March 4, 2019

Measures against static electricity: Making an environment free of static electricity (part 2)

Static-Electricity-and-Water

How to create an environment free of static charge?

Following the first article posted on the 18th of February, 2019, about the issues related to generated static electricity, today we are going to introduce the humidification method.

Last time we left with the solution “to create an environment where static electricity does not occur” to prevent static electricity from happening. Let’s dive deeper into this subject.

Environment where static electricity does not occur

In the last post, we mentioned 3 way to counter static electricity (release and/or neutralize the generated static electricity, and prevent it before it occurs). We already revealed the best way to prevent static electricity from happening is by creating an environment at the production site where static electricity does not occur.

So, what kind of environment is free from static charge?
A little hint? Think of a place in your daily life where you never ever encounter static electricity regardless of the season…?

The answer is “in the bath”.

How come static electricity never occur in the bathroom?

The reason is HUMIDITY. In a humid environment like a bathroom, there is a high level of moisture contained in the air and, thus, there is also a lot of moisture present on the surface of the surrounded objects. Static electricity will escape into the atmosphere through the moisture without accumulating and charging itself on the surface of the objects.

Relative humidity and absolute humidity

When talking about the right humidity level to have in your production site, we often heard 2 different terms:

  • Relative humidity
  • Absolute humidity

When we hear “Humidity 0%”, it actually represents the “relative humidity”. And the “absolute humidity” is the amount of water contained in the air.

As an indication, it is often said that “If you set the humidity to 50% or higher, it will be a countermeasure against static electricity”.

But 50% of humidity means 50% of relative humidity.

Even if the humidity is 50%, the amount of moisture (absolute humidity) contained in the air varies greatly (see Table 1) depending on the temperature at that time.

table-1.-Relationship-between-relative-humidity-and-absolute-humidity

Table 1. Relationship between relative humidity and absolute humidity

In other words, what is really important for countermeasures against static electricity is “the amount of moisture contained in the air”, that is, “absolute humidity”.

Which means you need to correlate “temperature and relative humidity”. There are cases in which static electricity countermeasures can be successful with a relative humidity of 40%. And in some other cases, static electricity countermeasures are not working even at a relative humidity of 60%.

Temperature is an important factor to consider also.

What about the humidification method?

In the last post we started our statement of static electricity being generated especially during winter season when it’s cold. Yes, in the winter when the temperature drops, the amount of moisture contained in the air drastically decreases, resulting in the generation of static electricity.

Therefore, at the production site, adding a humidification system brings a measurable and valuable measure against static electricity.

However, when mentioning humidification, there are various method (see Table 2). Each has advantages and disadvantages, so you need to choose a method that suits your production site.

Table-2.-Classification-of-humidification-method

Table 2. Classification of humidification method

Next time, while looking at the characteristics of each humidification method, we will explain in detail which one is the optimum humidification suitable for any type of production site.

Takahide-Muto