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eEdition Journal of System Safety
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Vol. 47, No. 4 • May-June 2011
In the Spotlight
Electrical Equipment in Fueled Areas
President's Message
From the Editor's
Desk
TBD
In the Spotlight:
Electrical Equipment
in Fueled Areas
A Case of ALARP
not being Applied to
Automotive Traffic
System Safety
Safety Heuristics for
Hospitals
Book Review:
How Reliable is Your
Product?: 50 Ways
to Improve Product
Reliability, by Mike
Silverman
Chapter News
Mark Your Calendar
About this Journal
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Contact Us
Puzzle
by Harvey C. "Chuck" Dorney, P.E., C.S.P.
Pages 1 | 2 | 3 | 4 | 5
At the last International System Safety Conference (ISSC), Terry Osborn presented a version of
"Electrical Safety 101" for hazardous areas. This paper will continue what Osborn started with
version "201." The U.S. Air Force (USAF) has completed extensive work to determine the safety
aspects of using electrical equipment around an aircraft containing fuel or undergoing fueling
operations. This paper will describe the methods of evaluating and controlling the hazards
associated with electrical power arcing, static electricity and radio-frequency (RF) radiation hazards.
Although the primary hazards are associated with igniting fuel products, other hazard effects will also
be discussed. Controlling these hazards has led to several safety policy and equipment changes,
which will also be described.
Introduction
Electrical energy is all around us, and is used for many things, such as transmitting power (in our
homes and offices) to operate devices and for communication (as in radio waves and data
transmission). Because it involves energy, many hazards can be present. The most common is
ignition, along with damage to personnel from electrical shocks. This paper focuses on ignition
effects of electrical energy on ignitable substances, mainly aircraft fuels. It also describes efforts to
provide confidence that portable electronic devices can be safely used around fueled aircraft.
The Ignition Phenomenon
To create a fire or explosion, certain things must be present: an ignition source, an ignitable material
and an oxidizer. A classical fault tree approach can be used to identify how these conditions can
co-exist. Figure 1 shows such an example. In addition to the items described, the proper conditions
must be present. The ignitable material must be in the proper form and environment. For example,
most hydrocarbon fuels must be in a proper fuel-air mixture to be ignited.
Figure 1 — Ignition Fault Tree
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Click to enlarge
Electrical energy causes ignition in several ways: electrical arcing (including static discharges),
heating a conductor (hot wire) and radio-frequency radiation. Each of these will be discussed
separately.
Electrical Arcing
Whenever electrical contacts are made or broken, as through a
switch, arcing occurs at the points of contact. The amount of
arcing depends on four factors: the amount of electrical current
(amperes), the electrical pressure (voltage), the size and shape
of the contacts, and the surrounding material (air, water, oil,
etc.). An example of significant low-voltage, but high-current,
arcing can be found in an automotive battery. An example of
high-voltage, low-current arcing would be static electricity
discharge. Finally, lightning is a well-known example of a
high-voltage and high-current arcing phenomenon.
...it can be seen that a
circuit having 50 volts and
200 milli-amperes does not
have sufficient spark energy
to ignite a Group D
substance, such as aviation
jet fuel. However, a circuit
with 50 volts and two
amperes can cause ignition
of the same substance.
Not surprisingly, there have been attempts to define the range of
ignition requirements. For example, when attaching a jumper
cable to start a car, are those sparks capable of igniting
flammable materials, such as gasoline or hydrogen? Apparently
so, because we have always been cautioned about igniting
materials when jump-starting a car. Underwriters Laboratories
Standard UL 913 [Ref. 1] includes several graphs that show
ignition ranges. Figure 2 is an example of such a chart, showing
ignition ranges for an electrical resistance circuit. (Similar charts
exist for inductance and capacitance circuits.) In the Figure 2
example, it can be seen that a circuit having 50 volts and 200
milli-amperes does not have sufficient spark energy to ignite a Group D substance, such as aviation
jet fuel. However, a circuit with 50 volts and two amperes can cause ignition of the same substance.
It must be noted that such charts are for the arcing from making or breaking electrical contacts;
these charts do not address heating of a conductor from high electrical currents.
Figure 2 — Ignition from Electrical Arcing
Click to enlarge
These charts have been used by a number of U.S.A.F. organizations to determine the relative safety
of using electrical devices in hazardous areas. Generally, these charts show that the vast majority of
devices powered by household 110- or 220-volt circuits are easily capable of serving as ignition
sources for a variety of materials. On the other hand, many low-voltage battery circuits (e.g., below
10 volts) would need substantial electrical currents to create ignition sources. A standard batterypowered wristwatch is not considered an electrical ignition source. These watches have no safety
labels or certifications, yet we are never cautioned against wearing them while refueling a car at a
gas station.
