Flash Powder (70/30) Sensitivity to Static

Quote: Originally posted by holmes1880

There are warning of FP static sensitivity everywhere- the manufacturers selling FP also say to use anti-static spray. The diaper method of mixing is an accepted form of mixing. All this leads to believe that the most common FP is very static sensitive. However, people also report that 70/30 FP can be difficult to ignite and that it does not ignite from a pizoelectric spark. Is there any official studies of regular KClO4/Al 70:30 being static sensitive? Time to investigate the sources of this claim.

Quote: Originally posted by holmes1880

Having so many kids playing with FP, we never seem to hear about those static accidents. They are probably improperly reported as ignition accidents, because nobody could figure out what exactly went wrong.

Ignition Of Electric Detonators Caused By Exhaust Fumes From Bulldozers

Quote: Originally posted by holmes1880

Anyways.....(what was the last post about...). They're saying that human body can easily work up 20mJ, but it is still possible to go to 500mJ. Correct?

If you rub your rubber soled shoes on a wool rug half-dozen
times you can create enough Joule's to drive your cat into the
middle of next week.

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Safety Evaluation Tests of Personal Protective Equipment for Ordnance Operations
Glen Prichard Augusty 1978
NWC TP 6008
ADA 058 987
[Free DL from DTIC.MIL]

Scanned and you know that that means!

DISCUSSION

100% Cotton (Thin) Socks. Thin socks of 100% cotton registered the most
satisfactory readings. This occurred not only immediately after personnel put on the
socks, but for the entire 2-hour evaluation period. The requirement for socks of high
cotton content in ordnance operations with potential electrostatic hazards is validated
by the results of this test. Cotton is hygroscopic, and as such will readily absorb
moisture from the atmosphere or from the feet of personnel. Moisture Collected on the
feet of personnel is absorbed and transmitted through the sock to the inner sole of the
conductive shoe: The shoe then provides a path to ground to bleed off electrostatic
charge buildup.

Internal body resistance and built-in shoe resistance keep readings from reaching
unacceptably low values. Current NAVSEA explosive safety requirements allow a
minimum shoe reading of 25K ohms. Several 40K-, 50K-, and 60K-ohm readings were
registered during the cotton sock test; however, none approached minimum
acceptability.

One somewhat disturbing aspect associated with the 100% cotton (thin) socks was
the fact that 107o of the readings registered above the IM-ohm maximum immediately
after the socks were put on. For operations where the generation of' static would create
a hazard, regulations require socks of" high cotton content. No time element ;s
involved, yet the test data indicate that perhaps as long as 15 minutes may be needed
before maximum safety, through acceptable conductivity readings, can be achieved.

75-857. Cotton/25-15%, Nylon Socks. All-cotton socks have become increasingly
difficult to procure. Cotton socks typically have a reinforced heel and toe made of nylon.
The small percentage of nylon has generally not affected the hygroscopicity of the
cotton, and the test results in this report would appear to valid-ate this. After 15
minutes, all reading-, registered 0 to 500K ohms. The only difference between the
all-cotton (thin) socks and the cotton/nylon socks appeared to be in the readings
immediately after the socks were put on. Twenty-three percent of the personnel wearing
the cotton/nylon socks had readings greater than IM, as opposed to 10% for cotton
(thin) socks. Based upon the test results, 15 minutes would appear to be needed to
achieve maximum acceptable conductivity.

100% Cotton (Thick) Socks. Thick socks of 100% cotton revealed some
surprisingly unsatisfactory readings. In fact, 71%, of the personnel wearing this sock
type registered over IM ohms immediately upon donning them. Only 29% fell into the
acceptable range. It should be understood that the requirement for socks with high
cotton content is applicable to those of thin construction only. As stated before, cotton is
hygroscopic. However, permeation of moisture through thick socks takes longer than
through thin socks. As a consequence, acceptable conductivity readings take longer to
achieve. The test data seem to substantiate this. After 15 minutes, 71% of the readings
were in the 0- to 500K-ohm range and 297c were in the >500K-<1M range Fifteen
minutes appears to be the minimurn time to achieve acceptable conductivity. Thirty
minutes seems most appropriate.

