1. Jeffrey Orling

    Jeffrey Orling Active Member

    I am not an engineer, just a dumb architect... and it seemed intuitive to me that if the entire EPH came down... and it was a large section of the East side of the roof... more than a single column would have had to fail. Of course NIST's explanation is that the failure progressed FROM the col 79 failure despite their animation not looking much like the actual collapse. And as it turned out... something I was unaware of at the time I had the intuition... there were several massive transfer trusses under the EPH and connected the west side of the core and especially the north column line... and the failure of the north column line of the core coincides with the westward progression of the collapse observed (WPH).

    Of course there would be no "office contents" fire in the transfer region and so the fuel would have to be diesel... and they dismissed diesel for some reason... although I am sure it burns hotter than paper. Go figure.
     
  2. benthamitemetric

    benthamitemetric Active Member

    Looking back at the 2005 presentation linked directly above, the short paper by the NIST authors I separately linked to in my aside with Tony, and even the NYTimes article linked to by John 85 above, I think it's clear that there was a lot of early speculation re the role of the diesel and, as far as NIST was concerned, a focus on the role of the transfer trusses.

    NIST, however, ultimately dismissed the role of the diesel fuel as follows:

    I believe this also came up in the Aegis Insurance case as Torero's original affidavit noted that he believed the diesel fuel played a role, but this point was later dropped by the plaintiffs to my knowledge. [EDIT: I was mistaken. See the final Torero expert report here (starting on page 66 of the PDF). He talks at great length about how a diesel fuel fire could have caused a failure of the truss system. Though this wasn't the main theory offered by the Aegis plaintiffs, the Torero report actually describes a fourth alternative fulsome failure model in addition to the models created by NIST, Arup and WAI.]

    Re the transfer trusses, while NIST ultimately seems to have concluded they were not the likely locus of the collapse initiation, its final report did outline (albeit without much narrative detail) a role that they played in the collapse propagation.
     
    Last edited: Dec 13, 2017
  3. Jeffrey Orling

    Jeffrey Orling Active Member

    I don't want to side rail the discussion. I find the NIST statement about the diesel inadequate. For example... the generators ran from fuel in in building smaller day tanks... which were replenished as needed from the below grade large tanks. Males sense. City probably insisted that as little fuel as possible be be stored INSIDE the building.

    The replenishment system was "automatic" presumably... ie no one checked the level and tuned on a pump manually... like at a gas station. There are various ways to automate the replenishment. The simplist is some sort of float switch. When level drops... switch turns on remote pumps which... like in a gas station send fuel up the pipes to the tank, The building likely had remote gauges for the main tank or the fuel company made periodic... presumably rare visits to keep the main tanks topped up. It's safe to say they WERE topped up on 9.11.

    There would also be some sort of pressure sensitive system in case a pipe leaked or was broken preventing the pumps from resupply the day tanks.

    NIST seems to assume that the supply lines were breached and the pumps automatically disabled... once the leaked fuel was consumed and the fuel in the day tanks no more fuel would be sent into the building. Fine... How can the make this claim... or use this reasoning without a basis for the piping being breached?

    Also... the pumps obviously did not use the mains for power but were powered by the emergency system.. makes sense. So a case can be made absent a demonstration that the piping was breached.... that fuel was able to be supplied to the day tanks. Now what if the day tanks had a leak? If they too were pressurized and monitored then a pressure drop in the day tanks would also stop the re supply lift pumps.

    We need to know more about the system... and what happened to it on 9.11. Presumably the entire system is part of engineering drawings and was reviews and approved by the DOB. Is this top secret?

    ++++

    The entire diesel system concept and implementation at 7WTC may be suspect. Back up power was mission critical for the main tenants' business... 24/7 trading uninterrupted. I am sure other business since then have the same requirements... But how many system similar to WTC7 have been installed in the last 16 years? I'll guess... Zero... Bad idea and they realized it after the fact. But it would certainly be something that some interests didn't want to see the light of day....because... maybe, just maybe there was a lot of diesel burning and it DID play some role. We need to know EXACTLY how many gallons were recovered from the main tanks... which were almost certainly full on the morning of 9.11. Some may have been consumed when the \mains went down.

    and... Why did the building's mains go down? At what time? We do know that the trade center's electricity came from.... WTC7's Con Ed substation... and Con Ed did report that they lost a bunch of main 13.7kv feeders when AA hit WTC1. Explain that. Likely explanation is that AA severed main 13kc risers to the mech floors at the top of 1wtc and the circuit protection for such "eventualities" was inadequate and cause a power surge and electrical explosions upstream in the system... such as across the street at ConEd in 7WTC.

    Diesel as the fuel for the 7wtc fires that led to its collapse should not be dismissed so easily as NIST did in your quote. in my opinion.,
     
  4. John85

    John85 Member

    I would agree that diesel may have made an unacknowledged contribution to the fires - it will be interesting to see if this is one of the scenarios Hulsey looks at.
     
