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Help, Explosives Experts  
User currently onlineAR385 From Mexico, joined Nov 2003, 6461 posts, RR: 32
Posted (1 year 9 months 3 weeks 1 day 20 hours ago) and read 1045 times:
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I have a few questions regarding an incident in Mexico last week. For those who don´t know, one building of the complex housing the headquarters of PEMEX was blown up. Thirty seven people were killed. Yesterday the government said that the explosion was due to an accumulation of gas. While I don´t doubt the version I do have some doubts and I thought someone here may help:

1) How much gas needs to accumulate in the basement of a 12 story, seismologically proof building for it to destroy 4 stories? The 1st. and 2nd. floors collapsed, the 3th. and 4th. are totally destroyed.

2) Would it be the same if it was Natural Gas vs. LPG Gas?

3) How come nobody smelled the gas?

4) Simplistically I understand the difference between a gas explosion and one through explosives. But exactly which would be the differences?

Thanks for your input.

15 replies: All unread, jump to last
 
User currently offlinecomorin From United States of America, joined May 2005, 4903 posts, RR: 16
Reply 1, posted (1 year 9 months 3 weeks 1 day 19 hours ago) and read 1007 times:

I can't add much but do find it ironic that a gas explosion would have flattened a PEMEX building.

RIP to souls lost.


User currently offlinehoMsar From United States of America, joined Jan 2010, 1200 posts, RR: 0
Reply 2, posted (1 year 9 months 3 weeks 1 day 19 hours ago) and read 987 times:

Anyone else read the thread title and think the OP was in an emergency situation trying to defuse a bomb and needed to know which wire to cut?


I was raised by a cup of coffee.
User currently offlinecomorin From United States of America, joined May 2005, 4903 posts, RR: 16
Reply 3, posted (1 year 9 months 3 weeks 1 day 18 hours ago) and read 960 times:

Quoting hoMsar (Reply 2):
Anyone else read the thread title and think the OP was in an emergency situation trying to defuse a bomb and needed to know which wire to cut?

I thought the OP was in the middle of blowing something up and needed tech support...


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 4, posted (1 year 9 months 3 weeks 1 day 18 hours ago) and read 950 times:

Quoting AR385 (Thread starter):
1) How much gas needs to accumulate in the basement of a 12 story, seismologically proof building for it to destroy 4 stories? The 1st. and 2nd. floors collapsed, the 3th. and 4th. are totally destroyed.

It all depends upon the amount of gas and the volume. I've seen results of approx 20 lbs of propane exploding totally destroy a two story solidly build brick and cinder block home. Barely a slab left.

Natural gas explosions have been felt 10 miles away.

This is an interesting article on the subject - http://www.science20.com/stars_planets_life/mystery_explosion-96312

According to his math - 10 cubic meters of gas equals the explosive power of 100kg of TNT.

Quoting AR385 (Thread starter):
3) How come nobody smelled the gas?

Most natural gas has no smell. The smell from gas, propane, etc - comes from a additive put into the gas to create the distinctive smell. From the media reports I've seen, they haven't identified the source of the gas, but the primary suspects of possible methane or a leak from an old pipeline easily could have been unnoticed as the critical volume built up.


Here in the town where I live a few years ago - three homes were destroyed and two people died. It was determined that the gas had seeped through the ground into the homes over a period of weeks. One family was staying away from their home because they all were having headaches.

The most common 'smell' agent used in gas apparently is scrubbed clean and out of the gas when it leaks through the earth. So you get high enough concentrations of natural gas to make breathing labored, yet no smell at all.

[Edited 2013-02-05 20:32:49]

User currently offlinePHX787 From Japan, joined Mar 2012, 7851 posts, RR: 19
Reply 5, posted (1 year 9 months 3 weeks 1 day 17 hours ago) and read 928 times:

Well We can possibly take the tragedy of TW 800 into effect-

Any amount of electricity that goes rogue can really ignite anything that is accumulated en masse.

We see the same effect happen when you ignite Axe cans. When an ignition source is present in a certain amount of compression, the imbalance in pressure makes the gas very vulnerable to igniting.

Quoting comorin (Reply 3):
I thought the OP was in the middle of blowing something up and needed tech support...