100% Nylon and 75% Orlon/25% Nylon Socks. Both types of synthetic socks worn
by personnel registered entirely unsatisfactory readings. After 2 hours. 25%. of' the
personnel wearing 100% nylon socks registered above IM, ohms. Fifty percent of the
personnel wearing 75% Orlon/25'% nylon socks registered above IM ohms after the
2-hour test period, Synthetics do not absorb moisture readily. In addition, they provide
good insulative effects. Both of these aspects contribute to their ability to maintain an
electrical charge for extended time periods before bleed-off occurs. This could be
catastrophic in those operations where electrostatic discharge may initiate loose
explosives or pyrotechnic powder, or vapor-air mixtures within ignitable limits.

VARIABLES AFFECTING CONDUCTIVITY

Several of the sock types proved to be effective for the hazardous conditions found
in ordnance operations. However, many variables were found that affect the adequacy
of conductivity afforded by the various types of socks. Variables that merit consideration
are listed below under the general headings of shoe tester, weather conditions, shoe
conditions, work conditions, and individual differences. These variable-should not be
considered all-inclusive.

Shoe Tester. The shoe tester used in this particular test. the Safe-T-Ohm, has a
scale range of 0 to I M ohms. This range is highlighted green to indicate acceptability.
Above 1M ohms it is highlighted red to indicate unacceptability. However, in the red
region there is no scale and, as a consequence, there is no satisfactory method to
determine whether the sock readings are just slightly above acceptable conductivity or
infinitely above. It is only known that the reading is unacceptable, not the extent of the
unacceptability. There is. probably enough machine-error variability to make the shoe
tester readings near the red-green borderline region a concern.

Weather Conditions. Relative humidity must be controlled to obtain reliable
conductivity measurements over time. A high humidity may cause enough moisture on
the socks and feet of personnel to cause most, if not all, readings regardless of sock
content, to he within acceptable limits. A low humidity keep even thin cotton socks at
unacceptable conductivity levels. Hygroscopicity is the ability to absorb moisture. If
there is little moisture in '!w air, such as may be found in the desert winter months.
hygroscropic socks will experience difficulty in moisture absorption. Consequently,
readings may stay elevated for extended time periods.

In summary, cold versus warm weather conditions coupled with wet versus dry
cliniatic conditions are variables that must be considered and controlled when
,evaluations of this nature are performed. This is why daily checks are important in high
hazard areas (e.g., primary explosive and pyrotechnic operations), per NAVSEA
explosive regulations.

Shoe Conditions. Ideally, the conductivity of shoes should be determined before
socks are tested so that a baseline of data can be established. Shoes in good
condition may initially show a conductivity reading as low as 25K ohms. Likewise,
shoes in bad condition may lead to greater than 1M-ohm readings, even with 100%
(thin) cotton socks.

Dirt, grime, grease, and wax are just a few of the materials that may provide
sufficient insulative effects to prevent reliable and accurate conductivity readings,
unless they are removed from the soles of the conductive shoes.

WORK Conditions. Pedestrian traffic may be a crucial variable in evaluating sock
conductivity. Field work that involves a great deal of activity on the part of personnel
should lead to copious amounts of perspiration, and as such. adequate conductivity
measurements. Likewise, office work involving a good deal of sedentary activity, and
only !sporadic field work, may preclude perspiration buildup and thus raise most
readings; above acceptability, regardless of sock content.

Individual Differences. Some personnel may naturally perspire regardless of their
activity, while others who do active work may not perspire at all. Blood circulation plays
a major part, and of course, varies with different people. Test results would seem to
verify this; the same personnel generally showed higher readings on all types of
socks-especially in initial readings. In summary, individuals must know their
peculiarities to truly derive maximum safety through the use of socks and shoes.

