Track Bolt/Spittle Core Grade Selection and Locking/Loosening Prevention Requirements
What are the core grades of track bolts and adapted track scenarios?
The mainstream track bolts are 8.8 grade and 10.9 grade high-strength bolts, plus special fish bolts, the grades are precisely divided according to line load and working conditions, and downgrade use is prohibited. 8.8 grade bolts are the main models for ordinary railway and factory tracks with tensile strength ≥800MPa and yield strength ≥640MPa, meeting basic locking needs with economical cost. 10.9 grade bolts are special for high-speed railway and heavy-duty tracks with tensile strength ≥1040MPa and yield strength ≥940MPa, extremely strong anti-loosening and deformation resistance, adapting to high-frequency impact working conditions. Fish bolts are special for rail joints, suitable for fish plate locking, specifications are M24/M27, selected according to fish plate models, and cannot be used universally with ordinary bolts. Heavy-duty anti-loosening high-strength bolts with anti-loosening threads are used for industrial and mining tracks, special for heavy-duty hoisting scenarios, and standard high-strength bolts can be used for ordinary scenarios.
What are the core specifications of spiral spikes and adapted sleeper types?
Spiral spikes are core accessories for sleepers to fix rails, the national standard mainstream is M24 upper thread and M25.6 lower special thread, suitable for special installation of concrete sleepers. The total length of spiral spikes ≥200mm, the lower thread is a special tooth type for sleeper pre-embedding, with strong locking force after screwing into the sleeper and not easy to loosen and fall off. Foreign standard spiral spikes are inch threads, suitable for foreign standard concrete sleepers, European standard uses M27 spikes, American standard uses inch 1-inch spikes, selected according to project standards. Ordinary railway tracks use standard spiral spikes, high-speed railway tracks use insulated spiral spikes to avoid track circuit short circuit, and the insulation layer can be used only if there is no damage. The spike material is Q235-A steel, galvanized for anti-corrosion on the surface, uniform hardness, no thread slipping and no fracture during screwing, ensuring the fixing effect of sleepers and rails.
What are the core locking torque requirements for track bolt/spike installation?
The locking torque of track bolts is strictly defined according to the strength grade, 8.8 grade high-strength bolts with torque 350-400N·m, 10.9 grade with 500-550N·m, deviation ≤±5%. The locking torque of fish bolts is 380-420N·m, which needs to be evenly applied to four/six bolts to ensure the force balance of the fish plate without unilateral loosening. Spiral spike installation does not require a torque wrench, use a special screwing tool, the screwing depth ≥150mm, and the spike can be used if there is no shaking or loosening after tightening. The torque deviation of high-speed railway bolts needs precise control ≤±3%, ordinary railway/industrial and mining deviation ≤±5%, meeting the accuracy requirements of different lines. Insufficient locking torque leads to easy loosening of accessories; excessive torque causes bolt slipping and fracture, both need to be strictly avoided and constructed according to standards.
What are the core anti-loosening measures and construction points of track bolts/spikes?
The core anti-loosening measures of track bolts are "precise torque + structural anti-loosening + material anti-loosening", triple protection to eliminate loosening, which is a key link of track safety. Structural anti-loosening is equipped with spring washers and lock nuts, the elastic deformation of spring washers provides continuous pre-tightening force, and lock nuts bite the thread to prevent reversal for double protection. Material anti-loosening uses high-strength alloy steel bolts with thread precision grade 8g, no thread slipping and no burrs, tight screwing to avoid loosening caused by thread gaps. Spike anti-loosening relies on the bite of the lower special thread and the sleeper, ensure the thread is clean without impurities during screwing, screw to full depth, and eliminate virtual screwing and suspension. Conduct regular inspection after construction, check the torque value and spike screwing state monthly, and inspect heavy-duty tracks every half a month, retighten and replace loose parts in time.
What are the common problems and maintenance measures of bolts/spikes in use?
Common problems of bolts/spikes are thread slipping and fracture, loosening and falling off, rust jamming, torque attenuation and thread damage, all need immediate rectification to avoid track locking failure. Bolt slipping and fracture are due to excessive torque or substandard materials, replace high-strength bolts of the same grade, lock according to standard torque, strictly prohibit over-torque construction, and check the bolt appearance before installation. Loosening and falling off are due to insufficient torque or anti-loosening failure, retighten to the standard torque, install anti-loosening accessories, and re-screw the spike to full depth if loose, reinforce the sleeper pre-embedded hole. Rust jamming is due to anti-corrosion failure, re-galvanize after derusting, replace directly if severely rusted, and use stainless steel bolts in wet track sections with better anti-rust effect. Torque attenuation is due to long-term use fatigue, retighten the torque regularly, install torque monitoring devices for heavy-duty tracks to monitor in real time. Thread damage is caused by installation jamming, replace bolts/spikes with intact threads, clean thread impurities before installation to ensure smooth screwing.