Haaaaaa I hope I didn't just give away some of my secrets of explosives to a terrorist  



我思うゆえに我あり。(Jap. 'I think, therefore I am.')
User currently offlineGeezer From United States of America, joined Aug 2010, 1479 posts, RR: 2
Reply 6, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 920 times:

Quoting AR385 (Thread starter):
1) How much gas needs to accumulate in the basement of a 12 story, seismologically proof building for it to destroy 4 stories? The 1st. and 2nd. floors collapsed, the 3th. and 4th. are totally destroyed.

2) Would it be the same if it was Natural Gas vs. LPG Gas?

3) How come nobody smelled the gas?

Martin;

I can't say how much gas it would take to destroy the building you're talking about, but I can tell you this; It's probably much less than you would imagine; leaking gas has destroyed many buildings; for example, on Halloween night, 1963, there was a "Holiday On Ice" show at the Indiana State Fairground's Coliseum; a food vendor beneath the seats had (i think it was two) 100 pound cylinders of propane, for frying hot dogs; the fellow who was doing the "frying" noticed that one of the cylinders was leaking; just as he was about close the shut-off valve on the leaking cylinder, something started up,( I forget just what it was at the moment) anyway, it cause a spark.....a HUGE explosion occurred, killing 74 people, injuring some 400 more, and came close to leveling the whole coliseum; we're talking a building where they have everything from monster trucks, to NBA games ! So yes, gas definitely will blow very large buildings up.

As for your #2 question; there actually isn't a whole lot of difference between the relative "power" between a natural a gas explosion and a propane explosion; there is however, somewhat more difference between the two products. Both are transported as liquid, through pipelines, and the internal pressures on pipelins is extremely high; there is a east to west pipeline "corridor" about 10 or 12 miles from where we live in western Indiana; there are something like 12 to 15 pipelines in this "corridor", the last one being completed about 5 or 6 years ago; About 3 years ago, one of the older gas line developed a leak, and the explosion that followed was heard in Terre Haute, In. more than 35 miles away.

A fellow that my wife and I know quite well, named Dennis Long, was in his bed asleep, less than 1/2 mile away from the explosion; Dennis used to come to "Fallen Rock" every Sat. night and play his bass in a little country music group; Arlene was at work at the antique shop in Rockville when it happened, which is about 6 miles from the blast; Dennis was knocked completely out of his bed, and was lying on the bare wood floor in his under shorts, thinking "WTF"???

Arlene said she though a USAF plane flying over had just "lost" one of it's bombs; I was outside sawing boards on my saw mill, and I also wondered,"WTF" ? I heard quite a bit about this event in the days after it happened; the blast created a crater about 50 ft deep, and about 100 feet across. When you have gas under very high pressure going through a 42 inch diameter pipe, all it take is one tiny "pin hole" to develop in the pipe, and the product escaping through that tiny opening creates it's own ignition source, and you get a very big "BOOM" ! ( Probably why I always tend to "speed up" every time I cross the pipeline corridor ?

Below are two links; one is to the story about the collesum explosion, and the other one is to a story about an explosion in Indianapolis just a few months back; at the time this story was written, the gas company was still trying to figure out what caused the "suspected" gas leak; sometime after that, I remember hearing something about the house that exploded becoming a "crime scene"; so this one (which destroyed half the neighborhood and killed two neighbors,) was NOT an "accident".

Back in the early 60s when I worked for F.J. Egner Tank Lines, we hauled a lot of propane; our propane tank trails had room for about 9,000 gallons, but we could only "scale" about 7,800 or so gal. Delivering propane as opposed to hauling gasoline or jet fuel has several "advantages", and several "disadvantages"; the two advantages were, it was much cleaner work, because you never saw the product. After making and tightening the connection, you turn a valve, and you have almost 2 hours to "do nothing"; (which was one of the two disadvantages); it pumped off slowly.

