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Old 28-01-2016, 09:00   #16
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Re: Explosion caused by OFF power tool???

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Originally Posted by a64pilot View Post
Yes absolutely I was looking for the film I saw years ago of static bolts being discharged in a big fuel tank being filled. Reason it didn't blow we were told was the mixture was too rich, not enough air in the tank.
US Army burned a fuel depot at Ft Irwin when I was there top loading a fuel truck without the dip tube.


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Most interesting, thanks!
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Old 28-01-2016, 09:06   #17
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Re: Explosion caused by OFF power tool???

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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)
Thanks for the info.
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Old 28-01-2016, 09:07   #18
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Re: Explosion caused by OFF power tool???

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Originally Posted by tinysailor View Post


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)
So does that mean the plastic ones you can get are conductive then?

I am always nervous of filling them from a petrol pump after reading about refueling helicopters in Vietnam or Korea (can't remember which), which was high speed and had plastic fuel tanks, which caused a build up of static, leading to explosions.

I also get the same feeling being near dive cylinders that are being refilled....
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Old 28-01-2016, 09:15   #19
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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??

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Fanciful scenario in open air.

More likely would be fuel vapour accumulating in a bilge or static buildup at the filler. Dissipating with a ground strap is standard practice in any refueling activity.

Bilge pumps are not normally electrically protected for use in explosive atmospheres.

Peteol vapours have a capability to travel along convoluted pathways, eventually accumulating in concentrations sufficient to create an explosive atmoshere.

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Old 28-01-2016, 09:17   #20
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Re: Explosion caused by OFF power tool???

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Originally Posted by philtrick View Post
So does that mean the plastic ones you can get are conductive then?

I am always nervous of filling them from a petrol pump after reading about refueling helicopters in Vietnam or Korea (can't remember which), which was high speed and had plastic fuel tanks, which caused a build up of static, leading to explosions.

I also get the same feeling being near dive cylinders that are being refilled....
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.

When filling drums with flammables regulations (and common sense) require the drum be grounded during the operation. This is a very real concern.

PS
I feel the same about getting SCUBA tanks filled. Usually like to walk around to the other side of the shop.
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Old 28-01-2016, 09:17   #21
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Re: Explosion caused by OFF power tool???

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Originally Posted by philtrick View Post
So does that mean the plastic ones you can get are conductive then?

I am always nervous of filling them from a petrol pump after reading about refueling helicopters in Vietnam or Korea (can't remember which), which was high speed and had plastic fuel tanks, which caused a build up of static, leading to explosions.

I also get the same feeling being near dive cylinders that are being refilled....

Plastic cans are fine to use here as long as they are Australian Standards approved and placed on the ground to fill.

Dive cylinders can be a worry too - especially when the idiot in your group gets grease into his O2 cylinder thread while screwing up the first stage. Biggest bang of my life! He was lucky to tell the tale as my unit was next to his when it went up in flames! I'm always a bit ginger with the O2 now :S
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Old 28-01-2016, 09:17   #22
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Re: Explosion caused by OFF power tool???

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Originally Posted by philtrick View Post
So does that mean the plastic ones you can get are conductive then?

I am always nervous of filling them from a petrol pump after reading about refueling helicopters in Vietnam or Korea (can't remember which), which was high speed and had plastic fuel tanks, which caused a build up of static, leading to explosions.

I also get the same feeling being near dive cylinders that are being refilled....
Dissipating static buildup is standard practice in any refueling activity.

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Old 28-01-2016, 09:24   #23
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Re: Explosion caused by OFF power tool???

This is not an answer to what happened but it demonstrates that gasoline will not light in liquid form.
Vaporized gasoline is required & it is the vapor that burns extremely rapidly giving the effect of an explosion.The remaining liquid gasoline will burn somewhat slowly if the initial vapor burn leaves enough latent heat to vaporize the surface a bit.
Note:this experiment was done with very cold gasoline in a cold climate which eliminates vapor until warmed by several hot extinguished matchheads.
On the other hand,hot climates or hot summer days produce large amounts of vapor rapidly & this vapor is heavier than air. If no wind,you can often see this vapor "pour" down the sides of containers & across the ground,etc. It can be ignited from a fair distance & ,in the case being discussed,I would be looking for "spark producers" anywhere within 10ft radius & down to the bottom of bilge.
It is good practice to ground the dispensing nozzle on a good earth before putting it into a filler hole.
If you are dispensing from a jerry can,use a short length of hose slid onto the spout of jerry. Insert hose in filler & then raise the jerry to pour. Eliminates spills & most of vapor.

Cheers/ Len

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Old 28-01-2016, 09:28   #24
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Re: Explosion caused by OFF power tool???

