DEFECTS OF FREIGHT LOCOMOTIVE WHEELS AND MEASURES OF WHEEL TYRE LIFE EXTENTION

Transcription

1 DEFECTS OF FREIGHT LOCOMOTIVE WHEELS AND MEASURES OF WHEEL TYRE LIFE EXTENTION Sergey M. Zakharov Prof., Dr.Tech,Sci., JSC Railway Research Institute (), Moscow, Russia Ilya A. Zharov Cand. Tech. Sci. (PhD) JSC Railway Research Institute, Moscow, Russia Sergey N. Bachurin Engineer JSC Railway Research Institute, Siberian Branch, Irkutsk, Russia SUMMARY Heavy haul operation in the Russian Railways is performed by trains 6, 8 and 9 tonnes that are sent on daily schedules. Among many problems associated with an operation, there is a problem of insufficient wheel tyre life of electric locomotives that hauled these trains. On electric locomotives of Russian manufacture, multiple wear wheel tyres are used. Wheel tyres are turned repeatedly in locomotive sheds when defects exceed the admissible level. A tyre s life is determined by the maximum tyre thickness allowed by rules for particular types of electric locomotives. The aim of the present work was to study locomotive wheel defects and to assess the contribution of various defects in the degradation of locomotive tyre life as well as assess ways for tyre life extension.. INTRODUCTION Important features of freight traffic in Russia are large distances from the extraction of minerals, particularly coal from seaports, where they are loaded on ships and difficult terrain conditions, with sharp curves and steep gradients, as well as severe climatic conditions. The second important feature is that the combined operation of freight and passenger trains on the same lines. The need to increase continuously the weight and length of trains on the Railways of Russia arose from the exhaustion of reserves of carrying capacity on many sections of railways. The increase of the volume of traffic on the lines, where the amount of traffic exceeds a rational level, proved feasible by increasing the mass of the train. Train mass of 6, 8 and 9 tons are sent on daily schedules from the Kuzbass mining region to four corridors to the West and to the East of the country. Among many problems associated with an operation, there is a problem of insufficient wheel tyre life of electric locomotives that hauled these trains. Widely used electric locomotives VL8 (2(2o-2o)) and VL85 (2o-2o-2o)) that are operating on Trans-Siberian heavy haul corridors were the subject of the present study. New powerful locomotives 2ES1, 3ES25 and problems of their wheel set performance require a separate study of defects and their causes. LOCOMOTIVE WHEEL DEFECTS, SURVEY METHODOLOGY AND MEANS OF TYRE LIFE EXTENTION 1. Wheel tyre defects The source of data for wheel defects is causes of tires turning that are registered in locomotive sheds. Types and distribution of locomotive tyre defects considerably depend on the area of a locomotive s performance. In the areas of locomotives operation under observation, causes of tyre turning were: flange wear (55%); rolling contact fatigue of various origins (25%); running surface hollowing (1%); slid flat (5%), and other (5%). Though distribution of wheel turning causes may differ considerably, flange wear was always the main registered cause and a subject of study. 2. Survey methodology of locomotives tyre uneven wear analysis These included study of electric locomotives wheel tyre performance on some of the sites

