The operators on a spot welding line complained of getting shocks. Since the tooling and parts were all steel, and conductive, it was not taken seriously, but we did some tests to be sure. We found a voltage on the secondary of the spot welding guns - the copper shanks that contact the part and conduct the welding current. The fix was to add a ground wire to one side of the secondary of the weld gun transformer.
Yes, it's interesting that we long ago solved the problem of protecting the product, but overlooked the problem of protecting the human. It's nice to know that someone finally analyzed and solved the problem going in the other direction.
Good, detailed article about ESD problems and temporary and permanent solutions. In addition to the active static eliminators, many companies also sell passive static eliminators as well that can be inexpensive also.
In this particular instance, the amount of static electricity being discharge likely justified an active system emitting ions. Note too that it was not the dry season, and they were still getting jolted. When winter rolled around I bet it got rather worse.
While I have long dealt with ESD of electronic assemblies at the solder & circuit level, its funny that I never experienced, or even considered ESD from large, heavy equipment machinery as you've described.
Even funnier is the comment about the intentional shock to your little sister's ear. Every Kid I knew growing up knew that torture routine very well! It was particularly popular in the carpeted school library ,,,,
A similar situation plagues the composite repair industry, to which we supply heat control equipment, commonly known as Hot Bonders. The bonder controls AC power to a silicone rubber heater blanket to heat the composite materials in order to cure the epoxy component. Almost every composite cure is performed under a vacuum bag composed of high-temperature plastic film (polyester or similar). (Think high-temperature Saran-Wrap). When the bagging film is handled or removed from the part, it can generate 1000's of volts of static charge that has to go somewhere. Very few users ground the part or the tool to dissapate the charge while in-process. The Hot Bonder is an industrial quality piece of equipment with a metal chassis connected to earth ground (as required by NEC and CE). Any guess where the static charge, through the user's body, goes to ground? That's right - the machine obviously is shocking the people and is at fault. Trying to educate a user community that knows as much about electricity as they do about brain surgery is a daunting proposition.
I totally agree that it is very important that people do not assume the Electro-Static Discharge (ESD) since they might just be as harmful as the effects caused by other currents. The whole idea of using the copper pipe ensures that the charges are released hence a reduction in the effect that people are likely to feel when they touch the equipment. What I would suggest is that people come up with more permanent solutions so that these are made problems of the past. In a company for example if these are well taken care of the workers will be able to offer better services hence efficiency is guaranteed.
Thanks, for such an interesting post, Basic sources of ESD are insulators and conductors. They consist of positive and negative charges. Positive charges accumulate through human skin and negative charges are common to synthetic material such as plastic etc. There are different sources of ESD that is touch of human beings to sensitive devices human body can store electrostatic between 500V and 2500V. ESD can damage circuit boards as well when humans touch circuit boards without electrostatic wrist strap because human body contains ESD at a very higher level compared to the level which can destroy circuit boards , If synthetic material is placed near electronic equipment , Movement of air nearr electronic devices and so on.
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