More than anyone ever wanted to know about ACCIDENTAL GAS EXPLOSIONS, can be found in the following online Gas Explosion Handbook (Access requires registration--and not for the mathematically faint-of-heart, but very informative, especially for systematic investigation of these types of explosions.) A sampling of the topics are shown in the list and links below, including the basic definitions, properties and different types of gas explosions, as well as, significantly for the authorities, accident investigation procedures. Of special interest to everyone following the investigation into last Friday's deadly blast at Glorietta 2 shopping mall is Item #5 above on explosive DEFLAGRATIONS, where an explosive fuel-air mixture, such as diesel fumes, acetylene or even methane is ignited by a spark, hot surface or other accidental or intentional heat source within an initially confined or highly obstructed small space in which tremendous temperature and pressure buildup occurs, and then exits or vents into a unobstructed space wherein the pressure drops to normal atmospheric levels and there is no fire or flame, but all the energy is carried by supersonic or hypersonic debris.
This type of accidental gas explosion, where there is little or no fire in the unobstructed space that the explosion vents to, but a lot of high speed shrapnel and debris from the destroyed "confinement boundary material" is consistent with the type of injuries sustained by the victims reported by the receiving hospitals of last week's Makati blast, as well as the notable absence of fire in the first second and third floor levels affected. (However, we should hear about extensive fire or flame damage in that basement after the authorities announce further findings of what they observed down there.)
Have a good night's sleep for a change everyone! Time enough to think of the political and publicity fall-out tomorrow. For now I will only say:: God Bless America (and the FBI!) God Bless the Philippines!
23 comments:
Now that you have explored this angle, an ignited gas leak could be a probability. And come to think of it, we here in the US have seen entire houses blown to bits, ripped apart from their foundation, from gas leaks. Even gas leaks emanating undergound have caused high explosive-like destruction. All because leaked gas has been allowed into tightly-sealed spaces like undergound tunnels or closed houses.
But as always fire has been an integral part.
But what if there is nothing flamable in its wake? Like an all concrete basement?
I think the mechanics of a "deflagration" is that first a fuel-air mixture builds up in a confined space like the basement.Then ignition occurs either accidentally or intentionally, which produces a flame front that rapidly builds up a high pressure zone within the confined chamber. If this pressure buildup exceeds a certain threshold the containment vessel will explode and burst apart, with the released energy being carried by the debris. But the rapid expansion of any unburned gas will also douse the fire, especially if there is little flammable material in the unconfined outside space, as you observe. That there was no fire in the mall is consistent with this type of explosion.
Whew! I hope this gets confirmed later today, and that our worst fears are wrong!
But isn't the air itself flammable? So the fire would have fed on the oxygen and continued to burn when it reached the unconfined space?
cvj,
yes, but look at the graph, notice that "flame speed" and turbulence is hundreds of times higher in the region of confinement and obstruction than in the unconfined space. think of it like a candle with your hand one inch away versus 200 meters away. the effect of the flame is much less in the latter case than the former.
cvj,
forgot to mention this, but 'flame speed' is directly related to flame temperature, in a manner of speaking since temperature is how much and how fast the molecules of something burning are moving.
I have the impression that the Ayala Land people are hoping that this was a terrorist attack and not an accident. Their spokesman, forgot his name, said somthing like 'Let's not be too hasty' when the explosive deflagration angle was put forth. I found that a bit odd.
Ok not really.
Jego,
It's understandable that they would not want this to be laid at their door as a matter of technical negligence. In the US it would mean billions of dollars in lawsuits.
But we cannot also fairly conclude that they are hoping this was a terrorist attack; they might wish it was the govt that did it, or Trillanes. Or maybe a vandal.
I concur with Amadeo. In fact, a year or two ago in Milwaukee there was a gas explosion at a plant near the Potawatomi casino. IIRC two people were killed.
Incidentally http://www.620wtmj.com/news/local/10716321.html WTMJ is reporting a gas line was breached near the casino spurring authorities and the casino operators to evacuate the facility.
Terrorism, incompetence, or cruel fate it is still a sad happening.
