The relationship between humidity and static is something we’re very familiar with at EXAIR. As temperatures drop and humidity decreases, the reduction in moisture content within the air translates to an increase in static . This is because higher moisture content in the air creates a surface layer of moisture that dissipates accumulated static charges. When this surface layer disappears, static forms quickly and easily.
Fortunately, we have a full line of static eliminating equipment suitable for use in removing static related process disturbances. For example, the photo above shows a plastic stretch wrapping machine at its dispensing point. As the plastic is pulled from the roll static builds up quickly and this customer needed an easy, reliable solution to remove the static. Ideally, they wanted something that would not require compressed air, but could still mount closely to the machine and remove the static charge.
The solution for this application was a series of two 24” Ion Bars mounted on each side of the film. As the plastic is unrolled it passes through the opening created by the Ion Bars, eliminating the static charge. The machine required no significant downtime to install this solution, and nothing within the machine setup had to be modified.
This type of setup was ideal because it treated the static at the proper point within the process, used no compressed air (as requested by the customer), and it provided a simple installation to solve the problem.
Plastic sheets and films that are being separated after full contact can generate significant static charge. If you have a film/sheet application, or another static related need, contact an EXAIR Application Engineer. We’d love to help you find a solution.
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.
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.
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.