  5. Jeffrey Orling

    Jeffrey Orling Active Member

    The main thrust of my sort of off topic post is that the sims model using assumptions and knowns... the building's structure should be a known... assuming they built according to the plans. The unknowns are the combustibles... They are more of a guess as there is no inventory of combustibles to calculate and their distribution and their source of fresh air for combustion and so on. There was something on the order of 20,000 or more gallons of diesel fuel some of which was INSIDE the building and some would be pumped in when the power went down. Does NIST tell us when the back up gens shut down? If so do they tell us why? The diesel was under the EPH albeit 40 stories or more below it.

    I find the fire load or whatever the term is... rather imprecise. And their dismissal of the diesel odd.
     
  6. Mick West

    Mick West Administrator Staff Member

    From NCSTAR 1-9
    They hardly dismissed it, there's an extensive analysis in section 9.2. The lack of smoke seems to be the main reason they thought there was no significant diesel fire.
     
  7. Jeffrey Orling

    Jeffrey Orling Active Member

    Thanks Mick.... what about the very thick black smoke pouring out of the SE corner or so quite low. I seem to recall seeing videos of this.
     
  8. Mick West

    Mick West Administrator Staff Member

    I'm sure they noticed that, so that can't be it. It's all in 1-9.
     
  9. benthamitemetric

    benthamitemetric Active Member

    Like I said above (and you may have missed the edit), Torero explicitly analyzed the possibility in his expert report (starting on page 66 of the pdf). As Mick pointed out [above], NIST did address the notion in some detail in its report.

    The WAI report, responding to Torero, also addressed the topic:

    upload_2017-12-13_22-45-39.
    upload_2017-12-13_22-46-53.

    Unfortunately, it seems some of the analysis by WAI that you would be most interested in was contained in a separate report by Dr. Craig Beyler, and that report has never been made public to my knowledge.
     
  10. Oystein

    Oystein Active Member

    Diesel has a volumetric energy density of 35.86 MJ/L, and thus the day tanks of 275 gallons = 1040 L have each, if full, a heat content of 37,300 MJ.

    The typical office content combustibles (paper, wood, plastic) would average something like 20 MJ/kg.
    The typical office workstation would contain something like 200 kg of combustibles.
    That's 4000 MJ/workstation, give or take.

    Each day tank would store the combustible heat of about 9 average office workstations.
    That's rather irrelevant in context.


    So you must be talking about fuel pumped from the basement to the day tanks to maintain significant heat loads.
    NIST explains that the basement tanks were missing no more than 2000 gallons of diesel. That's the equivalent of 65 workstations, or less. That would be significant. If the fuel pumps pump at a sufficient rate. What is that rate? Would the pumps still have been operative late in the afternoon?
     
  11. Jeffrey Orling

    Jeffrey Orling Active Member

    2000 gallons burning in a small area would seem to produce quite a lot of heat. If the leak and fire were "around" bolts fastening moment connections or a trust chord connection a joint failure could occur... with drastic results. We know that the failures progressed... that is to say it was not the entire set of columns which failed simultaneously... one failure led to another... which is how complex systems fail. 5 work stations would be over an entire floor... the density would be lower. The analogy is not valid.
     
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  12. Jeffrey Orling

    Jeffrey Orling Active Member

    The failure of the East-West girders at the north side of the core progressing east to west would explain the observed roof structure collapses east to west... thier failure would also undermine the floor support for the region north of the core and the columns supported on the transfer girders MG23 (?).

    The entire tower appears to rotate counter clockwise (as viewed from above) as it descends. This also seems to indicate the the NE quadrant and the structure to the west of it were undermined leaving some columns on the NW quadrant of the core coupled to the foundation a fraction long serving as a virtual pivot. The twist, rotation or torque of the entire building needs to be explained. If you have a better one... let's hear it.
     
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  13. LardyL

    LardyL New Member

    The issue is more to do with heat release rates (HRR) than the actual amount of heat that could be produced by a particular fuel package.
    Plus as Jeffrey indicates the location where the fuel may have leaked and burned.
    Having been involved in litigation related to fire cause, fire spread, fire precautions, etc for nearly 25 years then I'd be taking the various expert reports with a pinch of salt. The way that these things work out usually involves one party taking down the other party's expert account to the extent that either their client or the Court believes what they said on at least a balance of probabilities basis. Now just because one party seems to have been victorious does not necessarily mean that they were right or even more right than the other side.
    As far as the involvement of diesel goes, I would be looking for plenty of smoke from pools of diesel burning within a structure, but if the fuel is added more slowly than a total tank failure then that may not be obvious. So for me diesel fuel in day tanks could have contributed and as usual in ways that no-one has thought of or adequately addressed.