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eEdition Journal of System Safety
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Vol. 47, No. 4 • May-June 2011
In the Spotlight
Electrical Equipment in Fueled Areas
President's Message
From the Editor's
Desk
TBD
In the Spotlight:
Electrical Equipment
in Fueled Areas
A Case of ALARP
not being Applied to
Automotive Traffic
System Safety
Safety Heuristics for
Hospitals
Book Review:
How Reliable is Your
Product?: 50 Ways
to Improve Product
Reliability, by Mike
Silverman
Chapter News
Mark Your Calendar
About this Journal
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Puzzle
by Harvey C. "Chuck" Dorney, P.E., C.S.P.
Pages 1 | 2 | 3 | 4 | 5
Reference 2 provides another method of determining the capability of an electrical arc to be an
ignition source. Past experiments have shown that a spark with an energy level of 0.25 milli-joules or
more can be capable of igniting hexane gas. The U.S.A.F. is not aware of any similar experiments for
automotive or aviation fuels, but considers that energy level to be valid for such fuels, due to the
molecular similarity between hexane and the fuels. The 0.25 milli-joule level is not very high — this is
approximately the spark level that is seen when touching a metal doorknob after walking on a carpet.
In mechanical terms, this level is achieved by dropping a quarter from a height of one inch.
One must keep in mind that the above values are for ideal conditions. The fuel-vapor mixture must
be stoichiometric and the electrical contacts must be relatively small in the contact area. (Imagine
trying to achieve a high spark level when using two large plates as contacts, compared to two button
or needle contacts.) This latter consideration is due to the quenching effect from the contacts. If two
contacts are close together, they can actually cool the spark to a point that the spark will not have
sufficient energy to cause ignition [Ref. 2]. For example, a 0.25 milli-joule spark has a minimum
quenching distance of approximately 0.06 inch between flat plates.
Hot Wire Ignition
A second cause of ignition is a hot surface (usually a wire) from
excessive current. Just place a wire across the terminals of a car
battery, and you can see the immediate effects. For a given
voltage source, the current through a conductor depends on the
resistance in the circuit. Ohm's Law states that the current
multiplied by the circuit resistance is equal to the voltage. This
can work both ways. For a given voltage and a resistor, one can
directly determine the electrical current in amperes. In the other
direction, given a current and a resistance, one can then
determine the voltage drop across the resistance. Going back to
our car battery, let us assume that it is capable of a constant
13.5 volts. If we place a wire having a one-ohm resistance
across the battery terminals, the resulting current will be 13.5
amperes, which can generate considerable heating power.
Electrical power (in watts) is simply the voltage multiplied by the
current, which, in this case, is 188.25 watts. Unless the wire is
considerably large, it will readily heat up, possibly to the point of
failure or igniting a nearby flammable material. Past tests [Refs.
2 & 3] have shown that aviation and automotive fuels have a
minimum hot surface ignition temperature of 900 degrees
Fahrenheit (F) or higher. Other tests [Ref. 2] have shown that
when a steel wire begins to glow from excessive current, the
temperature is approaching 990 degrees F (A yellow wire glows
at 1,800 degrees F, and a white-hot wire glows at 2,220 degrees
F). In other words, if a conductor is visibly glowing, it is easily
capable of igniting automotive or aviation fuels. Accordingly,
circuits with high current capabilities must be controlled to
prevent excessive heating of a conductor.
Interestingly, hydrocarbon
fuels cannot be easily
heated in a microwave
oven, nor by other means of
generating RF radiation.
The molecular structures
(non bi-polar) of these fuels
do not lend themselves to
easy RF heating. It was
once thought, these fuels
could be easily heated by
radio transmissions, so
there was a universal
prohibition against
transmitting on aircraft
radios during refueling.
Radio-Frequency Heating
Anyone who has used a kitchen microwave oven has witnessed a form of heating due to radiofrequency (RF) radiation. Basically, RF radiation can act as an ignition source in two ways: It can
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directly heat a material, or it can induce voltages in conductive objects until arcing occurs. Both
phenomena can occur in microwave ovens.
