INTERESTING HEAT PHENOMENA AT DALLAS MAGNESIUM FIRE
Violent Up-Draught Draws Cold Air Along Ground to Fire; Interesting Effects Produced
THE following is the report of Chief L. M Funk of the Dallas, Texas, Fire Department, on the magnesium fire which occurred in that city last December 15. Although the account of the fire was published in the January issue of FIRE ENGINEERING, the Editor feels that the complete story will be interesting to the readers in view of the fact that magnesium fires are apt to be more frequent in the future because of the increased uses to which that metal is being put.
Austin Bridge Company, Dallas, Texas.
LOCATION OF PLANT:
1301 Singleton Blvd., In Dallas County—(Not in corporate limits)
The plant consisted of a succession of steel frame, iron clad buildings, the length of which extended north and south, all of which had a common north end line, but were of various lengths, having been erected at different times.
The buildings were divided into two groups with a 20′ alley or passageway between. This was crossed with a 12′ connecting tunnel of wooden construction. All partitions were broken with large openings giving easy access to any part of the plant. There were no fire doors, or other closing devices on any of these openings. Majority of all partitions were of wooden construction. The entire plant covered a concrete floor area of approximately 50,000 square feet.
Looking at the plant from the north end, (facing south) and beginning at the cast, or left side, we number the buildings as follows for the convenience of placing contents and areas.
No. 1—With a floor area 50′ x 75′ was occupied as a repair shop, and was of recent construction.
No. 2—With a floor area 50′ x 222′ was occupied as a warehouse for storage of stock metal and finished bomb cases. At the time of the fire there was 1,700,000 pounds of magnesium (17 car loads) stored in this area, a majority of which was in pies, or ingots.
No. 3—With a floor area 50′ x 182′ was occupied as a foundry consisting of 20 furnaces and pots for running magnesium bomb cases. (The fire originated in this room.)
Immediately following this area was a 20′ alleyway which was broken with a 12′ wooden tunnel connecting the two groups.
No. 4—With a floor area 46′ x 182′ was also occupied as a foundry, and contained 10 large furnaces and pots.
No. 5—With a floor area 46′ x 222′ was occupied as a machine shop where the bomb cases were finished.
No. 6—With a floor area 46′ x 182′ was also a machine shop supplementing area
No. 5—Adjoining this on the west were dressing rooms, showers, toilets, etc.
After the plant was in operation it was discovered that the ventilating louvers over the furnaces did not adequately dissipate the heat gases. A number of them were removed and large fans installed, the framework of which was of wooden construction.
The afternoon shift turned out for lunch at 8:00 P. M. and as the employees were leaving the building large, live embers were noticed falling from one of the ventilating fan cases in the east foundry (Area No. 3)
The foundry pots contained molten metal at this time, one of which became ignited and erupted, scattering burning magnesium over a large area. Several piles of recently run bomb cases were instantly ignited. The fire was then beyond control.
The Dallas City Fire Department received the alarm by telephone at 8:04 P. M., and immediately dispatched one engine company, which arrived at the scene of the fire at 8:10 P. M. The officer in charge immediately called for a chief officer and additional companies. At 8:14 P. M., two additional engine companies, the writer, and the First Assistant Chief were dispatched, all of whom had arrived and were in action prior to 8:30 P. M.
Three 2 1/2″ lines were laid in, one of which was later wyed with two 1 1/2″ lines and used for spot work. At no time were lines directed at burning metal.
Areas No. 1, 2, & 3 were completely involved at 8:30 P. M. Lines were placed at each end of the 20′ alley-way seperating areas No. 3 and 4, and one line placed inside of No. 4 at the entrance of the 12′ wooden tunnel. All firemen were instructed to hold the east wall of No. 4 at all cost, and to positively not spray water on the burning metal.
The slope of the entire floor area was from the northwest to the southeast. The bulk of the storage was in the southern portion of area No. 2. The flow of water on the floors was directly towards the seventeen car loads of magnesium stored in the warehouse, the upper portion of which was burning furiously by 9:00 P. M. and as large pieces of this burning metal dropped into the water on the floor heavy explosions or eruptions resulted. By 9:30 P. M. the entire storage of metal was burning, and the explosions were momentarily increasing in violence.
One noticeable feature of the explosions was the conical shape of the eruption. The force did not spread near the ground, but came up with a gradual spread like a large cone, and immediately following the explosion all loose particles were drawn into the burning area rather than being blown away.
By 10:00 P. M. the vibrations from the explosions became so great that the men were ordered outside of building No. 4. and in a very few moments the south half of this building collapsed.
The lines were immediately returned to cool this area. The peak of the fire was reached about 10:45 R. M. after which the explosions gradually ceased.
Although the fire was still burning at 10:00 A. M. the following day all danger from heat radiation was passed by 4:00 A. M.
Some 70′ east of the warehouse (area No. 2) there was a metal building. Inside of whioh was a 4′ aisle next to the wall, beyond which was stored large bundles of an insulating material (Not rockwool). The area between the fire and this building was an open yard. The temperature was 21 degrees, humidity 69% Wind was from north at 7 miles per hour yet the material inside this adjacent building became ignited (Extinguished with booster lines).
From 50′ to 100′ distance front the fire the ground was warmed) sufficiently to melt ice. From 50′ up to within 18″ of the fire the water was quickly frozen. The ground area close to the fire was extremely cold. An extremely heavy draft of air existed near the ground at the base of the fire. This draft was not felt or noticed 75′ away.
The force of the explosions, caused by water running under the burning metal, was always up—never out. The portion of building No. 4, which collapsed, was pulled in rather than being blown out.
Firemen could not stand near the fire without protection to face and upper portion of bodies, due to the intense beat radiation; however they were uncomfortably cold when in a prone position at the same, location.
Both stock metal and finished products should be stored in small quantities— storage area should be diked or scuppered to prevent water flow beneath metal in case of fire.
All partitions should be of fireproof construction, and if of masonry all openings should have approved fire doors on each side of wall.
No wooden construction should be permitted in connection with this type of business. Close inspection and supervision should be maintained at all times. If inter-factory trucks and carts have metal wheels they should be equipped with drag-scrapers to prevent wheels picking up and carrying small bits of metal from machine shops to other parts of plant. (Scraps of metal were very noticeable in all areas of this plant.)
The illumination from this fire was easily observed 80 miles away. In Lewisville. Texas, 35 miles north of Dallas, the light was sufficient to easily read a newspaper.
Firemen subjected to the possibility of having to deal with this type of fire should be provided with protective colored goggles. After an hours exposure to the extremely white light produced by the burning metal other colors lose their identity. Red becomes olive drab, etc. Several hours exposure, although not direct, is extremely dangerous, and may result in painful, if not serious burns to the eyes.
Due to the extreme heat radiation provision should be made to quickly spray water on all buildings or equipment whatever within a radius of 300′ or 400′. Even the metal cabs on dragline engines, and road graders 300′ from the fire were warped out of shape.
Immediately following an explosion, when the upward force had reached the peak, there would be a fountain shaped spray which spread over a large area, Particles of burning metal ranging in size from marbles to golf balls would fall. When these bits of burning metal landed on metal roofs they immediately burned through, dropping to the area below. One such fell upon a gasoline tank truck parked some 400′ away, results—the truck was completely destroyed: being filled to capacity prevented an explosion and an additional serious fire.
L. M. FUNK, Chief, Dallas Fire Department.