I hope this helps ^_^
Chemical experts doubt new blast theory
Experts teaching at the University of the Philippines College of Engineering are not buying the theory that the blast last Friday at Glorietta 2 mall in Makati City was caused by chemical and gas leaks.
Ernesto dela Cruz and Wilfredo Jose, both professors in chemical engineering, faculty members and students said it was unlikely that a leak from the tank containing thousands of liters of diesel at the mall's basement caused the blast.
The engineers said diesel is not a volatile substance and will not explode as a liquid at any rate. They said it has to be in a gaseous state and has to vaporize before it can explode.
They said that for diesel to vaporize, it has to be heated to up to more than 200 degrees Celsius inside a diesel engine.
Dela Cruz, Jose and the others also said that it would also be impossible that methane gas that allegedly leaked from the mall's septic tank caused the blast.
The experts, however, said that methane explodes only if ignited. They said a mixture of five to 15 percent methane and 85 percent oxygen may explode when lit.
They added that the mixture should contain a substantial amount of chemical components to reach a blast magnitude similar to the one at the mall on Friday afternoon.
The professors said they doubt that there was enough methane inside the Glorietta 2 sewer to fuel the explosion that reached up to the building's roof three stories from the basement.
They also said that the rate of reaction would have to be quick to attain an explosion with impact. There should also have been a bad odor, much like that of rotten eggs, if the cause of the blast was indeed methane gas.
Dela Cruz and Jose added that it would be impossible to have a chain reaction between methane and diesel. They said such a reaction could have resulted to a fire but not an explosion. With a report from Apples Jalandoni, ABS-CBN News
from:
http://www.abs-cbnnews.com/storypage.aspx?StoryID=96697
upoytao,
yeah, but not as much as this google search:
methane gas explosions
MLQIII states: For now, ksolaris points out one reason a gas explosion is the main theory right now:They’re still investigating the cause, and I’m wondering if it’s a busted LPG tank, since I do remember that some time earlier this year, one of the restaurants inside the mall caught fire…. The restaurant was back in business after about a week.A spokesman from Ayala Land says it doesn’t appear the explosion emanated from any restaurants. A gas bottle explosion makes sense especially if the usual plastic and other standard explosives are not found.
A PhilCentral list-mailing I just received is hyping diesel fumes but I too am skeptical of that.
Mythbusters talked about dealing with pressurized tanks. Jamie relates he was getting on his insurers about the steep rates & hoops they have go through to deal with explosives. Much to his regret, Jamie noted high pressure tanks are just every bit as dangerous if not more so. So, if a restaurant which is probably dealing with a large sized gas bottle had an accident I could see it doing quite a bit of damage just from the release of pressure alone and then combine that with cooking flames nearby.
Correct me if wrong, would there be a gas line to the restaurant or would they be using bottles? IIRC its bottles. Getting a gas line blown up is no nice thing either.
With all due respect to the UP profs, they arent at the site. No one is allowed in except law enforcement people. Although doubting is always good within reason.
Diesel fumes + Methane + enclosed space + spark = BANG. The machines there would make the diesel in the depot more volatile. Additives in the diesel would also make it more volatile and allow it to ignite at a lower temperature. This is an angle the bomb people are looking at.
Which brings me back to Ayala Land. They have vast resources. What are the odds theyll use those to push for the terrorist-or-Trillanes perception in the media?
Jego,
it's a test of their much vaunted corporate philosophy. but if they are smart they will do the right thing. listening to one of the victim's fathers it seems they are already on the right track by paying for all the medical expenses, etc. However in the US this might cause the destruction of their empire through the massive lawsuits that would result from possible negligence on their part.
I would not want that to happen, simply because at least they don't pay NPA revolutionary taxes, whereas smart apparently does. hehe.
Ayala has an excellent and largely well deserved reputation. As long as they do everything required to prevent this happening again, there will at least be the warning to others that they better check their dark dank basements.
DJB,
Ayala has an excellent and well-deserved reputation? Apparently you've never been exposed to the incompetence of Globe and BPI.
The absence of a blast crater is a sufficient condition to rule out a bomb blast.
viking, ur point is well taken about bpi and globe, though compared to others, they are not the worst. also you are right about the blast crater being absent.