Depending on its molecular structure, a substance can be quickly heated by RF radiation. In the low
gigahertz range (3 to 5 billion Hertz or cycles per second), water will heat quickly, depending on the
amount of RF power. However, other substances, such as cardboard and dry cereal, cannot be
heated in a microwave oven. Interestingly, hydrocarbon fuels cannot be easily heated in a
microwave oven, nor by other means of generating RF radiation. The molecular structures (non
bi-polar) of these fuels do not lend themselves to easy RF heating. It was once thought these fuels
could be easily heated by radio transmissions, so there was a universal prohibition against
transmitting on aircraft radios during refueling. Once it was discovered that the fuels could not be
directly heated, additional investigations were conducted; hence the second method of ignition was
examined - inducing voltages into conductors so that they arced between them. Anyone who has
placed aluminum foil in a kitchen microwave oven has probably seen this phenomenon. The exact
amount of RF radiation needed to create an ignition source is not totally certain, but early tests [Ref.
4] showed that an RF power density of five watts per square centimeter was sufficient to generate
sparks between metal shavings. That value was later adopted by U.S.A.F. technical Order 31Z-10-4
[Ref. 5] as the minimum safe power level to prevent ignition of hydrocarbon fuels. The manual states
that an RF power density of five watts per square centimeter is necessary to cause a spark with
sufficient ignition energy potential to ignite fuel vapors. For an omni-directional antenna, the RF
power density is calculated by dividing the peak-radiated power by the area of the sphere whose
radius is the distance from the antenna. For example, if a fuel line is 7.5 feet (225 cm) from a
high-frequency (HF) antenna radiating at 1,000 watts, the RF power density (pd) at the vent would
be:
pd = Power/Area
= 1000 w/4
(225)2
(1)
= 0.00157 w/cm2
This is far too low to present an ignition source hazard at the fuel line. To reach a five w/sq cm
density, a fuel line would need to be less than two inches from the 1,000-watt antenna. For a 10-watt
antenna, the hazard distance becomes 0.2 inches. Normally, fueling equipment is not close enough
to any antenna to create an ignition problem. As a result, UHF and VHF cockpit radios, hand-held
radios and cellular telephones can be operated in a fuel environment. Cockpit radios are 10 to 30
watts, while hand-held radios and cellular telephones transmit at five watts or less.
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eEdition Journal of System Safety
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Vol. 47, No. 4 • May-June 2011
In the Spotlight
Electrical Equipment in Fueled Areas
President's Message
From the Editor's
Desk
TBD
In the Spotlight:
Electrical Equipment
in Fueled Areas
A Case of ALARP
not being Applied to
Automotive Traffic
System Safety
Safety Heuristics for
Hospitals
Book Review:
How Reliable is Your
Product?: 50 Ways
to Improve Product
Reliability, by Mike
Silverman
Chapter News
Mark Your Calendar
About this Journal
Advertising in eJSS
Contact Us
Puzzle
by Harvey C. "Chuck" Dorney, P.E., C.S.P.
Pages 1 | 2 | 3 | 4 | 5
Directional antennas (e.g., radar, SATCOM) have higher RF power densities because they
concentrate their power into a narrow beam instead of in an omni-directional manner. The amount of
beam concentration depends on the antenna gain, which is an expression of the power ratio of a
concentrated beam compared to an omni-directional beam. In other words:
Gain (dB) = 10 log(P2/P1)
(2)
where P2 is the concentrated power and P1 is the omni-directional power.
For example, if the antenna gain is 30 dB, the concentrated RF
power density is 1,000 times greater than an omni-directional
beam. Ignition hazards are then controlled by two methods:
prohibiting the transmission (e.g., radar) or elevating the
antenna (e.g., using SATCOM only when the beam is aimed at
least 10 degrees above the horizon). Pulsed transmissions (e.g.,
identification friend or foe (IFF)) are time-averaged to determine
their RF power densities. IFF units can have power spikes up to
500 watts, but their effective radiating power is actually less.
Hand-held radios, cordless intercoms and cellular telephones do
not present a significant ignition hazard. Transmitting at five
watts or less, they are not likely to ignite fuel vapors by RF
radiation. In addition, under normal operating conditions, these
units are naturally safe due to their low battery voltages. In
general, batteries having less than 10 volts cannot generate
sufficient spark energy levels to ignite hydrocarbon fuel vapors.
Some can, however, generate enough current to heat a
conductor to an ignition temperature. As a result, some units
could be potential ignition sources if they fail internally (i.e., short
circuit), but these would present a problem only if near a fuel
vapor area.
