Report shows pictures of various wheel failures. One item that is noted that there has been more rim failures since 1990. Reason not determined yet.
Wheel Failure Investigation Program: Phase I | FRA (dot.gov)
That seems like an extremely complex problem. It even gets into the idea of grinding wheel profiles and reducing the grinding on rail profiles because they affect each other.
Report seems to indicate that there is more trouble with wheels in the West as opposed to the Eastern carriers and that Covered Hoppers and Gondolas (remember todays 'coal cars' are frequently AAR designated gondolas). The recurring theme that was mentioned numerous times was 'thin rim'.
Will be interesting if they can pin down some provable reasons.
Never too old to have a happy childhood!
Is it thin rim or sharp flanges*? Regardless, overly worn wheelsets that see so very few checks with AAR wheel gage templates... Lot fewer one-spot and car-knocker inspectors out there than there used to be.
(*) fun with switch point simple derailments, flanges sharp to the touch / hardly rounded edges and the cop-out is that the gage says it's OK. (pegging the needle on the ol' baloney-meter)... If it were not for the appearance of the new generation switch point protectors, we might see a lot more simple yard failures)
mudchicken Is it thin rim or sharp flanges*? Regardless, overly worn wheelsets that see so very few checks with AAR wheel gage templates... Lot fewer one-spot and car-knocker inspectors out there than there used to be. (*) fun with switch point simple derailments, flanges sharp to the touch / hardly rounded edges and the cop-out is that the gage says it's OK. (pegging the needle on the ol' baloney-meter)... If it were not for the appearance of the new generation switch point protectors, we might see a lot more simple yard failures)
I was an observer to a yard derailment that was associated with a sharp flange and a switch protector, back in 1976.
Thuis was in Mt Newman's port yard at Nelson Point, Port Hedland, in Western Australia.
I was sitting in the trailing cab of a three unit set of locomotives when I heard our train crew call the Yard Tower. "Has our train been cancelled?" Yard Tower "No, why?" Train Crew "Have you looked at the yard lately/" Yard Tower (expletive deleted).
A loaded train had derailed across the yard ladder taking out four switches, including the one between us and the main line, with 24 loaded 100 ton gondolas leaning at 45 degrees.
They worked out a path for us which involved backing the whole train through the car dumper and bypassing the derailment on the one remaining track. This was on a Friday and my train arrived back on Saturday night.
Since I'd been trained in investigating derailments, I spent my free time on Sunday morning trying to work out what had happened. (It was at least as interesting as anything else happening in town on a Sunday where we had one radio station and one TV station....)
I checked out the leading wheelset on the first derailed wagon and it did indeed have a very sharp flange which shouldn't have been running. I then walked back looking for the site of the derailment.
For those who haven't done this, all our wheels had been turned on Hegenscheidt lathes, and these use a single point tool, So the flanges have a distinctive pattern of parallel lines which under normal running are never affected.
When a wheel climbs on to the rail head, it leaves a distinctive mark with the parallel lines being embossed into the railhead.
I followed this back to the first switch in the yard, where it was clear that the sharp flange had hit the "Mack" switch protector, a casting designed to bump the flange clear of the adjacent switch blade.
There was a curve preceding the switch and the rail head up to the switch only had about half of the head remaining. The switch protector had been almost worn away, but had recently been reversed to provide a new wearing surface.
The sharp flange hit the switch protector and rode up over it, and climbed further on to the rail head. Then we had an amazing stroke of luck. Somehow the wheelset found its way through the switch frog and guard rails without further derailing, leaving the main switch complete and in place. It then dropped off clear of the frog and took out the next four switches.
But we still had two tracks out of the yard while the gang rebuilt the damage.
On Monday I tried to explain all this to the Track Superintendent but I think his eyes glazed over....
Peter
mudchicken(*) fun with switch point simple derailments, flanges sharp to the touch / hardly rounded edges and the cop-out is that the gage says it's OK.
There has to be a standard somewhere. Your issue should be with the regulation - not the person holding the gage that is following that regulation.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
According to this report, the wheel failure problem developed between 1990 and 2000. Does this coincide with the weight limits increase of rolling stock? It seems that the wheels in use before this failure phase began must have been just on the safe side of the “razor’s edge” of durability. Then it crossed over that edge and a vast array of consequent failures have ensued with many possible interrelated causes and effects.
