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Old 28-01-2016, 12:35   #31
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Re: Explosion caused by OFF power tool???

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Originally Posted by tinysailor View Post
Top loading and static are major issues. In NSW Australia, WorkCover made sweeping audits of all depots top filling after an incident in Parkes 2006 killed a driver performing top loading. Static was the root cause. The aim of the game is to have a slow fill rate for 2 mins then ramp up the fill rate before slowing down again. From memory I think a starting flow would be about 300ltr/min ramping up to 1500ltr/min depending on maximum flow rates.

This helps reduce static. Diesel is a major static issue, worse than petroleum.

Generally for earthing requirements, all readings must be below 10ohms here in Oz. This was often fudged in drier places buy pouring water over the grounding area.

When working or near petroleum / diesel etc, anything that's not intrinsically safe can cause a fire or explosion if the fuel / oxygen mix is between the lower and upper explosion limit - commonly referred to in the industry as the LEL and UEL.

A perfect storm when taking large fuel tanks out of service would be a dry windless day.





And this is why fuel cans should always be placed on the ground when being filled and definitely not be filled in the back of a vehicle.

(Sorry to harp on, my background is in downstream petrochem engineering)
No,please do harp on.Very instructive about the can on the ground about which I was unaware.
Thanks
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Old 28-01-2016, 13:22   #32
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Re: Explosion caused by OFF power tool???

A reading of the report on explosions aboard 3 similar 100,000 oil tankers, Mactra, Marpessa, and Kong Haakon V11, in '69/70, is very interesting. Hint: water can cause static electricity. I lectured on this stuff in the Fire Service.
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Old 28-01-2016, 13:26   #33
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Re: Explosion caused by OFF power tool???

It could have nothing to do with the drill or whatever... it could have been the bilge pump or the fridge starting up.
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Old 28-01-2016, 14:10   #34
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Re: Explosion caused by OFF power tool???

I think what you are asking, Mark, is does the dielectric breakdown voltage of gasoline vapor get low enough to ionize at a tool's spark gap at 220v. The answer is no. Air and fuel mix is still in the 3kV per cm range (1atm). Since almost nothing inside a boat is intrinsically safe, all sorts of items could have set off an ignition once the vapors reached their lower explosive limit though, as zboss notes.
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Old 28-01-2016, 14:27   #35
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Re: Explosion caused by OFF power tool???

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Originally Posted by Sailorbob8599 View Post
I'm surprised to see some folk here admitting to filling a gas can on the back of their pick-up truck. Any and every fuel pump I use at gas stations have notices clearly posted, advising customers to place fuel cans on the ground before filling.
I was at a gas station just a week ago where I witnessed a fellow (an idiot?) with an SUV attempting to fill a can on the back floor of the vehicle ... for some reason, there was an interruption of fuel flow. He removed the nozzle from the can and, holding the nozzle upright and pointed toward the interior of the vehicle, he tried a number of times to activate the nozzle trigger. Luckily for him, it did not work or he would have had a flow of gas right into his vehicle.
I got the hell out of there in a hurry. Oh yes, did I mention his engine was still running? Ya just can't legislate common sense.
A good enough reason to bring back full service at gas stations I'm thinking.
I don't think so.

The last time I was in OR, I pulled in with my diesel truck (clearly marked) and the gas station attendant came over and I told him to fill it up with diesel. He said "Huh?" and I said, "Please fill it up with diesel."

Whereupon he grabbed the gas nozzle and was getting ready to pump about 20 gal of regular into my tank when I stopped him by screaming DIESEL! in his face. He looked confused so I yelled DIESEL! again so he could finally get a glimmer of a clue in his face.

He finally hung up the gas nozzle and picked up the diesel nozzle, as I watched him to make sure he didn't second guess himself. I realize that OR passed that law forcing mandatory full service at every gas station so that even the brain dead children of Portlandia would be employed, if not employable, but I don't think it was a safe move, in my experience. I really don't relish the thought of getting stuck there while they pump out my fuel tank and flush it out and replace it with fresh diesel.

I don't let anyone else fill my truck, unless I select and put the nozzle in the filler neck and let them watch it pump. Too much at stake to let someone else screw it up.
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Old 28-01-2016, 15:47   #36
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Re: Explosion caused by OFF power tool???

When filling plastic cans or any fuel tank the nozzle should be placed against the throat of the tank and not removed till all fuel flow has ceased. no gap no spark.

did the guy have a cell phone on hand? wonder why they put a ground on built in tanks? it's not just for electrolysis.
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Old 28-01-2016, 17:32   #37
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Re: Explosion caused by OFF power tool???

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Originally Posted by AnglaisInHull View Post
As a former electrical engineer I would say very unlikely - I can't imagine that vapourized fuel would have sufficient conductivity.