Potential ignition sources
should always be
minimized, but there are
several areas where the
sources absolutely must be
prevented. Prime examples
of these areas are aircraft
and automotive fuel tanks,
and the immediate areas
around fueling operations.
Accordingly, several safety
"zones" need to be defined.
The Ignitable Material
The automotive and aviation fuels addressed in this paper have
many similar ignition properties. They have similar minimum hot surface ignition temperatures (900
to 1,100 degrees F), auto-ignition temperatures (where a heated vessel of fuel will self-ignite) of 450
degrees F and up, and the same minimum spark energy of 0.25 milli-joules. A major difference
between some fuels is the flash point, i.e., the minimum temperature where an ignitable vapor can
be found. For example, the flash points of gasoline and JP-4 jet fuel are below zero degrees F, while
the minimum flash points of JP-5 and JP-8 jet fuels are 140 degrees F and 100 degrees F,
respectively. (Commercial aviation fuels, e.g., Jet A-1, have flash points of approximately 100
degrees F.) If these temperatures are not present, the ignition source will not likely cause ignition of
the fuel. However, this case applies only to fuel vapors; liquid fuel in a fine mist can be ignited at
lower temperatures. This is evidenced by the ease of starting aircraft jet engines at temperatures
that are well below 100 degrees F. Nevertheless, when electrical arcing or RF heating occurs, any
fuel that is present is usually in vapor form, so the higher flash-point fuels will offer a considerable
increase in safety.
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One other point worth noting is that the fuel must be in the proper fuel-air ratio range to be ignited.
The ideal ratio, usually approximately 14 to 1 by weight, is termed the stoichiometric ratio. An
automotive carburetor or fuel injection computer has a primary function of ensuring the correct
fuel-air ratio (mixture) for proper ignition. If the ratio becomes leaner (too much air) or richer (too
much fuel), the minimum ignition properties change greatly. For example, a 40 percent leaning of a
stoichiometric mixture of methane will triple the minimum spark energy ignition requirement.
The Oxidizer
The third part of the classic "fire triangle" (after an ignition source and an ignitable material) is the
oxidizer. This paper deals with aircraft environments on the planet Earth, so the presence of an
oxidizer (air) is a given. However, with increasing altitudes and, to some effect, increasing
temperatures, the air becomes less dense, so its oxidizing capability is somewhat reduced. For
example, at an altitude of 18,000 feet, the minimum spark energy level can be quadrupled or more.
On the other hand, a higher altitude can improve the chances of ignition. On the ground, an aircraft
fuel tank containing Jet A fuel will usually have an overly lean mixture in the ullage (the air above the
fuel in the tank). However, at higher altitudes, the overly-lean mixture can approach a stoichiometric
mixture as the air gets thinner and the mixture becomes richer.
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Copyright © 2010 by the System Safety Society. All rights reserved. The double-sigma logo is a trademark of the System Safety Society. Other corporate or trade names may be trademarks or registered
trademarks of their respective holders.
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eEdition Journal of System Safety
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Vol. 47, No. 4 • May-June 2011
In the Spotlight
Electrical Equipment in Fueled Areas
President's Message
From the Editor's
Desk
TBD
In the Spotlight:
Electrical Equipment
in Fueled Areas
A Case of ALARP
not being Applied to
Automotive Traffic
System Safety
Safety Heuristics for
Hospitals
Book Review:
How Reliable is Your
Product?: 50 Ways
to Improve Product
Reliability, by Mike
Silverman
Chapter News
Mark Your Calendar
About this Journal
Advertising in eJSS
Contact Us
Puzzle
by Harvey C. "Chuck" Dorney, P.E., C.S.P.
Pages 1 | 2 | 3 | 4 | 5
Applications
Potential ignition sources should always be minimized, but there are several areas where the
sources absolutely must be prevented. Prime examples of these areas are aircraft and automotive
fuel tanks, and the immediate areas around fueling operations. Accordingly, several safety "zones"
need to be defined.
The National Electrical Code (NEC) [Ref. 6] defines Class I locations as those where flammable
gasses or vapors may be present in sufficient quantities to produce ignitable mixtures. Class II and
III locations are for ignitable dusts and fibers, respectively. A Class I location is sub-divided into
Division 1 and Division 2 areas. Class I, Division 1 areas are those where ignitable vapors are
expected to be present during normal operations; Class I, Division 2 areas are those where ignitable
vapors are not normally expected to be present, but can be if a failure occurs. To add to this
"alphabet soup," Class I, Division 1 and 2 locations have assigned groups A, B, C and D, depending
on the ignitable material that is present. Automotive and aviation fuels fall into Group D, a lesser
ignitable group (Group A is acetylene, which is very easily ignited).
