safety concerns volatile chemicals

Hi All,

I have an industrial customer that wants to put wireless into his factory floor. There are industrial chemicals involved -- basically fixings to make spray paint. Obviously, no smoking is allowed.

Is there ANY fire hazard involved with wireless and the accidental ignition of volatile chemical? (Bozos who talk on there cell phone while pumping gasoline comes to mind.)

Many thanks,

--Tony

Reply to
Tony
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Thank you. They do use two way radios. I will find out if they were specially certified. Also, where the real ignition danger is, they won't let but a select few people through the special doors. And they have a real expensive halon system to instantly extinguish anything. No electronics at all are allowed through that door. I will also make sure I am protected too.

--Tony

Pierre wrote:

Reply to
Tony

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If the factory does NOT require intrinsically safe equipment, then

Thank you! They have a lot of electrical equipment on the production line. Hmmmm. I wonder if it is certified or there if there is no danger.

I have gotten RF burns on my fingers before (don't ask!), but that was 30 watts.

--Tony

Reply to
Tony

Yeah, sorta. There's zero danger from the 50 milliwatts of RF igniting anything. That's not enough to generate a spark. I can't recall the name of the physics law that determines the energy necessary to create a visible spark. However, it's substantially more than what can be generated by a cell phone or wireless device.

However, the real danger in igniting volatiles and chemical fumes is from power connectors, AC outlets, and battery chargers. All of these will easily create a spark. Same with flashlight switches or any open power switch. If the factory requires intrinsically safe electrical devices and equipment, you will buy something that qualifies. In general, mummifying the wireless device in an explosion proof container is sufficient. This might be worth reading: |

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the factory does NOT require intrinsically safe equipment, then just make an effort to reduce sparking and be done with it. The RF won't do anything.

Reply to
Jeff Liebermann

It can be certified as intrinsically safe with solid state switches and non-sparking metals. I did such a conversion in about 1975 at chemical plant.

I found the physics principle I mentioned. Check Google for "Paschen Curve" or "Paschen's Law" which define what is necessary to create a spark. Note that it's horribly non-linear below about 500 volts.

Same here. I used to design marine radios for Intech Inc. I was doing battle with an antenna tuner for 1.6-30Mhz. The test radio ran

150 watts PEP and 15 watts CW for tuning. At the 1.6Mhz, it was possible to generated about 2000 volts at the top of one of the tuning coils. Man, did that hurt.

Incidentally, one of my dumber fun projects was trying to build a "modern" low power (QRP) miniature spark gap transmitter. The problem was that Paschen's Law showed that the spark would not jump with the

12 volts I had to work with. I even tried to partially ionize the air with some radioactive Thorium. Total failure. Oh well.

Again, incidentally, there are about 35 gasoline station fires each year started from some type of spark. None of them are caused by cell phones or radios. The most common culprit are relays, switches, and starter motors. I have yet to see one start with a cell phone. I once offered a friend $50 if he could ignite any flammable mixture using RF from an unmodified cell phone. It's been about 10 years and he still hasn't collected.

Where the original safety issue came from was from mobile radios that used dynamotors or vibrator type power supplies. In the 1960's, these huge radios (Motorola 5V, 40V, 80D etc) were mounted in the trunk, above the gas tank. If the gas tank filled full of gas fumes during filling, talking on the radio would generate a HUGE spark, that would set off an explosion in the confined space of the trunk. This happened to me in my 1960 Ford Falcon, which resulted in the back seat getting shredded and sprayed all over the interior. Other friends and customers had more spectacular explosions.

With the invention of solid-state radios, the elimination of open frame relays for T/R switching, and the elimination of vented gas tanks, the problem of exploding car trunks was almost completely eliminated. However, the paranoia surrounding the issue 50 years later, is still with us today. Sigh.

Reply to
Jeff Liebermann

Would you settle for exploding cell phone batteries?

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never know when someone's cell phone might burst into flames, ignite the gasoline vapors, and precipitate a litigatory and insurance calamity. I suspect the odds are similar to those of getting hit by a falling airplane, but why take chances?

Reply to
Jeff Liebermann

Can you find a single reference to demonstrate where this has happened?

Reply to
David Taylor

Y'er no fun. I guess the cell phone vibrator motor brushes could generate enough of a spark to ignite the fumes and start a fire.

Once upon a time, before skool safety regulations were discovered, our high skool brought in a fireman who demonstrated how critical the fuel air mixture was to obtain a proper explosion. Just about any concentration would burn, but you had to have about a 13:1 mixture in order to get a real explosion. That was fun (and noisy).

Judging by the number of electrical fire related automobile recalls, the most unsafe thing in the gas station is the vehicle.

Reply to
Jeff Liebermann

Generally electrical items must be certified safe in such environments. This usually means that switches etc must be completely gas tight so that there is no possibility of and arc or spark possibly igniting the environment.

As a guideline, find out if possibly portable two way radios are permitted or used on the factory floor. If not, then consider an AP or other electronic equipment in the same category. Process equipment will, or at least should be certified in that environment.

Whichever way, ensure you have a written clearance accepting all liability from the company that is legally sound, i.e. complies with any relevant legislation regarding that workplace, before you attempt to supply or install such equipment otherwise you could be in a sticky legal situation should anything untoward happen, even if it is not specifically caused by that equipment.

Incidentally, many gas stations now have signs stating that mobile phones must be turned off completely before entering the filling areas.

Peter

Reply to
Pierre

Bzzz, close but not quite. Your earlier post summed it up. Any suitable power source can cause a spark.

David.

Reply to
David Taylor

I know, thing is, how many of us have got a static shock when getting out of the car? Are they going to ban us wearing nylon or whatever? :)

David.

Reply to
David Taylor

"Tony"

| Hi All, | | I have an industrial customer that wants to put | wireless into his factory floor. There are industrial | chemicals involved -- basically fixings to make spray | paint. Obviously, no smoking is allowed. | | Is there ANY fire hazard involved with wireless | and the accidental ignition of volatile chemical? | (Bozos who talk on there cell phone while pumping | gasoline comes to mind.) | Little chance of ignition from cell phone BTW or the AP.

Regardless there are legal considerations you need to consider. Operation of an unapproved electrical device on the plant floor may void the guys insurance coverage and get him in sh|t storm with all sorts of regulators.

The installation by you of the device may put you a legal risk.

I'd recommend you look into explosion proof cabinets for the AP and other electronics. (better would be Intrinsically Safe but I doubt you'll find any wifi stuff that certified and likely could not afford it if you did) Watch what you use for cabling (antenna and CAT5) as the type of material used can be a safety issue.

As to the computers on the floor. If you're to supply them check out industrial grade machines as they are designed for the use and some are specifically designed for explosive/hostile environments. Check with the plant's electrical department for what is approved for their application.

Another point don't assume ANYTHING about the job, check it all out before you bid much less do the job.

Reply to
NotMe

Agree on the AP, but many cellphones have a vibrator, which is essentially a small DC motor (with brushes) spinning an offset weight. Definitely not intrinsically safe... 8*|

Reply to
William P. N. Smith

Did not say any of this was intrinsically safe. (the process cost far too much for the ROI) It's been a while since I did any hands on design work with wireless handsets but up to that time all I had any dealings with used a solid state 'vibrator', no points or mechanical contacts, etc. as the solid state stuff is cheaper, less prone to failure and required less power for the same result. Side benefit the same device could be used for a hands free speaker.

Reply to
NotMe

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