So something that has crossed my mind is why do oil train derailment tend to end up in fireballs?
I know the media has some effect on the perception that this happens all the time, I know that not every derailment ends in a fireball .
My question specifically is what is the ignition source of these fires? Crude isn’t particularly flammable like gasoline so I don’t see a spark from steel on steel impact starting the fire. My gut tells me that it’s something more akin to a long term heat source like a diesel glow plug.
Alas the only thing I can think of that may match that criteria would be extremely hot brakes and wheelsets.
What a catch 22! Is it better to have the hot brakes potentially start a fire or let many more cars pile up and potentially leak more oil?
Anybody have actual facts about this? Well reasoned theories?
This is actually one of the problems - apparently it actually is flammable like gasoline. At least the stuff that’s going up in fireballs is. That volatility has been discussed here in a couple of threads.
When one thinks of crude, methinks most folks picture something not far removed from sludge, or asphalt. In reality, crude exists in a number of forms, not unlike coal. I’ll leave it to others to discuss specifics.
As for ignition sources, don’t underestimate the heat that can be generated by metal-on-metal friction, or even the bending of metal. If there are enough volatiles involved (and again, there apparently are in some grades of crude) all it will take is one spark amongst the leaking oil.
Some years back, we went through the same thing with LPG in railroad tank cars. Look up Kingman, Crescent City, and Oneonta.
Not hauling crude notwithstanding, and derailments being a given, even with the best of intentions, the answer is to prevent the leaks, or at least minimize them.
Recall, to, that ethanol burns, and had been involved in several derailment incidents, at least one including a fatality. But ethanol doesn’t explode, so it’s not going to get the same attention…
ruderunner
Crude isn’t particularly flammable like gasoline…
This is actually one of the problems - apparently it actually is flammable like gasoline. At least the stuff that’s going up in fireballs is. That volatility has been discussed here in a couple of threads.
When one thinks of crude, methinks most folks picture something not far removed from sludge, or asphalt. In reality, crude exists in a number of forms, not unlike coal. I’ll leave it to others to discuss specifics.
As for ignition sources, don’t underestimate the heat that can be generated by metal-on-metal friction, or even the bending of metal. If there are enough volatiles involved (and again, there apparently are in some grades of crude) all it will take is one spark amongst the leaking oil.
Some years back, we went through the same thing with LPG in railroad tank cars. Look up Kingman, Crescent City, and Oneonta.
Not hauling crude notwithstanding, and derailments being a given, even with the best of intentions, the answer is to prevent the leaks, or at least minimize them.
Recall, to, that ethanol burns, and had been involved in several derailment incidents, at least one including a fatality. But ethanol doesn’t explode, so it’s not going to get the same attention…
Crude oil varies from condensate (which is like natural gasoline) to tar. It also has varing amounts of disolved natural gas, propane, etc. The lighter components evolve out of the liquid crude, and the vapors build up in storage tanks, including tank cars. The vapors are especially volatile.
It’s been established Bakken crude is particularly volatile. I was mystified myself as to why Bakken crude oil train wrecks were igniting and exploding when as far as I knew plain 'ol crude oil was very difficult to ignite. I even remember reading during the Iran-Iraq War thirty years ago of oil tankers being hit with anti-ship missles and not being heavily damaged, the missile being smothered by the dense crude in the hold. Obviously all crude oils aren’t created equal.
Crude oil is graded by weight of voilite compounds in it. Most Middle Eastern crudes are in the 60 range Western Texas is in the 60 range North Sea is in the 70-80 range Tar sand from Canada is in the 80 range. However Bakken is in the 40 range. That stuff is so lightweight that it requires blending with most refiners before it can be refined to useful goods.
Even though all BAKKEN is not equal it appears that generally it has a much higher percentage of volitiles. Start with methane, butane, ethane, propane, hexane, octane, etc. Then there may be as well complex hydorcarbons.
Some of the functions of a refinery are to separate out the various items and combine / separate other petroleum into these products and plastics are an important function.
I don’t think this is quite right. Has this been substantiated (asI think it was in some instances in the World Trade Center tower collapses, which involved more release of potential energy than any train collision)?