Both gasoline and AvJetA gravity off, usually in less the an hour. As far as "inherent risk"..........that depends mainly on the person doing the unloading; for anyone who tends to be a "klutz".......I highly recommend a career other than petroleum hauling. For anyone having their head screwed on fairly straight, it's less risky than many other things I've made a living doing. (and as you can see, I'm "still here") ( possibly to the "chagrin" of some people)

As far as comparing a gas explosion to a "chemical" explosion, I haven't had sufficient experience with explosives to discuss it very far. (a few tree stumps here & there) In all cases, the magnitude of any explosion depends largely on the quantity of "explosive material"; ( any of them will ruin your day)


http://www.indystar.com/article/9999.../RetroIndy-1963-Coliseum-explosion

http://www.huffingtonpost.com/2012/1...auses-investigation_n_2138230.html

Charley



Stupidity: Doing the same thing over and over and over again and expecting a different result; Albert Einstein
User currently onlineAR385 From Mexico, joined Nov 2003, 6461 posts, RR: 32
Reply 7, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 909 times:
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Quoting comorin (Reply 1):
I can't add much but do find it ironic that a gas explosion would have flattened a PEMEX building.
RIP to souls lost.

To be fair, it´s nothing strange. Every now and then they are in the news for the tragedies they provoke. I´m not sure this one was their fault, though.

Quoting hoMsar (Reply 2):
Anyone else read the thread title and think the OP was in an emergency situation trying to defuse a bomb and needed to know which wire to cut?
Quoting comorin (Reply 3):
I thought the OP was in the middle of blowing something up and needed tech support...
Quoting PHX787 (Reply 5):
Haaaaaa I hope I didn't just give away some of my secrets of explosives to a terrorist

I get the jest, and how my OP title (in hindsight) lends itself for it, but I did not mean it that way.

Quoting rfields5421 (Reply 4):
It all depends upon the amount of gas and the volume. I've seen results of approx 20 lbs of propane exploding totally destroy a two story solidly build brick and cinder block home. Barely a slab left.
Quoting PHX787 (Reply 5):
Any amount of electricity that goes rogue c
Quoting Geezer (Reply 6):
Martin;

I can't say how much gas it would take to destroy the building you're talking about, but I can tell you this; It's probably much less than you would imagine; leaking gas has destroyed many buildings; for example, on Halloween night, 1963, there was a "Holiday On Ice" show at the Indiana State Fairground's Coliseum; a food vendor beneath the seats had (i think it was two) 100 pound cylinders of propane, for frying hot dogs;

Thank you, invaluable answers and I´ve learned a lot.

Charley: Wow, I was not aware how such small amounts of gas, propane or natural could do so much damage. Incredible. I don´t even want to know how did the hot dog guy end up.


User currently offlineGeezer From United States of America, joined Aug 2010, 1479 posts, RR: 2
Reply 8, posted (1 year 9 months 3 weeks 1 day 15 hours ago) and read 897 times:

Quoting AR385 (Reply 7):
I don´t even want to know how did the hot dog guy end up.

it's funny you should mention that; I was just re-reading about that disaster a few months back; I'm not entirely sure of this, but I think it said he survive the explosion with fairly moderate injuries; the whole thing caused a HUGE re-thinking and FAR more serious inspections of food prep vendors, which have undoubtedly saved reoccurrence of the same ting happening again.

We have a huge big 10 day Festival in the village we live in, every October; my best friend rents out a lotv of vendor space, and he has a huge food business; I'm not sure just how many cylinders of propane he goes through in 10 days, but I know it's a lot; (he grosses over 100k during the 10 days; I help him out a lot the past 3 or 4 years, and I do a lot of hooking up cylinders to fryers, burners, and the like; there is already far less risk even if we did have a leak, because all of the cylinders and burners etc. are just "under roof", but NOT inside of any of food-prep kitchen area; the one exception I can think of, is open front building where the "beef tips" are sold, has a great big, 48 inch Wok, that has a small burner under it; allit does is keep the food hot; everything is cooked on bigger burners behind the sales place, and this small burner is only allowed to be fueled by a 20 pound cylinder. The County is VERY cautious about LPG usage, (as is my friend, Robert.)

