Dangers of ElectroStatic Discharges

 

Not all devices are ESD unprotected, particularly components in electronics for military applications (I guess that is why such equipment is far more expensive than  run-of-the-mill components).  Furthermore some electronics used on the Robotic industrial manufacturing are fairly resistant to ESD events (of course a more expensive gear). All other general consumer category devices where the bottom line / cost rules have no such a luck and that is where Risk Management dictates (I really miss TQM).

In computer environments AirConditioning with Temperature and Relative Humidity (RH) control are a must. Temperature around devices may be required to be at around 23DegC and a good level of  RH around 50%. The higher is RH the better as it will reduce the build up of charges around the place, however, what if room Temperature or RH is suddenly lowered? Water condensation is produced within electronic modules and we have a big corrosion/rust problem in our hands over the next few weeks.

Additionally to provoking sudden failure or even worse, latent faults to electronic components in equipment there is danger to persons, directly or indirectly. The latter may occur indirectly eg an ESD event fails a crucial electromechanical device, for example in an aircraft, car, submarine, etc... but also sparks in between charged conductors eg a person or metallic objects, may initiate other catastrophic type of events like fire and explosions whilst in the vicinity of volatile ignitable products like gas, fuel, etc... these are usually strong capacitive sparks. In industrial workplaces it is not unusual to have operating belt drives which if not ESD controlled may accumulate large amount of charges due to their triboelectric interactions with the metallic rollers. In an Office environment an ESD event may alter/erase magnetic media. Ensure there is no flammable or explosive materials in locations where ESD cannot be fully controlled .

 

 

There are some documented incidents in the USA where motorcar fuel has ignited due to ESD sparks, hence seriously injuring people. It has been learnt that whilst filling a metallic can with petrol at a service station it is recommended to have the can firmly placed on the ground while doing so, any accumulated charges around the body of the can will neutralise consequently avoiding sparks, explosions have occurred where the can has been placed on an insulating plastic mat on a pick up truck. This is similar to the reasoning as to why aviation procedures specify that a loading fuel truck must be connected by an electrical wire to the metallic structure of the plane being refilled so as to ensure them to be at a similar potential hence reducing the danger if fuel igniting.

 

The US Chemical Safety and Hazard investigation Board (Washington) informed the press in June 2003 that the well known Kinston explosion at the West Pharmaceutical Services that killed six workers and injured dozens in the manufacturing of rubber products section was due to fine dust plastic powder mixed with air. The area affected by the explosion was where rubber sheet strips where coated with moisten polyethylene, hence the formation of the explosive mix (there was a suspended false ceiling where the mix accumulated out of check, this is a bad design for ignitable gases). The investigation is still going on an a final report is expected soon. The investigators agree that the polyethylene powder recovered from the explosion site is in fact explosive, once mixed with air.

And NASA (Space News Sep'09) is working hard on a new Fuel propelant for their rockets that it would have a negligible danger from ESD events. Named Alice is a propelant made of aluminium and ice, there are other logistic advantages, like it can be made anywhere. Another advantage is that rockets/Shuttle take off emissions are minor and hence benign on the environment compared to current fuel where large amounts of hydrochloric acid are emitted.