On the other hand, there is no doubt that heavy sparks with enough energy and duration to ignite both vapors and liquid hydrocarbons will frequently be present, as will be heating due to deformation or tearing of car structure, and there is certainly both shock and deformation to spray and perhaps carburete liquid being transported…
White steel is up arounde 2400 degrees F, so I’m somewhat vexed what process could cause this too. You’d be describing something more energetic and faster reacting than the exhaust that burned through the side of a Space Shuttle booster and ate a hole through the bottom of Challenger’s external tank…
A year or two back, North Dakota passed a law requiring those volatile elements removed before loading into the crude into tank cars. Something that had already been required for pipe lines. Since the new regs took effect, I haven’t heard of any derailed oil tanks exploding like previous derailments. Burn yes, but no large explosions.
All it takes is one spark and vapors between the upper and lower explosive levels (UEL & LEL) to start the fire.
For fuel oil #1, the LEL is .7% of the volume of air, the UEL is 5%.
For gasoline, it’s 1.4% to 7.6%, ethanol is 3.3% to 19%.
Without knowing the specifics of the crude in question, we can’t know the exact LEL and UEL, but I’d bet that at least some of the vapor from any spilled oil was at some point within the required concentration, and thus easily ignitable.
I don’t know that there needs to be the energy of the Space Shuttle to melt steel in a train wreck. Sliding wheels or failed bearings seem quite capable of melting steel.
Of course they are. But those won’t produce large quantities of yellow-hot metal flying through the air.
In my opinion, most of the collision force itself produces bending or breaking, and only incidentally (via friction) produces high heat directly. Of course essentially all the kinetic energy in a moving train that derails winds up as heat relatively quickly – but I think you are overestimating how much of that energy can be concentrated into high temperature in a large mass of contiguous material through typical processes that occur in accidents.
What I said is just a generalization. I cannot certify it to be true. Perhaps one of our railroad experts could chime in and provide a certified answer as to what ignites flamable materials in a train wreck.
I have witnessed a derailed loaded hopper picked up at one end by the hook with the cable running about 45 degrees. It was thus lifting and dragging at the same time to draw the hopper toward the hook. Suddenly the hopper surged ahead in travel and dropped in elevation. The hopper bottom hit the rail and skidded on it for about 8-10 feet. It spewed out molten steel leaving spill of yellow molten steel like you might see on the floor in a foundry. It instantly set several ties ablaze, and the section men immediately shoveled dirt on it to put it out. It was pretty amazing because it all seemed like slow motion and it was something that I never expected. I would estimate that it melted 25-50 pounds of ste
I don’t have the time and the access to the rubber bible to pull the constants and do the mathematics to debunk this. But it occurs to me that the combination of gravitational potential energy and lateral excursion available in the incident Euclid describes is orders of magnitude less than that required to raise the mass of steel he describes to the temperature he describes, even if the heat transfer could be accomplished ‘perfectly’ through the contact area between car structure and railhead in ‘about one second’. If I am wrong, I’d like to see how wrong in actual numbers.
On the other hand, it would be interesting to see what Euclid did, especially the part about enough evolved metal to set multiple ties promptly on fire. Are there videos of simulated accidents at Pueblo or elsewhere that show contact which melts a significant amount of structural metal?
Euclid
Sliding wheels or failed bearings seem quite capable of melting steel.
Of course they are. But those won’t produce large quantities of yellow-hot metal flying through the air.
In my opinion, most of the collision force itself produces bending or breaking, and only incidentally (via friction) produces high heat directly. Of course essentially all the kinetic energy in a moving train that derails winds up as heat relatively quickly – but I think you are overestimating how much of that energy can be concentrated into high temperature in a large mass of contiguous material through typical processes that occur in accidents.
What I said is just a generalization. I cannot certify it to be true. Perhaps one of our railroad experts could chime in and provide a certified answer as to what ignites flamable materials in a train wreck.
I have witnessed a derailed loaded hopper picked up at one end by the hook with the cable running about 45 degrees. It was thus lifting and dragging at the same time to draw the hopper toward the hook. Suddenly the hopper surged ahead in travel and dropped in elevation. The hopper bottom hit the rail and skidded on it for about 8-10 feet. It spewed out molten steel leaving spill of yellow molten steel like you might see on the floor in a foundry. It instantly set s
The car was filled with crushed rock. The car hopper contacted the rail with its lowest edge at the bottom of its triangular shape, so the area of contact was very small, maybe only a couple square inches or so at the initial contact before sliding. The sudden production of that much molten steel seemed very intrusive and surprising. I was about 50 feet away from it, at a somewhat higher elevation.