SUMMARY OF SOCK TESTS

This section has described conductivity tests made to determine the relative
conductivity of various sock types that may be worn in ordnance operations and to
indicate to personnel the acceptability or unacceptability of such socks. Observations of
sock conductivity as a result of the tests, and conformance to current NAVSEA
explosives safety regulations indicate the following:

1. When conductive shoes are required to be worn, only lightweight socks of high
cotton content should be worn.
2. Even after donning lightweight (thin) socks of 100% cotton content, perhaps as
long as 15 minutes may be needed before adequate conductivity readings can be
achieved.
3. Seventy-five to 85 cotton socks, with some nylon reinforcement still meet the
requirement of high cotton content and appear to provide acceptable conductivity
readings after a 15-minute waiting period.
4. Thick 100% cotton socks do not appear to meet current NAVSEA conductivity
requirements, and test results seem to support this. Thirty minutes may be an
appropriate waiting period, after donning heavy cotton socks, before hazardous
operations should commence. This long waiting period would be economically
impractical.
5. Synthetic socks do not meet current conductivity requirements, and this is
reinforced by the data. They do not belong in ordnance operations where electrostatic
discharge is a concern.
6. Many variables, such as measuring equipment variability, weather, shoe
condition, work conditions, and individual body differences, affect sock conductivity. To
gain reliable information on actual sock conductivity, these variables need to be
controlled.

---
Three manikins were placed on one side of a table, on which
was placed approximately 30 pounds (13.6 kilograms) of composite
propellant shavings salvaged from processing operations and laid
to a depth of 5 to 6 inches (0.13 to 0.15 meter).

To simulate body flesh, each manikin had a hot dog secured to
its neck and one tied to its arm, only half of which was protected
by the cotton T-shirt.

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Extracted from :—
Longhorn Army Ammuniton Plant PYROTECHNIC MIXING ACCIDENT
19th EXPLOSIVES SAFETY SEMINAR
L.A. CALIF 1980

The incident resulted in the death of one operator and injury to another, the loss
of two 158 pound ALA-17 mixes, damage to the building and a temporary loss of
production capability. (Figure 2)

The firemen checked
for life signs; all were negative. The operator received burns to the head, neck,
arms, hands and lower extremities. The probable cause of death, as determined
by a doctor, was inhalation of smoke and flash fire affecting the respiratory
system to a massive enough extent to precipitate a cardiac arrest. The operator
in Bay D received first and second degree burns of the hands and lower
extremities.

The ALA-17 mix consists of atomized magnesium, nitrocellulose, teflon, and acetone. (Figure 3)

The clothing worn by the Bay C operator was significant in steering the
investigation to static discharge as the initiation stimuli. Figure 36 describes the
clothing worn by the Bay C operator. The operator was wearing an aluminum
coat and hood, Nomex coveralls, nylon undergarments, nylon stockings, cotton
socks, conductive shoes, and rubber gloves.

A number of circumstances made it possible for static electricity to ignite the mix
(Figure 43). (1) Nylon is an excellent generator of static charges and an
extremely poor conductor of these charges, (2) Nylon worn on a person's body
isolated from ground car. build up significantly, (3) Test results of a similarly
dressed person measured more than 800 volts existing on the surface of the
coveralls, (4) Nylon socks can effectively insulate a person from ground, (5) The
instantaneously discharge of a charge would generate enough energy to ignite
an explosive mixture of air and acetone vapor or the ALA-17 illuminate mix and,
(6) Tests conducted revealed that the nylon socks inhibited the draining off of a static charge.

[They believed static discharge ignited acetone vapour.]

-=-=-=-=-
I know this is not static discharge it is simple induction. Like the farmer
below the overhead HV line with a large coil of wire in his barn.
File it under — Beware of things in the shadows.

good evidence

Quote: Originally posted by quicksilver

An Asian technique was to place the components separately within the enclosure or what-have-you in a SEPARATE fashion. After they were within, to subject that (burst charge, rocket cone, or whatever) to a physical shaking; mixing the ingredients when sealed from direct atmospheric contact & using either distance, shielding, or other means to provide further distance from human involvement while actual mixing took place. This concept has the rewards of safer transportation for a completed project, with the caveat of knowing that mixing must take place prior to the shoot.