On Wed, 17 Mar 2004 21:33:43 GMT, Dave Shrader
wrote:

John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

This reminds me of a story... (pause while room clears out).
Years ago I was an engineering student working for Cadillac
Motor Car. Electronic fuel injection was new then, and there
had been a couple of fires in the field that were suspected to
have been caused by leaky fuel lines, which were at higher
pressure than on the old carbureted cars. There were competing
theories, however, as to what exactly was setting off the fire.
I got assigned to help the guy doing the experiments to find out.

He had a car fitted with a plexiglas hood, topped by a small tower
with a high-speed movie camera pointing down for a good look
at anything happening in the engine compartment. Two fire
extinguishers were arranged to cover the under-hood area,
and a fuel vapor sensor was also installed there. The way
it was supposed to work was that he would drive and I would
operate the hand-pumped sensor, and at the first sign of fire
he would trigger the extinguishers. We ran all the tests
at the GM Proving Grounds in Milford, Michigan.

We tried making leaks in the fuel injection hoses. We had gas
spraying all over under the hood, collecting in pools on the
hot exhaust manifold. We tried poking holes in the spark
plug wire insulation. Nothing, no fire.

Finally I got a bright idea, and loosened the ground for the
air conditioner compressor clutch. The idea was that this
was a big inductor, and if the circuit opened there would
be a big spark. Then all we needed to do was get the
wire to bounce. We tried swerving from side to side,
and driving on bumpy tracks, but no deal. I was *sure*
that this spark would do the job, but we couldn't tell
if we were really getting the spark. So finally I stood on the
hood, holding on to the camera tower, so I could see
for myself if there were sparks. He drove down the
bumpy road one more time, and I did in fact see a spark:
The high-speed movie shows the fire spreading out
from it, more and more on each frame. Also on each
frame was the back of my head, moving away more
and more on each frame, until the extinguishers doused
everything. What a rush!

Them was the good ole' days.....


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

Dave Shrader wrote in message news:Xu36c.33004$po.292953@attbi_s52...
John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

So, it is possible that pressing the PTT or the ON/OFF switch causes the
necessary spark. Remember the Apollo ground fire. A switch/spark caused
an oxygen explosion.

Actually, anyone who has worked in the offshore oil industry will be
familiar with the concept of intrinsic safety. This requires that no
electronic instrument shall be able to ignite a mixture of air and
inflamable vapour or gas. All handheld radios used on rigs are
intrinsically safe, making them far more expensive than the standard
variety.

I very much doubt that cell phones are buit to intrinsicly safe
standards, and under those circumstances I would certainly not feel
safe near someone yacking while filling.

So, an interesting querstion is; does your phone conform to UL
requirements for intrinsic safety? And if not, why are you using it
in an area where an explosive gas air mixture is possible?

Cap

I read in sci.electronics.design that The Captain
wrote (in ) about 'CB
Radios, Cellphones and Gasoline Vapor Ignition', on Thu, 18 Mar 2004:
All handheld radios used on rigs are
intrinsically safe, making them far more expensive than the standard
variety.

But do they NEED to be that costly or is that what the market will
stand?

I very much doubt that cell phones are buit to intrinsicly safe
standards, and under those circumstances I would certainly not feel safe
near someone yacking while filling.

So, an interesting querstion is; does your phone conform to UL
requirements for intrinsic safety? And if not, why are you using it in
an area where an explosive gas air mixture is possible?

We are effectively discussing whether there are any grounds for
requiring cell-phones, non-intrinsically safe, to be switched off, or
not used, at gas stations. So far, the numbers suggest that the hazard
is minute and the risk is also minute.

There is a relatively new philosophy being applied to safety standards,
including UL standards. It's called 'hazard-based', and requires a
logical chain of reasoning to justify every provision of a standard.
This is likely to result in significant changes to such standards over
the next decade or so. Many current standards have 'just growed' over
many years, and in some cases no-one knows why a certain provision is
included.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

In article ,
(The Captain) wrote:

Dave Shrader wrote in message
news:Xu36c.33004$po.292953@attbi_s52...
John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

So, it is possible that pressing the PTT or the ON/OFF switch causes the
necessary spark. Remember the Apollo ground fire. A switch/spark caused
an oxygen explosion.

