What is Electrostatic Discharge? (ESD)
Static can be a major problem for many industries, it is a natural phenomenon that shouldn’t be underestimated. Static is generated by various sources depending on the industry. In electronics, people are the main generators. With relative humidity at 10% to 20%, a person walking across a carpet can generate as much as 35,000 volts, across a vinyl floor 12,000 volts, and a worker at a bench 6,000 volts. In the processing industries, the main source of static is fast moving materials, integrated circuits can be damaged by as little as 5 volts. This damage may not always be visible and degradation can be caused over time that will eventually cause the electronics to fail.
Back in 1984 independent American research estimated in the electronics industry losses directly attributed to ESD amounted to 18 billion dollars. This may have been a conservative estimate as the figure was based on only 40% of the industry sales and were projected on a survey of around 50 electronic companies.
This is a massive loss and is repeated across the world in many industries with reports of millions of pounds of damage caused by ESD. For this reason we cannot ignore static electricity.
The loss is not just financial, ESD also causes industrial equipment to fail and electrostatic sparks cause fires, explosions and personnel injury. Many industries have suffered, and it’s not restricted to the little guys. In 1964 NASA, the multi billion dollar, US government space programme lost four of their scientists in an accident caused by static electricity, while over 50 major incidents occur in the UK each year.
What causes static?
Static electricity is generated by friction and separation of materials, called triboelectric generation. Electrons are transferred from one material to the other, leaving both materials charged. Since electrons have a negative charge, the material which acquires electrons is left negatively charged while the one which surrenders electrons becomes positively charged. The triboelectric series is often used in explaining static electricity. There are many materials that can cause static electricity, this list is just a few of them. If your industry uses any of them then you may need to outfit your company to prevent static electricity.
- Air + (Positive)
- Human hand
- Human hair
- PVC (Vinyl)
- Teflon – (Negative)
How to prevent static electricity
By eliminating as many materials as possible that generate static, and ensuring that you take static precautions at the workstation, during material handling, use static measurement and monitoring equipment, and most importantly train staff to be aware of the problems. ESD related damage will then be reduced to a minimum, improving product quality and increasing profitability.
However, the best way to reduce static electricity build up is to outfit your employees with anti-static clothing. This clothing is made using fibres that stretch instead of break eliminating triboelectric generation. Natural fibres usually have a low tensile strength meaning they break easily and are not suitable for anti-static clothing, so man-made fibres are combined with plastics and rubbers to ensure the fibres stretch and generate as little static as possible.