Sorting this out and resolving the problem with just the adequate remedies must be the biggest technical challenge the industry has ever faced. It involves changing the mass of the various wheel features, changing the metallurgy, changing the manufacturing process, abandoning the single-use wheels, adopting wheel truing equipment and methods, evaluating rail grinding, balancing the wheel truing with rail grinding, evaluating the heat effect of braking, evaluating the effect of ambient temperature, and evaluating how the wheel, axle, and rail loading re-forms metal and adds residual stress.
It seems strange that with this wheel failure issue being a systemic problem with the wheel and rail standards, it is consistent, but the failure rate is extremely low. And this despite the fact that the conditions are standardized over such a high number of wheels in use. If wheel durability has reached a tipping point, I would expect the majority of wheels to be failing.
zugmannThere has to be a standard somewhere. Your issue should be with the regulation - not the person holding the gage that is following that regulation.
I had thought that sharp flanges were in themselves so important a safety consideration that they had their own regulation -- so much so that I never looked in the CFR to see exactly how inspection and condemnation standards might have been worded. What exactly IS present Federal practice regarding sharp flanges?
Car loaded weight increases might also be relevant?
charlie hebdo Car loaded weight increases might also be relevant?
charlie hebdoCar loaded weight increases might also be relevant?
From the PDF:
As previously discussed, VSRs are extremely rare—if not non-existent—in domestic and international passenger wheels, and international freight wheels, including Australian mining railroads which operate at higher axle loads than the North American freights. The aforementioned railroads generally utilize multi-wear wheels and routinely turn their wheels. However, the North American freight railroads use single wear wheels which typically have zero or one turn before end of life. It appears that the U.S. freight railroads are an outlier in the world for not utilizing multi-wear wheels and routinely turning the wheels.
The loading of the wheel onto the rail cold forms and changes the profile of both the wheel tread and the rail. Much of this change is just the plastic flow of the metal being reshaped as though it were dough. It has been discovered that rail grinding to maintain its correct profile adds life to the rail. It seems counter intuitive because grinding removes metal, which seems equivalent to wearing the rail out. But re-truing the rail head profile adds life that exceeds the life lost by wear between re-truing operations.
When they refer to hollowed wheel threads, I understand that to be a result of the cold reshaping due to metal flow under pressure. This cold flow not only changes the profiles of wheel and rail, but it also induces stress areas that become prone to breaking out of the wheels. It also moves metal out of the rail/wheel contact and brings the rail contact deeper into the critical mass fiber of the wheel. Moving this load into that weaker area of the wheel causes stress cracking to begin. The cracking then lengthens deeper into the wheel toward the center, and further weakens the wheel.
Note: I have revised my understanding of the fracture process detailed here in green text, and the next post reflects that new understanding.
VSR WHEEL FAILURE
The focus seems to be on a type of wheel failure called VSR for “Vertical Split Rim.”
The fracture separation plane falls on a vertical reference plane that is perpendicular to the axle of the wheelset and parallel with the rail. This vertical reference plane falls within an inch or so from either the outside of the wheel or the flange side of it.
This vertical reference plane passes entirely through the wheel tread, although the fracture itself starts at one location on the thread where it intersects the reference plane and progresses around the tread circumference.
The fracture may ultimately pass through the tread over its entire circumference and thus break off a solid ring as part of the tread from the near outside of the wheel or from near the inside, in which the broken off portion would be essentially the entire flange as a solid ring.
Also, the fracture may not progress entirely around the wheel circumference and then release as s continuous ring. Instead it may progress only part way around the circumference, and break off as just an arc shape. The fracture may continue to propagate and break off additional arc shapes in succession.
This is my understanding of what causes this fracture: Wheels and rail are malleable and so the pressure contact “compacts” the steel into a higher density near the surface. It would be like squeezing a steel ball and thus decreasing its diameter as the total weight stays the same.
The wheel tread is much wider than the rail head. So the loading of the tread onto the rail is concentrated at a relatively narrow band of the wheel thread. As the wheel accumulates mileage, the tread is compressed or “cold worked” into a recessed configuration that is referred to as being “hollowed out.” But this hollowing is not caused by a wearing away of metal. Instead it is caused by compacting the metal. So the effect is a trough of compacted steel all the way around the wheel, centered on the wheel tread.
As the metal is compacted into that trough shape, it pulls on the wheel tread metal on each side of the trough where there is no loading of the wheel tread. You can clearly see this effect if you push your finger into a chunk of bread dough. The finger makes a dimple that draws the surrounding dough toward the dimple and into it. So that area around the dimple is being stretched.
So as the rail compresses the hollowed trough into the wheel tread, it produces a stretch (tensile stress) into the metal on each side of the trough. Eventually, that stretching of material causes it to pull apart as a fracture, on one side of the trough or the other. Then depending on which side begins to fracture, it will break off all or a portion of either the wheel flange or of the outside portion of the wheel that generally overhangs the rail.
