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@REPLYADDR Joe Gwinn <joegwinn@comcast.net>
@REPLYTO 2:5075/128 Joe Gwinn
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On Fri, 29 Sep 2023 14:10:51 -0700, Bob La Londe <
none@none.com99>
wrote:
>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.
It`s impossible to tell exactly what happened without high-def videos,
and memory is famously unreliable about things not noticed.
>Is acetylene gas conductive?
No.
> 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.
It`s true that acetylene has all manner of ways to go boom, but most
such methods are very unlikely in practice. But ESD is not rare.
Joe Gwinn
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