Cold Dry Air of Winter

Today, we are getting one of the  larger snow storms for Cincinnati, OH.  Compared to cities north of Dayton, OH, we don’t get very much snow, but once or twice a year we get 4-5 inches and the drivers in this city go crazy.  You won’t see anyone on the freeways driving faster than 35 MPH, but you will see a few people spun out on the side of the road.  It reminds me that winter is here.  With the snow, winter also brings dry low-humidity air which increases the number of electrostatic discharge (ESD) occurrences. ESD is the proper term for a static electricity shock.  At EXAIR, we have an entire line of products that are designed to neutralize static on a surface or a product.  To neutralize the static, we use a 5kV power supply which supplies voltage through a sharp point (emitter point) on all of our products.   This high voltage generates positive and negative ions, which we then deliver to the charged surface using compressed air to eliminate static on the surface.  See this video for more information.

So why do we have more static electricity in the winter?  Actually, we don’t.  The same amount of static is generate year round.  Here is a better question – Then why do we get shocked more often in the winter?  It really all comes down to humidity.  Water is a very conductive material. This allows the charges to spread out, around the surface area of the water and any conductive surfaces that are electrically linked with where the static charge was generated.  The charges spread out across the surface are dissipated without any ESD (shock).  For instance, a plastic sheet bolted to a metal plate.  During the more humid summer the moisture in the air will electrically link the bolt, metal plate and the plastic sheet because of the thin microscopic layer of water across the plastic sheet.  This combined surface allows the charge to dissipate by any ground that the metal plate may be attached or slowly dissipated into the air.

This week I had a customer who was looking to dissipate static in his entire facility.  This would not be a typical solution for our electric static elimination product line  but we were able to provide a different solution.  The customer had an air recirculation system that they used to heat their building.  The air would pass through a 24″ X 24″ square duct.  With the knowledge of what causes static shock, the maintenance department called asking for a recommendation for an atomizing spray nozzle that would humidify the duct without leaving a large amount of moisture.  The customer had two questions. First, which nozzle would cover a 24″ square area? Second, how to control the amount of moisture added to the ventilation system, so as not to create a hazard of standing water in the duct work.  For the first question, I was able to recommend the Internal Mix Wide Angle AW1040SS.  I recommend he use two nozzles to cover the entire duct.  The second problem would need more work on the customer’s end.  Any of the atomizing spray nozzles can come with a liquid adjustment knob, which would allow the customer to control the amount of liquid added to the duct, but the customer would need to determine how much moisture was needed in their system.  The liquid adjustment could control the flow of liquid from zero flow up to maximum flow  of 24.0 GPH.

Dave Woerner
Application Engineer
Davewoerner@EXAIR.com
@EXAIR_DW