But if someone with more recent experience would like to express another opinion, go for it.
I AGREE. However, the usual fire from dispensing fuel is: Fuel transfers through air, an insulator, and builds a static charge. Charge is equalized through the easiest rout. In this case, the ground or the power tool's neutral terminal. This is not unlike lightening finding a convenient path. An unplugged tool would not have contributed.

In the Chemical industry and in commercial fuel hauler transfer from trucks, the truck or other vessel must be connected to ground as well as the nozzle. This puts all points of the transfer at the same potential and that potential at ground. No potential is then permitted to grow - no spark.

When you transfer fuel, all points of the system should be connected and to ground.
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Old 28-01-2016, 17:41   #38
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Re: Explosion caused by OFF power tool???

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Originally Posted by Nicholson58 View Post
I AGREE. However, the usual fire from dispensing fuel is: Fuel transfers through air, an insulator, and builds a static charge. Charge is equalized through the easiest rout. In this case, the ground or the power tool's neutral terminal. This is not unlike lightening finding a convenient path. An unplugged tool would not have contributed.

In the Chemical industry and in commercial fuel hauler transfer from trucks, the truck or other vessel must be connected to ground as well as the nozzle. This puts all points of the transfer at the same potential and that potential at ground. No potential is then permitted to grow - no spark.

When you transfer fuel, all points of the system should be connected and to ground.
Aha. I have (vague memories of) the electrical knowledge, but not the related chemical knowledge.

But definitely supports what I have learned in practice - ground everything in sight.
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Old 28-01-2016, 19:04   #39
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Re: Explosion caused by OFF power tool???

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Originally Posted by MarkJ View Post
Yesterday's fire that destroyed 3 boats has an interesting bit of unsubstantiated gossip that I wanted to get your thoughts. 3 boats on fire in St Martin


Hypothetical scenario: a person is decanting petrol/gasoline so the fluid is going through air. Next to the person is a power tool, say a cutter or drill, which is off, but plugged in.
Could the fuel vapor enter the tool and close the switch contacts making a spark causing an explosion??

.

Sent from a stupid phone that replaces words with weird stuff.
I would say yes but only if the powertool is faulty in the first place. (i.e. a broken cable causing sparks or a faulty battery.)

All the best

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Old 28-01-2016, 19:23   #40
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Re: Explosion caused by OFF power tool???

Fuel air mixture needs to be correct for combustion.
Can it happen? Yes. Likely? maybe.
If you were filling your fuel tank (vapor goes down hill) and using a grinder close by on the SAME deck, I would say its likely.
If you were using the grinder on the next boat over I would say highly improbable.

FYI all brushed motors emmit sparks.
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Old 28-01-2016, 19:57   #41
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Re: Explosion caused by OFF power tool???

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Originally Posted by tinkrman69 View Post
When filling plastic cans or any fuel tank the nozzle should be placed against the throat of the tank and not removed till all fuel flow has ceased. no gap no spark.

did the guy have a cell phone on hand? wonder why they put a ground on built in tanks? it's not just for electrolysis.
This is what I do filling the 50 gallon, all plastic gasoline fuel systems on my boat.
Am I 100% safe?

Advice, tiny sailor?
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Old 28-01-2016, 19:57   #42
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Re: Explosion caused by OFF power tool???

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Originally Posted by sailnow2011 View Post
FYI all brushed motors emmit sparks.
Not when the tool is OFF.
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Old 28-01-2016, 19:59   #43
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Re: Explosion caused by OFF power tool???

Yes, even crude oil vapors can explode.
SS Sansinena, San Pedro CA, 1976
That pile of debris on the dock is the deck and bridge, blown there by the explosion


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Old 28-01-2016, 22:18   #44
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Re: Explosion caused by OFF power tool???

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Originally Posted by adoxograph View Post
Not when the tool is OFF.
Correct. The power switch breaks the 120Vac circuit, leaving an air gap sufficient to disallow current (no spark). An air/fuel mixture in that gap will not be more conductive than air alone.

However, if the power cord was damaged, a spark could occur inside or outside the unit whether the unit was on or off.
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Old 28-01-2016, 23:21   #45
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Re: Explosion caused by OFF power tool???

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Originally Posted by skipmac View Post
There are conductive plastic drums used in the chemical industry for flammable materials but they are quite expensive and used only for very high purity solvents that are otherwise compatible with PP. I doubt the fuel jugs we buy are made of the conductive grade.
Yes, They are by law. Funnels too, if they are rated for gasoline. The conductivity is too low to measure with most multimeters.

I've done a number of accident investigations (for job as chem e in oil business) where static cause by pouring or pumping was the cause. The power tool had nothing to do with it.

* Only gasoline-rated funnels and cans
* In contact with the filler filling at all times
* Conductive hose to the tank
* Tank is earthed
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