Crushing of Steel Drum

Dan Stamm, a physics teacher at Campbell High School in Smyrna, GA constructed a platform for heating water in a steel drum. The drums used had a surface area of about 3000 square inches. The force of one atmosphere of pressure on that area is about 44,000 lbs or 22 tons! Nevertheless, such cans can be made of reasonably thin steel because the same force normally acts outward from the inside of the vessel. The procedure involved pouring about a gallon of water into the drum (just enough to cover the bottom) and and heating it over a propane burner for 15 to 30 minutes. The water is brought to the boiling point where its vapor pressure is equal to atmospheric pressure. The vapor will then push most of the air out of the can. The can is then sealed as the heat is removed. If the drum is cooled quickly, the sudden drop in vapor pressure will result in enough net inward pressure to crush the can.


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Atmospheric pressure demos

Producing a vacuum by boiling water

Pressure concepts
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Boiling Water to Produce a Vacuum


Drum crushing experiment"

Boiling water in a steel drum drives the air out. Since the definition of the boiling point is the temperature at which the vapor pressure is equal to atmospheric pressure, it follows that boiling water for a period of time will force most of the air out of the vessel. If the drum is then sealed, then the pressure inside is just the vapor pressure of the water. This vapor pressure drops precipitously as the vapor is cooled below 100 degrees C. Dropping the temperature to 60 degrees C lowers the vapor pressure to about 20% of atmospheric. The drums used had a surface area of about 3000 square inches. The force of one atmosphere of pressure on that area is about 44,000 lbs or 22 tons! Even the modest cooling to 60 degrees C would result in an inward crushing force of over 17 tons! Sudden cooling to 20 degrees C would lower the pressure to just over 2% of an atmosphere and provide over 21 tons of crushing force.


Index

Atmospheric pressure demos

Pressure concepts
  HyperPhysics***** Mechanics ***** Fluids Go Back