Examples of these locations can be found in and near an aircraft. The space inside an aircraft fuel
tank is considered a Class I, Division 1 location, while the area outside a hangared aircraft, but within
five feet of its fuel tanks and engines, is considered a Class I, Division 2 location (as long as the fuel
temperature is above its flash point). If an aircraft is inside a hangar, then areas below the hangar
floor level are considered Class I, Division 1 locations, and areas above the floor up to a height of 18
inches are considered Class I, Division 2 locations.
For aircraft ground refueling operations, the area inside a 50-foot
bubble around the aircraft is termed the fuel servicing safety
zone (FSSZ) and is treated as a Division 2 location. During
these operations, fuel entering the tank forces air outside the
aircraft vent outlet, so this vapor-laden air is treated like a
Division 1 location for 10 feet around the vent. (A similar, but
much smaller, bubble is present around the tank filler port on an
automobile being refueled. However, this bubble is almost
non-existent if the gas station pump has a vapor recovery
system that vacuums the fuel vapors.)
Hazard Control Methods
Given that air is present during all operations, the presence of
an ignition source or a fuel source must be prevented. In some
cases, such as in Division 1 locations, the presence of fuel
cannot be prevented, so the ignition source must be prevented.
There are several methods of preventing electrical ignition
sources:
Something to ponder: Many
automobiles have electrical
fuel pumps that are
submerged in the fuel tanks,
and use the fuel (gasoline)
as a pump lubricant and a
coolant. These pumps use
quite a bit of energy. How
do you suppose they keep
from starting fuel tank fires?
Using explosion-proof housings (usually used in Division
1 areas). Such housings are strong enough to contain
potential explosions resulting from electrical sparks.
Using sealed, or vapor-proof, housing (usually used in
Division 2 areas). Such housings have gaskets or sealants to prevent fuel entry.
Purging or filling with an inert material, such as nitrogen, to prevent entry of an ignitable
material. Some oils have also been used for this application.
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Using non-incendive circuits, which, under normal use, have insufficient energy to be capable
of serving as an ignition source. A battery-operated wristwatch is a good example.
Using intrinsically-safe circuits, which are similar to non-incendive circuits, but also are
considered low-energy even if certain faults occur, such as a short circuit. Such devices are
usually tested in an explosion chamber and are certified and labeled as such.
However, there are many applications where none of the above conditions apply to an electrical
device around a fueled area, so the U.S.A.F. has undertaken risk management procedures. Again,
for a high ignition risk to be present, there must be a likely ignition source and a likely presence of
fuel in an ignitable form (near stoichiometric and above its flash point.) With the exception of the
spaces inside fuel tanks and around fuel vent outlets, the presence of such fuel is rare in aircraft
operations. Accordingly, the U.S.A.F. has approved the operation of several non-certified or
non-compliant electrical devices around an aircraft containing fuel or being refueled. A general
summary of U.S.A.F.-accepted practices is shown in Table 1.
Table 1 — Accepted Practices
Battery voltage less than 12 volts
No making or breaking connections
Secured connections (locking rings on plugs)
Do not open the case
Do not change or charge the battery
No evidence of physical damage
Do not use dropped unit
Do not use in Class I, Division 1 area
Do not use near aircraft fuel vent
Continuous vigilance for presence of fuel
RF power density less than 5 watts/sq cm
Something to ponder: Many automobiles have electrical fuel pumps that are submerged in the fuel
tanks, and use the fuel (gasoline) as a pump lubricant and a coolant. These pumps use quite a bit of
energy. How do you suppose they keep from starting fuel tank fires?
Special Tests
This paper identified several sources of safety data and criteria. However, there were still some
cases where the data or criteria were non-existent. It became necessary to conduct some tests to
verify the above-listed accepted practices. These tests were accomplished at the author's personal
residence, but should not be tried at home without some safety precautions, such as eye protection
and a standby fire extinguisher.
Gasoline in Kitchen Microwave Oven
Earlier in this paper, it was mentioned that automotive and aviation jet fuels could not be directly
ignited by radio frequency radiation. This skeptical author placed a few grams of gasoline inside a
sealed plastic bag, and inserted the bag into the household microwave oven. The oven was turned
on at the "high" setting for a few seconds at a time, until about 30 seconds of cooking time had
passed. The gasoline did not increase its temperature, thus verifying, to a small effect, that it is not
susceptible to RF heating. (Incidentally, the sealed bag was used to ensure that the gasoline vapors
did not reach the electrical portions of the oven.)
