for insulators that cannot be made conductive include inhibition of static generation by humidification and static elimination using an ionizer. However, it is difficult to completely prevent static generation from insulators by humidification. Excessive humidification may also accelerate deterioration of facilities or degrade product quality. Ionizers continue to produce an effect while not being so greatly affected by the environment, so they are applied in a wide variety of fields as an effective countermeasure against static in insulators.

Ionizer principles

A voltage-applying static eliminator (ionizer) applies high voltage to the discharging electrode by using a high-voltage power supply. This causes generation of corona discharge between the discharging electrode and grounding electrode. The static eliminator (ionizer) ionizes the air by using the corona discharge, thereby generating positive and negative ions. Of the ions generated, those needed for static elimination (q) are moved to the charged object by Coulomb force (F) that acts in the direction of the object due to its electrolysis (E). This causes the charge on the object to be neutralized (static elimination).

Example of ionization from a negatively charged object with an AC-type ionizer

Precautions for use of an ionizer

1) The static-elimination effect of an ionizer must be confirmed after its installation. The effect varies greatly depending on the installation distance, angle, air volume (applicable to fan-type ionizers), and air pressure (applicable to nozzle-type or gun-type units). There are two methods of confirming the effect. One is to measure the quantity of electric charge on the object after static elimination (by using a static meter or Coulomb meter). The other is to confirm the effectiveness of the ionizer itself by using a charge plate monitor (NK-7001).

2) An ionizer needs regular maintenance. The discharging electrode needle generating ions and the area around it become dirty over time. This causes degradation of static elimination performance and loss of ion balance. The performance will be recovered when the discharging electrode needle and the area around it are cleaned. For a unit with a filter, air volume is reduced if the filter becomes dirty, so cleaning the filter is important.

3) The appropriate time for maintenance changes greatly depending on the usage environment. This time can be recognized through numerical management of ionizer performance with the charge plate monitor (NK-7001). A unit with a cleaning lamp also informs of when it requires maintenance.