#engineering disasters

A train hauling ethanol derailed Thursday morning in Raymond, Minnesota, igniting several rail cars and forcing nearby residents to evacuate, officials said.

Preliminary information suggests 14 of the train’s 40 cars were carrying hazardous material, “including ethanol, which was released – leading to a fire,” US Transportation Secretary Pete Buttigieg told CNN on Thursday.

The train was carrying mixed freight, including ethanol and corn syrup, said Lena Kent, general director of public affairs for BNSF Railway.

So two important things about me: 1) i have a degree in materials science and engineering 2) i have an obsession with aviation disasters

So opinions that I feel I am qualified to talk about b/c of my degree

1) Carbon fiber - the choice of carbon fiber for the bulk of the hull for this was weird. Carbon fiber has a fairly high tensile strength and fairly low compressive strength. Tensile is when you are pulling something apart, compressive is when you a smushing something. Its tensile strength (how much stress it can withstand) is around 500,000 psi (3.5GPa) [this is dependent on other factors but lets go with it for now] it’s compressive strength is closer to 145,000 psi [again depends on a lot of factors, we are just going with this for the sake of my discussion]. It’s compressive strength is nothing to sneeze at, but it is much lower than its tensile strength. 

The important part of a submersible is it’s compressive strength, the pressure from the ocean is going to be trying to collapse the submarine it and it needs to be able to withstand that. Can carbon fiber withstand the ocean? By the numbers I have found, technically yes. NOAA says that pressure increases about 1 atmosphere per 10 meters of water depth putting us at around 4400 psi for 3000m. The thing to know about pressure vessels is that they degrade every time they are pressurized and unpressured (a cycle). The pressurization can create defects in the material, and these defects often lead to a lower stress required for failure. The more cycles something undergoes, the more likely it is to fail. I am not sure how much research has been doing in cyclic loading of this specific carbon fiber under compression. I am dying to see the research data that went into this design, how much material testing did they do? 

Third important thing about carbon fiber - the weave. Essentially, when using carbon fiber, you weave them together in different orientations to build the size/shape of composite you need. A typical weave would have the fiber all going in one direction, then the next layer would rotate the fiber 90 degrees in comparison to the first, then back to the original orientation. Or perhaps a 0/45/90 degree wave. This weave ensures that the material has similar properties when undergoing stress from all directions, not just one. If you have all the fibers going in the same direction, it will likely fail when being pulled any other way with little stress. And for a pressure vessel, you need to withstand stress in all directions. I heard from a friend they had their weave in the same direction, but I have not found sources confirming that. Frankly I am having trouble finding any sources about the specifics of the carbon fiber at all.

Finally, ceramics (like carbon fiber) tend to fail quickly with little warning. Metals tend to bend before the break. Carbon fiber and other ceramics won’t. It will get a crack that starts to grow and reach critical size and break with little or no sign visually. Nondestructive testing of ceramics is also harder than metals. We have some tests to find small cracks inside of metals, but using those on ceramics is not as well documented or are more expensive.

2) Mixing titanium and carbon fiber - why? Mixing materials is always something you need to be careful when doing. We want those materials to match some specific properties as best we can. One such property would be coefficient of thermal expansion. AKA how much does the material expand or shrink when exposed to hot or cold temperatures. If those materials do not have similar values, one will expand or shrink faster than the other, and causing the seal between the two to be weaker. The coefficient of thermal expansion for carbon fiber depends on the weave, but is much different than titanium. This means the seal could become an issue at low temperatures (such as occur down 3000m below the surface of the ocean)

3) The timeline - according to recent sources the design of this sub occurred in a very short period of time. Which is concerning. The amount of testing needed to design something like this should be many months, not a few weeks. This is experimental and it will carry people. You want to take your time to collect data, consider other materials or design choices.

4) Using the porthole that was only certified to 1300m for a sub that went to 3000m - i feel like I dont need to expand on why that was dumb :/

Now to the things I am not qualified for with a degree but I feel qualified to talk about because I am obsessed with aviation disasters and there's a lot of overlap here. 

1) The remote controller - my problem with the video game controller is not its use, there is some good application for it, my problem is how it was the only way to control the sub at all. There was no redundancies in the sub so if something went wrong, there was little to be done. 

2) The lack of oversite - I love innovation. I love seeing engineering trying new things and going to new places. I also love rules and regulations that stop people from doing really really dumb shit. And this sub was subject to none of them (?) at least not that I can tell. Which is awful. There needed to be someone else there making this company stop and breath. To not rush. To think about safety more. To consider plans B and C. And to ensure they were making good engineering choices. What was the factor of safety with this submersible? The fact that this thing could carry paying passengers w/o being certified by anyone is insane to me. No one looked at this and said: hmm, this seems dangerous lets do more testing b/c no one was required to.

