The WiZard is In - 8-8-2011 at 07:51
ADA529550
New Concepts in Studying Electrostatic Discharge Hazards of
Propellants, Pyrotechnics and Explosives
Dahn, C. J. ; Jennings, Diane ; Kashani, Abdollah ; Nguyen, Missy
AUG 1990
Conclusion
The overall conclusion that can be drawn from the tests
performed at Safety Consulting Engineers is that the combined
effect of electrode configuration and circuit configuration makes
explosive materials respond differently under varying test
conditions. Thus, it remains a difficult task to specify a
minimum initiation threshold value that could be used reliably
in any situation for a given explosive.
Attachment: Electrostatic Hazards.pdf (793kB)
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Bot0nist - 8-8-2011 at 09:57
Thanks for the ref! That elaborates on what quicksilver was mentioning in the SA thread.
[Edited on 8-8-2011 by Bot0nist]
quicksilver - 8-8-2011 at 14:18
Please note the date on WIN's material is NEWER (1990) than my material (extrapolated from OSHA's Wiki insert on explosive dust hazard). The D/C of
"static" (non-flow) and the electrical (D/C=discharge) of AC or DC energy is VERY difficult to measure.
Crude Example:
We have often seen the display of static electrical D/C via a Van de Graff generator. This static energy may vary based on a variety of conditions.
Where as the use of electrodes in a managed energy dump can be engineered, it's current and carrier voltage* monitored. If we look at voltage and
current (that flows, i.e. non-static) as "'water", the volume of water is similar to amount of water and the current as the "opening" from which it
would flow (a garden-hose with a nozzle for instance or a river). The greater the constriction of flow (to an extent) the higher the current.
Static electrical energy is more complex and differing elements act upon it's D/C from source.
We may be able to say that in ultra-fine particulate we have one level of energy transmission and in larger crystalline particulate we have another.
So that measurement in terms of Joule level may pose a degree of inaccuracy.
This is NOT to say that crystalline particulate of 325mesh or .25mm is less susceptible to transmission of energy; in fact it MAY (under certain
conditions) pose more conductivity.
Imagine the common display of the individual with a full hand contacting the top of the Van de Graf generator and their hair stands on end - then
pose the example of the slight shock from a finger touching a door-knob. Here we have a smaller contact point, yet the flow may be equally measurable.
Therefore the Joule measurement may be a difficult one to utilize. But with static electrical D/C we have such low current and such high carrier there
may be little choice. This is an important area where our situation becomes more complex.
Just a thought. Yet in defining energetic response to static electricity the complicating factors are more than a flow unit generative device.
*One reason why many SMAW welding boxes (stick welder) maintain their carrier voltage at about 50v is that several hundred amps can be delivered in
arc where needed and some safety maintained. There IS a threshold for voltage where is become a serious safety concern & OSHA monitors this in
differing welding devices. This "flow" consideration throws further light on what levels may "move" or be conducted in what would be commonly
considered "non-conductive" items such as a pair of shoes. This aspect of energy movement further complicates safety considerations in static
electrical D/C exposure w/ energetics.
Bot0nist - 8-8-2011 at 18:20
Thanks for that quicksilver. Between the <a href="http://www.sciencemadness.org/talk/viewthread.php?tid=17122">silver acetylide static
thread</a>, WIN's article, and your post I have learned a great deal more about static discharge and it's hazards and insidiousness in the
lab/workshop.
My interests in chemistry stems from an amateur pyrotechnics background. I always loved to make homemade displays, most of them from skylighter
articles. From these, I new of the danger of static from the many warnings and preventative measures in place for working with
Al/KClO<sub>4</sub> flash, but I never had, or imagined to have such a deeper understanding of its cause, variability, and prevention.
Thanks again.