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On 9/29/2023 8:45 AM, Joe Gwinn wrote:
> On Thu, 28 Sep 2023 15:55:39 -0700, Bob La Londe <
none@none.com99>
> wrote:
>
>> On 9/28/2023 3:19 PM, Joe Gwinn wrote:
>>> On Wed, 27 Sep 2023 16:07:16 -0700, Bob La Londe <none@none.com99>
>>> wrote:
>>>
>>>> On 9/27/2023 1:05 PM, Leon Fisk wrote:
>>>>> Hi,
>>>>>
>>>>> Interesting news article on the power of leaking acetylene?
>>>>>
https://www.mlive.com/news/grand-rapids/2023/09/explosion-in-allendale-injures-1
-damages-vehicles.html
>>>>>
>>>>> ===
>>>>> OTTAWA COUNTY, MI - Police believe a leaking cutting torch stored in a
>>>>> vehicle`s trunk caused an explosion early Wednesday morning.
>>>>>
>>>>> A 21-year-old Allendale woman suffered minor injuries and two cars were
>>>>> damaged as a result of the blast, Ottawa County sheriff`s deputies said.
>>>>>
>>>>> Allendale Township firefighters and deputies responded to a 6:30 a.m.
>>>>> report of an explosion Wednesday near 68th Avenue and Sunset Drive in
>>>>> Allendale.
>>>>>
>>>>> Police said a leaking acetylene torch was stored in the trunk of a car
>>>>> overnight. Investigators determined the explosion was triggered either
>>>>> when the electric release was used or when the trunk was opened.
>>>>>
>>>>> There was also damage reported to the garage`s structure.
>>>>
>>>>
>>>> I have been told more than a certain volume of acetylene in "free air"
>>>> can self detonate or detonate from turbulence. I had an accident here
>>>> at the shop some years back where there was no apparent source of
>>>> ignition. Just somebody in open air sticking their hand in front of the
>>>> flow the flow from a cracked valve. There was no physical contact, and
>>>> no obvious source for static. I mentioned it in this group not long
>>>> after it happened. Gunner and a few others told me there had to be an
>>>> ignition source, but I was standing right there. In fact I was reaching
>>>> towards the valve to shut it off when it ignited. Then we had a blow
>>>> torch pointed at the corner of my shop building. I went back in the
>>>> shop to grab a welding glove so I could shut it off.
>>>>
>>>> The person with their hand in front of the valve got burned, but not as
>>>> badly as you might think. Their whole hand was red, and the outer
>>>> layers of skin all sloughed off over the next few days. They got their
>>>> hand out of the fire pretty quick. Worse than a regular first degree
>>>> burn, but not the worst burn I`ve seen called a second degree burn. It
>>>> was mostly bad because it was over their whole hand.
>>>>
>>>> We could argue about whether it was an explosion or a conflagration. It
>>>> had a pretty healthy pop for an uncontained event. Faster than a
>>>> whoomp, but maybe not quite a crack.
>>>
>>> What was the humidity then?
>>>
>>> I`d bet on an unnoticed ESD (electro-static discharge), which can be
>>> caused by the air causing things to flutter against one another.
>>>
>>> Just walking across a carpet can generate enough static electricity to
>>> make a sharp crack sound.
>>>
>>> Joe Gwinn
>>
>>
>> Standing on concrete outside in one of the driest climates on earth. I
>> wear rubber sole shoes pretty much all the time. Either sneakers or
>> walking boots. The OP usually wears rubber sole shoes as well. I still
>> have very good discrete hearing. (I still have my high frequency
>> hearing as well.) The only sound I heard was the detonation. Its
>> possible, but it sure didn`t seem like it.
>
> The ESD spark and the detonation would likely be too close in time to
> be told apart, and the boom is far louder.
>
> Joe Gwinn
So how for does the invisible arc jump. His hand was 8-10 inches away.
It wasn`t me. My hand was maybe 6 inches away, and I felt no static
pop. The only time I`ve seen a normal static arc jump much longer than
an inch or so was in extreme circumstances. Arc gap generators, St
Elmos fire discharging off an antenna cable in a fog on boat. That sort
of thing. In those cases it was quite visible.
Maybe you are right, and I am full shit, but the detonation happened at
exactly the moment the OPs hand broke the flow from the valve. I was so
surprised that I spent quite a bit of time researching it to see what
could have caused it. There was no obvious arc source. Not even a
nearby motor starting up. Closest motor was the AC heat pump condensing
unit about 15 feet away and it was not running.
Is acetylene gas conductive? I guess if it is that could have provided
the "invisible" arc path. I am aware that vulcanisates of acetylene
black are conductive, but I can`t find anything that specifically says
acetylene gas is.
That acetylene "can" detonate from when certain conditions are met not
necessarily requiring a spark is established. Whether or not that is
what happened when a bottle turned into a blow torch outside my shop we
will never know for sure. I have no desired to perform experiments to
prove it one way or another. Okay maybe a little but I am not yet
senile enough to let my curiosity over ride my common sense.
--
Bob La Londe
CNC Molds N Stuff
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