- February 01, 2007, By David J. Bentley Jr. Contributing Editor
An earlier column in this space on static elimination resulted in a response from a reader that is very illuminating. Following are summaries of the five main points from that response.
1. A man in Barcelona, Spain, was sandblasting the outside of a thirteenth-century building and was standing on scaffolding on the third floor. The static from the sandblasting in the tube he was holding caused him to receive a severe shock. He jerked backward and fell to his death. His equipment should have had conductive tubing and nozzle and should have had grounding.
2. A man was sandblasting a large metal part using equipment that was not conductive and grounded. The work caused him to receive a shock. He put on a wrist strap thinking it would help. When he bent over, an electrostatic discharge hit him in the head. Because of the wrist strap, this went into his head and out his wrists, causing permanent brain damage.
3. Many people in call centers receive large shocks. In these workplaces, the people are tethered to ground by their headsets. This places ground as close as 1?8 in. from their ears. When they generate high charges walking or especially standing up from chairs, they discharge to the headset. Some serious problems have been reported, including loss of hearing, loss of muscle use, and loss of eyesight. Fortunately, these results often are temporary.
4. In high-speed unwind situations, potentials as high as 2 or 3 million volts are possible. The breakdown of air is 3 mV/m. In some cases, arcs that were 2–3 ft long occurred. In one case, an operator walked between an unwinding roll and the machine frame as an arc happened. He received an electrostatic discharge of 2–3 mV to his chest, causing him to fall. He went to a hospital emergency room with heart problems.
5. Commercial products sometimes receive charges from corona treating and other methods during production. Products such as shampoo bottles can become Lyden jars waiting to shock a user in the shower.
This information shared by a reader should scare you. It indicates dramatically that electrostatic discharge is extremely dangerous. The examples cited above illustrate that two possible hazards exist: the danger from receiving a shock and the danger of something untoward such as a fall occurring as a result of reaction to the shock.
The message here is quite simple: Be aware of any situations in your facility that possibly could generate an electrostatic shock, and then take all possible precautions to make certain you have eliminated the potential for such a shock to occur.
If you are a worker exposed to areas where shock can occur, ensure that all the required systems are in place to protect you from such an incident. As the examples above illustrate, the possibilities of death or permanent disability definitely exist! For additional information about electrostatic discharge, you can visit the on-line magazine esdjournal.com.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at firstname.lastname@example.org.