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Title: A Dangerous Worksite: The World Trade Center
Source:
U.S. Department of Labor
URL Source: http://www.osha.gov/Publications/WTC/dangerous_worksite.html
Published: Mar 30, 2007
Author: OSHA
Post Date: 2007-03-30 13:16:03 by honway
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Keywords: None
Views: 180
Comments: 6
HOT STEEL Even as the steel cooled, there was concern that the girders had become so hot that they could crumble when lifted by overhead cranes. As a result, additional safeguards were put in place to limit the dangers associated with lifting the damaged steel and to protect the workers in the vicinity. Another danger involved the high temperature of twisted steel pulled from the rubble. Underground fires burned at temperatures up to 2,000 degrees. As the huge cranes pulled steel beams from the pile, safety experts worried about the effects of the extreme heat on the crane rigging and the hazards of contact with the hot steel. And they were concerned that applying water to cool the steel could cause a steam explosion that would propel nearby objects with deadly force. Special expertise was needed. OSHA called in structural engineers from its national office to assess the situation. They recommended a special handling procedure, including the use of specialized rigging and instruments to reduce the hazards. 
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Begin Trace Mode for Comment # 5.
#2. To: All (#0)
(Edited)
http://www.doctorfire.com/flametmp.html Flame temperatures in room fires Of interest, however, is the peak fire temperature normally associated with room fires. The peak value is governed by ventilation and fuel supply characteristics [12] and so such values will form a wide frequency distribution. Of interest is the maximum value which is fairly regularly found. This value turns out to be around 1200°C,(2192°F) although a typical post-flashover room fire will more commonly be 900~1000°C. The time-temperature curve for the standard fire endurance test, ASTM E 119 [13] goes up to 1260°C, but this is reached only in 8 hr. In actual fact, no jurisdiction demands fire endurance periods for over 4 hr, at which point the curve only reaches 1093°C.
http://www.wpi.edu/News/Transformations/2002Spring/steel.html The "Deep Mystery" of Melted Steel There is no indication that any of the fires in the World Trade Center buildings were hot enough to melt the steel framework. Jonathan Barnett, professor of fire protection engineering, has repeatedly reminded the public that steel--which has a melting point of 2,800 degrees Fahrenheit(1538 degrees Celcius)--may weaken and bend, but does not melt during an ordinary office fire. Yet metallurgical studies on WTC steel brought back to WPI reveal that a novel phenomenon--called a eutectic reaction--occurred at the surface, causing intergranular melting capable of turning a solid steel girder into Swiss cheese. Materials science professors Ronald R. Biederman and Richard D. Sisson Jr. confirmed the presence of eutectic formations by examining steel samples under optical and scanning electron microscopes. A preliminary report was published in JOM, the journal of the Minerals, Metals & Materials Society. A more detailed analysis comprises Appendix C of the FEMA report. The New York Times called these findings "perhaps the deepest mystery uncovered in the investigation." The significance of the work on a sample from Building 7 and a structural column from one of the twin towers becomes apparent only when one sees these heavy chunks of damaged metal. A one-inch column has been reduced to half-inch thickness. Its edges--which are curled like a paper scroll--have been thinned to almost razor sharpness. Gaping holes--some larger than a silver dollar--let light shine through a formerly solid steel flange. This Swiss cheese appearance shocked all of the fire-wise professors, who expected to see distortion and bending--but not holes. A eutectic compound is a mixture of two or more substances that melts at the lowest temperature of any mixture of its components. Blacksmiths took advantage of this property by welding over fires of sulfur-rich charcoal, which lowers the melting point of iron. In the World Trade Center fire, the presence of oxygen, sulfur and heat caused iron oxide and iron sulfide to form at the surface of structural steel members. This liquid slag corroded through intergranular channels into the body of the metal, causing severe erosion and a loss of structural integrity. "The important questions," says Biederman, "are how much sulfur do you need, and where did it come from? The answer could be as simple--and this is scary- as acid rain." Have environmental pollutants increased the potential for eutectic reactions? "We may have just the inherent conditions in the atmosphere so that a lot of water on a burning building will form sulfuric acid, hydrogen sulfide or hydroxides, and start the eutectic process as the steel heats up," Biederman says. He notes that the sulfur could also have come from contents of the burning buildings, such as rubber or plastics. Another possible culprit is ocean salts, such as sodium sulfate, which is known to catalyze sulfidation reactions on turbine blades of jet engines. "All of these things have to be explored," he says. From a building-safety point of view, the critical question is: Did the eutectic mixture form before the buildings collapsed, or later, as the remains smoldered on the ground. "We have no idea," admits Sisson. "To answer that, we would need to recreate those fires in the FPE labs, and burn fresh steel of known composition for the right time period, with the right environment." He hopes to have the opportunity to collaborate on thermodynamically controlled studies, and to observe the effects of adding sulfur, copper and other elements. The most important lesson, Sisson and Biederman stress, is that fail-safe sprinkler systems are essential to prevent steel from reaching even 1,000 degrees Fahrenheit, because phase changes at the 1,300-degree mark compromise a structure's load-bearing capacity. The FEMA report calls for further metallurgic investigations, and Barnett, Biederman and Sisson hope that WPI will obtain NIST funding and access to more samples. They are continuing their microscopic studies on the samples prepared by graduate student Jeremy Bernier and Marco Fontecchio, the 2001–02 Helen E. Stoddard Materials Science and Engineering Fellow. (Next year's Stoddard Fellow, Erin Sullivan, will take up this work as part of her graduate studies.) Publication of their results may clear up some mysteries that have confounded the scientific community.
That sounds like a smokescreen to me. Why had this process never made itself apparent in any other buildings that we know of, yet it happens 3 times on 9/11? Acid rain, my ass. lol
#6. To: Critter (#5)
I agree with your asessment of the inadequate attempt to explain the observations. The important point in the article is this,imo: The "Deep Mystery" of Melted Steel
Top • Page Up • Full Thread • Page Down • Bottom/LatestUnderground fires burned at temperatures up to 2,000 degrees.
#3. To: All (#2)
(Edited)
#5. To: honway (#3)
Replies to Comment # 5. That sounds like a smokescreen to me.
End Trace Mode for Comment # 5.