2 S.Zakharov, I.Zharov, S.Bachurin of the Trans-Siberian Railway. The survey continued for a year and included monthly measurements of basic geometrical parameters of tyres. These are flange & rim thickness, running surface hollowing, tyre diameter, wheel tread profiles, hardness of the running surfaces & flanges before and after turning, and type & availability of flange lubrication. In addition, there was selectively controlled track gauge geometry by track measuring cars. In curves of radii 3, 4 and 6 m., more detailed information was obtained such as railhead profiles, lateral and vertical railhead wear, rail cant and super elevation. Factors affecting the flange wear rate could be divided into two groups: Operating conditions of the locomotive and specific features of the particular locomotive. Factors determining operating conditions are characteristics of the vertical and horizontal track geometry, super elevation of the high rail, freight train average speed, and rail lubrication. Factors determining features of particular locomotives are the difference in traction loading, wheel tyre profiles, wheel tyre steel mechanical properties, flange lubrication, wheels diameter differences, and various unevenness in the wear rate of locomotive flanges & running surfaces. For convenience of analysis, the amount of wear was divided by the average wear of all wheel tyres of the locomotive thus obtaining the normalized wear. Eight indicators of non-symmetry of the wear characteristics of wheels and wheel sets in locomotive sections were suggested (Table 1). To evaluate indicators of wheel wear unevenness it is necessary to have a criterion. The evaluation criterion H of uneven tyre wear above which it requires to pay attention to the corresponding indicator was suggested as: Н >.7. (1) The criterion (1) was found with the help of random normally distributed variables simulation. 3. Uneven tyre wear analysis We obtained values of the above indicators for 29 locomotives under control. Indicators could be both positive and negative. The indicator No 8 was higher than the criterion (1) in 17 locomotives (Figure 1), while other indicators exceeded the criterion in three to five locomotives. Further study had shown that many wheel tyre wear asymmetry indices of locomotives under observation are varying considerable particularly after subsequent runs followed by tyres turning. For now, a practical interest was found in the eighth indicator showing the difference between leading and non-driven axles of the locomotive trucks. If the indicator is positive, then the locomotive during the time between examinations often moved in front, and if negative, then backwards. If the locomotive will constantly move in one direction, then the difference between the diameters of the pairs of wheels in the truck exceeds the allowable value. To prevent this, it is enough to change the direction of movement of the locomotive in operation. This is particularly applicable for push locomotives that are used for track section with high gradients and sharp curves. The described method could be used to identify sustainable non-uniformity in the wheel wear of locomotives in operation. We have to note that about the time when these experiments were carried out the reliability analysis for degradation of locomotive wheels using parametric Bayesian approach was suggested [1]. Table 1: Indicators of uneven tyre wear N Indicator What it characterize 1 The maximum value of normalized wear 2 Dimensionless standard deviation. 3 Difference in wear between each wheel of the first and the second loco section 4 The difference in wear between the first section and the turned second section 5 The difference between tyre thickness of left and right wheels 6 The difference in thickness between the inner and outer bogies 7 The difference between the rightto-left of leading and trailing axis. 8 From the leading (odd) axis subtractted trailing (even). Shows how the maximum value exceeds the average Overall wear irregularity Characterizes the difference in wear between the first and second section Difference between the first and second section depending on the direction of the movement Longitudinal asymmetry of the wheel wear. The difference between the outer and inner bogies of the locomotive Characterizes truck axis misalignment. The difference between odd and even axis wear

3 Wheel flange wear rate,mm/1km Values of indicators S.Zakharov, I.Zharov, S.Bachurin 1,5 1,5 -,5-1 -1, Uneven wear indicators Figure 1: Example of uneven wear indicators diagram 4. Ways to increase service life of locomotive wheel tyres Means to increase service life of locomotive wheel tyres could be divided into three groups. The first group has an impact not only on the formation of wheel and rail defects, but also affects the overall performance such as the probability of derailment, the lateral track forces, and the resistance to movement in a form of rail and flange lubrication. Technologies of rail lubrication were introduced in all railways of the JSC RZD [2, 3]. Figure 2 shows how the introduction of these technologies had affected locomotive wheel flange wear. The locomotive flange wear rate decreased from 4 to 5 times by introducing rail lubrication technology. It is worth to note (see Figure 2) that when violation of lubrication technology took place the wear rate increased (from 2 to 23) Years Figure 2: Changes in the locomotive wheel wear rate in a process of introduction of rail lubrication in the Russian Railways The second group of measures directly aimed at the reduction of tyre defects such as flange and tread wear, rolling contact fatigue, etc. One of the most effective means to decrease locomotives tyre defects is improving properties of wheel tyre steel. This had been done by the development and introduction of the new steel grade 4 to replace steel grade 2. Steel grade 4 had hardness HD instead of HB (steel grade 2) and correspondingly increased the mechanical properties. To the same group could be attributed the locomotive wheel profile. It is necessary to note that the selection of locomotive wheel and car profiles that are matched to the rail profiles is a systematic and complex problem that should be solved based on vehicle track simulation, experimental studies to satisfy selected criteria and limitations, in particular, vehicle stability [6]. However wheel tyre profile selection could be done based on locomotive performance within the area of locomotive operation. Our study of locomotive VL85 and VL8r wheel performance operating on increased distances with measurements of wheel profile evolution by the MiniProf Wheel system [6] enables us to find an average wheel profile (flange angle degrees, flange root radius 15 mm, and wheel tread angle of about.13). This profile was suggested for application on locomotives operating in this type of service. The third group of measures to increase tyre life was aimed at decreasing the amount of material removed from a tyre when it is turned due to surface defects (thin flange, rolling contact fatigue, slid flats, etc.). The application of these methods and their combinations depends on the type of rolling stock. In a joint application of the above methods, the following should be considered: Even in the condition of complete elimination of wheel defects of one type, locomotive tyres will be turned because of other types of defects. Therefore, it is wise to reasonably allocate efforts to fight against various types of defects with the aim to maximize the service life of the wheel tyres. Service life of wheel tyres of the most common freight locomotives should be increased to the extent that it is equal to the run between locomotive overhauls. 5. The estimation of the average thickness of turned layers This section of the paper focuses on the influence of locomotive wheel tyre turning (due to flange wear and RCF) on the