Lucky it wasn't a terrorist attack too because we wouldn't even be able to prosecute using the HSA, which is suspended for 3 months in view of the barangay elections!
DJB,
A lot more science will come out in court, when Makati files a criminal suit against Ayala and Makati Supermarket. Ayala will hire the best forensics experts to make its case but I don't think they'd lean on these experts just to cover its ass. In that Ayala's executives are professionals.
marcus,
actually there is a 4000 liter diesel containment tank down there supplying generators for the electrical needs of restaurants which are all around the tank. The tank is rectangular instead of the standard cylindrical shape, and today investigators were showing an "open leaf" gash along the top seam weld of the tank, which pretty much locks down the idea of a pressure induced rupture of the tank, creating a highly explosive mixture of diesel fumes and methane in the tightly confined space, closely approximating coal dust + methane explosions in mines, like the one that killed over a hundred Russian miners last March!
Also, it is now being reported that investigators last night discovered there is no ventilation system down there! This was apparently discovered last week by maintenance of Ayala who were in the process of designing one for installation next month! My recollection of the report may be a lil sketchy but in essence that's what I heard on this afternoons news report.
So far the deflagration theory is holding up well. There might have been a methane fire that heated up the diesel container, which ruptured after internal pressure had built up, mixed with the methane, caused a turbulent mixture in the confined space, and blew out the ground floor of the mall above it, sending supersonic debris all the way upward towards the roof as reported.
But the sudden release of pressure would've doused the flame, hence "deflagration". Which is why there was little or no fire damage in the mall space.
More details to come to be sure.
BTW, the tank being rectangular, according to GEXCON Handbook was a no no because rupture pressure is lower than for cylindrical.
First, I worked for BankPI for almost 12 years, and during that time earnestly tried to learn its corporate history and structure. Thus, am very interested where the claim of incompetence lies and on what levels. During our time in the entire banking community, BankPI employees and officers enjoyed the best reputation and credence. And BankPI was (and is) the envied flagship of Ayala Corp., the mother company.
Secondly, Ayala Land has been the pioneer in building malls and we could probably assume that at this time their mall structures follow certain architectural and structural models that are replicated in newer ones. Thus, it would serve everybody well, if they have not already done so, to find out if the Glorietta 2 structure is a replication of other Ayala malls. Not only with the purpose of preventing possible recurrences, but also as a staging area to possibly determine how the blast could have happened.
Some local university should write a computer program that can model things like this for use in analyzing future events of a similar nature. Then they can publish it in a peer-reviewed journal of computer science or forensics or whatever. Start writing your grant proposals, professors.
Unless DJB, you want to take it on yourself. How are you at computer programming? :-)
jego,
if you register and go into the GEXCON site i've linked to in this post, they have a complete computer simulation program called FLACS that is precisely used for just the kind of computer modelling you mention. no need to re-invent the wheel. check it out, it's really fun. they also have animations that are produced by the program. i'll be the Explainer next Tuesday to go through some of this physics.
I am in agreement we are looking at a deflagration as opposed to a detonation. Most garden variety explosions are the result of deflagrations, gunshots are generated by a deflagration in the gun's shell chamber and the gas expanding pushes the bullet or shot out of the barrel. Once the pressure wave leaves the barrel of the gun it quickly dissipates. Detonations can be similarly harnessed, but readily detonated materials are closely watched and the authorities tell us they found no sign of detonation material residue.
However, the idea we have a deflagration indicates an unsophisticated intentional act or as is now widely held an accident not what set it off.
Diesel has a high flash point (that is, at the start of the event there was not enough diesel mixed in with the air to ignite similar to what gasoline does), but given a gas explosion first it could have set off a chain where the diesel added to the situation. However, I think a big natural gas tank going boom would do a whole lot of damage and would not need any other source of combustible material.
Here is the link to JS Online article about the December 2006 Falk Corporation gas explosion. Contains a photo, huge devastation.
thanks for link marcus!
too late my comment, djb, but i should've read this through while i drafted my CSI:Makati post.
good to know that in the end, science wins out.
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