Safe Speed Forums

So, it's OK for the police to use a Taser in a petrol station forecourt (see news), discharging 50,000 volts, but if anyone dares try to make a 'phone call, that's NOT ok?

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COAST Not just somewhere to keep a beach.

A young loner on a crusade to champion the cause of the innocent, the helpless, the powerless, in a world of criminals who operate above the law.

And perfectly safe and legal to start up a 25 year old Marina...

(... with a dirty commutator with worn brushes in its starter motor. Have you seen them go when they are old? 'Ring of fire' is a fair description.)

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Yeek!
A mobile phone may generate a spark in very rare circumstances. (most likely I believe is dropping it and the battery coming loose)
A taser creates a spark every time you press the button.
A nice big spark too.

That's a bit mad really.

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Andrew.

almost a darwin awards entry there then.

Marina owners? A little harsh, but then I suppose...

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

hmmmm you havent seen the what i've been driving around in for the past week.... i crawled under it yesterday and discovered i could see the clutch plates

acksherly i was trying to work up a line about cops & robbers and survival of the fittest, but i haven't got there yet

OK, so it ain't scientific in the slightest, but did anyone see the Braniac episode where they spilled several gallons of petrol in a caravan and left a dozen or so mobile phones in it, then called them?

Not even a peep of a flame...

Then they ran a long wire from the interior of the caravan to someone wearing a nylon jumper, got the jumper wearer to run around a biit and then touch the wire - static charge.....

BANG!!

Maybe we should ban all man-made fibres from forecourts then?!

Isn't there something about petrol stations being quite open places, so the vapours don't usually get into a high enough concentration to be spark ignited?

I suppose this could all be about fear... If you see someone smoking while filling up with petrol you aren't likely to stop for fuel there. That's understandable. But if people are afraid of seeing others using mobile phones at a petrol station then they might not stop, even though the risk from a mobile phone is pretty low. So the petrol stations 'ban' the use of mobile phones to get more customers?

I suppose this incident is really completely different if it happened inside the shop compared to if it happened as she was filling her car up right next to the pump.

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Andrew.

Snopes has a page on the subject including the following.



Considering virtually every driver has a mobile phone and almost none ever turn them off when they fill up I would have expected to have seen at least one recent cellphone induced explosion in recent history in the UK.

A few weeks ago, I stopped at petrol station a couple of miles away from where I live. After filling my car with that over-taxed petrochemical substance , I saw a group of bored teeenagers throwing a metal pipe against the wall of the station shop, attempting to break a floodlight.

Now I just happen to know that you may generate sparks if you strike masonry with metal. And just think of things that could happen if you smash an electrical appliance in a petrol station and what happens if you mix sparks with petrol fumes. Are we all familiar with what happens when you mix air, sparks and petrol inside your average internal combustion engine? Those stupid kids obviously hadn't a clue.

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Anyone who tells you that nothing is impossible has never bathed in a saucer of water.

Not forgetting the Mythbusters version of the same experiment, which similarly failed to get any sort of kaboom - not even a small one - out of the phone+fuel vapour mix.

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Chris

IIRC there is a chance that mobiles can affect the pump readings. Why they can't say that instead of using scrae tactics I'll never know.

Mind you, it's the same in hospitals; there are very few areas where the use of a mobile will cause any problems, but blanket bans are easier to impose?

The garage forecourt rules about mobile phones and leaving engines running are bullshit, plain and simple. I suspect they are imposed in order to give their customers a feeling of security, but either way they are not necessary.

As far as H & S legislation defines it, the only hazardous zone in a fuel station is inside the cabinet of the fuel pump, where fumes might accumulate in a high enough concentration to form an explosive mixture.
Outside in the open air the risk is zero and the area is not classified as hazardous. If there really were any risk then H & S would classify the area as hazardous and impose rules like these:

* No petrol engined vehicles
* Diesel engines, if stopped, not to be re-started without performing a "sniffer test" first
* anti-static footwear to be worn
* no matches or sources of ignition to be carried about the person.

And you certainly wouldn't have unattended petrol stations like the one at our local supermarket. Instead you'd have inspectors checking each car and person for sources of ignition before they entered!

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!

Good clear stuff JT, as ever...

But what about soon after a spill? I presume on a still day we could have a few inches of explosive mixture above the spill.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Not really. I guess if you spilt it into a container with sides then you'd collect some flammable vapour in it, but remember that the vapour is heavier than air, so if you spill fuel on a flat surface the ensuing vapour postively "rolls" away to be displaced by lighter air.

You can drop a cigarette in spilt petrol and it won't ignite. It needs to be contained to become explosive.

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!

I agree!

On 2 seperate occasions I have heard drivers tell other drivers off for using their mobile phones on the forecourt saying dramatic things like: "Put that away love, or you'll blow yourself up!!" or "EXCUSE ME, EXCUSE ME! You can't use that [mobile phone] here, its REALLY dangerous!".....................Well it made me laugh anyway...


As far as I know, most forecourt fires have been caused by the vapour being ignited by static electricity as it regurgitates from the tank, caused by the driver failing to 'discharge' themselves before filling.

Interesting. I can see that you're right and it does tend to roll away.

But speaking theoretically, now suppose we have a big spill on a warm day. What's going on in the middle of the spill? For a start, the molecules don't know which way to roll. The rate of evaporation is high because of the warmth. Surely the possibility of an explosive mixture must exist above the middle of a big spill?

And what about drains? What do they do for petrol forecourt rainwater drains that might help avoid an explosive mixture in the drains after a fuel spill?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I think the answer to both questions lies in the issue of volume.

Most petrol station spills are a matter of a few tablespoons of fuel. Petrol is like blood in that a teaspoonfull looks like a pint when it's on the floor!

So when you over-fill your tank and it splashes back, typically it's about an egg-cup full of fuel and it is dispersed around even before it lands on the floor. Any risk of explosion is negligible for the reasons outlined earlier.

I can't really see how a larger spill could happen without being detected and dealt with at the time. For example a tanker spill will be in the presence of a driver (presumably) trained in dealing with it. Larger spills from pumps don't really happen because the trigger needs to be depressed by the user for fuel to come out, and people tend to stop doing that when they see it's going on the floor and not in the tank!

But yes, clearly a few tens of gallons of fuel spilt in a puddle on a hot day will result in a localised explosive risk, also an extremely strong stench of petrol plus a tendency for everyone who sees it to do like a shepherd, ie get the flock out of here!

In the event of a big spill, I think the general idea is to clear folk out and then get the fire service to come and pump foam everywhere to dilute and disperse it (esp. in the drains), so that it returns to a concentration lower than that required for combustion.

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!

I might be way off here, but here’s how I see it in the grand scheme of things.
I reckon what goes on inside your petrol tank would be absolute worst-case scenario. As it empties it’s gonna draw in air (is this correct?), but there’s also going to be one heck of a contained vapour build-up (amplified by the nearby hot exhaust). Add to that the high power DC motor (with its coils and commutators) and it’s associated mechanics sucking up the fuel from the tank. Granted this will usually be completely covered with fuel providing an oxygen barrier, but it won’t if the tank tends towards empty. So we have Oxygen, fuel and a source of ignition, yet I’ve never heard of a fuel tank spontaneously exploding.

A worse case than what goes on in a cylinder?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety