Railway grinding key equipment development status quo

At present, the railway system is the most widely used, the market share of relatively large grinding method for active grinding technology, high-speed passive grinding technology and milling and grinding composite grinding technology. The following three typical rail grinding equipment development status is summarised.

1.3.1 Rail active grinding key equipment

Active grinding technology is currently the most widely used, the largest market share of the grinding method, grinding car models more. Foreign grinding car manufacturers are mainly the United States HARSCO and LORAM company and the Swiss SPENO company and so on. Domestic rail grinding technology started late, after decades of development, the current domestic grinding car manufacturers are mainly Golden Eagle Heavy Construction Machinery Company Limited (Golden Eagle Heavy Industry), CNR Beijing Erqi Vehicle Company Limited (CNR Erqi), Zhuzhou CNR Times Electric Company Limited (Times Electric), China Railway Construction High-tech Equipment Company Limited and so on. Golden Eagle Heavy Industry (GEHI) and CNR Erqi have independently developed GMC-96X and GMC-96B sanding vehicles by introducing technology from HARSCO (USA) and SPENO (Switzerland), respectively, as shown in Figure 1 and Figure 2. The GMC-48JS sanding vehicle, independently developed by TIME ELECTRIC, has been approved for operation in March 2020 [1].

Fig.1 GMC-96X

Fig.2 GMC-96B[2]

At present, the line commonly used GMC-96X (Golden Eagle Heavy Industry), GMC-96B (China Railway Erqi), PGM-48 (HARSCO, USA) models and the new line of GMC-48JS models (Times Electric), the main operating parameters and operating requirements are shown in Table 1. The data show that the operating speed of the grinding car is about 3~24 km/h, lower than the critical operating speed may result in the rail Below the critical operating speed may cause excessive grinding in local areas, and the local grinding heat of the rail at low speeds is actively prone to burn the rail [3]; if the operating speed is too high, the ideal removal efficiency cannot be ensured. A grinding car designed for the maximum operating gradient of 30 ‰ can handle the vast majority of line grinding maintenance. However, for some long-gradient lines (gradient greater than 30 ‰), especially the Sichuan-Tibet Railway under construction, the coordination of grinding car operating performance and traction problems will be one of the important challenges.

Tab1. The operation parameters of the typical rail grinding train[2]

1.3.2 Key equipment for high-speed passive rail grinding

High-speed passive grinding car is mainly produced by the German company VOSSLOH HSG rail grinding car, which is mainly composed of grinding car and auxiliary car, Figure 3. Grinding operations require locomotive traction, operating speed up to 60 ~ 80 km / h; the whole vehicle 4 groups of grinding unit total of 96 grinding stone at the same time in the operating state and at a speed of about 6000 rpm high-speed rotation, as shown in Figure 4; each group of grinding unit is equipped with 2 sets of grinding frame, the operating process of the grinding stone can be achieved without stopping the whole group of fast, continuous rotation, that is, a single grinding stone loading can be continuous grinding About 70 km [4], as shown in Figure 5. During the grinding process, the amount of grinding sparks, grinding wheel wear and grinding pressure can be monitored in real time. After grinding, the rail profile is tested to check the grinding effect. The high-speed grinding vehicle relies solely on the resistance of the grinding train to remove the rail head material, as the grinding wheel has no drive. Therefore, the working speed has a significant impact on the working effect of the grinding vehicle. When the high speed grinding car performs the grinding operation in the inter-station line: in the acceleration phase of leaving the station, when the speed is higher than 30 km/h, the grinding frame is lowered and the grinding operation is started; in the deceleration phase of entering the station, when the speed is lower than 15 km/h, the grinding frame is raised and the grinding operation is finished. Therefore, in the area corresponding to the acceleration and deceleration of the sanding vehicle, the sanding effect is reduced due to the reduction in vehicle speed; part of the area that cannot be sanded due to the lifting of the sanding frame must be covered by the turnout sanding vehicle in the station during the following operation.

