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CN derailment findings lead to new inspection practices
This article needs more proofreading.
Also, I don’t get how the problem of broken or missing lag screws is solved by removing lag screws. Unless they’re being replaced with something else, but the article doesn’t say that.
Unclear to me, not a M of W type, tho’ I spiked a few rail-lengths while firing a work train west of King City in 1962, end of digression, what the lag screws held together?
Was it the ties to the bridge structure? Was it bridge timbers to each other. Was it some arrangement for fastening rail to ties, or rail directly to bridge structure?
Track inspectors in hi-rail trucks are not able to notice defects as well as they could in the days when they used speeders. Some railroads, the Southern being one, kept motorcars in service for track inspection for many years after other railroads switched to hi-rails for this reason.
Really, how well do the tracks get inspected by hi-rail? Those pick ups are all medium or heavy duty so they sit high up already. Your view angle between the front of the hood and rail bed means your view point on the rail are several feet in front of you. There is no way they can see enough detail from that far away to spot defects. You can’t view the railbed from top down either. How many times have we heard of a big derailment and the railway claims the tracks were “just inspected yesterday”? Hi rail inspections are minor at best. Walking the line is the only way to have a good thorough inspection.
I agree with Mr. Streeter. I suspect that lag screws are used instead of traditional spikes to hold rail in place in certain situations but am in no way certain. I’d like to know more about this - and also why removing lag screws helps to make things safer.
I agree with Mr. Streeter. I suspect that lag screws are used instead of traditional spikes to hold rail in place in certain situations but am in no way certain. I’d like to know more about this - and also why removing lag screws helps to make things safer.
I agree with Mr. Streeter. I suspect that lag screws are used instead of traditional spikes to hold rail in place in certain situations but am in no way certain. I’d like to know more about this - and also why removing lag screws helps to make things safer.
The article raised more questions than it answered. Perhaps the writer wasn’t given any more info than he gave us.
I would imagine that testing methods such as Magna-fluxing wouldn’t work, where manually removing one lag screw every 100ft. would give the inspector a pretty good idea of how frequent bad lags are. If they’re frequent, well, we know what comes next. I’d be very interested to learn what they find.
Let me add my name to those of all other readers scratching their forefronts about the refered to lag screws. I can imagine lag scews replacing spikes for fastening the rails to the ties, nothing more, and wonder why this would be done now after two centuries of spiking! That would go anyway only for new ties replacing spike-holed ones. We are obviously not discussing bolts holding fishplates here so what gives? A 3 rating for the piece but really it should be a 1.
Nor does it say that track inspectors will be given the necessary time to inspect the track by walking it…
Some outfits use lags rather than cut spikes anymore, all of our timber tie turnouts use lags which hold better, but not necessarily longer. I don’t get the part about removing some either.
Actually, lag screws don’t really hold the track to the tie. The lag screw holds a special tie plate to a wooden tie. The plate has two metal loops that the rail sits between and parallel to, that a steel ‘curly-cue’ retainer made of 3/4" hardened rod is driven through. When the retainer is in place, one end holds the lower web of the rail securly to the tie plate. When concrete ties are used, lag screws aren’t necessary, since the metal loop is imbedded in the concrete, and the rail rests on a cushioned pad between the two loops - one on each side of the rail. This system has been used extensively in Griffith, IN, where the CN has been continually remaking the interlock to their own design.
As for the missing lag screws, I’ve noticed this pretty frequently, especially near the diamonds where special tie plates are used, and CN’s maintenance personnel don’t take the time to install them. When the old spikes were used, it wasn’t unusual to see the rail move up and down as the wheels passed over some areas, where the spikes tended to work themselves out of the tie silghtly. With lag screws, this isn’t possible.
On a side note, if they would first drill a ‘starter hole’ in the wooden tie, it probably wouldn’t have a tendency to split when the lag screw is screwed into it.
Is CN pioneering some new type of rail to tie fastening system? How are lag screws superior to spikes or clips? I think more description of the use of lag screws and the problem of why broken lag screws matter need to be given so that this article makes sense to people who may not understand all the ramifications.
Get those hiking shoes out and put them to work.
The Transportation Safety Board of Canada Report on this derailment can be found at this link:
http://www.tsb.gc.ca/eng/rapports-reports/rail/2012/r12e0008/r12e0008.asp
The TSB of Canada Report on this derailment can be found at this link:
http://www.tsb.gc.ca/eng/rapports-reports/rail/2012/r12e0008/r12e0008.asp
TO CLARIFY
Lag screws tend to break below the top and inside the tie losing their ability to restrain the rail and tie plate from moving. You know that they are broken only if you kick or tap them or try to pull them out by hand. Another good indicitation of a series of broken screws is to see a shiny area at the outside edge of the tie plate that indicates the rail is being pushed laterally by the passing train under load. The rail is no longer being restrained by the broken screws. Walking is the best method to find this condition. It is not unusual and as you see it is extremely dangerous because they break gradually one tie at a time. Once you exceed 3 consecutive ties you can have trouble. Spikes are also known to do this.