Fishplate Connection Reliability and Maintenance
- How to match the type of fishplate with the rail specification?
The type of fishplate must be strictly matched with the model and weight of the rail. For example, 43kg/m rails need to be matched with fishplates of 43kg/m specification, 50kg/m rails correspond to 50kg/m fishplates, and 60kg/m rails use 60kg/m fishplates. The length, number of bolt holes, and hole diameter of fishplates of different specifications are adapted to the rails. If the fishplate does not match the rail specification, it will lead to loose connection, inability to effectively transmit loads, easy vibration and impact when the train passes, increased wear of the fishplate and rail, and even joint failure.
- What are the requirements for the tightening sequence and torque control of bolts when installing fishplates?
Bolt tightening must follow a diagonal symmetry sequence. For example, for a four-hole fishplate, first tighten the diagonal bolts 1 and 3, then tighten bolts 2 and 4 to ensure that the fishplate is evenly attached to the rail and avoid local stress concentration. Torque control is determined according to the fishplate material and bolt specification. Ordinary carbon steel fishplates matched with M24 bolts generally have a torque controlled at 300 - 350N·m; high-strength fishplates (such as Q345 material) matched with high-strength bolts require the torque to be increased to 400 - 450N·m. Insufficient torque will cause bolts to loosen, and excessive torque may cause bolts to break or fishplates to deform, affecting connection reliability.
- What are the common damages of fishplates during use, and how to repair them?
Common damages include bolt hole wear, surface corrosion, and local cracks. When the bolt hole wear is slight, reaming repair can be used, and bolts with a slightly larger diameter can be replaced; when the wear is severe, new fishplates need to be replaced. Surface corrosion can be removed by rust removal tools, and then anti-rust paint can be applied for protection. If cracks are found in the fishplate, no matter the size of the crack, it cannot be repaired and must be replaced immediately, because the crack will expand rapidly under load, leading to fishplate fracture and causing track safety accidents.
- What are the differences in performance requirements for fishplates in different track sections (such as straight lines, curves)?
Trains run smoothly in straight sections, and the main requirement for fishplates is to ensure connection strength and stability. Ordinary specifications of fishplates that meet material standards can be selected. When trains pass through curve sections, large lateral forces will be generated, so higher requirements are put forward for the shear strength and wear resistance of fishplates. High-strength and wear-resistant fishplates need to be selected, such as fishplates made of low-alloy high-strength steel. At the same time, the fishplates on the outer side of the curve wear faster, so the inspection and replacement cycle needs to be shortened to ensure that their performance meets the use requirements.
- How to evaluate the service status of fishplates through regular inspections?
Regular inspections include appearance inspection and performance testing. Appearance inspection checks whether the fishplate has cracks, deformation, corrosion, bolt hole wear, etc.; a feeler gauge is used to detect the fitting gap between the fishplate and the rail, which should not be greater than 0.3mm; a torque wrench is used to sample and test the bolt torque to determine whether there is looseness. For fishplates with a long service life or high damage risk, ultrasonic flaw detection can be used to detect hidden cracks inside, and the service status of the fishplate can be evaluated based on the comprehensive results of various inspections to determine whether maintenance or replacement is needed.