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I wonder if a sander or drill might develop a static electrical charge that could spark a fire. I have also been led to believe that gasoline flowing into/from a plastic container can develop a static electrical charge on the surface of the container near the throat and, if so, such a charge might "spark" to a plugged in tool even if in the off position. (I had the misfortune of being at a gas station on one occasion when a fellow filling a plastic gas jug sitting in the bed of his pick-up had his truck and himself set alight by static electricity. It was pretty horrible.)
Your static electricity theory is the one that I think is the most likely. There are several gas stations around here that won't let you fill up a gas jug in the bed of a truck, it must be sitting on the ground, no exceptions. Until recently, all of the gas stations had warning stickers on the pump telling people not to use their cell phones due to RF energy possibly setting off gas vapors. Those have been removed, but other stickers warning not to get back into and out of your car while refueling for fear of static discharge are still on most pumps.

If he was on the dock when this happened and the dock is made of some synthetic material (Trex or similar) then it might be possible a static charge built up there just from pouring the gas, even though the jug was sitting on the dock.

There was definitely an ignition source, but a dormant power tool seems highly unlikely.
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Old 28-01-2016, 10:02   #25
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Re: Explosion caused by OFF power tool???

I'm not overly buying the static electricity theory. The humidity would have to have been well over 60% and that, to me, makes it difficult to build up enough charge to throw a spark in any kind of scenario I could think of on a boat.



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Old 28-01-2016, 10:34   #26
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Re: Explosion caused by OFF power tool???

Quote:
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.
Petroleum and other organic compounds are insulating, not conducting, as would be required to cause a short circuit, as compared to the air (at whatever salty and humidity content) between the contacts. That is, if the tool doesn't start on it's own when exposed to air, it shouldn't when exposed to fuel/air mixture.

In this case, it indicates the source was someone working on a gas cylinder, perhaps a propane cylinder?

Note that 1 lb propane cylinders are notorious for leaking after they have been disconnected only once. When we used them, after disconnecting a 1 lb cylinder, I would spit in the top to see if it bubbled. (About 25% of the time, it did.) I would then push and release the little valve until it stopped leaking.

Never, ever, ever, store propane cylinders in a confined, unventilated space, and ensure any escaped fumes can flow overboard and not into the boat.

It is amazing how complacent people become when dealing with flammable and explosive materials.

I won't work on customer boats stored in buildings, unless the propane and flammables are first removed.

One boat in particular had a 25 year old (15 years beyond re-certification requirement) 20 lb half full propane tank, rolling around (unsecured) in an 150 sq ft sealed storage compartment (unventilated), under the flybridge helm (right between the operators legs.) In the same compartment, were a number of DPO wiring mods using wire nuts. In the same compartment, was a current propane tank, secured, but with about 10 ABYC standards violations. Additionally, there were all kinds of heavy and metal objects, loose in the compartment.

The owner was so $%%^ that the surveyor cited the propane system rework as a Mandatory Requirement for insurance, stating "Well it's been that way for the 25 years I've owned the boat."

This boat also had some funky duplex electrical receptacles, 12Vdc on the top, 120Vac on the bottom, both standard 2 prong, not installed in boxes, with backs exposed to the space between hull and hull liner throughout the boat. Per the owner, "But it was manufactured that way!" (In Taiwan I believe.)

Reminder to all, "Just because you haven't been killed yet, does not make any practice safe."

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Old 28-01-2016, 11:29   #27
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Re: Explosion caused by OFF power tool???

Google Flash Point, Auto-ignition temperature, Flammability Range, Lower Explosive Limits, Upper Explosive Limits, Fuel/Air Ratios. Class & Division Types of Hazardous Materials.

Rookie FireFighter stuff.
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Old 28-01-2016, 11:36   #28
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Re: Explosion caused by OFF power tool???

I'm a watchmaker. In my store I have to unplug all my electrical tools. Due to power surge or who knows what my tools have turned on on their own. I cover everything with sheets at the end of the day. To avoid dust accumulation. My auto winder that looks like a wind mill turned on one day got caught on the sheet. The security noticed the smell but didn't catch on fire. Don't know how long it was on for.
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Old 28-01-2016, 11:39   #29
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Re: Explosion caused by OFF power tool???

There was some very good info in this thread. Gases, either liquid or gaseous, demand our full respect.

When I was at the university I had a class in organic chemistry. No one was killed or even injured in the flash explosion. But what had happened was one student was doing an extraction with a highly volatile reagent. It might have been xylene or something akin to that. It was 40 years ago...I digress. He had the liquid in an open top beaker. He had not read the instructions very carefully...it was clearly in the warnings for this experiment. The gaseous vapors, which were much heavier than air, crept along the counter top over 20 feet away and hit a lit Bunsen burner. Ba-boom...It was quite exciting.

So, I am wondering if the vapors crept along a surface and hit some sort of electrical device like an operating music radio...or????
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Old 28-01-2016, 11:45   #30
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Re: Explosion caused by OFF power tool???

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.
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