In the case of breaking at the flange, this not just the standing flange breaking away from the wheel rim beneath the standing flange. It is instead a breaking away of the entire flange height plus the portion of the wheel rim beneath the flange. So the breakage is in the wheel rim, and the flange just comes off as a part of the broken off wheel rim.
Article from Trains magazine:
https://www.trains.com/trn/railroads/the-mystery-of-vertical-split-rims/
Article from Railway Age:
https://www.railwayage.com/mechanical/freight-cars/wheel-failures-digging-down-to-the-roots/
How might this mechanism be affected by repeated passage through retarders?
I don’t know if retarders would have much effect. Some kinds of track impact may cause the actual breaking away of the wheel material, but the initiating cause is the development of the stress crack.
The basic fundamental cause is the development of the zones of tensile stress on each side of the zone of rail contact. That happens without impact. Eliminating those stress zones seems like it would be a major threading of the needle in the manufacturing process. As I understand it, the malleability of the steel wheel tread is apparently intended and quantified by specification. But the tensile stress zones are apparently undesired and unanticipated.
There is discussion about adopting the practice of periodic wheel truing by reshaping the treads by grinding. The grinding would cut deep enough to take the hollowness out of the tread face. So it would cut deepest into the outer edges of the zone “compacted” by running under load. So that would remove the most embedded tensile stress. Actually, I would think the entire wheel tread, including the flange, would have to be cut down while maintaining the proper form until the hollow zone of the tread is eliminated. But even doing that will leave the work-hardened loading zone completely intact at the center of the zone, and then diminishing toward its edges where more metal will be removed.
Interestingly, Rio Tinto in Australia runs higher wheel loads than U.S. practice, and they have no failing wheels. It is said that they run multiple use wheels and true their treads and flanges on a regular basis.
The big mystery in this problem in U.S. and Canada is why such a small percentage of wheels are failing. If you have so many wheels running in nearly identical use patterns, and built to nearly identical specifications; it is hard to understand how so few of those wheels are failing with VSR events.
The issue is likely not the 'work-hardened zone' in the affected tread, but the material cold-flowing under it. Think of it as the counterpart to martensite breaking up into platelets on the railhead at 315K axle load... or induction of gauge-corner cracking and then propagation.
Yes, the reprofiling would have to extend out to the face, and yes, that might thin the rim.
Look up the theory of the 'magic wear rate', which in theory would just get rid of SCC and other micro cracking or platelet deformation before cracks could turn in/down and propagate. Some of the early rail-grinding discussions involved 'realizing' this rate by organized means.
The Australians also figured out you could get safer performance and longer life by using a shorter roller bearing... something I did not see coming. It would not surprise me to find they have done their HAL homework and understand the wheel/rail system better. I would not be surprised to find ECP involved somehow.
OvermodThe Australians also figured out you could get safer performance and longer life by using a shorter roller bearing... something I did not see coming. It would not surprise me to find they have done their HAL homework and understand the wheel/rail system better. I would not be surprised to find ECP involved somehow.
Well, brake friction heat is said to play a role in the VSR wheel failures. An air brake application must dissipate a specific amount of heat to the atmosphere. If all brakes, during an application, set up simultaneously, each wheel should reach the same temperature in the same amount of time. ECP brakes would set up simultaneously.
However, conventional airbrakes will set up sequentially, and the ones setting up first, will get hotter during the brake application than the ones setting up later. So, the earlier/hotter wheels will likely reach a temperature higher than the uniform wheel/braking temperature rise of the wheels braking with ECP.
I wonder if some type of relatively rare anomalies in the practice of setting up brake service applications might explain why these VSR failures occur consistently, but so infrequently compared to the number of wheels in service.
From reading that report it sounds like a triple failure. Improper metalurgy in the wheels. To much deferred maintance waiting until they are just at the minimum before doing anything to fix the issue. And the last one is not enough inspections to catch the problems before they fail. The railroads have gotten way to reliant on technology to catch problems. Wheel dynamic impact sensors to catch flat wheels hot box dectection by remote. So instead of having people look at things with the mark 1 eyeball they go by what the computer says is good. Doing things like that leads to massive problems down the line that tends to cost millions of dollars when they fail. We have all heard it that the carmen are under pressure to get the trains out of the yard. So instead of fixing them properly they say they are good and pray they make it to the next 1000 mile inspection point. You are just lucky that PSR hasn't caused a major TIH spill in a major city yet. The odds will catch up to the penny pinchers in the Boardrooms sooner than later and when it does I do not want to be a shareholder in the company it happens to be with.
