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Acoustic Signatures Reveal Railway Bearing Defects

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Jim_E
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Another interesting railroad technology
Jim_E   11/15/2012 11:25:22 AM
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Another interesting railroad technology, is the application of Electronically Controlled Pneumatic (ECP) brakes.

Railroads have been using the same brake technology since the late 1800's!  Here's an over simplification: Basically, there's a continuous air line that runs the lenght of the train.  The locomotive generates air that charges a small resevoir under each car.  When sufficient air is present in the system, the brakes on the train release.  To activate the brakes, the engineer releases a small amount of air from the system, which propogates back through the train, applying the brakes an amount related to the amount of air released.  With long trains, it takes a long time for this air control to pass through the train, resulting in odd train handling where brakes are applying and releasing at different times in different parts of the train.  Worst of all, is that if the engineer makes too many brake applications without recharging the system, the train can lose all braking ability!

With ECP, air is still used to operate the brakes, but an electrical system is used to tell the brakes when to apply and release.  With this system, the locomotive can keep charging the air line so that the train won't lose braking power.  They can also apply and release the brakes with more precision, and all cars react at the same time, decreasing stopping distances.  And, there are individual car brake diagnostics available.

http://www.fra.dot.gov/downloads/PubAffairs/ECP%20Brakes%20FINAL.pdf

Testing has shown it to work well, but adoption is slow due to the cost and amount of rail cars out there.  It's primarily being used to "unit" trains in captive service, but I hope that the technology becomes more widespread eventually.

William K.
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Platinum
Railroad wheel bearing failure detection.
William K.   11/15/2012 10:18:44 PM
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Back about 1987 I designed a system using spectrum analyzers designed for exacly that purpose, industrial fault detection. I coulkd set the frequency range to examine and then have ten "boxes" around the PSD (Power Spectral Density) trace, and if the amplitude went outside the "box" a TTL signal would pull low and my equipment would know that the part being tested was outside of the specification. I believe that package was produced by Spectral Dynamics, but I don't recall the model number. One of the last testers used it to check in-tank fuel pumps, and I gather that it worked quite well. What I don't know is if they are still using that device to chek pumps. IT was an easily upgradeable test stand, so it could be still checking those pumps now, 32 years later. We did build equipment to last.

It would seem that a similar system could listen for bad bearings, but the train speed would need to be quite closely controlled.

Jon Titus
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Blogger
Rail grinding & sparks flying
Jon Titus   11/16/2012 11:03:30 AM
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Railroad companies have special cars that grind the rails to specifications, and sparks do fly out of the grinders.  A water car at the end of this type of train sprays any small fires that get started in brush.  Here's a short video: http://www.youtube.com/watch?v=6pAfMlr4Pko.

Buring a trip through Evanston, Wyoming my wife saw one of these grinding trains and thought it was on fire.  So sometimes sparks are intentional.

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