www.arcanegazebo.net/2006/08/measurements_of_gravity_using.html
True Lab Story: Condensed matter labs such as ours receive frequent deliveries of liquid nitrogen in one- or two-hundred liter dewars. Unfortunately, most of the Berkeley cond-mat labs are in Birge Hall, which has no loading dock, so that the LN2 dewars arrive on the first floor of neighboring LeConte where they must be wheeled over to their destination by some low-seniority student. Since the Berkeley campus is on a hill, the loading dock at the back of the building is one floor higher than the other entrances to LeConte and all the entrances to Birge. One can push the dewar around the outside of LeConte, but a shorter route is to take the elevator down one floor and go out the side door. Yesterday the LeConte elevator was out of order, which for most of us would have meant taking the long way around. However, one undergrad, tasked with transporting a full 230L dewar, simply decided to take the stairs. At about 80% the density of water, 230 liters of liquid nitrogen weighs about 400 pounds, not counting the additional weight of the steel vessel containing it. When rolled onto the stairs, the dewar promptly tipped over and plummeted downward on its side, knocking deep gouges in the marble steps and dragging along the unfortunate student, who inexplicably held on as his cargo began to tumble. Miraculously both student and dewar arrived at the landing without rupturing, but the dewar was still on its side and pressure was building up. This was the situation when we got the frantic call from the building manager; once enough of us arrived at the scene we were able to pull the dewar upright and release the pressure. This averted any imminent explosion, but now we had a different problem: 400 pounds of liquid nitrogen stranded on a landing between the ground and first floors. Suggestions were floated including emptying the nitrogen out the nearby window, but ultimately we found another dewar which was wheeled to the top of the stairs on the first floor, and the nitrogen was transferred there through a long hose. The empty dewar was then carried up the stairs, a task requiring four men and gouging new (but shallower) grooves in the staircase.
note the bent and broken posts for the rail as well as the dents in the steps. The white hose is being used to transfer nitrogen out of the dewar; it's naturally more of a beige but it's covered in frost.
It was not dented by the fall, but the white streak isn't paint off the wall, it's frost. Normally there is a vacuum space between the inner and outer walls of the dewar, but here the inner wall has apparently bent to touch the outer wall.
This reminds me of a story I recently heard from a chemist working in industry. A PhD biologist was in a small, enclosed room filling up a very large dewar with liquid nitrogen. He staggered out after a good deal of filling and asked the people in the lab, "Um, is nitrogen toxic?" It helps to keep the door open so as not to asphyxiate oneself.
August 16, 2006 08:33 AM Reminds me of the fact that Florida State used to let Sophmores mix two different viruses together in a blender to see what kind of recomberant DNA we could create, then cultivate them in a petri dish.
August 16, 2006 03:12 PM Whew, that's a pretty stupid accident. I work on the second floor of LeConte and came by in time to watch them move the LN to the dewar on the higher floor. I can't believe somebody was stupid enough to take a half-ton dewar down the stairs by, I assume, themselves. Arcane Gazebo, please post a picture of what the dewar did to the wall.
August 16, 2006 06:26 PM I've seen hundred liter dewars hauled down stairs fairly routinely when elevators went out. Admittedly, they weren't quite this big, but they weren't exactly small, and the only problem I recall was when one slipped in the grip of the stockroom anager and chipped her front tooth. Maybe the dollies they used at the stockroom in my old department were just easier to use?
August 16, 2006 09:00 PM Ketoglutaric Acid: I actually almost posted my picture of the wall. It's on my other computer so I'll put it up tomorrow morning. Kiwi Carlisle: In our group we use 100L dewars and transport them on carts with a long wheelbase. I could imagine taking one of these down stairs although I certainly wouldn't recommend it. In this incident, though, the dewar was not only twice as heavy but had wheels attached to the bottom (instead of being rolled on a cart) with a small wheelbase that allowed for only very shallow tipping angles, so stairs should have been out of the question.
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