August 15, 2006
Measurements of gravity using cryogens [Updated]
Posted by Arcane Gazebo at August 15, 2006 7:00 PM
This is what Chad Orzel refers to as a 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.
Recalling what happens when a LN2 cylinder does rupture, it's the general consensus that this student is lucky to have survived and LeConte Hall is lucky to still have a staircase.
Photos below the fold [updated with photo of wall damage]:
Here's the staircase; note the bent and broken posts for the rail as well as the dents in the steps. The face shield was fortunately not needed. 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.
This is the side of the steel dewar. 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.
The dewar stranded on the landing. Here some nitrogen is being transferred into a much smaller flask, before the larger vessel arrived.
UPDATE: By request in the comments, here is a photo of the damage inflicted on the wall:
Tags: Lab, Photos, Physics, Science
First of all, this is extremely impressive. I am highly amused. (I had more than my share of "impressive" achievements just from one term in Chem 3a and another term in CS/EE 11, but I never did this kind of damage---I just did some stupid things and conveyed very clearly that my future was in theory, which was already something I had pretty much known since about age 10.)
Second, I always thought that a "true lab story" was kind of like a "true Hollywood story" except with fewer whores. But, then again, you do go to Berkeley.
Fewer whores??? One MORE reason for me to stay an actor!
Wow, vaguely reminds me of Jaideep's fire extinguisher story.
Holy crap, that's something. Big oops.
This reminds me of a story I recently heard from a chemist working in industry. A Ph.D. 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?" in all seriousness.
It helps to keep the door open so as not to asphyxiate oneself. >.
I don't find it amusing at all. In fact, as I read it I started to feel sick. Go to the link if you don't understand why.
For a school full of smart people...
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. (circa 1974) I hear that only lasted a couple of years before it got nixed as a general open lab project.
For a school full of smart people...
They're not smart yet, that's why they're in school.
Can you hear my eyes rolling from way over there?
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. It's kind of impressive.
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?
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.
Sharon want to know if it was her high school Jascha who attempted this transport?
We always have our large dewars frost at that spot for some reason. I don't think it's damage, but I don't know what it is.
>>..For a school full of smart people...
i thought you were speaking about US Beserkeley..
for smart people you need to go down the peninsula to STANFORD.. :-)
Ah, misjudging weights...
A second-hand tale: A physics department that shall remain nameless had a brand new elevator installed, making transferring equipment up from the loading dock to the upper floor much easier. A lab doing experiments involving radiation had a large quantity of lead bricks delivered to the loading dock. Enterprising students decide to take them up to the lab, and transfer them into the new elevator, a couple at a time. After all the bricks are in the elevator (they don't take up much space...) they hit the button. The elevator makes strange groaning noises and does not move. They sheepishly realize they might have overloaded it a bit (!) and move bricks out into hallway. Try elevator again and it still won't move.
Elevator repairman is called, and is quite distressed. He's never seen an elevator shaft with bent guiderails before...
Uh oh, the Berkeley-Stanford rivalry has reared its ugly head. :)
It's actually the fault of the lazy ass grad students who don't bother to train the undergrad lab monkeys. This happens a lot. I see imbiciles running with siscors all the time while grad students stand with their arms folded, smirking amongst themselves. They should be kicked out, or worse yet forced to stay 10 years extra.
It's as foolish to trust a baby with a grenade as it is to trust an undergrad with anything remotely important.
By the way, liquid nitrogen tanks probably won't explode on account of the standard 3 stage pressure release valves. Also, the frost on the side could result from the pressure builder getting shocked loose. Not "the inner wall" touching "the outer wall". The pressure builder works by running liquid nitrogen through intermidiate heat shields to boil off some controlled amount. Way to exaggerate.
Whatever. What do you expect? Physics is thankless, loveless, and above all, sexless. Might as well blow some shit up.
Those stairs are not marble. They are terrazzo.
Repairs can be made that will be almost invisible, a task not possible with marble.
Amazingly similar incident, w/ a happier ending - a fellow researcher had some summer help for his lab that turned out to be a rather husky football player. He was tasked with transferring some gas cylinders (the std steel, high pressure ones) from the loading dock to the lab. He was left to do his job but he was taking a long time. He was eventually found (as you may have guessed) in the stairwell, hauling the cylinders by hand. He was subsequently introduced to Mr. Cylinder Cart and Mr. Elevator. The other obvious point is to not make assumptions about what someone knows and doesn't know about what is considered standard lab practice.
A dewar that is outfitted for liquid service with a 22psi relief valve is not going to have anywhere near the explosive energy of a dewar that has been stoppered up and allowed to reach the burst pressure of the inner vessel. Dewars used for gas service can be rated at 235psi, and I am sure that the actual burst pressure of the vessel is many times that to give a safety factor for rough handling, tipping over, etc. Bursting was a very low risk in this situation.
Getting flattened by the 4-foot-tall 625-pound wheeled cannister that you push down the stairs...now that's a real danger especially if you're dumb enough to hang on and ride it down!