4 Y,мм Minimal thickness of turned layers, mm S.Zakharov, I.Zharov, S.Bachurin 1 thickness of turned layer with the aim to find ways to increase tyre service life by reducing the thickness of removed layers in the process of turning. First of all, it was necessary to estimate the average thickness of turned layers. This estimation was carried out based on measurements of profiles of the wheel tyres before and after turning (see Figure 3). 5 (Table 2, highlighted). Those tyres apparently were turned because of the running surface damage. The remaining total amount of the minimum turned layer was still 1.45 times larger than the total amount of the flange wear. Thus, it can be assumed that the minimum tyre turning thickness due to flange wear on average is 1.5 times larger than the flange wear (Figure 4, Table 2) , , X, мм Figure 3: Profiles of the wheel tires before (1) and after (2 -red) turning and their difference (3-green), shifted profile (4- blue) 3 The measurement was performed by laser based instrument that was previously checked against MiniProf-Wheel measuring system [4]. The thickness of the flanges before tyre turning (Figure.2, curve 1) and after turning ( curve 2) are found as abscissa X of these lines with the ordinate Y equal to 2 mm that corresponds to the level of measurements with the normal template. Curve 3 shows the difference between the ordinate of the profiles before and after turning. Curve 4 is the profile shifted by the maximum value of the curve 3. It touches the line 2 and the difference along entire profile shows the minimum thickness of metal to be turned to get the profile 4. The minimum amount of turning is the difference between lines 2 and 4 when the abscissa is equal to 7 mm, which corresponds to the wheel rolling circle. Table 2 presents flanges thickness before and after turning. The difference of thickness is considered as flange wear. As can be seen from Table 2, the total amount of minimum thickness of turned layers is 18.6 mm. This is 1.45 times more than the total amount of the flange wear (12.46 mm). To check the stability of this ratio, we removed a part of the data where a real value of turned layers is noticeably larger than the minimum value 1,5,5 1 1,5 Flange wear, mm Figure 4: Minimal thickness of turned tyres layers versus flange wear Since the total amount of turned flange thickness is 1.5 times more than the total amount of the minimum machined layers, it can be concluded that 35% of the turned tyre layers are caused by reasons that are not related to the flange defects. 6. Percentage of turned layer thickness due to tread surface defects According to Table 3, the total amount of turned flange thickness (28 mm) is 1.55 times more than the total amount of the minimum machined layers (18.6 mm). The analysis of data for turning and wear of locomotives tyres showed that the additional turning due to reasons not related to flange wear is about 31% of the total tyres turning. Thus, evaluation in 3% of additional turning due to reasons not related to the flange wear is fairly stable. This means that to eliminate the cause of tyre turning not associated with flange wear, the service life of tyres could be increased by 1.45 times, that is at 45%.

