Interesting story in the LA Times from last week…
http://www.latimes.com/nation/la-na-crude-train-safety-20151007-story.html
Not so sure the oil trains are the sole cause of track issues, unless it’s just the increase in traffic they represent.
I’m no expert on the relative weights of the various types of unit train traffic - coal, ethanol, etc. If the oil traffic is on routes not used to the weight, that could be a factor.
A hundred cars continuousy hitting a potential defect might be like bending a wire back and forth. Eventually it will break. Manifests might not have the same effect.
I’d have to believe that the reason the oil trains are getting the attention is that they go boom. An equivalent grain train derailment doesn’t garner the same national news lead as something that explodes.
I had assumed that often cited “rise in oil train derailments” was due to an increasing number of oil trains.
However, this article is saying that oil trains actually are derailing more often than other types of trains. I don’t know whether that claim is accurate, but if it is, it poses a big question of why oil trains would be derailing at a higher incidence than other types of trains.
The article also raises the question of oil slosh causing or contributing to the cause of oil train derailments. That question has been raised several times in recent discussion here and in Fred Frailey’s blog without much of a conclusion. Now this article brings it up as a possible culprit in causing derailments.
I wonder what type of testing has been done on slosh effect. While it may not be enough to tip cars over, there may be certain harmonics set up in a tank of liquid that would cause unusual car bounce that could significantly raise the pressure on the rail and track bed.
Quote from the article:
“Track problems were blamed on 59% of the crashes, more than double the overall rate for freight train accidents, according to a
"Weight, oil sloshing and cold temperatures are among the issues that might be exacerbating the problem, according to rail safety experts.
Investigators at Safety Transportation Board Canada, which is investigating the eight accidents that have occurred in that country, are beginning to suspect that the oil trains are causing unusual track damage.
“Petroleum crude oil unit trains transporting heavily loaded tank cars will tend to impart higher than usual forces to the track infrastructure during their operation,” the safety board said in a report this year. “These higher forces expose any weaknesses that may be present in the track structure, making the track more susceptible to failure.”
Rick Inclima, safety director at the Brotherhood of Maintenance of Way Employees, also said that oil trains could be creating unique stresses on the track. “You can certainly get some rhythmic forces in … oil trains that you might not see on a mixed freight train with cars of different sizes, weights and commodities,” he said."
I’m not sure that we have seen enough oil train derailments to really concretely identify if they are causing any track failures that other train types are not. This may be a case of insufficient data.
Coal trains are just as heavy, and travel at about the same speeds, but they do not slosh.
Maybe not, but the rate from derailments is double that of other cargos. Sure sounds like something differs.
As always, statistics may not paint a true picture. Rather than compare unit oil train derailments against all freight traffic, a more reliable comparison would be to compare them against other types of unit trains. I didn’t see any indication that main line and yard derailments had been separated out, and by their nature unit trains tend to avoid the ministrations of intermediate yards.
I suspect what we are really seeing is that Oil Trains are being operated on many lines that were never constructed or maintained as ‘heavy haul’ lines. No matter what commodity would be handled in unit trains with 286K per car loads would stress the track structure beyond it’s limits unless the track had had a sub-grade up rebuilding to handle these kinds of loads.
With the oil originating in the Dakota’s, Alberta and Manitoba is suspect most of the branch line mileage was constructed for it’s ‘Granger’ use in supporting local agriculture. While the lines may have been upgraded with newer rail and tie projects, I suspect they did not receive a sub-grade up rebuilding.
I am suspect of a lot of these numbers. Yes oil trains are heavy, yes the cars are rigid, yes unit trains are harder on track than a mixed freight train. Yes metal becomes more brittle the colder it gets. None of these are news flashes. The question is, is that significant?
I am also struggling with the “oil trains are breaking the rail” argument. I don’t see where, if you actually examine the details, the latest two findings support that conclusion.
In one case there was a defect in the rail, which the NTSB says was overlooked for 2 years. That’s not an oil train problem, the oil train didn’t “break” the rail, it finally failed under the oil train. The rail was going to break in any case (except if it had been repaired). In the other case the rail actually broke previously and what broke under the oil train was a temporary repair. In both cases it really wasn’t the oil train that was the root cause of the defect. In both cases there was a previous defect that went uncorrected or wasn’t sufficiently corrected and the oil train, probably the heaviest train on the route, found the weak spot. Pretty much the heaviest train is always going to find the weak spot, its kinda obvious.
So really that is the question. Are the oi
It may be that the article is misinterpreting the facts, but I see no reason to jump to that conclusion right off the bat. If oil trains are derailing at over twice the rate of other types of trains, that is a giant red flag that deserves a full investigation.
It is well known that unit trains behave differently than mixed freight trains and have differing effects on track. I would like to know if oil trains derail at a higher rate than other unit trains with the same car loading.
If they do, then the only difference is that oil trains have a higher center of gravity and their load is liquid with room to shift in the tank. No other freight car undergoes load shifting while traveling.
