Composition and Compatibility Principles of Rail Fastening Systems
What are the core product composition and respective functions of the track fastening system?
The track fastening system is mainly composed of five categories of products: elastic bars, bolts, spikes, pressure plates and under-rail pads, and some scenarios also include auxiliary parts such as lock nuts and spring washers. Elastic bars bear the elastic compression function to ensure the rail is closely attached to the sleeper and reserve expansion space. Bolts/spikes are core connectors that fix pressure plates and elastic bars on sleepers and transmit vertical and horizontal loads. Pressure plates are responsible for restricting the lateral displacement of the rail, preventing rail deviation and improving track stability. Under-rail pads play the role of buffering vibration reduction and uniform load distribution, reducing the damage of wheel-rail impact to the track, and all components cooperate to ensure the function of the fastening system.
What types can the fastening system be divided into according to line type, and which scenarios are they suitable for?
The fastening system is mainly divided into three categories: railway main line fastening system, metro light rail fastening system and industrial and mining lifting fastening system, suitable for different operation scenarios. The railway main line fastening system is suitable for ordinary speed and high-speed railway lines, adopts elastic bar type fastening, requires high elasticity and high fatigue life, and matches 50/60kg/m national standard rails. The metro light rail fastening system focuses on vibration and noise reduction, adds rubber vibration reduction components, adapts to urban rail transit, and meets the low-noise operation requirements. The industrial and mining lifting fastening system is pressure plate type fastening with a compressive strength of ≥500MPa, suitable for QU70/QU120 lifting rails, meeting the heavy-load operation needs of factory cranes. Different lines have different load and speed requirements, which determine the differentiated selection of fastening systems.
What are the core adaptation requirements of the fastening system to the rail model?
The fastening system must be accurately matched with the unit weight of the rail, 50/60kg/m national standard rails are suitable for type Ⅱ/Ⅲ elastic bar fastening systems, and 75kg/m rails are suitable for heavy-duty fastening systems. Foreign standard UIC60 rails need to match European standard SKL15/SKL30 fastening systems, and AREMA rails are suitable for American standard fastening accessories, and cross-standard mixing is strictly prohibited. The pressing force of the elastic bar must match the rail cross-section to avoid rail loosening due to insufficient pressing force or rail deformation due to excessive force. The pressure plate model must correspond to the rail base width, QU80 rails are equipped with QU80 pressure plates, and 60kg/m rails are equipped with special national standard pressure plates to ensure fit. The specifications of spikes/bolts shall be designed according to the load of the fastening system, and high-strength bolts of grade 8.8 and above shall be selected for heavy-duty lines to ensure connection strength.
What is the core difference between high-speed railway and ordinary railway fastening systems?
The high-speed railway fastening system adopts special elastic bars for ballastless tracks, such as type Ⅴ elastic bars, with a static stiffness of 60±10kN/mm and a dynamic-static stiffness ratio ≤2.0, which has better elasticity and reduces wheel-rail vibration. The ordinary railway fastening system mostly adopts type Ⅲ elastic bars with slightly lower elastic indicators, adapting to the foundation deformation of ballasted tracks and more economical cost. The bolts of the high-speed railway fastening system are 10.9 grade high-strength bolts with a torque control accuracy of ±5% and stronger anti-loosening performance, meeting the vibration requirements of high-speed driving. The ordinary railway fastening system can use 8.8 grade bolts with relatively loose torque requirements, adapting to the load characteristics of ordinary speed driving. The high-speed railway fastening system includes special vibration-damping under-rail pads, while the ordinary railway pads focus on foundation buffering, and the vibration-damping and fastening precision indicators of the two are significantly different.
What impact does the installation quality of the fastening system have on track operation?
Insufficient bolt torque during the installation of the fastening system will lead to insufficient elastic bar pressing force, longitudinal displacement of the rail, gauge deviation, and affect driving smoothness. Skewed installation of pressure plates will cause uneven lateral stress on the rail, aggravate rail head wear and shorten rail service life. Uneven laying of under-rail pads will lead to load concentration, cause sleeper cracking and ballast bed deformation, and increase line maintenance costs. Excessive deviation of the elastic bar installation angle will reduce the elastic buffering effect, increase the impact noise when the train passes, and affect passenger experience. Unfirm spike anchoring will lead to overall loosening of the fastening system, and even rail displacement in extreme cases, seriously threatening driving safety, so installation quality is the key for the fastening system to function.