Charley



Stupidity: Doing the same thing over and over and over again and expecting a different result; Albert Einstein
User currently offlineiakobos From Belgium, joined Aug 2003, 3316 posts, RR: 34
Reply 9, posted (1 year 9 months 3 weeks 1 day 14 hours ago) and read 890 times:

Some good info here
http://www.aria.developpement-durabl...7681_ghislengheinv_jfm_anglais.pdf


User currently offlineBMI727 From United States of America, joined Feb 2009, 15810 posts, RR: 27
Reply 10, posted (1 year 9 months 3 weeks 1 day 14 hours ago) and read 872 times:

Quoting rfields5421 (Reply 4):
According to his math - 10 cubic meters of gas equals the explosive power of 100kg of TNT.

At what pressure? To get a gas explosion you need the right mix of air and gas, that's why TWA 800 happened and if the tank were full it wouldn't have been a problem. If you drop a match in a bucket of gasoline chances are all that will happen is the match will go out, it's the vapors that are dangerous.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineMadameConcorde From San Marino, joined Feb 2007, 10925 posts, RR: 37
Reply 11, posted (1 year 9 months 3 weeks 1 day 13 hours ago) and read 855 times:

Never believe everything your government says especially in circumstances like this.

I have made it a rule my whole life.

Governments will only make you believe what they want... but what they tell you isn't always the truth.

 Wow!      



There was a better way to fly it was called Concorde
User currently offlineGeezer From United States of America, joined Aug 2010, 1479 posts, RR: 2
Reply 12, posted (1 year 9 months 3 weeks 1 day 13 hours ago) and read 848 times:

Speaking about gases that are explosive...........if you have ever done any welding or metal work, you'll know that oxygen and acetylene are mixed together and used in cutting torches; acetylene mixed with oxygen creates an extremely hot flame......(more than 1000 degrees hotter than the temp that steel melts at ). Acetylene is also extremely explosive, although I don't know how it comparesv to NG an LPG; anyway, what made me think of this was.......when I was in either the 7th or 8th grade, someone, ( I have no idea who, but probably a "chemistry geek), figured out an easy way for stupid teenagers to actually "make" acetylene gas; and it's very simple; I'm sure everyone has heard that coal miners used to use what were called "carbide" lights, back in the "un-enlightened" days of coal, mining. (anyone for a stroll in a mine, noted for having all sorts of flammable gases present, with an open-flame for a light ?) ( I shdder to think about mining back then)

These little carbide lights had a small "screw-on" cup on the bottom; you place a few small bits of carbide in the cup, sprinkled a few drops of water on the carbide, screw the cup back on the light, and light the thing with a match; I'm sure we must have some chemistry majors or minors who can explain just what carbide is ? I never have known; I just know that it comes in a small metal can with a "press on" lid, and that it is little 1/4 to 1/2 "chunks" of "stinky" "rocky" like "stuff", and that when it gets wet, it starts giving off this REALLY "stinky" gas (that smells like rotten eggs on a red hot steel pie pan) The "stinky" whitish gas is acetylene gas. If you light it, it will burn just fine, but without adding pure oxygen, it burns with a very low temperature orangeish flame; Dry carbide can be found in about any hardware store; (or at least it could in the early 1940s, when I was a very devious 13 yr old.) So, someone even MORE devious discovered that any old paint can (paint cans always have "press-in" type lids), with a small hole from an ice pick or a nail in the bottom end of the can, then stick a few grains of carbide into the can, sprinkle a few drops of water on the carbide, press the lid back on the can, and while holding one foot on the can, light a wooden match, and hold the match by the nail hole on the bottom of the can; BOOM ! A small explosion happens as the acetylene gas inside the can explodes, and the lid flies 15 feet ! That's how it "started out"; but everyone KNOWS what happens when 13 yr olds "discover" something that will create a small explosion; they make a BIGGER explosion; (now we move from quart cans to gallon paint cans; (they hold more gas, right !) ( the lid goes farther) What started as being called a "carbide canon", is now a carbide 4 times bigger canon ! Next came two table spoons of carbide, in a garbage can; ( garbage can kids were known to achieve 20, even 30 feet,,,,straight up ! )

This went on for a months or so; enter one Linville Johnson: Linville was a nice kid; we used to climb a lot of trees together when we were still in grade school; Linville was also something of a "nerd", always did well in science class. Linville was also something of a "loner" when we was in Jr. High School; anyway, we had blown all the garbage can lids in the neighborhood all over the neighborhood, with our carbide howitzers ( I think we called the the big one) At this point, Linville decides HE's gonna build....................a carbide VOLCANO ! ( I don't know what he used in the construction of the "volcano", but it must have been pretty big; Linville only "tried out" his "VOLCANO" one time; when the Volcana had it's first "eruption"...........about half of Linville's face went "with it"; Linville was in the hospital for a LONG time; maybe a year or two; but he finally go out of the hospital; I think I only saw him once after that; he didn't look like Linville any more.