Shadow the Cats ownerFrom reading that report it sounds like a triple failure. Improper metalurgy in the wheels. To much deferred maintance waiting until they are just at the minimum before doing anything to fix the issue. And the last one is not enough inspections to catch the problems before they fail. The railroads have gotten way to reliant on technology to catch problems. Wheel dynamic impact sensors to catch flat wheels hot box dectection by remote. So instead of having people look at things with the mark 1 eyeball they go by what the computer says is good. Doing things like that leads to massive problems down the line that tends to cost millions of dollars when they fail. We have all heard it that the carmen are under pressure to get the trains out of the yard. So instead of fixing them properly they say they are good and pray they make it to the next 1000 mile inspection point. You are just lucky that PSR hasn't caused a major TIH spill in a major city yet. The odds will catch up to the penny pinchers in the Boardrooms sooner than later and when it does I do not want to be a shareholder in the company it happens to be with.
How many truck accidents are there yearly because of unsafe, under standatd maintenance are there vs. train derailments because of your perception of railroad maintenance?
The Mark I eyeball is not as good a hidden defect detector as you may think it is.
https://www.fmcsa.dot.gov/safety/data-and-statistics/large-truck-and-bus-crash-facts
EuclidI wonder if some type of relatively rare anomalies in the practice of setting up brake service applications might explain why these VSR failures occur consistently, but so infrequently compared to the number of wheels in service.
I suspect there might also be a connection with flats; I don't know how carefully wheels are NDT-tested when the flats are trued out.
If you look at the metallurgy in crack propagation you'll get an idea of how difficult it might be to detect this particular thing with a running inspection: I think it's a bit like a collar-button abscess with the real damage invisible in a volume within the wheel difficult to 'visualize' on ultrasonic scan.
I'd at least look at the contemporary history of brakeshoe composition; it may be that some formulations intended to outgas less (and hence have lower tendency to runaway fade) might spot-overheat damaged tread adjacent to the 'depressed' rail/wheel contact zone.
Wheel manufacture - not US
https://www.youtube.com/watch?v=8hBeeZ1Pvsg
EuclidMy bet is that they will not admit to that failure, but will instead decide that the problem is so small that the best solution is to just live with it; no need to “reinvent the wheel,” they will say.
This would follow closely the "Pinto Principle," wherein the manufacturer decided it was cheaper to pay off lawsuits than it was to actually fix the problem.
Without a detailed cost analysis, though, we may never know.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Euclid Single-wear wheels are “run-until-failure”, with only one wheel truing operation allowed during the wheel life. The rest of the world uses Multiple-wear wheels which are intended to be re-trued on a regular basis. Changing the wheel standards from single-wear to multiple-wear wheels would definitely be a sweeping change.
That would explain why one hears so many flat-spot wheels on our freight compared to ones in Germany.
charlie hebdo Euclid Single-wear wheels are “run-until-failure”, with only one wheel truing operation allowed during the wheel life. The rest of the world uses Multiple-wear wheels which are intended to be re-trued on a regular basis. Changing the wheel standards from single-wear to multiple-wear wheels would definitely be a sweeping change. That would explain why one hears so many flat-spot wheels on our freight compared to ones in Germany.
Apples and Oranges
The only thing multiple wear wheels would accomplish is to increase the tare weight of a car by several hundred to 1K pounds, thus decreasing the amount of freight that the car can haul at capacity each trip. Germany has 2500 foot trains; USA is approaching 20K foot trains as normal.
BaltACD charlie hebdo Euclid Single-wear wheels are “run-until-failure”, with only one wheel truing operation allowed during the wheel life. The rest of the world uses Multiple-wear wheels which are intended to be re-trued on a regular basis. Changing the wheel standards from single-wear to multiple-wear wheels would definitely be a sweeping change. That would explain why one hears so many flat-spot wheels on our freight compared to ones in Germany. Apples and Oranges The only thing multiple wear wheels would accomplish is to increase the tare weight of a car by several hundred to 1K pounds, thus decreasing the amount of freight that the car can haul at capacity each trip. Germany has 2500 foot trains; USA is approaching 20K foot trains as normal.
It is not apples and oranges. Multiple wear wheels periodically have their treads re-trued in order to reestablish the proper tread/flange profile and eliminate surface defects such as flat spots, cracks, and residual stress that are induced as the wheels run in service. It is all of those defects that accelerate tread deterioration and causes the wheel to be condemned or to fail in service, sometimes with catastrophic results.