Actually, anyone who has worked in the offshore oil industry will be
familiar with the concept of intrinsic safety. This requires that no
electronic instrument shall be able to ignite a mixture of air and
inflamable vapour or gas. All handheld radios used on rigs are
intrinsically safe, making them far more expensive than the standard
variety.

I very much doubt that cell phones are buit to intrinsicly safe
standards, and under those circumstances I would certainly not feel
safe near someone yacking while filling.

So, an interesting querstion is; does your phone conform to UL
requirements for intrinsic safety? And if not, why are you using it
in an area where an explosive gas air mixture is possible?

Cap

Actually the electronic portion of the Intrisically Safe Radio is
the same as the regular Radio of the same model. What is different is
the Battery and the Battery Connections. On an Intriscally Safe Radio
the Battery and Battery connections are Specifically Designed so as
to not spark when changed, while the radio is turned on. This design
change isn't really that expensive, but the testing that is required to
receive the "Intrinsically Safe" Lable, is extremely expensive.

me

I read in sci.electronics.design that Me wrote (in Me-
) about 'CB Radios,
Cellphones and Gasoline Vapor Ignition', on Fri, 19 Mar 2004:
This design
change isn't really that expensive, but the testing that is required to
receive the "Intrinsically Safe" Lable, is extremely expensive.

There are strong suspicions in some countries that it is quite
unjustifiably expensive, because only a few facilities offer it. More
competition is required. Or a government investigation.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

(The Captain) wrote in message . com...
Dave Shrader wrote in message news:Xu36c.33004$po.292953@attbi_s52...
John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

So, it is possible that pressing the PTT or the ON/OFF switch causes the
necessary spark. Remember the Apollo ground fire. A switch/spark caused
an oxygen explosion.

Actually, anyone who has worked in the offshore oil industry will be
familiar with the concept of intrinsic safety. This requires that no
electronic instrument shall be able to ignite a mixture of air and
inflamable vapour or gas. All handheld radios used on rigs are
intrinsically safe, making them far more expensive than the standard
variety.

I very much doubt that cell phones are buit to intrinsicly safe
standards, and under those circumstances I would certainly not feel
safe near someone yacking while filling.

So, an interesting querstion is; does your phone conform to UL
requirements for intrinsic safety? And if not, why are you using it
in an area where an explosive gas air mixture is possible?

Cap

Actually, a former maritime safety engineer Emailed me
about this. However, he could not locate the law or regulation
which defines "intrinsic safety". If you can find a law
or regulation governing operation of a transmitter around
a gas pump, please post it.

I have no idea how UL testing would pertain to a battery operated
device incapable, itself, of electrocuting anyone. However, the
battery eliminator which I have (but did not use in the
experiment I described) is UL approved.

On the safety issue, the same engineer also told me he was able
to create visible sparks with a 100 W transmitter, holding
the antenna near a piece of metal. However, for the following
reason, I suspect the sparks were because his transmitter was
earth-grounded:

The handheld CB I used had a completely insulated rubber antenna
and of course had no ground connection. I replaced the rubber
antenna with a telescoping metal one. I then keyed the transmit
button (as above) in the dark, while trying to get a spark by
bringing the tip near a 1 m x 1 m aluminum 1/4 in plate (ungrounded).
I could see nothing, although touching the metal caused the CB's
power out bar to indicate a drop in power. The plate should have
been an effective AC ground at ~27 MHz.

So, neither induction into a wire nor electrical direct contact
seems likely to make a visible spark, with a 5 W CB transmitter.

I would only expect a 100 mV or so spark anyway, which would be
hard to see.

So, I'm not convinced that a cell phone could cause a spark, either.


I agree that key closure sparks might be possible internal to
the device, and that neither it nor a cell phone would be likely
to have been designed to suppress a flash from such a source.

However, the issue I have tried to address here is a spark from
the RF, not from generic electrical causes. I don't doubt that
gasoline vapor is inflammable in a generic sense.

