Why does static electricity make electricity

The dangers of electrostatic discharge

Low humidity increases the risk of static electricity, which can damage equipment and harm people. Humidity control is key - this way.
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What is Static Electricity?

Static electricity is actually an imbalance of electrical charges in a material. The imbalance - d. H. missing or excess electrons - occurs when two surfaces touch and exchange electrons in the process.

One of the main causes of static electricity is static electricity, which means that certain materials become electrically charged when you touch them. A thunderstorm is mainly caused by electrostatic charges that build up between the clouds and the earth.

Static electricity builds up when various materials are touched by exchanging valence electrons. However, the humidity makes the air more conductive so that it can absorb excess charges and distribute them more evenly.

Static charge: valence electrons transfer and create an imbalance

In an environment with high humidity, bodies are therefore less able to maintain their static charge.

Voltage build-up during everyday events (kV)
Walking over a carpet30
Tear off the polyethylene bag20
Walking on a PVC floor15
Working on a workbench5

This table shows the build-up of tension in everyday life - and what difference the relative humidity makes. A relative humidity of more than 40% does not remove static electricity, but only allows it to flow away safely. Source: electronics-notes.com

Why moisture matters

Water is a good conductor of electricity. An electrically charged body will therefore dissipate its electrical charge in moist air, which reduces the risk of a sudden electrostatic discharge.

Compared to metals, however, the electrical conductivity of pure water is surprisingly low:

Conductivity table (S / m)
Pure water (reverse osmosis)5.5 × 10-6
Aluminum3.5 × 107
steel6.21 × 106

The electrical conductivity is measured in Siemens (S) or A / V = ​​1 / Ω. Overall, the dissipative effect of water vapor means that the electrostatic discharge is quickly used up in moist air..

Moisture does not prevent the electrostatic discharge, it just absorbs it better

In air with low relative humidity, the unbalanced charges only equalize their charge difference when they come into contact with another conductor. In air with higher humidity, the humidity provides a medium through which the charge can be released in a more harmless way.

This is because the individual water molecules have a much higher conductivity than the surrounding air, so that the charge is transferred to the water in the air. The electrostatic discharge still takes place, but is distributed over countless water molecules or droplets.

So there are no high charges when the relative humidity is above a certain value.

Electrostatic discharge as a real danger

Static electricity is always built up somewhere in production environments; no technology can prevent this. It is the location of the electrostatic discharge that causes problems.

In electronics production, even the smallest electrostatic discharge can damage semiconductors and render the product worthless.

Even small electrostatic discharges can have a huge impact on sensitive electrical equipment, affecting yield, quality, and reliability, and costing manufacturers enormous amounts of money.

Even without a blow: Static electricity as the cause of the problem

The risk of electric shock from electrostatic discharge is not the only problem with static electricity - or, to be more precise, with the build-up of static electricity imbalances on the surfaces of bodies.

At a relative humidity of less than 40%, the risk of static charging increases significantly.

In order for an electrostatic charge to build up, friction is necessary: ​​two materials have to rub against each other, so to speak, and exchange valence electrons in the process. Most production environments have all the prerequisites for the formation of static electricity: an environment with strong local heat sources leads to a decrease in humidity.

The solution is to ensure a relative humidity of at least 40% - in most cases around 60% is ideal. This is done by supplying the air with sufficient moisture at all times.

How can electrostatic discharges be counteracted?

In production engineering, the avoidance of electrostatic discharges is a standard discipline that is taken very seriously. Protection against electrostatic discharges is usually divided into passive and active measures - passive measures are, for example, insulating floor mats, earthing of personnel and tools and the like.

The regulation of the air humidity is an active measure against electrostatic discharge. As soon as the optimum degree of humidity is reached - typically between 40 and 60% relative humidity - it is sufficient to safely release electrostatic charges into the air. At the same time, with such a moisture level, moisture also precipitates on the surfaces and forms a conductive layer that offers further protection.

Installing a high pressure humidification system is one of the most cost effective ways to improve productivity and reduce the risk of electrostatic discharge.

See how we did this for others

Airtec® has decades of experience in the planning, installation and maintenance of this type of air humidification system - take a look here our case studies.

 

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