Periodic re-truing of wheels offers the same benefit as periodic re-truing of rail.
Whatever weight penalty there is in multiple wear wheels compared to single wear wheels, it is a tradeoff to the benefit of multiple wear wheels lasting longer than single wear wheels; and not causing train wrecks as they wear out, as is possible with single wear wheels.
Euclid BaltACD charlie hebdo Euclid Single-wear wheels are “run-until-failure”, with only one wheel truing operation allowed during the wheel life. The rest of the world uses Multiple-wear wheels which are intended to be re-trued on a regular basis. Changing the wheel standards from single-wear to multiple-wear wheels would definitely be a sweeping change. That would explain why one hears so many flat-spot wheels on our freight compared to ones in Germany. Apples and Oranges The only thing multiple wear wheels would accomplish is to increase the tare weight of a car by several hundred to 1K pounds, thus decreasing the amount of freight that the car can haul at capacity each trip. Germany has 2500 foot trains; USA is approaching 20K foot trains as normal. It is not apples and oranges. Multiple wear wheels periodically have their treads re-trued in order to reestablish the proper tread/flange profile and eliminate surface defects such as flat spots, cracks, and residual stress that are induced as the wheels run in service. It is all of those defects that accelerate tread deterioration and causes the wheel to be condemned or to fail in service, sometimes with catastrophic results. Periodic re-truing of wheels offers the same benefit as periodic re-truing of rail. Whatever weight penalty there is in multiple wear wheels compared to single wear wheels, it is a tradeoff to the benefit of multiple wear wheels lasting longer than single wear wheels; and not causing train wrecks as they wear out, as is possible with single wear wheels.
That I am aware of, there is no existing infrastructure on the US carriers to permit for the routine truing of multi-wear wheels. How long would a car be out of service in having each of its 8 wheels set up in a appropriate lathe to have the wheels trued, versus the time required to to change out wheel sets?
To my mind, the fix, is not multiple wear wheels but increased used of WILD detectors and changing out WILD detected damaged wheel sets.
Fig and prunes [since this is largely a forum for the elderly ]. Why would length of train result in more flat spots that continue uncorrected? Excessively long and heavy, slow trains running with "precision" are all part of a corporate policy of short-term profits and looting.
Whales and flowerpots (to invoke infinite improbability).
Multiwear wheels are so because they are cast with different metallurgy and treatment to have a thicker rim, which is where the extra tare weight, rotational moment, etc. live. As Balt implies, this adds up to an enormous aggregate mass penalty (albeit a variable one as some percentage of the wheels presumably wear down to the condemnation limit) and very little time or effort would be saved in turning them in three-piece trucks in situ with an underfloor-lathe setup vs. just changing out wheelsets and bearings and then 'remanufacturing' in more-or-less interchangeable single-life units.
Now I among others have argued that this would be different if wheels with extended 'wear life' matching that of modern AP bearings with M-942 lubrication were used -- at present perfectly-serviceable bearings with long prospective safe wear life are destroyed in order to press condemned single-wear wheels on and off. Something I have never gotten good data on (and would like to see, if it exists in proper form) is whether running flat at various intensity short of the actual time of reprogoling in fact does damage the bearing in some way that increases risk of far more catastrophic failure than a rim breakage would cause.
I'm surprised no one has brought up the arguments pro and con about how the wheels handle high braking heat. In interchange service, braking has to be scaled to the 'least common denominator' of wear limit anyway, so the discussion usually turns to induced-crack propagation in the absence of widespread effective field NDT testing of wheels for induced or SCC damage. There has been plenty of discussion whether a 'magic wear rate' exists for multiple-wear wheels but I confess I'm far more concerned with "mistakes of assumption" in wheels than in rails, which can be and are readily and repeatedly tested analytically for stress-raising issues on a systematic and regular basis (at least by the sensible)...
In the old days when 'tired' wheels were legal, it made better sense to repeatedly reprofile 'faceted' wheels until, as on some classes of steam locomotive, the ride height had decreased by a number of inches. It looked for a while in the 1980s as if modern one-piece wheel mandates would apply to 'modern' reciprocating steam, particularly the ACE 3000 project, and there was as I recall specific discussion of how the drivers and spring rigging were designed for repeated multiple underfloor turnings.
Incidentally I was not aware that single-wear wheels couldn't be turned to remove surface damage... just that they couldn't be turned beyond the effective wear limit. Assessing this for a given 'flat' depth is not particularly rocket surgery, slthough it does require some care where and how you measure a few thicknesses...
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