Hard to believe
The Great Molasses Flood of 1919 that killed 21 people in Boston
12 min
A giant storage tank burst and sent a wave of molasses through Boston's North End at an estimated 35 miles per hour, killing 21 and injuring 150 — a bizarre disaster that led to landmark safety rulings.
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Show notes
Management painted the tank brown to hide persistent leaks from the public and employees.
The two million gallon molasses wave reached speeds of thirty-five miles per hour.
Rapid temperature changes triggered internal fermentation and gas pressure that caused the structural collapse.
Cooling molasses acted like cement, causing victims to die from asphyxiation during rescue efforts.
The company unsuccessfully blamed Italian anarchists for the disaster to avoid liability for poor engineering.
This tragedy led to mandatory engineering oversight and professional licensing for private construction projects.
In this episode
- 1Intro1 min
- 2The Pressure of War and Prohibition2 min
- 3The Physics of a Sticky Tsunami3 min
- 4The Aftermath and the Rescue Struggle2 min
- 5Landmark Litigation and Safety Rulings3 min
- 6Outro1 min
Sources
- 207.2 - The Great Molasses Flood of 1919 - American English Podcast
- The Great Boston Molasses Flood - HISTORY This Week™
- Great Molasses Flood | Definition, Fatalities, & Facts | Britannica
- The Great Molasses Flood - 5 Minute Disasters
- The Boston Molasses Flood — Death on the Assembly Line — BackStory Archive
- The Great Molasses Flood of 19… — American English Podcast — Apple Podcasts
- Why the Great Molasses Flood Was So Deadly | HISTORY
- The Boston Molasses Flood - by Keith Conrad
- Great Molasses Flood–History Dispatches – Apple Podcasts
- Great Molasses Flood
- The Science of the Great Molasses Flood | Scientific American
- A Deadly Tsunami Of Molasses In Boston's North End : NPR
- Nearly a century later, structural flaw in molasses tank revealed - The Boston Globe
- The Great Boston Molasses Flood of 1919 - New England Historical Society
- Safety Lessons from the Great Molasses Flood of 1919 | Chemical Processing
- Problem 4I. Molasses Flood of 1919 For additional information related to this problem, the interested reader is directed to Dark Tide by Stephen Puleo (Beacon Press, 2003) and the article by Burtis S. Brown in the May 15, 1919 issue of Engineering News Record (Volume 82, Number 20, page 974). In late 1915, USIA (United States Industrial Alcohol) erected a riveted steel tank on the Boston north end waterfront to store molasses. This tank was 50 ft tall and 90 ft in diameter and its capacity was 2,300,000 gallons. The molasses was transported to Boston by ship from sugar plantations in the Caribbean. It was used to manufacture “industrial alcohol” (ethyl alcohol not intended for beverage uses) which was then sold by USIA to munitions companies engaged in explosives production. On January 15, 1919 at about 12:45 PM, the molasses tank burst, releasing a destructive flood of molasses near the Boston waterfront that killed 21 people. Various reports have suggested that the flood wave traveled initially at speeds of 25 to 45 mph (the prevailing temperature was about 44 °F). It destroyed buildings and knocked the one of the elevated railroad tracks’ supporting columns backwards under the structure. Naturally, it was extremely difficult for a person or animal to escape once engulfed by the molasses. The plates for the steel tank had been manufactured by Hammond Iron Works; they were thinner than the original plans had specified. In fact, Brown (1919) reported that post accident measurements indicated that many of the plates were ½ inch thick. Lap joints were used in the construction and the rivets were 1 inch in diameter. Brown noted that many of the rivets simply dropped out of their holes after the shearing action—indicating that they may have been driven cold (common practice in riveted construction was to heat rivets to red-hot prior to driving). This may explain why witnesses noted that the tank leaked at the seams constantly. Since the density of molasses is about 1.4 g/cm 3 (11.7 lbm/gal), the maximum pressure on the side walls of the tank can be estimated: ρghP . The tank had been filled to a depth of 48 ft 10 inches on January 12-13, 1919; therefore, the pressure at the bottom was approximately 4250 lbf/ft 2. This introduced a tension (stress) in the plates themselves that corresponded to about 31,000 psi, according to Professor C. M. Spofford (of MIT). Burtis Brown reported that this stress (for ½ inch plates) was about 36,000 psi, approaching the ultimate strength of the steel itself. Examination after the accident revealed that in some cases rivets were sheared off and in other locations the plates themselves were fractured. Municipal court judge Bolster concluded from the evidence that “….this tank was wholly insufficient in point of structural strength to handle its load, insufficient to meet either legal or engineering requirements.” We would like to explore the dynamic behavior of the flood wave, and we would particularly like to know if there is any way that the flood wave velocity was ever as great as 45 mph. Let us assume that the viscosity of the molasses was about 7000 cp. Some significant assumptions must be made—particularly with regard to the initial size and shape of the flow. For simplicity, assume that the flow starts out as a plug, 30 ft tall,
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