There were five emergency power systems in WTC 7. Three of them (American Express, OEM, U.S. Secret Service) drew fuel from the other two and larger systems (Salomon Smith Barney, Silverstein Properties). (1c), (8)
The emergency power for the building (Silverstein Properties) was provided by two 900 kW generators on the southwest corner of Floor 5. They drew fuel from a 275 gallon tank nearby, and this was replenished by pumps drawing from two 12,000 gallon tanks at ground level under the loading dock, at the southwest corner of the building.
The SSB emergency power system used nine 1,725 kW generators on Floor 5: three in the southwest corner, two near the west end of the north face, four at the east end of the north face. Louvers for air intake and exhaust were situated on the building faces near the generators. Because there was already a 275 gallon "day tank" on this floor, the SSB system pumped on demand from their own pair of 6,000 gallon storage tanks, also situated under the loading dock, under the southwestern part of the building.
The fuel supplier was contracted to keep the tanks full, and they were full that day.
Fuel pipes for all systems except SSB ran up the western side of the core of the building, along elevator shafts. The SSB pipes ran up a shaft through mechanical spaces near the southwest corner of the building.
Kindling
After 1 p.m. on September 11, 2001, WTC 7 was an evacuated, stricken building. The southwest corner and central third of the south face had been ripped open by the cascading debris from the collapse of WTC 1. Fires burned in sections of Floors 6 through 30 at different times, and they migrated along their floors independently, seeking new sources of fuel. From the street the fires on Floors 11 and 12 appeared most intense. Many fires in the area went unchecked because utility power for electrical pumps, and water pressure for fire engines had either diminished or been lost.
This is what happened.
A Pumped Oil Spill
The debris fall ripping into the southwest corner ruptured the oil pipes of the SSB pressurized fuel distribution system. Operating as intended -- the lack of utility power triggering the "need", and the lack of pressure due to a severed pipe signaling the "demand", the SSB system pumped oil up from its 12,000 gallon basement reservoir, maximally with a pressure of 50 psi (pounds per square inch) and flow rate of 75 gpm (gallons per minute), onto Floor 5.
Pumping would have started at 9:59 a.m., when Con Ed cut utility power to WTC 7; and the spilling would have started a half hour later when the pressurized pipe was cut. The SSB pumps could have drained the two 6,000 gallon tanks in 2 hours and 40 minutes. Engineers from the New York State Department of Environmental Conservation found that "there was a maximum loss of 12,000 gallons of diesel from two underground storage tanks registered as 7WTC." (10)
Additionally, "Both tanks were found to be damaged by debris and empty several months after the collapse. Some fuel contamination was found in the gravel below the tanks and the sand below the slab on which the tanks were mounted, but no contamination was found in the organic marine silt/clay layer underneath." (7)
By contrast, 20,000 gallons of oil was recovered from the two 12,000 gallon tanks of Silverstein Properties. (10)
Pulled up by the emergency pumps, the SSB diesel fuel went , from the 6,000 gallon storage tanks, under the loading dock, under the southwestern part of the building, to floor 5.
It may all have been pumped out by 1 p.m., or it may have been pumped out at a rate as low as 29 gpm for 7 hours. Since this fuel was absent from the wreckage, it was burned. You can see it as the huge plume of black smoke rising from the World Trade Center, in panoramic photographs of that day. Diesel fuel can supply 2.13 MW of power per gpm given an air supply of 1333 cfm (cubic feet per minute). (11)
Thus, a diesel fuel gusher of 75 gpm burning with excess air would produce 160 MW of heat; a total energy of 1536 GJ for the 12,000 gallons. This energy is equivalent to that released by an explosion of 367 tons of TNT. If the pumping rate is lower, or the air supply is throttled, then the burning would occur at a lower rate. Since the louver system along Floor 5 was designed to supply each of the nine SSB engines with 80,000 cfm, it seems likely that a fuel oil fire there would find sufficient air for combustion.
For a discussion of heat at 9/11, and energy units, CounterPunchers will soon be able to have my study, "the Thermodynamics of 9/11", to be published shortly on the CounterPunch website as part of our final package on the actual physics and engineering realities of the collapse of the WTC buildings.
The debris fall ripping into the southwest corner ruptured the oil pipes of the SSB pressurized fuel distribution system.
That would work out as a fine explanation, but the SW corner was not damaged very much. The gouge out of the corner that NIST portrays in their report is not a gouge at all, but smoke obscuring the corner. The SW corner actually only suffered superficial damage.
That would work out as a fine explanation, but the SW corner was not damaged very much. The gouge out of the corner that NIST portrays in their report is not a gouge at all, but smoke obscuring the corner.
You wouldn't need a big gouge.
All you'd need is a piece of debris puncturing a pressurized fuel line, which was designed to provide emergency power without external electricity.
So....What did happen to the 12,000 gallons of diesel fuel, which was not found at the site.
And where did all the black smoke come from during the hours preceding the collapse if not from the 12,000 gallons of diesel fuel?