Fishplate Connection Methods and Maintenance Tips
1. What are the common methods for connecting fishplates?
The primary method is bolted connection. Bolts are inserted through the bolt holes in the fishplate and rail, and nuts are tightened to secure the fishplate securely to the rail joint. This method is easy to install and remove and is widely used. Welded connections are also available. In areas where rail joint smoothness is extremely important, such as some seamless high-speed railway lines, fishplates are welded to the rail to reduce joint gaps and improve track integrity and smoothness. However, welding requires high-tech processes and subsequent maintenance is relatively complex.
2. What are the key steps in installing bolted fishplates?
Before installation, check that the bolt holes in the fishplate and rail are aligned and free of deformation or obstruction. Select bolts and nuts of appropriate specifications and apply a moderate amount of thread lubricant to facilitate tightening and subsequent removal. During installation, tighten the bolts from the center toward the ends, gradually reaching the specified torque in 2-3 steps to ensure even force on each bolt. For example, for fishplates with 60kg/m rails, the bolt torque is generally controlled between 600 and 800 N·m.
3. What are the technical requirements for welded fishplates?
Before welding, the welded areas between the fishplate and rail must be polished and cleaned to remove impurities such as rust and oil, exposing the metallic luster and ensuring weld quality. Welding materials must match the materials of the fishplate and rail. For example, if the fishplate is made of Q235, E43 series welding rods can be used. During welding, the temperature and speed must be controlled to avoid defects such as overheating and incomplete penetration. After welding, insulation treatment and slow cooling are required to reduce welding stress. After welding, the weld must undergo non-destructive testing, such as ultrasonic testing, to ensure the absence of internal cracks and other potential hazards.
4. What are the common types of damage to fishplates during use? Common problems include bolt hole wear, which occurs when the bolts rub against the hole wall for a long time, causing the hole diameter to increase and affecting the connection tightness. Cracks in the fishplate body often develop in stress concentration areas due to long-term exposure to alternating loads. Surface rust, especially in humid environments, can weaken the fishplate's strength. Deformation, such as uneven loading, can also occur due to improper installation. These damages can reduce the fishplate's connection performance and require prompt attention.
5. How should fishplates be maintained and serviced daily?
Regularly check the fishplate connection for loose bolts and re-tighten them with a torque wrench to ensure the specified torque is met. Clean rust and debris from the fishplate surface, remove rusted areas, and apply anti-rust paint to prevent further rust. Inspect the fishplate for cracks and deformation, and replace any problems immediately. For bolted fishplates, apply thread lubricant regularly to facilitate disassembly and maintenance. During railway line overhaul, the fishplates are fully inspected to evaluate their performance and decide whether to continue using them or replace them.