What is the potential for load shifting to beat up track by overloading it?
The data, of course, does not show cause. But anybody who ignores such a strong correlation does so at his/her peril.
Oil sloshing? I understand that the tank car isn’t filled completely, to allow for expansion of the contents. But to read a lot news stories and online articles, they make it sound like the tank car is half full of oil, and the oil is sloshing around like crazy. How full is a loaded tank car anyway? I can’t believe that a tank car designed to carry oil it’s whole lifetime would be too overbuilt in size.
That’s not exactly what they said.
What they said was that oil train derailments were twice as likely as other trains of having a track related cause. They did not say that oil trains were derailing at twice the rate of other trains. Very, very big difference.
A key measure not discussed is what are the cause distributions of other unit trains (coal, grain, double stack, ethanol, etc.). It might be that unit trains have a higher incidence of track derailments because they aren’t subject to as much switching as non-unit shipments, eliminating a whole host of human error causes. They may also be newer cars or inspected more thoroughly than the general car population so the mechanical failure causes are less than the car population as a whole.
The statistics are carefully selected and phrased to support the agenda they pushing.
Yes, the article does comprise the usual modern inability to speak logically in terms of statistics. For instance, in the statement starting with: “Track problems were blamed on 59% of the crashes,…”, they probably mean that 59% of the crashes were blamed on track problems. I guess they made a typo when they said “on” instead of “in.” So the sloppy writing of the article does raise serious questions as to whether they have reached any logical conclusions from their data.
Generally, their premise seems to be that oil trains are unusually hard on track. So they cause the most track defects, and then they are the most likely train push the defects into failure mode.
Murphy S.: The capacity of a Tan Car is based on the calculation of weight allowed for the specific type of car: [ Loaded Wt (less) Tare wt (equals) Capacity of Product carried in car]. Bear in mind that every product has its own weights .
Like the problems with dry freight in rail cars or trucks[ a lighter product will ‘cube out’ before it fill the container provided for transport. Heavier weights of products will ‘gross out’ before the cubic capacity of the container is reached.
“Sloshing” possible? You betcha! Ever see a truck approaching a traffic signal too quickly and make a heavy brake application? With an internally, un-baffled, tank, The ‘slosh’ (liquid hammer’?) caused by the rapid stopping can cause the truck to be propelled foreward into the intersection by almost a truck length. Potential consequences? Better believe it!.. No reason to believe that a partially laden railroad tanker would not develop a ‘sloshing action’ relative to its motion(?).
Just for the sake of conversation : [Frm: Ask.com] "…The weight of a gallon of oil depends largely on the oil type. The exact weight can also vary based on what temperature the oil is stored at. Most common oils stand between 7 and 8
How would “sloshing action” fore and aft on a tank car cause damage to the track?
I can see maybe shoving the train past a signal. I can see problems holding the train steady after its stopped. How does sloshing damage the track? In most cases track is damaged by vertical forces, impact loading or lateral forces, side to side.
If oils weighs 7 to 8 pounds per gallon, tank cars would have to be about 14% oversized(?) in order to carry 7# oil and 8# oil. If oil weight varies, is every tank car weighed after it’s filled?
Side note: My father was an over the road trucker. He hauled a lot of cement out of the S.D. Cement plant in the 70’s/80’s. They had a terrible loading process that took many hours. They would load a truck to what looked like the right amount, and then weigh it. Then they ineveitablly had to blow some back out because it was overweight. Then weigh it. Then add more. Then weigh it. Then blow some off etc… When the truckers asked why loading train cars with cement didn’t require the same process, they were told that they just knew how much to put in each rail, and besides, “everyone knows the railroads are way overbuilt anyway”. [:O] This was in the era where the Milwaukee Road and the CNW were both falling apart in S.D.
I have some theories about the so-called “sloshing” effect, but I would not call it “sloshing”. Sloshing sounds like a random wave action in all directions on the oil surface, induced by the ride of the tank car.
The effect that I am curious about is the full load surging forward during brake application and/or slack run-in. This oil surge moving from car to car in sequence might act as its own sort of slack run-in, that is to say a chain reaction of building surge force.
Depending on how much air space is in each tank car, this forward surge of the oil would take significant weight off of the trailing end of the car and add it to the leading end, thus overloading the lead truck. Furthermore, the force of the overload might exceed that actual weight increase because of the abruptness of the weight transfer. It would be like a hammer impact.
Is is possible for the oil to slosh side-to-side? I have no idea about tank car internals, but it is just a thought.
Anthony V.
I was thinking along these lines, too. A higher percentage of oil train derailments are caused by track failure, but maybe that’s because the cars in the oil trains are in better shape. They don’t sit idle as much, they don’t get banged around in switching as much and I would guess that they are not as old as many general purpose cars. If other cars have more failures, then the pecentage of rail-related failures go down. In interpreting statistics, you can play with percentages and absolute numbers and come to all kinds of different conclusions.