John

John Michael Williams

See my post titled Intrinsic Safety

--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
have an "impossible" engineering project that only someone like
Doc Brown can solve? My resume is at http://www.guymacon.com/

Guy Macon http://www.guymacon.com wrote in message ...
See my post titled Intrinsic Safety

I did. Thanks.

It appears that the laws involved pertain to manufacturers
and commercial operations. So, I think none would
govern use of a cell phone while gassing up.

I once wired a farm house, but that was before the NEC
included the concept, I think.

John

John Michael Williams

John Michael Williams says...

Actually, a former maritime safety engineer Emailed me
about this. However, he could not locate the law or regulation
which defines "intrinsic safety". If you can find a law
or regulation governing operation of a transmitter around
a gas pump, please post it.


The National Fire Protection Association’s (NFPA) National Electrical
Code (Article 500, NFPA 70) defines Hazardous Locations as those areas
"where fire or explosion hazards may exist due to flammable gases or
vapors, flammable liquids, combustible dust, or ignitable fibers or
flyings."

NFPA-NEC Intrinsic Safety ratings detail the specific Hazardous
Location in which an electrical device can be used without fear
of electrostatic discharge that may cause an explosion. The
classification that applies to auto fuels a Class I: Gases,
vapors and liquids - Group D: Hydrocarbons, fuels, solvents,
etc. - Division II: Not normally present in explosive concentrations
(but may accidentally exist).

Other standards that apply to Intrinsic Safety a


ANSI/UL 913 Intrinsically Safe Apparatus and
Associated Apparatus for Use in Class I, II, and III,
Division 1, Hazardous (Classified) Locations

US Mine Safety and Health Administration (MSHA)
Mine Wide Monitoring Systems (MWMS) Program:
MSHA ACRI2001 - 30 CFR Part 18, Part 23

CENELEC/EN European Standards for electrical
apparatus for potential explosive atmosphere
General requirements EN 500 14 [IEC 60079-0]
Increased safety "e" EN 500 19
Intrinsic safety "i" EN 500 20 [IEC 60079-11] [BS 5501 part 7]

Canadian Standards Association (CSA) C22.2 No. 157-92

ANSI/ISA RP 12.6 Wiring Practices for Hazardous (Classified)
Locations Instrumentation - Part 1: Intrinsic Safety

Factory Mutual Research Corporation (FMRC)?

American Society for Testing and Materials (ASTM)?


Also see:

http://www.crouse-hinds.com/CrouseHi...afe/insafe.cfm
http://www.ascojoucomatic.com/images...f1/V1005gb.pdf
http://www.mtlnh.com/datashts/sensors/Sen%20Specs.pdf
http://www.msha.gov/S&HINFO/TECHRPT/...ICAL/imisf.pdf
http://www.gexcon.com/index.php?src=...HBcontents.htm
http://www.electrona.se/pdf/tp_1110_3.pdf
http://www.ieee-pcic.org/archive/pcic98.pdf





--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
have an "impossible" engineering project that only someone like
Doc Brown can solve? My resume is at http://www.guymacon.com/

On 17 Mar 2004 12:02:15 -0800, John Michael Williams wrote:

Claims that people have started fires by using
their cell phone while refueling a car apparently
are false: See
http://www.snopes.com/autos/hazards/gasvapor.asp
and other sites.

There was discussion of this and bad electric fuel pump designs last
year, but I don't recall anyone testing it out.

snip

So, I think sliding over on a car seat, and thus generating a
possible static charge, would be more likely to ignite gasoline
vapor than talking on a cell phone while refueling.

It is more likely and there's a gas station here that has a memo to
that effect (static - mainly in winter) posted where the customers
can *not* see it, duh! No signs on the pumps... The memo says you
should shock yourself on the car befor going to the pump. No one
thought about the vapor from the car on the other side of the
island.

However, it
would be useful for someone to repeat this kind of test with an
actual cell phone, as opposed to a CB radio. The wires should
be shorter, for one thing . . ..

I'm cross posting to an antenna group, looking for criticism.

John

John Michael Williams


--
Best Regards,
Mike