The aviation industry is not and has not been perfect. But the aviation industry has overall, done a good job and looking at mistakes, disasters, incidents, and near collisions  and changing how they do things. They engineered planes to be safer. They set up maintenance procedures that test parts to see if they have critically large defects. Clearly we need to think about doing some of the same here since damn, someone really dropped the ball on this. 

Anyone I’m dying to see the materials testing data they did in advance of using this thing cause I want to know what they saw that they feel would make it safe.

Ah, I see you found my reblog about my hyperfixation!

I like engineering disasters in kind of the same way people like true crime podcasts- there's this element of mystery and suspense as the stage is set, the accident unfolds, and then the race to find the "killer" (the failure point) is on. Airplane crashes and building collapses are the most dramatic of these, but all kinds of accidents intrigue me.

The Bhopal disaster, though. . . Bhopal is a story of decay. It's a story about a failing pesticide plant's spiral into neglect, just as much a product and victim of the tired system that made it. Bhopal is the abandoned smoke stack that fell down in the wind or the shed that rotted away behind a derelict cottage, only the Bhopal disaster instead cost thousands of lives.

The Union Carbide Pesticide plant in Bhopal, India, was created for a market that did not exist. From its inception, the plant was unwanted and unloved. It got permission from the Indian government to produce five times the amount of pesticides it expected to sell, and then hardly sold one fifth of that projected margin. Within a few short years the plant was all but gutted of everything it had- engineers first, and then maintenance quickly to follow. Next followed safety regulations, suffering already from extremely reduced staff and now reduced to nothing. Last to go was the replacement of failing parts. To put it simply: nothing worked, no one cared, and there was no way to fix it.

These are other factors you need to know:

there was a chemical stored on site called Methyl Isocyanate.

Methyl Isocyanate is extremely toxic.

A runaway, pressure-building reaction is created when it is exposed to water.

It was stored under pressure in great quantities beneath the Union Carbide facility.

Surrounding this facility were thousands of civilians who would pay the price.

---

On the 2rd of December, 1984, water was introduced to a Methyl Isocyanate holding tank by an untrained worker hoping to unclog the pipes. Nearing the 3rd of December, reports of rising pressure within the tanks were not believed due to the previous unreliability of the instruments. The emergency gas scrubber, attached to the pressure relief valves, was long since broken and never replaced. Forty tons of Methyl Isocyanate were released through the emergency relief valve. Two hours later, the first public alarms were sounded.

Thousands died. Hundreds of thousands needed treatment in hospitals. I don't like to focus on these parts of the disasters I study out of respect. All that needs to be known is that those affected suffered immensely, and that the effects lingered in the years that followed.

I prefer to study disasters where something is learned to improve the safety of related work. Bhopal was not one of these. I prefer to study disasters with standout heroes, a light in the darkness, perhaps an averted further crisis. Bhopal is not one of these. There is only one way to describe it as, and that is a tragedy. It is fitting that its primary comparison is to the bombings of Hiroshima and Nagasaki. It's the same kind of senseless violence, albeit with a different cause.

For this reason, Bhopal is my "least favorite" disaster, if such a statement can be made. There's very little mystery to it at all, and nothing but tragedy as a result.

Remembering July 17, 1981: The Hyatt Regency Walkway Collapse

The Hyatt Regency hotel, a symbol of modernity, opened its doors in 1978, boasting an impressive atrium with suspended walkways. These walkways, designed to be both functional and visually appealing, connected different levels of the hotel, including the lobby where a tea dance was taking place on that fateful evening.

The collapse of the walkways was a result of critical design flaws and miscommunication between the engineering firm and the steel fabricator. Changes in the original design compromised the structural integrity of the walkways, leading to a severe overload on the connections holding them in place. The fatal decision to use offset sets of rods instead of the original design proved to be disastrous.

Source

Why that happened

You know those handles on doors that are long (across the door’s entire width) and you have to push them down to open them? Those are called “push bars” and  were invented shortly after the Victoria Hall Disaster of 1883. On the 16th of June, 1883, there was a variety show held at the Victoria Hall by Mr and Mrs Fay who were travelling entertainers. The hall was located in Sunderland, England but was destroyed during the bombing raids in World War 2. 

The disaster itself happened like this: The performers announced that there would be a treat for 20 kids who had lucky ticket numbers. Now, what happened was, the kids from the top galleys surged downstairs towards the stage. What resulted was a mass of kids being essentially falling into this narrow corridor that made up the stairway. They couldn’t open the doors because they had been bolted to only allow one kid through at a time. The reason for bolting the doors like this was to ensure orderly ticket checking. The kids in the front were crushed by the pressure created by the kids in the back. By the time the adults realised what was happening, they had to scramble to be able to do anything about it. 

They could not open the doors, because it was bolted on the kids’ side, and therefore they had to pull one kid through at a time while someone had to run around and redirect the kids away. 600 kids were saved, but 183, who were in the front, got crushed. This lead to the invention of the Push Bar door handle, to prevent incidents like this, and there was an increase in the amount of safety doors that a theatre or concert hall was mandated to have.