Here is basically how AC static eliminators work with air knives. (There are DC type static eliminators as well but normally AC static eliminators are used with air knives). Static bars “ionize” the air utilizing a corona effect at the pins along the static bar. They create positive and negative “ions”. 

 

The negative ions created cancel out the positive charge on a charged surface and the positive ions cancel out the negative charge on a charged surface. It takes time for the ions to migrate to the surface so the amount of “ions” and the “exposure time to the ions” is important. When an air knife is utilized it “pushes” the “ions” toward the charged surface. 

 

As the ions are pushed, even with the laminar flow of the air knife, some ions recombine actually reducing the strength of the static bar the further the surface is away from the static bar.  The laminar flow minimizes this ion recombination effect but it still happens.  For fast moving webs, or sheet fed operations that can generate significant charges on material, an air knife with a regular static bar will rarely have the strength to remove static charge because the exposure time is not adequate. 

 

In such cases and extra strong static bar can be used with an air knife to increase the amount of ions hitting the charged target to remove the static.

 

Nex Flow™  has such an extra strong static bar (the triple X) bar with produces significantly more ions than a normal static bar. In fact, the bar alone without an air knife will remove static at 4” or more from the target on applications such as at slitters where you cannot get close.  

 

Combined with an air knife, this static bar can do the job at much greater distances in a reasonable amount of time where the traditional static bar fails and in fact eliminate the static on fast moving webs, or sheet fed operations with high static charge. It can even eliminate static charges at 20 feet away in a reasonable amount of time! Again, the key is phrase is “reasonable amount of time”.

 

One of the key questions we get is “how do I know if the static bar is working?”  AC testers (sometimes at inflated prices) have sometimes been promoted to check if static bars are working.  However, these AC testers are misleading. 

 

They only indicate if there is power going through the static bars.  It does not indicate if they are working properly at all!  

A static bar requires 3600 volts (at very low current of course) at the pins located on the static bar to generate the “corona” which creates the ions that do the job of removing static charge. 

 

This voltage can be easily measured qualitatively with something like our Multicheck which indicates if there is adequate voltage at the pins. 

(A light turns green if the voltage is adequate.)  The voltage, if too low can be from a bad static bar, or power supply or may simply be dirty and cleaning can bring the voltage back up to normal. 

 

The Multicheck is a low cost device to accurately indicate of a static bar is working.