5 Sum of thickness difference, mm Wheel Flange thickness before turning, mm turning, mm Flange thickness after turning, mm Difference in flange thickness, mm Tyre thickness before turning, mm Tyre thickness after turning, mm Difference in tyre thickness, mm Minimal turning thickness, mm S.Zakharov, I.Zharov, S.Bachurin Table 2: Thickness of the locomotive tires parts before and after turning of wheel sets 1 Left 2 Left 3 Left 4 Left 5 Left 6 Left 7 Left 8 Left ,6 There are several different ways to increase tyre life by decreasing turned layers: Installation on the locomotives antiskid devices (where they are not provided). Presumably this will reduce the average thickness of turned layers for other causes to the level of turning because of the flange wear. Since turning for other reasons may be performed during operation at other depots (not included in the statistics of the depot), the average thickness may be even less. Use a more fatigue and wear resistant steel grade. If we assume that the wear rate of tyre flanges of locomotives will be reduced by 3 times (together with the use of rail lubrication), then turning will only be.14 mm, and the total amount of turned material will be.72 mm ( mm) instead of 1. mm. Turning wheels to the individual profiles that are close to worn profiles. Worn profile templates, allow increased thickness of tyre

6 S.Zakharov, I.Zharov, S.Bachurin flanges when turning on the value greater than the minimum required. It is possible to use a more advanced approach. After measuring profiles by a laser device, a computer issued recommendations on tyre turning within the permitted tolerances. CONCLUSIONS 1. Means of increasing locomotive wheels tyre life were discussed and their effectiveness was evaluated. 2. A method of evaluation of uneven wear of the locomotive tyres was suggested and applied to wheel tyre flange wear of the locomotives operating on heavy haul routes. 3. Eight indicators of longitudinal and transverse asymmetry of tyre wear show the difference in wear between the first and second section, the difference in wear between the first section and the expanded second, the difference in wear of the left and right wheels; a differential wear between the inner and outer bogies, possible wheel axles misalignment, the difference between the wear even and odd axles. The evaluation criterion of uneven tyre wear above which it requires to pay attention to the corresponding indicator was found. The most stable uneven wear (up to 2 times) manifests itself in the difference between the wear of wheel flanges of odd wheelsets compared to even wheelsets. To prevent this, it is suggested to change the direction of movement of the locomotive in operation. This is particularly applicable for push locomotives that are used for heavy trains in complicated track sections with steep gradients. 4. Means to increase service life of locomotive wheel tyres are divided into three groups. The first group has an impact not only on the formation of wheel and rail defects, but also affect the overall performance such as the probability of derailment, the lateral track forces and the resistance to movement applied in a form of rail and flange lubrication. The second group of measures directly aimed at the reduction of defects of tyres such as flange and tread wear, rolling contact fatigue etc. One of the most effective means is the improving of mechanical and tribological properties of locomotive tyre steel. The new grade of the locomotive tyre steel that is more resistant to wear and rolling contact fatigue defects was introduced [5]. 5. The second group of measures could comprise locomotive wheel profile selection. Study of wheel performance of locomotives operating on increased railway sections enables to find an average wheel profile that was suggested for application on locomotives operating in this service. It is worth noting that wheel and rail profile selection and optimization is a problem that needs a system approach [6]. 6. The third group of measures to increase tyre life was aimed at decreasing the amount of material removed from a tire when it is turned due to surface defects. Based on the analysis of the profile of the tyres before and after turning it was found that the minimum turning layers of the tyres due to flange wear is 1.5 times larger than the flange wear. This means that 35% of the turned tire layers caused by reasons that are not related to the flange defects are mostly tread surface defects. One of the ways to decrease these defects is the installation of anti-slippage devices on the locomotives where they were not installed. REFERENCES 1. J. Lin, M Asplund, A Parida. Reliability Analysis for Degradation of Locomotive Wheels using Parametric Bayesian Approach. Quality and Reliability Engineering International. DOI: 1.12/qre V.Bogdanov and S.Zakharov. Development of Lubrication Technologies in the Russian Railways/Guidelines to Best Practices for Heavy Haul Operation. Wheel and Rail Monitoring and Management Systems, IHHA, L.Barteneva,V.Tiytin,V.Kartzev, D.Veniaminov, V.Nikitin. Lubrication of Rails and Wheels on Russian Railways. IHHA STS-Conference Wheel/Rail Interface. Moscow, 1999, pp MiniProf Wheels. Greenwood Engineering A/S, Danmark. 5. G.I.Bronchukov,A.V.Sukhov,A.V.Kushnarev. Locomotive Tyres of Increased Hardness. Railway Transport. 21, 9, С (In Russian). 6. S.Zakharov, I.Goryacheva, V. Bogdanov, I. Zharov. Problems with Wheel and Rail Profiles Selection and Optimization. Wear, V.265,28, pp