Shorting an Automotive Battery with Gasoline Present
Some of the previously mentioned UL ignition curves imply that electrical energy sources that have
12 volts or less might not have sufficient energy to be capable of spark ignition. However, anyone
who has jump-started a car battery has probably observed substantial sparking that appears to be
easily capable of igniting fuel. This once-again skeptical author placed a car battery on the ground
and applied a very small amount of gasoline at both bare terminals. He then placed a steel shorting
bar across the terminals, and, not surprisingly, ignition immediately occurred. Due to the very small
amount of gasoline present, the small flame was quickly extinguished before it had an opportunity to
ignite hydrogen from the battery.
Shorting AA-, C-, and D-Cell and 9-Volt Batteries
This test was also conducted at the author's home to determine the effects of a short circuit on
standard household batteries, many of which are used to power portable electronic devices around
fueled aircraft. For this test, standard AA-, B-, D-cell and square 9-volt batteries were held in a long
shorted condition by using a C-clamp to see if they would rupture, explode, vent gasses or even
elevate their temperatures. In all cases, no ruptures, explosions or venting occurred after being
shorted for 30 minutes. However, each battery case temperature reached approximately 130
degrees (as determined subjectively by the author). These tests provided additional confidence in
the safety of battery-operated portable electronic equipment around fueled aircraft.
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Vol. 47, No. 4 • May-June 2011
In the Spotlight
Electrical Equipment in Fueled Areas
President's Message
From the Editor's
Desk
TBD
In the Spotlight:
Electrical Equipment
in Fueled Areas
A Case of ALARP
not being Applied to
Automotive Traffic
System Safety
Safety Heuristics for
Hospitals
Book Review:
How Reliable is Your
Product?: 50 Ways
to Improve Product
Reliability, by Mike
Silverman
Chapter News
Mark Your Calendar
About this Journal
Advertising in eJSS
Contact Us
Puzzle
by Harvey C. "Chuck" Dorney, P.E., C.S.P.
Pages 1 | 2 | 3 | 4 | 5
Conclusion
Several U.S.A.F. organizations have been able to safely use portable electronic equipment around
fueled aircraft without expensive and time-consuming testing for each item. In these cases, the risk
of ignition is low. The equipment evaluated herein does not create a likely source of ignition. Further,
the likelihood of having ignitable fuel present is quite low, due to existing standard procedures for
preventing fuel leaks and spills. Finally, there is only a small likelihood of having any present fuel in
an ignitable form, i.e., near a stoichiometric ratio and above its flash point. Combining these three
factors allows the U.S.A.F. to operate portable electronic equipment at a low risk around fueled
aircraft. By determining ignition potentials for families of electrical devices, the U.S.A.F. has
determined appropriate electrical safety criteria, and has used these criteria to save taxpayers
money by purchasing commercial off-the-shelf equipment, instead of relying on expensive "military
rugged" equipment.
About the Author
Chuck Dorney was born an Air Force "brat" in Olney, Illinois, on June 13, 1944. He attended grade
school in many locations and graduated from high school from the International School of Brussels,
Belgium. He has a B.S. in aerospace engineering and an MBA. He has worked in system safety for
32 years and is currently the chief of system safety for the U.S.A.F. Materiel Command. He is also
responsible for developing and publishing MIL-STD-882. Chuck is a registered professional engineer
(Ohio) and a certified safety professional (CSP). He is currently president of the Ohio Chapter of the
ISSS.
References
1. Underwriters Laboratory Standard UL 913. Intrinsically Safe Apparatus and Associated Apparatus,
May 20, 1988, p. 41.
2. Clodfelter, R. and J. Kuchta. Aircraft Mishap Fire Pattern Investigations, Air Force Wright
Aeronautical Laboratories Technical Report (AFWAL-TR-85-2057), August, 1985, p. 176.
3. Knezek, C. et al, General Dynamics, Forth Worth Division, Fueling Ignition Study/Test, F-16,
Report No. 16PR1360, April 31, 1980, p. 336.
4. Burkett, V. et al. General Electric Co., Final report of the Radio Frequency Radiation Arcing
Hazard in Refueling, Contract AF 30 (602) -1419, Feb. 29, 1956, p. 72.
5. USAF Technical Order 31Z-10-4, Electromagnetic Radiation Hazards, McClellan AFB CA, Oct.15,
1981, p. 110.
6. National Electrical Code, Article 500.
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