Cell Phone Spark 1

[chicopee]

Is there enough spark energy generated in cell phones to ignite air ladden w/ gasoline fume while cars are being refueled? Just read an article relating several incidents on this topic. I can not seem to believe it.

 

[melone]

The maximum output RF power is 20-25dBm, depending on the carrier / technology. This is approximately 200-250mW of power (dBM = 10 * LOG (Power) + 30).

 

[OperaHouse]

I got on a state regulation site for blasting caps and you only needed to be about 2,000 feet away from a 10,000W transmitter. You wouldn't catch me that close!

Hey, it's just the lawyers. A friend was on a jury for a colapsed deck. The lawyer asked if anyone had worked with wood. The people who raised thier hands were immediately dismissed from the jury pool. They want people who are easily swayed by a weak argument. In the end, this jury was hung till one person said they had to catch a buss at 3 and changed her vote. You don't want people like this deciding why a person blew up!

I went into a rest room and the recirculating cotton towel machine had a label saying not to use the cotton towel to lift heavy machinery. The things that go on in rest rooms! Never thought they might be pulling engines there.

 

[waross]

I've heard nasty rumors about restrooms like that!!

 

[VEBill]

Our hand-held cell phones are (supposedly) up to 600mW output.

They're the very ancient and old fashioned analog FM type from the previous millennia (circa 1999).

 

[Comcokid]

As the saying somewhat goes - "Stuff Happens".

Intrinsic safety views electrical devices from the ability of the circuits to create a spark under operation or failure. IS guidelines not only look at energy sources (batteries), heat generation (resistors, light bulbs) and maximum voltages, but also the circuits ability to store enough energy in the inductance and capacitances to create an ignition source for flammable vapors/liquids. IS standards are designed to be very conservative (sometimes seemingly ridiculous) - but with the idea to keep "Stuff" from "happening". Within a few feet of a gas pump is a potential hazardous environment by definition.

The main issue of a cell phone or pager is NOT the RF - it is things like the battery, vibrator motor, and maybe that charge pump for the LED, florescent, or incandescent bulb backlight. From a IS standpoint, a good portion of a cell phone is unsafe.

How many of you remember as kids the pretty arcing/sparking you could get from your slot cars in the dark? Remember those Boy-Scout fire prevention examples using batteries, a little steel wool, and some gasoline vapors?

Stuff happens even when previously examined in detail by very experienced people and put into practice over years. How long were 747 aircraft in service before TWA fight 800 went up in a fireball over Long Island Sound? Supposedly the vapors in the 747 center fuel tank never reached an explosive ratio. They still don't exactly know what the ignition source was, but the fuel probes are suspect. Prior to this incident it was believed the low energy of the fuel level probes (a capacitance measurement device) was safe.

I have no doubt that under the proper conditions, a cell phone or pager could easily cause a fire at a gas pump. It might be rare, but it could, and possibly already has happened.

 

[VEBill]

All true, but the argument still falls apart because everything that could be claimed for a cell phone is even more true for an automobile.

 

[Comcokid]

No doubt that a car is even a bigger potential ignition source. Hence the "Turn vehicle off while fueling" signs.

 

[itsmoked]

Yes but that infernal dome light switch!!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

How about banning cars from the vicinity of gas pumps until the catalytic temperature has been check and found to be below the safe limit.
Don't forget the turn signal with the corroded connection a couple of feet from the gas filler.
I agree with VE1BLL
respectfully

 

[stevenal]

Please stop engine and remove all batteries and portable electronic equipment from vehicle prior to approaching the pumps. Allow vehicle to sit for ten minutes to allow all capacitances to discharge, then proceed to push vehicle to pump bay where our highly trained (Oregon) fueling technician will assist you. The management.

 

[itsmoked]

Yukyuk! Yeah if you tried to commission vehicle fueling in the second millenium. Course, vehicles would be illegally dangerous to even field now.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[davidbeach]

Actually, you'd just have to use diesel as the fuel. Just doesn't have the problems that gasoline does. So benign that if you are only dealing with diesel, there are no requirements for classified areas around the fuel or while working on the vehicles.

 

[ruggedscot]

Cell Phones and Fuel dispensing pumps

This is a recognised issue and one that people do have to be aware of as it can and it does happen. Its a one in a million chance but you go buy lottery tickets dont ya ?

It may never happen but if it does then the losses can be huge. There could be a loose cell in the phone or the likes and there you go an arc hot enough to cause the fule vapour to ignite. Ex rated equipment can deal with and contain ensuring that the combustion products leave cool enough not to cause an issue. Your phone doesnt have that sort of protection so it does cause an issue.

rugged

 

[VEBill]

We've entered an endless loop.

21 Apr 06 4:54 = 17 Apr 06 11:22

^C

 

[VisiGoth]

Deja Vu!
Not a one in a million chance. It is not a chance. Each explosion has a definate, but maybe unknown cause.

Some cell phones have independent cells and not soldered tabs. They can bounce and disconnect. The voltage jump is very small and known.

Fuel ignition safety requires a 500 Volt limit. Since cell phones are well below this limit, the cell phone arcs are not involved.

Spreading fear and misinformation is bad to do. It can be counterproductive to true solutions.

What human damage could have been avoided if the energy going into misinformation was directed to problem reduction?


jsolar

 

[waross]

Hey VisiGoth
On the one hand, I don't believe that cell phones are a hazard but on the other hand I don't understand your statement "Fuel ignition safety requires a 500 Volt limit. Since cell phones are well below this limit, the cell phone arcs are not involved."
Does this mean that I can use my 200 amp arc welder on the full gas tank? The open circuit voltage is only 70 volts.
????

 

[itsmoked]

Try it! Have your heirs tell us the results.

Believe it or not our city's fire chief tried it.. He's dead now.

Visigoth; I don't have the tables with me, but if I remember correctly, you need about 9 Volts to set off gasoline.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hi itsmoked
Actually I think that I'ts an energy thing and any quoted voltage will have a corresponding current that may not be mentioned. I'm pretty sure we could generate an appropriate send-off for your old Renault with 2 volts from one cell of the battery.
Take lots of pictures!!
Respectfully

 

[itsmoked]

Ha! No it already died.. It was hit by a drunk cop who also went across our sidewalk thru our 15 foot high hedge, across our apricot tree, thru the hedge again, clipped off our mailbox,(which stuck on his rear bumper), across our driveway, thru our board fence, thru our other hedge, into our neighbors yard, clipped of their clothesline 4x4, thru their back hedge, across the alley and into a creek. Which he backed out of and then fled down the alley, but not before my dad noted our mailbox on his bumper and his licence plate. But anyway that gives you the measure of the energy put into my faithful R-10. All the wheels on one side where folded under the car when they fetched up against the curb. I pulled the freshly rebuilt engine out and it now powers a 10kW two bearing generator.

As for energy, you do actually need that voltage +/- 1 or 2V to ignite flammable mixtures and that is even boosted with inductors or capacitors. As far as I know you can not ignite a flammable mixture with less than 9V or so. You can scratch a dry cell all day long and you will not get ignition. Now I am not talking about heating a thin wire up with 40A at 2V I am talking about the sparks from opening a circuit.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

I'll plead "No contest". Not sure but I'm not going to contradict you and I'm not going to try any experiments. I don't want to be trading stories with your fire chief.
BTW, what did you use for a governor?
Respectfully