Static Returns with Colder Temperatures

The temperatures have been dipping a bit in Cincinnati.  One day it might top 80F (26C), the next it could only get up to 60F (15C).  So, its typical Cincinnati weather.

With the fluctuation in ambient temperatures comes a fluctuation in humidity and varying propensity for static.  Lower temperatures, and the corresponding aridity in the air which usually accompanies them, are prime conditions for generating static.  This is because the relative humidity (which is a percentage of moisture held in the air compared to the maximum it could hold (at a given temperature)) normally drops below 30%, which promotes static.

But why?

Lower relative humidity essentially means less moisture (water) in the air.  And, water conducts electricity very well.  So when relative humidity is above 30%, the surfaces and materials in a given environment will absorb the moisture in the air or they will form a very thin surface layer of moisture which dissipates accumulated static charges.  The thickness of the moisture layer increases with increased relative humidity, so when relative humidity drops, so does this layer on surfaces and materials.  Then, when this layer of moisture is no longer present, static can easily build up.

Such was the case for the end user in the application photos shown below.

IMG_0894

Stacked plastic sheets experiencing a static problem

IMG_0896

Additional view of plastic sheets

This system began experiencing a process disturbance when separating stacked plastic sheets.  The operation is supposed to remove a single sheet at a time, but static was causing the machine to pick up multiple units in each pass.  (Separating two insulators such as these sheets is enough to create a static charge in any environment, let alone when humidity drops and static is more prevalent.)

For this application, we recommended a set of Super Ion Air Knives with the ionized air stream aimed along the short edge of the sheets.  As the sheets begin to separate, the ionized air flow from the Super Ion Air Knife has a chance to penetrate in between the sheets and eliminate the static charge. This prevents the machine from picking up more than one sheet at a time.

As the temperatures and humidity drop it is common to experience static problems.  For help with a solution, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

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