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1. General aspects of monitoring and diagnostics.

Question 1.6.

Your diagnostic systems are used by many Russian railways. We would like to know what problems is it possible to solve with its help, what specific peculiarities in railway vehicles have you met and how do you take into account these peculiarities?
(The question was asked by the specialists of Byelorussia car stock maintenance teams.)

The question is answered by Alexej V. Barkov. 2 Feb. 1999:

We supply the railways with the diagnostic systems beginning from 1996. Nowadays they are used in many locomotive depot of the main Russian railways. The most deliveries we make via two companies that are our dealers and who made with us the a large amount of work concerning the customization and certification of the systems to the railway cars. These companies are «Transport» from Omsk and TST, Saint Petersburg. Nowadays the volume of deliveries are increased because the orders for diagnostic systems we receive not only from the locomotive but also from railway car depots.

The main problems that we solve for the railways are the diagnostics and long term wheel gearing blocks and wheel pairs condition prediction. In the wheel gearing block the system diagnoses the box bearings, the gearing wheels and bearings of the gear box, the couplings and electric motor bearings. Now, by the request of the servicemen, we are customizing the system for diagnostics of the direct current electric motor magnetic system in the wheel gearing block.

The wheel gearing boxes’ diagnostics is made or in situ on the locomotives and motor cars during the months or quarter’s maintenance or on the stands where the boxes are run in after maintenance. The wheel pairs are diagnosed on the stands with special electric drive for their rotation.

Now about the peculiarities of railway vehicle’s diagnostics. Only a limited number of rotating equipment types have the peculiarities that must be taken into account during constructing the diagnostic standard. Firstly, they are concerned with the not fully run in of the rotating units when the final check of the maintained equipment is made, viz. when the mating parts are not yet will aligned. Besides that any transport vehicle has such peculiarities as:

  • the inability to reproduce during the diagnostic measurements the same modes of operation, especially the value and direction of the load, that accompany the development of the defects,

  • the influence on the diagnosed equipment of the vibration of the electric driver that is used on the stand to rotate the equipment, or the instability of the equipment rotating speed if it is driven by its own motor,

  • limitation of time for measurements and the necessity to give the diagnose and condition prediction for repair determination in field,

  • a high probability of foreign particle invasion in the lubrication during the operation. They can express itself only after changing the mode of operation, viz. during diagnostics in the first stages of running the equipment.


The general peculiarities of transport vehicles diagnostics are taken into account very simply in customization process or the software and in the last versions this work is made automatically after diagnosing a group of about ten similar machines. While gathering the machine vibration measurement results all the customized parameters in the program are automatically corrected.

But in the diagnostics of the railway transport there are specific peculiarities that must be taken into account additionally. The first of it is the impossibility to place the railway train or a separate locomotive for a long period of time in the same climatic condition before driving its wheels, especially in winter period. As a result the lubrication in the friction units can have a low temperature and comparatively large and hard particles can appear in it. These particles form the unit vibration the same features as many incipient defects. To avoid the false warnings during diagnostics of cold equipment now we discuss the possibility of inductive heating of wheel pair bearings before diagnostics.

The second peculiarity concerns the wheel pair’s diagnostics just under the lifted locomotive (motor car). In this case the direction of load applied on the outer race of the box bearings is changed by 180 degrees. If the bearing has a gap because of the race wear, then during rotation of the wheel pair in the lifted wheel gearing box the loaded, during the normal operation, part of the outer race does not take part in forming the friction forces and its defects will not be detected. To avoid missing such a defect during diagnostics better to rotate the wheel gearing box on a special roll stand as it is done for automotive transport diagnostics. Such a stand is now mounting for one of Russian railroads. For diagnostics of separate wheel pairs it is possible to use not only roll stands, but any other stands with electric drivers for wheel rotation. It is necessary to bear in mind that in this case when the wheel pairs are assembled on the stand their boxes should be turned 180 degrees.

One more peculiarity of practical wheel gearing box diagnostics is concerned with the existence for some types of locomotives in these boxes thrust bearings that are loaded only when the large centrifugal forces apply to the locomotive when it runs on curved parts of the railway path. The existing stands for such box diagnostics cannot create such loads, so the certainty of thrust bearing diagnostics and condition prediction is not very high yet. To increase it several railways is now searching simple technical solutions to create additional axial loads applied to the wheel pairs with thrust bearings.

Up to date we have accommodated a good experience in wheel pairs and wheel gearing box’s diagnostics and in the last third version of the software all the peculiarities of transport diagnostics, including the railway transport, are taken into account.

 

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