Fig.3 HSG high-speed grinding car

Fig.4 Grinding unit

Fig.5 Grinding frame structure

In the past decade, many domestic institutions have been committed to the research and development of high-speed grinding car. On June 18, 2021, the first domestic Beijing-Shanghai high-speed rail intelligent high-speed rail grinding prototype test prototype jointly developed by Southwest Jiaotong University, Beijing-Shanghai High-Speed Railway and Southwest Jiaotong University Railway Development Co Ltd came off the production line, realizing the original innovation of "zero to one" [5] as shown in Figure6. On 22 July 2021, the KGM-80II rail grinding vehicle independently researched and developed by China Railway Construction High-Tech Equipment Co., Ltd. passed the evaluation and was approved for trial operation [6], as shown in Figure7. The introduction of the self-developed high-speed rail grinding vehicle is of great significance for China to realise the complete autonomy of railway system equipment.

Fig.6 Beijing-Shanghai high-speed railway intelligent rapid rail grinding prototype test car[5]

Fig.7 KGM-80II. Rail Rapid Grinding Car[6]

1.3.3 Rail milling and grinding composite grinding key equipment

At present, rail milling and grinding coaches are widely used in domestic and foreign heavy-load railway lines. Germany's GMB company, as well as Austria's LINSINGER company, MFL company, etc., are the main manufacturers of overseas milling and grinding wagons [4,7]. Figure 8 for the LINSINGER company's SF03 milling and grinding car, the total length of the car 25 m, the weight of the car 120 t, equipped with two three-axle bogies, self-propelled speed up to 100 km / h, the maximum operating speed of 0.36 ~ 1.20 km / h, the whole car is equipped with a total of two sets of milling discs and two sets of grinding wheels [7,8,9]. Domestic manufacturers mainly include China Railway Times Construction Machinery Co. in Baoji and China Railway Construction High-Tech Equipment Co. Figure 9 shows the XM-1800 milling and grinding vehicle produced by China Railway Construction High-Tech Equipment Corporation, which has the advantages of high operational efficiency, flexible grinding, environmental protection, and less spark splash in the internal rail shape trimming and special rail profile grinding [10]. Table 2 compares the main operational performance parameters of the SF03 milling and grinding vehicle and the XM-1800 milling and grinding vehicle, which shows that the XM-1800 milling and grinding vehicle developed in China has reached the world's advanced technical level in terms of material removal efficiency and operational precision.

Fig.8 SF03 milling car

Fig.9 XM-1800 Milling Car[10]

Tab.2 The comparisons of the operational performance between SF03 and XM-1800 rail miling train

1.3.4 Comprehensive comparison of the main rail grinding equipment performance

Active grinding, high-speed passive grinding and milling and grinding composite grinding three typical rail grinding equipment performance comparison, such as Table 3. active grinding material removal, grinding light belt envelope contour is good, fast running speed, is currently the largest share of the market share of the operation. For active grinding, the key point is to solve the problem of grinding rail burns, so as to improve the surface quality of the rail after grinding. Studies have shown that the optimisation of grinding parameters [11,3,12], grinding wheel structure [13] can effectively improve the burns, of which the development of high performance active grinding wheel is the focus of future research.

High-speed passive grinding operation speed, theoretically can be intermodal with ordinary passenger / truck, without the need for "sunroof", does not affect the normal passage of the line. In addition, high-speed passive grinding based on the rail preventive grinding strategy proposed to extend the service life of the rail with significant advantages. Therefore, high-speed grinding has important competitiveness in the future development. Serving in high speed, high load, strong vibration and other harsh conditions, while meeting the high efficiency, high quality and other operational requirements, to ensure that the grinding wheel has excellent mechanical properties (strength / toughness), service performance (cutting performance, wear resistance, etc.) is one of the important challenges in the future.

Composite grinding has significant advantages in material removal efficiency, contour finishing, surface quality, etc. However, its operation speed is slow, in the future, with the development of the economy, the grinding time is extremely compressed, the grinding operation efficiency requirements are increasing, the coordination of the future line capacity and the length of the grinding time will be the focus of attention. At the same time, in order to ensure the rail profile correction accuracy and operational efficiency, the development of rail grinding to withstand the harsh operating conditions and highly wear-resistant carbide cutting tools is also one of the future research focuses.

Tab.3 The comparisons of the three kinds of typical rail grinding equipment

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