This just all popped back into my head, talking about gas blowing up; thinking about it now, as "cold" of a flame carbide makes when burned without adding oxygen, I really wouldn't expect that it would have anything near the power that a "like " quantity of NG or LPG would have. I would really like to be enlightened about this if there happens to be anyone having technical knowledge along these lines. I guess if there's anything to take away from reading this, it would be to keep a VERY close eye on all of your young boys about this age. I got a post card wanting me to attend the "reunion" of the Class of 1950 about ten or twelve years ago; it seemed that quite a few of them were "still around" then; I was just telling Miss Arlie the other day, I wonder if there will be a reunion this year ?


Charley



Stupidity: Doing the same thing over and over and over again and expecting a different result; Albert Einstein
User currently offlinerwessel From United States of America, joined Jan 2007, 2392 posts, RR: 2
Reply 13, posted (1 year 9 months 3 weeks 1 day 12 hours ago) and read 841 times:
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Quoting BMI727 (Reply 10):
Quoting rfields5421 (Reply 4):
According to his math - 10 cubic meters of gas equals the explosive power of 100kg of TNT.

At what pressure? To get a gas explosion you need the right mix of air and gas, that's why TWA 800 happened and if the tank were full it wouldn't have been a problem. If you drop a match in a bucket of gasoline chances are all that will happen is the match will go out, it's the vapors that are dangerous.

It's a bit tricky to compare the two. TNT is self contained, but methane needs an oxidizer. TNT has about 4.6MJ/kg of chemical potential energy. Methane, about 56MJ/kg, but it needs an oxidizer - roughly 4kg of oxygen for each kg of methane, or about 19kg of air (as air is only 21% oxygen).

But if you created an ideal mixture of air and methane (~9.5% methane, 90.5% air, or 19% oxygen, by volume), with a volume at STP of 10 cubic meters, you'd have about 681g of methane for a total of about 38MJ, or about 8.2kg of TNT equivalent. If you had 10 cubic meters of methane at STP, you'd have the potential of about 82kg of TNT, but you'd need to mix it with roughly 100 cubic meters of air before it could be released.

So 10 cubic meters of methane is in the ballpark of the 100kg of TNT figure.


User currently offlinePellegrine From United States of America, joined Mar 2007, 2472 posts, RR: 8
Reply 14, posted (1 year 9 months 3 weeks 1 day 12 hours ago) and read 829 times:

LPG is heavier than air, unlike natural gas (methane). This could easily settle in a basement if there is a leak in a tank near enough, or with a pathway to, such as a building with a basement. It would take a big tank/leak (from a pipeline) of LPG to blow up a building though. A leak from a cooking stove wouldn't do it. NG can blow up a building too, if there is a leak in a confined space with no means of adequate escape. There are many instances of such.

People would probably smell LPG quicker than NG, because the higher percentage of heavier hydrocarbons and aromatics.

Sounds very tragic. http://www.plasticsnews.com/article/...or-pemex-headquarters-explosion...

Did someone accidentally hit a pipeline (or compromised sewer/drain line) in the area?



oh boy!!!
User currently offlineMadameConcorde From San Marino, joined Feb 2007, 10925 posts, RR: 37
Reply 15, posted (1 year 9 months 3 weeks 1 day 11 hours ago) and read 822 times:

MEXICO CITY -- An accumulation of methane gas was to blame for the Jan. 31 explosion that killed 37 people and injured 100 others (from above link)

RIP explosion victims.

I feel for those who have been injured.
Burns are really horrible and painful.

Now I highly doubt the real truth about the cause of this explosion will ever be known.

 



There was a better way to fly it was called Concorde
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